Conservation of Wall Painting Department
COURTAULD I NSTITUTE OF ART Somerset House, Strand, London WC2R 0RN Telephone +44 (0)20 7848-2848 [email protected]
This is a dissertation accepted for a Postgraduate Diploma in the Conservation of Wall Painting in the Conservation of Wall Painting Department, Courtauld Institute of Art, University of London.
It is unpublished and copyright is held by the author. No quotations or information derived from it may be published without the prior written consent of the author, who may be contacted through the address above. AN INVESTIGATION OF THE USE OF SOLVENT GELS FOR THE REMOVAL OF WAX-RASED COATINGS FROM WALL PAINTINGS
TOBIT CURTEIS
Courtauld Institute ofArt/Getty Conservation Institute,
Conservation of Wall Paintings Department.
July 1991 CONTENTS
Acknowledgements.
1. Summary.
2. Introduction.
3. Solvent Gel Principles.
4. Gel Components.
4.1 Carbopol
4.1.1 Thickening mechanisms of Carbopol.
4.1.2 Amines for Neutralisation.
4.1.3 Surfactants.
4.1.4 Clearance.
4.1.5 Possible drawbacks with Carbopol.
4.2 Pemulen.
4.2.1 Thickening mechanisms of Pemulen.
4.2.2 Drawbacks of Pemulen.
4.3 Cellulose materials
5. Desiderata for Test Sites.
6. Test Methodology and Procedure.
6.1 Examination and Analysis.
6.2 Preparation of Carbopol gels.
6.3 Test Procedure.
6.4 Clearance Tests. 7. Holcot Church.
7.1 Introduction.
7.2 Painting Condition.
7.3 Cross-section analysis and SEM.
7.4 FTIR and Thermomicroscopy.
7.5 Solvency parameter tests.
7.6 Solvent gel tests.
8. The Holy Sepulchre Chapel,
Winchester Cathedral.
8.1 Introduction.
8.2 Technique.
8.3 Conservation History.
8.4 Painting Condition.
8.5 Cross-section analysis and SEM.
8.6 FITR and Thermomicroscopy.
8.7 Solvency parameter tests.
8.8 Solvent gel tests.
9. Westminster Abbey Chapter House.
9.1 Introduction.
9.2 Technique.
9.3 Conservation History.
9.3.1 G. G. Scott.
9.3.2 Prof A. H. Church
9.3.3 H. M. Office of Works.
9.3.4 English Heritage.
9.4 Painting Condition.
9.5 Cross-section analysis and SEM.
9.5.1 Binding Media.
9.6 FTIR and Thermomicroscopy.
9.7 Solvency parameter tests.
9.8 Solvent gel tests. 10. Analysis for Residual Materials.
11. Conclusion and Further Research.
12. Bibliography.
13. Appendices.
1. Recipes for wax and wax resin preservatives advocated by Professors Church and Tristram. 2. Solvent Gel formulas. 3. Teas Chart showing the solvency parameters of the most effective solvent gels in relation to the solubility region of beeswax. 4. Solvent Gel Tests,Summary of results reported in the proformas. 5. Fourier Transform Infrared Spectra. 6. Nitromors paint stripper. 7. Solvent Gel Tests Carried out in the Chapel Of Our lady Undercroft, Canterbury Cathedral. 8. Site proformas.
14. Plates. Acknowledgements
For permission to examine and sample the paintings at the four sites studied I am grateful to the Dean and Chapter of Canterbury Cathedral and to Mr. Wolfgang Gartner of the Wallpaintings Workshop; the Dean and Chapter of Winchester Cathedral and especially to Mr. John Hardacre for his help and advice, the Parish Council of Holcot Church and the Rev. Anthony Watkins; and to Mr. Jan Keevil, Head of the English Heritage Conservation Studio, for Westminster Abbey Chapter House.
For technical information on materials and for product samples I would like to thank Mr. G. Stead and Mr. John Gallagher of B. F. Goodrich and Mr. C. Drake of AKZO Chemicals. Ms. Zahira Veliz, Mr. Alan Phenix (Courtauld Institute) and Ms. Lucia Scalisi (Victoria and Albert Museum) gave much helpful advice on formulation of the gels.
I am particularly grateful to Ms. Marianne Odlyha of Birkbeck College for her constant help and valuable advice especially in regard to the analysis including Fl'lK, DSC and Thermomicroscopy. I am also very grateful for the help of Mr. Raymond White, Scientific Department, National Gallery, particularly in the area of interpretation of IR spectra.
For their advice and support throughout and in all areas of this research I would especially like to thank my two supervisors Ms. Aviva Burnstock, Scientific Department, National Gallery, who also carried out the SEM and EDX analysis, and Ms. Katherine Powell of the Courtauld Institute.
Finally I would like to thank Mr David Park and Ms. Sharon Cather of the Courtauld Institute for their continual help during the course of this work. -5-
Summarv
The effects of the preservative' coatings commonly applied to wall paintings in the 19th and first half of the 20th centuries, have been both damaging and disfiguring in the longer term. Typically these coatings consist of either pure beeswax or a mixture of beeswax and a natural resin applied to the painting surface. The penetration of the coatings due to the porosity of wall paintings and the fragile nature of many of the paint surfaces, when treated, has made the removal of such materials extremely difficult.
The solvent gels formulated for this study were intended to have very specific solvency parameters allowing them to dissolve a particular material, without endangering the other vulnerable components of the paint surface. The system was not be intended as an all-encompassing solvent mixture for the removal of all coatings on the paint surface. If there were more than one coating of a different nature, for instance a varnish layer covered by a wax resin coating, it would be necessary to use two different gels, each tailored by their solvent mixtures to the specific problem of each layer.
The complete removal from the painting of all components of the gel system, forms an integral part of gel cleaning process. The long-term effects of the non-volatile components and their interaction with the materials of wall paintings are not fully understood and to ensure that no damage is caused by these materials the implementation of an adequate system of clearance must be undertaken.
The investigations into the feasibility of such a cleaning system drew heavily on the work of Richard Wolbers who was responsible for developing the theory and formulating a range of organic solvent gel systems for particular cleaning problems in the field of easel painting conservation. The formulas developed by him provided the starting point for the development of a series of solvent gels that were applicable to the problems faced in wall paintings.
Materials were chosen that had a known history of usage in general conservation, although some of these had not been applied to wall painting conservation. Much of the initial work was theoretical, involved with the chemistry of producing a gel system with the necessary attributes. The main gelling agent, a high molecular weight polyacrylic acid, Carbopol, was chosen due to its ability to effect very viscous gels at relatively low percentages. Due to the high wax component of the coatings it was necessary to produce a series of highly aromatic solvent gels. A program of tests was undertaken on a number of wall paintings that had been treated with a wax or wax/resin coating in order to evaluate both the cleaning effect of the gels and their subsequent clearance. The possibility of conducting the tests on laboratory models was evaluated, but despite the complications caused by the lack of chemical control on actual paintings, it was felt that due to the problems of reproducing the necessary conditions on a model, the results obtained from actual paintings would of be more value in examining the effects of the gels.
Cross-sections were taken to establish the stratigraphy of both the coatings and the painting. This enabled the characterisation of differing surface coatings and the their relative thickness to be established in order to make a comparison with the situation after cleaning. These samples were examined both on the surface and in cross-section using visible and ultra-violet microscopy and scanning electron microscopy. Samples of the surface coating were analysed using FTIR in order to establish the exact nature of the material. This was necessary so that the solvent -6-
component of the gel could be prepared to dissolve that particular material.
After the cleaning and clearance tests had been carried out, further samples were taken in order to evaluate the effects of the gels as well as to check for possible residues. Examination was carried out using visible, ultra violet and scanning electron microscopy. In order to examine the problem of clearance more fully, controlled tests were carried out on a laboratory model, allowing a more detailed series of experiments to take place.
The results of the project were extremely encouraging indicating that it is possible to produce a solvent gel system with the necessary solvency parameters to remove the commonly encountered wax coatings. No residues of the material from the cleaning system were detected with FTIR or SEM after clearence had taken place. This latter result must however be qualified. A negative result such as this means simply that no residue has so far been found, it is not a guarantee that no trace of the material is present and further more sensitive analysis should be carried out to ensure this. -7-
2. Introduction
During the nineteenth and the first half of this century, wax and resin based treatments were commonly believed to be the most effective method for the
'preservation' of wall paintings. The original premise behind the application of such coatings lay in the mistaken belief that classical Roman paintings were executed in encaustic technique, thus leading to the conclusion that wax was responsible for their longevity and survival. The writings of both Pliny and Vitruvius appeared to confirm that the use of wax was advantageous in protecting fresco paintings.1
The saturation of the painting with such coatings was seen as a general cure for the various types of damage encountered and with the active involvement of respected men such as Professors E. W. Tristram and A. H. Church, who were regarded as authorities on such matters, became the accepted treatment for almost all wall paintings. An application of such a coating effectively restored cohesion to powdering surfaces, and was equally effective at readhesion of flaking layers.
Perhaps the effect which was initially most apparent was the immediate visual change caused by the saturation of the paint layer. The result was to change wall paintings from damaged'and apparently faded objects into bright, sound decorative elements more in keeping with the contemporary aesthetic.
Such effects were relatively short term, and it soon became apparent that the use of wax and resin coatings was the major cause of the damage that began to appear on paintings. Serious discoloration and flaking were seen to occur. This damage fell broadly into two categories, aesthetic and structural. The aesthetic alteration brought about by such coatings are often the most noticeable forms of damage. Pure beeswax is a very stable polymer, that does not discolor or break down with age. The main reason beeswax coatings appear to darken is that at room temperatures the
1 Cather & Howard 1986 -8-
wax is relatively soft,2 and will absorb atmospheric dirt that settles on it, including the byproducts of the burning of fuels such as oil and coal (commonly used in the past to fuel heating systems in parish churches), which will remain fixed to the surface of the wax, thereby obscuring the painting. A further reason for the discoloration is that some of the preservative coatings consisted of a mixture of wax and a natural resin such as copal.3 During the oxidization and aging process of natural resins darkening occurs, thus further obscuring the paint surface.
The main reason for the physical damage caused by these coatings relates to the porous nature of lime-based wall paintings. This porosity allows moisture and water- soluble materials such as salts to move freely through the structure of the painting.
If this porosity is significantly reduced by the application of an impermeable coating over the surface of the painting the effect will be to set up internal stresses within and below the paint layer. Soluble salts that would have crystallised on the surface of the painting causing little or no physical damage will now crystallise in the restricted space of the pores below the surface. The expansion of volume that occurs in the process of crystallisation will cause the pores to break and thus disrupt the paint surface causing both decohesion and delamination. The application of wax based coatings to oil or secco paintings was in some ways potentially less damaging.
Due to the nature of the medium, such paintings were far less porous than lime- based wall paintings, and therefore a coating of wax would not considerably alter the rate of penetration of moisture. The damage caused in these cases is aesthetic with the darkening of the coating, described above, obscuring the paint surface.
It was not until 1953 when the committee set up by the Council for the Care of
Churches (CCC) to examine the practices employed in the conservation of wall
2 The glass transition temperature of beeswax is 3 Appendix 8. -9-
paintings, published a letter in the Times denouncing the use of '....Wax or any other surface coating which may impeded the free evaporation of any moisture...' that the damage caused by the practice was generally acknowledged.4 In 1959 the CCC published a full report on the subject setting out the damaging effects caused by such 'preservative' treatments and advising against their use.5
Traditional methods for the removal of these coating have relied on the use of strongly acting organic solvents which aim to remove all components of the surface coatings through the application of a single type of cleaning agent. The advantages of organic solvents supported in a gel system rather than as free and highly volatile agents have long been apparent to conservators.6 The most commonly used cleaning system in recent years has been Nitromors, a commercially available paint stripper.
The formula for this product has changed a number of times since it was first introduced in the early 1940s, but its main components have altered little and have
always been based on a mixture of methanol and dichloromethane supported in a gelling medium containing both paraffin wax and a small component of cellulose.7
The disadvantages of such a material are twofold. The first is that a commercial paint stripper such as this is intended to encompass the removal of as wide a range
of organic material possible. The structures of wall paintings can be very complex with a number of delicate and soluble layers. Such a material will not only dissolve the wax and resin coatings, but also any other vulnerable organic components such
as surface glazes and medium found in secco wall paintings. The second
disadvantage lies with the components of the material themselves. For a long period of time, Nitromors has been used without a full knowledge of its chemical
4 The Times, 21st February 1953. 5 Central Council for the Care of Churches, 1959. 6 The use of gels in wall painting conservation is not limited to organic solvents. The use of AB 57, a combination of sodium and ammonium bicarbonates in a cellulose gelling medium, is a well established treatment for the removal of insoluble salts. Mora, Mora and Philippot 1984. pp.342. 7 Appendix 6. -10-
components or the possible effects of chemical decomposition that may occur in the longer term if any of the material is left on the painting. A commercially available paint stripper would tend to be concerned with the short-term effects of the material and not the longer term that would be of concern to the conservator.
3. Solvent Gel Principles
The principles behind the use of a gel system to alter the working properties of
organic solvents has clear advantages in areas of conservation. The gel support
reduces the rate of evaporation and diffusion of the solvent mixture in which it is
dissolved by increasing the viscosity of the system thus enabling an increased contact period in a discrete localised area of the surface of the object. The result of this
reduction in solvent volatility is to 'concentrate' the effect of the solvent, increasing
the ability to more effectively dissolve the material on which it is working. There is
no evidence that the use of a gel support alters the solubility parameters of the
solvent, simply that within those parameters the action of the solvent appears to be
enhanced. The direct application of this phenomenon is that where a 'strong' free
solvent (a solvent with a solubility parameter in the center of the region of the
solute), would be required the same effect could be achieved using a ^weaker'
solvent (one with a solubility parameter towards the edge of the of the region of the
solute) supported in a gel system. Containing the solvent in such a way might also reduce the amount of undercutting, as discussed by Burnstock and White,8 that can
occur when there is no control over the penetration of a free solvent. This is of
course an advantage when dealing with complex layer structures of soluble organic
materials as it allows far more specific solubility to be achieved, more readily
allowing the removal of individual layers with potentially less 'strong' and hazardous
solvents.
8 Burnstock and White 1990. -11-
Recently significant advances have been made with the application of such gels to cleaning problems encountered on easel paintings through the work of Richard
Wolbers. His use of an acrylic acid polymer, Carbopol, as a gelling agent for organic
solvents marked a significant advance on the use of the cellulose materials more commonly used.9 Carbopol had the advantage of producing a thixotropic viscous gel
at a very low percentage due to its high swelling ability and could more easily be used in conjunction with a wide range of solvents. Wolbers developed the rationale for the use of such gel systems with very specific parameters to work on individual parts of a particular cleaning case, rather than on the case as a whole.
The application of these principles to the removal of wax and wax/resin coatings from wall paintings was clearly desirable as the problems associated with the removal of soluble materials encountered in this field of conservation are complex.
The most important difference between easel paintings and wall paintings in terms
of surface is the high level of porosity and topography of many wall paintings. The effect of this is that at the interface with the paint surface, there is no longer the relatively discrete separation between coating and pigment layer encountered on
easel paintings, but with a coating that penetrates the surface to various depths, becoming an almost integral part or the matrix of pigment and binder. The degree to which this occurs depends on the nature of the painting technique and its condition. In cases where there is decohesion occurring within the paint layers this situation is further complicated. The problem is further complicated by the method in which the coating was applied. In many cases this was carried out using heat treatments in order to drive the material deep into the painting in the belief that the greater the penetration, the more stable the treatment.10
9 HPMC is used by Wolbers as a support for resin soaps and enzyme cleaning systems. 10 Appendix 1. -12-
The ability to finely control solvency parameters offered by gels has a number of further advantages which apply in all fields of painting conservation, but are particularly important in the field of wall paintings. First among these is the scope for a reduction in toxicity of the solvents used. In many cases when free solvents are used it has been necessary to use those with relatively high levels of toxicity to gain the solvency parameters required. The use of large quantities of dichloromethane with a MEL of 350 mg/m3 and LD 50 of 2136 mg/kg oral, ratn both free and in
Nitromors paint stripper, is the standard method for the removal of wax coatings from English wall paintings.12 Using solvents in a gel system a similar area of solvency can often be achieved with a less toxic solvent. The toxic effect on the conservator would also be limited due to the reduction in evaporation rate of the solvent caused by the gel.
A further advantage in the use of solvent gels is the reduction in mechanical action on the paint layer from that caused by continual swab rolling with free solvents.
Solvent gels are applied to the wall with a swab and then gently moved, until they area removed with a second swab. Contact between the surface of the painting and the swab is minimal. Such mechanical action as there is can be further reduced by the use of an intervention layer of a permeable material such as Japanese tissue between the gel and the paint layer, thus reducing the risk of damage when working on a damaged or delicate surface. The use of an intervention layer also acts as a
considerable aid in the removal of the majority of the gel from the surface of the painting.
An essential part of the cleaning process using solvent gels is the clearance
11BDH Hazard Data Sheets. MEL or Maximum Exposure Limit is taken from the HSE guidance note EH40, 'Occupational Exposure Limits', and is an indication of the maximum amount of the material that it is considered acceptable to be exposed to. LD or Lethal Dose indicates the toxicity of a material on a rat or mouse (as stated) as a guide to its toxic effect on humans. 12Ballantyneetal. 1988 -13-
procedure that must be undertaken in order to remove all residues of the gel from
the painting. Although a number of recent studies have examined the possible
effects of some residual materials,13 the long-term effects of many of the gel
components and any interaction with the materials of the painting have not been
fully examined. The complete removal of residual material must therefore form an
integral part of the overall cleaning method.
4. Gel Components
The two basic components necessary for a solvent gel are the gelling agent and the
solvents themselves. Further components are subsidiary to these in that they are specific to a particular gelling agent (or solvent) and are intended either to make
the solvent and the gelling agent compatible, or to alter the effect of the gel on the
solute. Into this secondary category can be placed surfactants, pH buffers and neutralising mechanisms. It is principally, therefore, the choice of gelling agent which dictates the nature of other components in the solvent gel.
4.1 Carbopol™
Carbopol resins are long-chain acrylic acid polymers cross-linked with a polyalkenyl polyether (carboxy polymethylene), with pH of 2.5-3.0 in a 1% water dispersion.14
Carbopol in its undissolved state is a white powder consisting of tightly coiled long- chain molecule. When it undergoes certain reactions, the molecule uncoils, thus causing the viscosity of the solution to rise. It is available in a wide range of molecular weights ranging from approximately 450,000 (Carbopol 907) to 4,000,000
(Carbopol 940).15 The molecular weight affects the surface tension and viscosity of the final product therefore it is important that the most suitable one is chosen to
13 Wolbers 1990A, Burnstock and White 1990. 14 Goodrich B.F. CARBOPOL Water Soluble Resins. Technical data. Ohio. 15 Molecular weights given by the manufacturers are approximate. Carbopol 907 = 450,000, Carbopol 910 = 750,000, Carbopol 941 = 1,250,000, Carbopol 934 = 3,000,000, Carbopol 940 = 4,000,000. (Carbopol 954 mw 3,000,000 is no longer widely available.) -14-
achieve optimum performance for the solvent gels.16
Carbopol 934 or 940 were chosen as the most suitable gelling agents for the gels
tested in this project due particularly to their ability to produce the necessary high
levels of viscosity at very low percentages. They were also adaptable to all the
solvent mixtures required, both polar and non-polar, for the cleaning of wall paintings.
Fig.l. Structural Formula of Carbopol
4.1.1 Thickening Mechanisms of Carbopol.
Although Carbopol resins are predominantly hydrophilic they can also be used in non-aqueous solvent systems. There are two basic methods for using Carbopol as a thickening agent. The first, the hydrogen bonding method, can only be employed in polar systems, while the second, the neutralisation method, is suitable for both polar
and non-polar systems.
Hydrogen Bonding.
This system requires the use of a solvent capable of donating an hydroxyl group. The resulting hydrogen bonds between the carboxyl groups of the Carbopol and the hydroxyl groups of the solvent donor will cause the molecule to uncoil and thickening to occur. The solvents capable of this are limited to polyhydroxy, and polyethoxy solvents such as diols, triols and polyols. This process is far slower than
16 Carbopol 934 and 940 were found to be the most efficient in terms of the low percentage required to produce the desired viscosity for the solvent gels. -15-
the neutralisation method and it may take a number of hours for full thickening to occur. Empirical observation through experimentation undertaken in the course of this work has shown that this process does not achieve the viscosity of neutralised systems using the same percentage volume of Carbopol. A further problem for this study is that the use of the necessary hydroxyl donor solvents may adversely effect the solubility parameters required for the particular gel.
Fig.2. Schematic Depiction of a Molecule of Carbopol in its
uncoiled state with hydrogen bonding.
V
Neutralisation.
For this method the resin is neutralised by the use of a base to produce a salt soluble in the required solvents. In an aqueous or polar solution this can be achieved using a base such as ammonium or sodium hydroxide. A 3% aqueous solution of Carbopol can produce a viscosity of 30,000 to 40,000 cP without neutralisation. A level of viscosity from 40,000 to 60,000 can be produced by a 0.5% solution of Carbopol in water after neutralisation to pH 7 - 7.8 with sodium hydroxide.17 In a non-polar solvent system (such as those considered in these tests) or in one where the use of these bases is undesirable the resin can be neutralised in the same way with an amine.18
17 Goodrich B.F. CARBOPOL Water Soluble Resins. Technical data. Ohio, pp 13-14 18 The use of sodium hydroxide as part of a cleaning system for wall paintings is considered undesirable as the free sodium ions introduced into the wall will readily react with other free ions producing highly soluble salts which are inherently dangerous to wall paintings. Ammonium hydroxide is sometimes used for cleaning wall paintings, and it is possible that it could also be use -16-
The pH of the overall gel is not only important for the effect it may have on the paint surface, but also for the stability of the gel.19 It was possible that during the cleaning process the dissolved material from the surface of the painting may cause the pH of the gel to alter to an extent that it would break down. The use of a pH buffer was considered to counter this effect. Buffers are solutions that will enable the main solution to retain a constant pH when small quantities of acids or bases are added. Empirical experiments were carried out to establish whether the pH of the gel was altered, during its application, to an extent where the use of a buffer solution would become necessary.20 The results showed that the alteration in the pH of the gel was negligible. It remained physically stable throughout the test, even when applied to a volume of wax far greater than that which would be encountered in the field.
Fig.3. Schematic Depiction of a Molecule of Carbopol in its
uncoiled state after neutralisation with ammonium hydroxide.
4.1.2 Amines for Neutralisation. For the purposes of this study it was necessary to work with aromatic and aliphatic
as the neutralising agent in a polar solvent gel, without risk to the paintings. 19 The pH of the gels formulated for this work was approximately 7.5. 20 The pH of the solvent gel was tested in its fresh state. A given quantity of beeswax was then dissolved in the gel and a second test for pH was made. These were found to be the same. -17-
hydrocarbon solvents in order to obtain the required solvency parameters to remove wax-based materials. The use of a neutralising mechanism offered the most
adaptable and viscous gel, and the non-polar solvents were not suitable for
hydrogen bonding. It was therefore necessary to use an amine that would produce a
Carbopol salt soluble in aromatic and aliphatic hydrocarbon solvents.
A wide range of amines were examined and/or tested as possible neutralising agents
for the gels.21 Ethomeen C-25, (polyoxyethylene(15)cocoamine) and Ethomeen C-
12, (Cocobis(2-hydroxethyl)amine) appeared to offer the most efficient
neutralisation enabling the Carbopol to be dissolved in the required aromatic
solvents22. However after extensive testing Ethomeen C-12 proved to be the most
effective of the two at the lowest percentages.23 Virtually insoluble in water, it is
readily dissolved in aromatic solvents, and has a relatively low cationic surfactant
HLB value of 10 compared to that of 19 for Ethomeen C-25.24 It also has the added
advantage of relatively low toxicity with an LD 50 of 1500 mg/kg.25
Fig.4. Structural Formula of Ethomeen C-12
CH2.CH2.OH
R-N (R = Coco alkyl)
CH2.CH2.OH
The fact that Ethomeen C-12 is not only an amine but also a surfactant, albeit a
21 Those considered included Ethomeen C-12, Ethomeen C-25, Armeen-OD (products of AKZO Chemicals), Dodecylamine & Triethanolamine. 22 xylene and White Spirit. 23 Tests using Ethomeen C-12 to gel Carbopol with aromatic systems have already been carried out by a several easel painting conservators, showing successful results had depended on the use of very exact amounts. (Pers. comm. Lucia Scalisi and Alan Phenix) 24 Hydrophile/Lipophile Balance value. The HLB value is a scale used to compare the relative emulsifying properties of surfactants. It runs from 0 to 40 (0 is the weakest) and is established by either experimental or mathematical methods. 25 AKZO Chemicals. -18-
mild one, is of concern due to the possible problems of clearance that might be presented.
4.1.3 Surfactants.
By forming bonds between polar and non-polar materials surfactants reduce the surface tension between the gel and the solute increasing the intimate surface contact (Vetting') and thereby increasing both the homogeneity and the potency of the cleaning action.26 This same action could also cause greater penetration of the substrate resulting in problems of clearance. The inclusion of a suitable surfactant in a gel can also allow the addition of a solvent that is not miscible with the main solvent, thus permitting a fine manipulation of the solubility parameters of the overall system, however the surfactant may itself alter the solubility parameters of the gel.
The possible problems involved with the use of surfactants in painting conservation have been the subject of a number of recent discussions.27 All of these have concentrated on the effect of surfactants on easel paintings, and while many of these also occur on wall paintings, there are further complications associated with wall paintings. Most important of these are the effects of the surfactant on the irregular topography and porous substrate typical of wall paintings. Due to the ability of surfactants to reduce surface tension there is a greatly increased tendency to penetrate the painting to some depth. The danger that this could result in the surfactant remaining within the substrate, avoiding the clearance procedure, is present in all paintings, however the open structure of wall paintings makes it all the more acute. The long-term results of this are unclear and it appears probable that the presence of a residual surfactant could increase the hydrophilic tendency of the
26 This effect will vary in relation to the polar/non-polar nature of both the gel and the solute. 27 Southall 1990, Wolbers 1990A, Burnstock and White 1990. -19-
painting. This would encourage increased penetration of moisture commonly present in an uncontrolled atmosphere, which in turn could effect the movement of
soluble salts and other water-related damage mechanisms in a way that would
clearly be detrimental to the painting as a whole. The possibility in the long term of
damaging interaction between any residual surfactant and the materials of the wall painting is an area that is as yet unclear and requires further investigation. It is therefore of the utmost importance that if surfactants are used as part of a cleaning system, they are completely removed afterwards.
4.1.4 Clearance.
As the solvents are volatile they do not present a direct clearance problem, however
the two non-volatile components, the Carbopol and the Ethomeen C-12, are the
materials that must be considered. Ethomeen C-12 is virtually insoluble in water,
however it can be dissolved in aromatic solvents. This is also true of most of the
Carbopol which will have been converted by the amine to a salt. There is a possibility that some of the Carbopol may not have reacted to form a salt and in this form will be insoluble in aromatics but readily water-soluble. Although this would represent only a tiny proportion of the overall volume of the Carbopol, it is
necessary to deal with it at this stage, because once it has been allowed to dry, it becomes far more difficult to redissolve.28
Clearance is further complicated be the physical nature of the surface of many wall paintings. As well as the porosity associated with medium-thin secco or buon fresco technique there are the complications caused by the very uneven surfaces commonly encountered on wall paintings. The particular hazard associated with the clearance of solvent gels is the tendency of the deep interstices to retain relatively large
28 Pers.comm. G.Stead. The reason for this is not a change in the chemical structure of the Carbopol, but rather the physical structure that occurs when it dries and reforms into larger lumps. This reduces the ability of the water to gain the surface contact with the individual grains required for the quick dissolution. -20-
amounts of the gel.
The clearance procedure must therefore involve both aqueous and aromatic solvents. In order to avoid increasing the risk to soluble components of the painting, the aromatic solvent used should the same that contained in the gel. The same caution exercised when applying the gels should be continued here as the solvency parameters of other soluble materials of the painting may coincide with those of the material removed by the gel. This should be followed by aqueous clearance which requires further caution. The gel itself contains very low concentrations of water, so it is possible to use it with minimal risk over a water-sensitive surface that may be put at risk by this stage of the clearing. Both clearance solvents are applied using cotton wool swabs, in order to absorb the dissolved residues.
4.1.5 Possible drawbacks with Carbopol
A possible disadvantage with the use of Carbopol as the gelling medium is its tendency to react with certain of the materials commonly found in wall paintings.
The polyacrylic acid produces COO" ions which can complex certain bivalent and trivalent ions such as calcium and magnesium. Such a reaction would be of serious concern in the field of wall painting conservation due to the presence of large amounts of both these ions either as part of the original material or in the form of soluble salts. Once this reaction has taken place the Carbopol becomes insoluble in water and could present a serious clearance problem. It is possible that once the
Carbopol is formed into an amine salt during gelling, less reactive sites will be available for the complexing to occur, thus reducing the possibility of a reaction. No hard data is available on the exact nature of these reactions, however certain empirical tests have been carried out which indicate that in its unneutralised state the Carbopol reacts swiftly with the metal ions to become insoluble.29
29 Pers. comm. G.Stead. 14.3.91. Empirical tests were carried out with Carbopol and cement in order to test the complexing of ions present in the mixture. Dry Carbopol was added to dry cement which was then mixed with water. At first the result was viscous, but in a matter of minutes it -21-
42 Pemulen™
Pemulen, a product of B.F.Goodrich, is described by the manufacturers as a
^polymeric emulsifier'. It consists of a polyacrylic acid backbone similar to Carbopol, copolymerised with fatty comonomers (the nature of which is proprietary information). The polyacrylic acid part of the molecule is hydrophilic while the comonomer is lipophilic resulting in a molecule with amphipathic or surfactant properties. The effect of this is that the molecule is soluble in both polar and non- polar solvents and is able to act both as a thickening and emulsifying agent.
4.2.1 Thickening mechanism of Pemulen.
The method recommended by the manufacturers of thickening a solution with
Pemulen (pH 2.5-3.0 at 1% in H2O) is by neutralisation using a base such as sodium hydroxide. It would also be possible to thicken an aqueous solution by adding
Pemulen directly to it, however without neutralisation, the solution would remain strongly acidic.
4.2.2 Drawbacks of Pemulen.
As with Carbopol, the polyacrylic acid will produce COO- ions able to complex bivalent and trivalent ions such as calcium or magnesium.30 The copolymer is considered to be very stable and this reaction would not cause it to break up, however the reaction does cause the molecule, like Carbopol, to become
thinned to a liquid. This was thought to be due to the Carbopol chelating the calcium ions of the lime in the cement and thus becoming insoluble in the water and thus inactive. A second experiment was carried out neutralising Carbopol with sodium hydroxide in order to fill all the reaction sites and inhibit the reaction with the calcium ions. This was then mixed with the cement that had already been mixed with water. The result was a stable viscous mixture which did not break down, suggesting that in its salt form the sites on the Carbopol were not free to complex other ions. 30 It is possible that the occurrence of complexing would be reduced by the process of neutralisation in much the same way as was proposed for Carbopol. -22-
insoluble.31 Apart from the obvious undesirability of leaving foreign materials on the wall painting there is the possibility of further complications caused by the amphipathic properties of the molecule, (discussed in section 4.1.4 on clearance), resulting in ionic bonding of the surfactant molecule to the painting.
4.3 Cellulose Materials
Cellulose gelling agents such as carboxymethyl cellulose or hydroxypropylmethyl cellulose have commonly been used as thickening agents in certain areas of conservation.32 The principle by which they work is one of bulking out the system into which they are introduced. When in aqueous solution the tightly packed long cellulose chains are swollen by hydrogen bonding of the water. The gelling efficiency is relatively low in terms of percentage weight to viscosity, and the amount needed to achieve the degree of gelling required for this work would be extremely high compared to a system based on a swelling material such as a polyacrylic acid polymer. A further problem with the use of cellulose gelling agents on wall paintings is one of clearance. Carboxymethyl cellulose is hygroscopic with an equilibrium moisture content of approximately 18% at 60% R.H.33 Were some of the material to become trapped in the porous substrate, it would provide nutrition for the microbiological growth common in an uncontrolled environment. It is also known to contract on drying which could present the danger of flaking of the paint layer.
5. Desiderata for Test Sites.
It was decided that the majority of the tests would be carried out on actual paintings as opposed to specially prepared models. The main problem with such models is that of aging and reproduction of the widely ranging contaminants. The alteration of
31 pers.comm., Mr C.Drake 21.2.91. 32 CMC is used as the gelling agent for AB 57 and HPMC in Wolbers resin soaps and enzyme cleaning systems. Wolbers 1990B. pp.148. 33 Hone 1987, pp.129. -23-
the solubility of aged materials is well documented for easel paintings,34 however
little or no work has been carried out in the field of wall paintings. The physical problems of the solubility of aged polymers would almost certainly be complicated by the intimate contact with the dense crystalline matrix encountered with a porous wall painting. To simulate such a situation on a model would be extremely difficult.
The major disadvantage encountered carrying out the tests on actual paintings is the reduced level of chemical control that can be exercised due to the complex nature of the painting itself. The interaction of materials on a wall painting that has undergone restoration is difficult to understand without a full knowledge of the constituent parts of both painting and previous treatment. For this study sufficient knowledge of the present state of these materials was needed to clearly define the effects of the gel tests. To overcome this problem it was necessary to carry out detailed analysis of the paintings in their present state, before any tests were begun.
The choice of paintings was intended to encompass a sufficiently wide range of dates, techniques, and previous restoration treatments in order that the project should give a representative view of how the gels perform in a range of different situations. The decision to carry out the tests on a number of such sites introduced an additional series of variables, such as state of conservation and interaction between multiple previous treatments, that should be considered when examining the results of each individual series of tests.
The three sites chosen ranged in date from the 12th to the early 15th centuries and varied in painting technique with both organic and inorganic media.
34 Mills and White, 1987. -24-
6. Test Methodology and Procedure*
The intention of using the solvent gels was to dissolve a single specific layer of material on the painting. In order that the components of the gel were tailored to this layer it was necessary to have a certain knowledge of the nature of the particular material to be dissolved.
6.1 Examination and Analysis
Initial examination of the surface coating was carried out on site under low magnification using normal and ultra violet illumination. Under UV by examining the colour and intensity of the fluorescence, it was possible to distinguish in detail the variations in nature and thickness of the coating. Such information was important in establishing where samples were to be taken, and in identifying any anomalies that might occur during the examination of particular samples.
Two types of samples were taken. Cross-sections of the painting were taken for examination with optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).35 Samples of the individual surface coatings and samples of pure materials to act as controls36 were taken for analysis by Fourier transform infrared reflectography (FTIR)37 and Thermomicroscopy.38
In order to establish the solubility parameters of the surface coatings, standard solvent tests were carried out using free solvents. This established broadly, the types of gels that should be tested on each site.
35 Cambridge Stereoscan 200. 36 Spectra were obtained from Ethomeen C-12, Carbopol 934 and 940, and BDH bleached beeswax. 37 Tests were carried out on a Perkin Elmer 1710 FTIR. All FTIR analysis for this study was carried out in the Diffuse Reflectance Mode. 38 Analysis was carried out on a Mettler FP800 hot stage, and samples were examined at a magnification of xlOO. -25-
6.2 Preparation of Carbopol Gels. To prepare the gels used in the tests the first stage was to calculate the solvency parameters required to dissolve the coating. In order to do this a Teas chart was prepared with the solvency parameters of both the major solvents and the solutes plotted over each other.39 The overall solvency parameters of each solvent mixture was then plotted, giving a clear visual representation of the areas in which the work was to take place, allowing fine tuning of particular gels to be undertaken with greater ease.
The two main criteria for the gels are the viscosity and the solvency parameters of the solvent mixture. A neutralising amine should be chosen that forms a salt with the Carbopol that is soluble in a solvent with the required solubility parameters.
Certain further solvents can be added at a later stage in order to adjust the overall solvency parameters of the gel. The order in which the materials are combined was established through a series of empirical tests and is an important to achieve a successful gel.
1. principal solvent. 2. Carbopol. 3. Amine. 4. Polar solvent. 5. Secondary solvents.
During the whole process there should be constant agitation of the mixture to ensure that the individual materials are sufficiently dispersed throughout the system.
First the Carbopol is evenly dispersed in the principal solvent. Then the amine is added to form the salt necessary for the uncoiling of the Carbopol. Initial gelling occurs at this stage. Since sufficient viscosity is an important property of the cleaning agent extensive testing was undertaken to examine how the degree of viscosity could be enhanced. Increasing the amount of Carbopol had little effect apart from bulking
39 The nature of the solutes had first been determined by analytical means. (See below under 6.2). -26-
out the solution. However the addition of small quantities of a polar solvent was particularly effective. Therefore on the basis of empirical observation the procedure was modified to include the addition of a polar solvent (normally water) at this stage. This produced a suitably viscous gel to which could be added the secondary solvents necessary to achieve the correct solvency parameters.
The addition of the secondary solvents after the initial gelling had occurred was found to be of utmost importance. If the secondary solvents were mixed with the principal solvent before the addition of the Carbopol it was observed that the gelling process often failed to occur. This appeared to be due to the fact that the salt formed by the Carbopol and the amine has been specificly chosen for its solubility in the principal solvent. The addition of the secondary solvent at this point may have altered the solubility parameters of the mixture so that the dissolution of the
Carbopol would be partially or totally inhibited.
The following materials were examined for their suitability as gelling agents for non- polar solvent systems, but were considered to be less suitable than Carbopol.
6.3 Test Procedure The procedure for the gel test was the same at each site. The gel was applied by cotton wool swab and left static on the surface for a recorded period of time. After this it was gently moved around with the swab in order both to remove swollen material from the gel/surface interface and to move fresh gel into contact with the
surface. At the end of this period the gel was removed with a dry swab and the area of the test was thoroughly swabbed with the aromatic solvent base of the gel (white
spirit or xylene) in order to clear any residues of the gel. Finally the area was
swabbed with deionised water to remove any remaining residues. The area was allowed to dry before further samples were taken in order to asses the level and -27-
effect of cleaning. In some cases an intervention layer of Japanese tissue was used during the tests. This was removed before clearance was carried out. The result of each test was used to determine which gel was used for the following tests.40
6.4 Clearance Tests Analysis to establish whether the clearance procedure was successful in removing all residues of the gels was carried out in two stages. Initially all samples taken after clearance were examined with normal light and UV microscopy and SEM to see if any deposits of residue could be identified. In order to undertake more detailed tests it was considered most expedient to use a model rather than carry out the tests on actual paintings. This was necessary primarily due to the relatively large size and controlled nature of the sample required. It was expected that if a residue was present, its volume would be extremely limited compared to the that of the overall sample and FTIR analysis would be further complicated by the interference of high background 'noise' from the inorganic material from the surface of the painting that would make up the major component of the sample. To take samples of the necessary size from actual paintings would be nether justified or practical.
40 Appendices 1 & 5. -28-
7.0 St. Marv and All Saints Church. Holcot.41
7.1 Introduction
There are a number of different painting schemes in the church, all of which were coated with wax, possibly by E.W.Tristram42 who describes them in his 14th-century volume.43 The area selected for the tests was part of the immense area of painting
(54 x 12ft) on the north wall of the north aisle said by Tristram to depict 'six
Apostles, one probably StJohn, bearing the cup, and another St.Bartholomew with the knife;'.44 Although the paint layer is flaking in certain areas, apparently due to the activity of soluble salts, a suitably sound and accessible area was found on the lower part of the painting. The painting is simple and linear in style, and probably dates from the early 14th-century.45 It is very medium thin but probably painted with a combination of organic and lime media.46
7.2 Painting Condition
Initial examination of the painting on the North wall showed that the surface was coated with a relatively thick homogeneous layer of a translucent waxy material.
This was covered with a large amount of what appeared to be surface dirt. UV
examination showed that the coating had a weak fluorescence, and losses due to
damage showed clearly. The condition of the paint layer varied considerably, with
some areas suffering severe flaking and loss. Much of this damage appeared to be
due to the decohesion of the upper part of the substrate causing the surface layer to
break up. This may well have been due to the movement and crystallisation of the
soluble salts within the wall rather than on the surface, due to the impermeable wax
coating. However, much of the painting was sound, and it was in such an area that
41 Appendix 8. 42 The beeswax-based material found on the wall is consistent with Tristram's recipe of c.1926. Appendix 1. 43 Tristram 1955, p.181 44 Ibid. 45 Ibid. 46 See section 7.3 -29-
the tests were carried out.
7.3 Cross-Section Analysis and SEM.
The thickness of the coating varied in some areas, but it appeared that there was only a single coating present. In cross-section under both UV and normal illumination this appeared to be the case (PI. 1). On top of this coating there appeared to be a thin layer of crystaline material, which was discrete from the coating and did not penetrate it. Under SEM this material could be seen on the surface of the sample over the soft coating that covered the paint layer in a thick unbroken layer (PL 12). At a higher magnification of xl380 the material appears to be some form of effluorescence over the surface of the coating (PI. 13). It was however easily removed with a soft sable brush, suggesting that it may simply be an unusually thick layer of ambient dirt that had settled on the soft surface coating.
In cross-section, the structure of the painting can be seen to be relatively simple.
Above the plaster (not shown in the cross-sections) are two layers of tinted limewash of varying thickness. In areas of background the limewash would have formed the original paint surface over a lime ground. In figurative areas there is a pigment layer over a single limewash ground. Media stains were carried out on a number of samples, but the only positive result was achieved with Acid Fuchsin which weakly stained the upper part of the limewash and pigment.47 This suggests
that for the limewash ground a small amount of protein was used as an additional binder in what is mainly a calcium carbonate matrix. This relatively porous matrix
can be seen in SEM under relatively low magnification on the lower left hand side
of PL 12. The paint layer is very fine with a dense pigment content, and
identification of media by staining did not prove conclusive, however it appears
possible from the other analysis that an proteinous binder was used.
47 Acid Fuchin 2% vol/vol in deionised water. Rinsed with deionised water. -30-
7.4 FTIR and Thermomicroscopv Samples of the coating were taken for organic analysis from two areas on the edge of a large loss, where there was enough depth to avoid contaminating the sample with large amounts of inorganic material from the surface of the painting. With
FTIR both samples produced similar spectra,48 showing that the majority of the sample consisted of beeswax.49 This interpretation appeared to be confirmed by the results of Thermomicroscopy which showed that the coating had a melting point of approximately 64°C.
7.5 Solvency Parameter Tests
The free solvent tests carried out showed that the coating was readily soluble in a range of aromatic and aliphatic hydrocarbons. A large part of the surface coating was removed using xylene, without any apparent damage to the paint surface below which appeared to be insoluble in the solvents.
7.6 Solvent Gel Tests
Solvent gel tests showed that the most effective cleaning action was achieved with gel 7.50 Clearance was carried out with xylene and water. The optimum application
time was 20 seconds stationary on the surface followed by 60 seconds agitation with
a swab.51 SEM analysis of sample HO9/567 taken from this area show that the gel
had achieved a considerable level of thinning to a consistent level over the surface
of the sample (Pis. 14 & 15). This shows that there is still a fine film of the wax over
the paint surface, but that it is so thin that the material on the paint surface is
breaking through. PL 16 also clearly shows the limited level of penetration of the
wax coating and it would appear that a longer application of the gel would be
48 Appendix 5. 49 persxomm. M.Odlyha and R.White. 50Apendix3. 51 Appendix 8. -31-
necessary to achieve complete removal.
Tests with gel 7 were also carried out through an intervention layer of fine Japanese tissue for a period of 70 seconds. The effect of this was to considerably reduce the amount of mechanical action on the surface of the paint film. During the period of application less of the coating material was removed from the surface than without the intervention layer, the majority of the cleaning action occurring when the tissue was removed and the area swabbed with xylene. This appeared to lift off the heavily swollen organic coating, with very little mechanical action necessary. Two applications of the gel were necessary over an intervention layer to obtain the same level of cleaning as a single direct application. The level of mechanical action on the surface was however considerably reduced. This appeared to be confirmed by SEM which shows a similar level of cleaning to that seen in Pis. 14 & 15. The SEM also suggested that there were no significant residues of the gels present on the samples.
The wax coating was readily soluble in aromatic solvents in either a gelled or free state and the best level of cleaning achieved by the gels in these tests was slightly greater than that achieved with free solvents. The advantages of using a gel was the dramatic reduction in mechanical action necessary to achieve the results and the homogenious nature of the removal of the wax coating. The area on which the tests were carried out was relatively sound, however much of the painting is in a far less stable condition, and such a reduction would minimise the risk of damage to the paint surface during cleaning. -32-
8. Holv Sepulchre Chapel. Winchester Cathedral,
8.1 Introduction
The earliest of the three sites is the Holy Sepulchre Chapel in Winchester
Cathedral. This contains two schemes of painting, the earlier of which dates from between 1175 and 1185 and the later, from c.1220.52 Until the 1960s the only visible part of the 12th-century painting was that situated on the south wall of the west bay, depicting the Resurrection of the Dead. The main area of the earlier scheme, situated on the east wall, was revealed in 1963 during work carried out by Mrs. Eve
Baker and her assistants. The 13th-century scheme, depicting the Entombment and the Resurrection of Christ, was detached to reveal the very fine earlier painting of the same subject.53 The newly revealed areas of 12th-century painting survived in remarkably good condition, despite the heavy keying marks inflicted when they were covered by replastering for the 13th-century scheme.
8.2 Technique
While the 13th-century paintings have always been assumed to be in a secco
medium, the appearance of the 12th-century paintings has suggested that they are in
fresco technique.54 The discovery under the 13th-century painting on the south wall
of the east bay of part of a 12th-century sinopia overlayed with a small area of painted intonaco depicting the head of a male figure, suggested that the technique was very similar to the Italian buon fresco technique, as described by Cennino
Cennini in his Libro dePArte. Recently, analysis undertaken on areas of the painting
on the east wall has shown that the technique is more complex than has so far been
assumed. Pigments not commonly associated with the boun fresco technique such as
red lead and vermilion were identified, suggesting a combination of both organic
and inorganic media.55
52 Park 1983, pp.53 & 48 53 Ibid., pp.38 54 Park 1983 pp.40 -33-
The technique on the west bay of the south wall appears to be somewhat different.
Analysis of sample HS6/530 taken from the black outline of one of the angels flying down to take up a resurrected soul again showed a thin layer of coating with small wax residues on the surface; more importantly however it showed that this area of painting is not in the same technique as the area in the east wall. Deep losses on the painting reveal that there is only a single layer of plaster in this area. On this is a layer of limewash on which is painted the under-drawing in a red pigment. Over this is not an intonaco, but a second layer of limewash over which is painted the final outline of the figure in carbon black apparently with a lime binder (PI .6). Further examination of the painting confirms that this is the case, as in areas where the paint surface is lost the red underpaint is clearly visible under a limewash and not an intonaco.
8.3. Conservation History
The early restoration history of the paintings is undocumented, however it appears from analysis carried out in the course of this project, that all the areas of painting visible before the most of restoration in the 1960s were treated with one or in many cases two layers of organic 'preservative' coatings. E.W.Tristram is thought to have worked on the paintings which are documented in his volume on the 13th-century56 published in 1950 and it can be assumed that it was he who applied the upper (wax) coating over a previous varnish layer, however the exact date of its application is unknown. In 1959 The Eve Baker Trust began a program of restoration that continued until 1970.57 It was during this period that the 13th-century paintings on the east wall were detached to reveal the very fine 12th-century paintings below.
During this period also, work was carried out on the 12th-century scene of the
55 Hluvko 1991. 56 Tristram 1950 57 Baker 1964,1967,1970. -34-
Resurrection of the Dead on the south wall of the west bay. A certain amount of cleaning took place on the coated areas, probably with Nitromors or a homemade mixture based on this formulation58, and an area of 13th century painting on the right hand side of was removed to uncover a well preserved figure of a trumpeting angel of the earlier scheme.59
The 12th-century scene of the Resurrection of the Dead (with the exception of the recently uncovered angel) is therefore unique in the chapel in terms of conservation.
It is the only area of the 12th-century painting to be exposed at the time of the early restorations, and so it is the only area of predominantly lime bound painting to have been coated with organic preservatives. This area of the painting was therefore selected as a suitable site to carry out the solvent gel tests.
8.4 Painting Condition The initial examination of the area of 12th-century painting to be tested in the Holy
Sepulchre Chapel showed that it was unusually dark for a wall painting treated only with a wax-based material. Under low magnification a thin layer of coating could be
seen, the surface of which was covered with a number of residues as well as normal
surface dirt. One of these residues, which appeared to have been left in circular
patterns consistent with wiping action, was distinct from the surface, with a white
papery texture and a bright whitish fluorescence under UV illumination.
Examination of the rest of the area under UV illumination showed that the organic
coating, although very thin, was fairly homogeneous being broken in a few areas by
later damage. The only exception to this was in deep interstices or small losses,
58 Pers. comm,, David Perry. 59 This area had previously been ignored by past restorers as it had been covered by a spiral staircase inserted at the request of Samuel Wesley during his time as organist at the Cathedral (1849-1865), to enable him to reach the organ loft more easily. The staircase was removed and broken up in 1938, pers. comm. John Hardacre. This revealed a badly damaged area of 13th-century painting that was detached in the 1960s restoration by the Eve Baker Trust, to reveal the 12th- century angel, pers.comm. David Perry. -35-
where the coating was thicker. Here it fluoresced slightly differently to other areas with a weak greeny/yellow tint. Samples were taken from these areas for analysis as they were the only areas with sufficient material available for FTTR analysis. The condition of the paint surface below the coating is varied. In some areas there is considerable flaking, some of which appears to be relatively old, but some is more recent, suggesting that the damage in this case is active. There are also widespread losses of the paint surface, revealing the red under-drawing below, however the majority of these appear to have occurred before the application of the surface coating.
8.5 Cross-Section Analysis and SEM.
Visible light microscopy clearly showed a fine translucent layer of material over the
surface of the painting (Pis. 3 & 5). Under UV illumination this layer had little or no
fluorescence, however in this light source it was possible to see isolated areas of a
second fine layer on the surface which fluoresced differently, being slightly brighter.
This layer was very fine and broken and was just discernible in visible light at a
magnification of x400. With SEM this material can be seen on the surface of sample
HS5/529 as a disrupted residue incorporation surface dirt that obscures the crazed
surface of the more homogeneous coating below (Pis. 17 & 19). The SEM clearly
illustrates the way in which the lower organic coating penetrates the porous matrix
of the lime-bound pigment (PL 18).
8.6 FT1R and Thermomicroscopy
The FITR spectra of the samples of the surface coating obtained from the interstices showed that the majority of the material in the samples was beeswax,60
contaminated with large amounts of inorganic material, possibly from the paint
layer. No further organic material was apparent.61 These results were further
60 Appendix 5. 61 Pers. comm. M.Odlyha and R.White. -36-
supported by Thermomicroscopy which showed that the coating had a melting point of approximately 64°C. These results in combination with those described in 8.5 suggest that the material analysed here was not the coating now generally visible on the paint surface, but the remains of a second more recent coating. It appeared therefore that until the 1960s there had been two layers of organic coating on the paint surface,62 and that the upper one of these, the beeswax, had been partially removed at this time leaving the thin wax residue on the surface of the earlier hard coating, but remaining in quantity in interstices or damages. This may also explain the presence of the other Vhite papery' material found on the surface which may well be the residue of the cleaning agent used at that time. FTIR analysis carried out on a sample of this material, indicated that it was possibly some form of cellulose.63 This was also suggested by Thermomicroscopy which showed the material charring at approximately 250°C.
8.7 Solvency Parameter Tests
A range of solvent tests was carried out to establish the solvency parameters of the
coating, however the results were limited. Strongest solvency was in the region of
the aromatics, but it was observed that after an initial removal of a small amount of
material (probably beeswax) no further action took place.
8.8 Solvent Gel Tests The results of the gel tests appeared to confirm the observations made with visual
62 David Perry, of the Perry Lithgow Partnership, and former conservator with the Eve Baker Trust, confirmed that this is probably the case. He carried out much of the work in the chapel during the 1960's program, and said that he came across a second coating under the wax that was impossible to remove in certain areas. He felt that it may have been a resin varnish. 63 It was thought possible that the material was a residue of the cellulose part of the gelling medium of the paint remover Nitromors (Celacol MMPR1) that may have been used as a cleaning agent in the 1960s intervention. Celacol MMPR1 was produced by Courtaulds Ltd. It is however no longer in production and an infra red spectra of the material was not available. The material produced today considered to be the closest chemically to Celacol MMPR1 is Celacol HPMMPR1, an hydroxypropyl methyl cellulose (pers.comm. Dr.N.G.Todd). IR spectra of this material, compared one from the Winchester sample (KMHS2) showed similarities in diagnostic frequencies, suggesting that it was a similar cellulose material. Appendix 5. -37-
examination and analysis. The optimum effect was obtained with gel 7 applied for
10 seconds static and moved for a further 60 seconds.64 Clearance was then carried out with xylene and water. The cleaning was very limited and similar in effect to that achieved by the aromatic free solvents applied in the tests to establish solvency parameters. A small amount of material including dirt and residues of the upper wax layer on the surface of the coating were removed, but the lower resin coating appeared to remain unaffected.
Analysis of sample HS7/571 taken from the area of this test would appear to
confirm that the residues of the wax layer had been removed leaving the lower layer untouched. In cross-section at magnification up to x400 the lower layer was clearly visible over the pigment surface (PL 4), and under UV the remains of the upper layer were no longer visible. This was further shown by the SEM examination of the
surface of the sample (Pis. 20 & 21). Comparing this to the surface of sample
HS5/529 before cleaning (PL 19), it is apparent that the disrupted material on the
surface has been completely removed, while the lower layer remains in tact.
Clearly the gel is working efficiently and thoroughly on the material for which it was
designed. The earlier resinous layer should be further analysed in order to establish
its exact nature, and a second cleaning system should be designed to remove it.
64 Appendix 2. -38-
9. Westminster Abbev Chapter House.
9.1 Introduction
The Chapter House of Westminster Abbey has a complex history and the survival of the paintings on its walls is remarkable considering the number and scope of interventions that have occurred. The paintings, depicting scenes from the
Apocalypse of St. John were probably carried out sometime between 1372 and 1404, and are of the highest quality.65 Each side of the octagonal Chapter House, except for the west entrance wall, contains five bays separated by Purbeck marble
arcades.66 The condition of the individual areas of painting varies according to that
of the ashlar masonry support, and the type of previous restoration. The only
internal wall is the north west (side 1), and here not surprisingly, the paintings
survive in the best condition.
The Chapter house was built by Henry III from c.1245-1255, and was apparently
intended from the outset to serve an additional function as a secular meeting room.
The Great Council met there in 1257, and it was a frequent venue for parliament
until 1547. From the dissolution it served as a store for public records, and the provision of a gallery and book-shelves against the walls caused a certain amount of
damage to the architecture. The first restoration was carried out by George Gilbert
Scott from 1866-73.
92 Technique The painting are carried out on a white ground directly over a substrate of tooled
closely jointed ashlar masonry the shows through paint layer. The paint layer itself is complex with a number of different pigment layers and surface glazes,67 with
pigments of the highest quality.68 It would appear likely that there would have been
65 Turner 1985 66 Numbering of the 7 sides is carried out clockwise from the entrance. 67 Hluvko 1991. -39-
an original varnish, however this is no longer visible.
9.3 Conservation History
The conservation history of the paintings, although better documented than in most
cases, is complex and unspecific in the location of particular treatments.
9.3.1 G. G. Scott
The first recorded treatment to the paintings was probably carried out under Scott.
The exact date and method is not recorded, however references to the paintings in
his book of 1863 throw some light on the subject.69 Scott refers to his discovery of
the paintings behind the bookcases that had obscured them and agrees with
Eastlake that they date from the mid 14th-century and with his suggestion that the
medium is oil.70 Although Scott does not refer to treatment of the paintings, he does
describe the treatment of the stone tympanum over the entrance. This was first
cleaned with a soft jet of air, and then injected with an (unspecified) solution, the
effect of which was to harden the decayed stone. It is possible that a similar
treatment might have been used on areas of painting where the stone support was in
the same condition as the tympanum. The only direct reference to Scott's treatment
of the paintings is by Prof. A. H. Church who in his report of 1904 refers to the
difficulties he had treating the paintings in the North West arcade, which he said
that Scott had varnished.71
9.3.2 Prof. A. H. Church
Church himself carried out work on the paintings between 1901 and 1903. In his
report of 1904 he claims that the damage to the paintings was due mostly to the
68 Hluvko 1991 and Howard 1988. 69 Scott 1863, pp. 40-43 70 Eastlake 1947. pp.5 71 Church 1904 -40-
attack on the stone by the 'acidic atmosphere', which not only broke down the weak structure of the stone, but introduced further soluble salts to the paintings. In his analysis Church discovered that as well as chlorides, the stone contained large quantities of sulfates, the source of which he thought to be atmospheric sulfur dioxide. This had reacted with the calcium carbonate in the wall to form larger and water-soluble calcium sulfate crystals, causing the breakdown of the cohesion of the stone, resulting in the damage to the paintings. To counter this Church treated the paintings with baryta water applied six to twelve times in order to introduce enough barium hydroxide into the wall for the treatment to prove effective.72 This in turn introduced a large amount of water into the wall which Church had himself acknowledged was causing damage due to the mobilisation of soluble salts.
9.3.3 H.M.Office of Works
The third treatment took place in 1929 and is recorded in an anonymous article in the Museums Journal of that year which mentions that in many of the bays there was a severe deterioration of the stone and that the paintings had a uniformly gray
appearance.73 This could have been due to the barium carbonate bloom which
Church himself acknowledged as a possible consequence of the 1901-03 baryta water treatment.74 To fix, consolidate, and restore the aesthetic quality of the
paintings, a coating of bleached beeswax dissolved in turpentine with 2% linseed oil was applied to the paintings.75 Flaking paint was readheared by injecting this
solution behind the paint layer with a syringe and pressing the flakes back by hand.
Consolidation of friable areas was carried out by spraying the solution onto the
72 Baryta water is an aqueous solution of barium hydroxide. The theory behind the treatment was that calcium sulfate crystals would be converted into the more stable and insoluble barium sulfate crystals. This would leave calcium hydroxide which would reconvert to calcium carbonate with atmospheric carbon dioxide. 1. CaSO4 + Ba(OH)2 -> Ca(OH)2 + BaSO4 2. Ca(OH)2 + CO2 -> CaCO3 + H2O
73 H.M.Office of Works. 1929, pp.376 74 Church 1904. pp.5 75 The same mixture without the turpentine was applied in some areas with the use of heat administered by a baffled blow torch. -41-
surface and then encouraging its penetration with the use of a paraffin blow torch fitted with a baffle.76
9.3.4 English Heritage
The most recent treatment was carried out in 1985 by English Heritage, when the
paintings on the north west side were cleaned and the coating (there was only a
single wax coating on these paintings) removed with a mixture of 80% White Spirit
and 20% Propan-2-ol. At at the same time a partial cleaning was carried out on all
the other paintings in the Chapter House. This was undertaken using a hot-air
blower to melt the wax on the surface, which was then removed with large cotton wool swabs.77
9.4 Painting Condition
The initial examination showed that the surface was very uneven and broken in
some places and that areas of the paint surface were seriously disrupted, apparently
due to the damaged stone support. There were areas where serious flaking had
occurred in the past, but all of these had been coated and consolidated with the
waxy coating. The overall condition of the painting was therefore sound in that no
active damage was occurring, however the true state of the painting below the
coating was far less solid. It was clear that more than one coating was present, but
the exact limits of each layer was difficult to establish. Under UV it could be seen
that there were two dominant coatings. The upper one appeared to be a soft waxy
material, and was very thin in some areas. Towards the edge of the painting where it
was protected from the 1985 partial cleaning by the pillars this coating is far thicker,
up to lmm in some areas, suggesting that the majority of the material had been
76 During the process a certain amount of the old varnish was removed. This was usually carried out with a mixture of methelated spirits, benzene or turpentine, however where the material proved particularly hard to remove, pyridine (C5H5N) was used. H.M.Office of Works 1929. pp.376. 77 Pers. comm. J. Keevil, Head of the English Heritage conservation studio. -42-
removed in the 1985 treatment. Beneath this layer was a second coating, consisting of a thick layer of a hard dark resinous material. Both layers were heavily contaminated with paniculate material, apparently a combination of ambient dirt and material from the paint surface.
9.5 Cross-Section Analysis and SEM.
Samples were taken in most cases from sections of white pigment on and around the scroll in the center of the area in an attempt to obtain similar layer structure to facilitate comparison in the cross-sectional analysis. In practice this failed to occur
due to the severe damage and the complex nature of the painting which was further
confused by the effects of earlier restorations. It was clear from all the samples that
there were two separate surface coatings as had been expected. The upper coating was very fine in some areas, and had very little autofluorescence under UV
microscopy. Under SEM this layer had a soft feathery appearance characteristic of wax (PL 24),78 and although thin was fairly homogeneous over the paint surface.
The lower layer fluoresced with a yellow/green tinge under UV and was relatively
thick. Under SEM it was possible to see the hard fractured edges typical of a natural
resin varnish. The interface with the paint surface was very disrupted with what
appeared to be material, possibly salts, effluorescing through the paint surface itself
(PL 7).
9.5.1 Binding Media The structure of the painting itself was immensely complex with up to six often
discontinuous layers present in the same sample. On a number of the samples taken
from the edges of more prominent losses, the lowest layer (above the stone
substrate) consisted of the same wax material to be found on the surface. This
showed how the wax had been used as both fixative and consolident, and was
injected behind such loose edges in order to readhere them as explained in the 1929
78 pers. comm. Aviva Burnstock. -43-
report and is apparent in PI. 10.
The nature of the medium of the painting is of obvious importance when
establishing the solvency parameters of the gels. Past analysis79 and the survival of
records regarding the purchase of large quantities of oil80 appeared to suggest that
the predominant medium was indeed oil. In order to confirm this, stain tests were
carried out with Sudan Black B,81 Acid Fuchsin,82 and the fluorochrome stain for
lipids, Rhodamine-B.83 The Sudan Black failed to stain the apparently medium-rich
pigmented layers, but took strongly to the thick lower layer of the coating. Acid
Fuchsin only stained in a single case when it took to two small isolated areas on the
lower side of the sample, suggesting that protein was not commonly present, and
that these two areas were anomalous. Under UV the Rhodamine-B was seen to
have stained the central pigment layer, which appeared to be the most medium rich,
a light purple indicating the possible presence of lipids. The stain was far too weak
in this area to suggest the presence of any large quantity of oil, but was stronger on
the bottom of the sample where an area of wax appeared to have penetrated behind
the paint surface (PL 9.).
9.6 FTIR and Thermomicroscopy
Samples taken of both surface coatings were examined with FTER and
Thermomicroscopy in order to further identify and differentiate between the two
layers.84 The resulting spectra had diagnostic frequencies clearly showing the
presence of beeswax in both samples,85 and neither contained any peaks that
79 Howard 1988 80 Eastlake 1847. pp.49-55 81 Sudan Black, a saturated solution in IMS. Rinsed with IMS. 82 Acid Fuchsin 2% vol/vol solution in deionised water. Rinsed with water. 83 Rhodamine-B. 0.02% vol/vol solution in IMS. Rinsed with IMS. 84 To enable a larger volume of sample to be gathered, they were taken from the edge of the painting, where less of the upper layer had been removed in 1985. 85 Appendix 5. -44-
indicated the presence of an organic resin. Thermomicroscopy showed that the samples had a melting point of approximately 64°C, also indicating the presence of beeswax. The conclusion to be drawn from these results is that the resin layer which is clearly visible in SEM and visible microscopy failed to be collected in the sample.
Both samples were heavily contaminated with what appeared under low magnification to be dirt, resulting in the high level of background noise on the spectra.
0.7 Solvent Parameters Tests The area of painting chosen for the gel tests was in the third (central) bay of side 6. Although much of the painting in this bay is severely damaged, the area in the lower right hand scene appeared to be reasonably well preserved beneath its coating of dark wax and resin. A range of solvent tests showed that the upper coating was most soluble in the aromatic region, with a mixture of xylene and benzyl alcohol in the proportions 2:1 having the strongest effect. None of the tests appeared to have any effect on the lower resin layer.
9.8 vSolvent Gel Tests Due to the lack of solubility demonstrated by the resin layer in the earlier solvent tests it was felt that tests with aromatic solvent gels could take place on the upper wax layer without affecting the lower layer.
As with the Holcot and Winchester tests, the most successful cleaning was achieved with gel 1J86 Applied for 105 seconds in all and cleared with xylene and water, this successfully removed the upper wax layer while leaving the lower resin layer apparently untouched. Using SEM this can be seen on sample WA8/558, leaving the smooth resin surface and the pigment layers below (PL 25). In order to remove the resin layer two resin soaps developed by the National Gallery Scientific
86 Appendix 2. -45-
Department, and described in the 1990IIC Brussels conference,87 were tested on
areas already cleaned with gel 7. The 9-fluorenone-4-carboxylic acid soap (9FOC),
applied for 120 seconds, and cleared with xylene and water appeared to have little
or no effect on the material. The Anthracene-9-carboxylic acid soap (A9C), did
appear to have some cleaning effect. Also applied for 120 seconds, and cleared with xylene and water, the effect was noticeable even at low magnification. Under SEM
the cleaning action is more apparent. The surface of WA14/564 (PL 26) shows that
the soap had significantly thinned the resin without disrupting the paint layer by undercutting. Examination under UV illumination appeared to show a bluish fluorescence in the area of the A9C test; none was seen in the area of the 9FOC test. As the A9C is not known to be autofluorescent, it is possible that the apparent fluorescence was due to the materials of the painting rather than those of the cleaning reagent.
10. Analysis for residual materials
It was clear from both visible microscopy and SEM that at the three sites where tests were undertaken that the majority of the gel was removed from the paint surface,
and that any residues that may remain would be relatively small. With the type of
organic analysis available, the size of sample necessary to obtain a volume of
residue that was identifiable would have to be relatively large. It would have been impossible to take such samples from the surface of the test paintings, and so it was necessary in this case to use a studio model. This had the added advantage that the materials could be controlled, thus avoiding the contamination with unknown materials that samples taken from actual paintings would be likely to have and that could mask the results.
87 Burnstock and White 1990. -46-
The model was a small block of approximately 3.5cm sq., constructed of two layers
of plaster, an arriccio with a large aggregate, and a thin lime-rich intonaco (pi. 11).
The surface was painted in buon fresco technique with yellow ocher. The block was
made and painted in 1988, and so the lime would have been well carbonated at the
time of the tests. Three weeks before the tests were carried out, half of the surface
of the block was treated with a wax-based mixture typical of the type used by
Tristram during the second quarter of this century.88 The day after application this was polished with a dry cloth as was recommended.
Before the gel tests were carried out surface scrapings were taken from both the waxed (KSR 1) and unwaxed surface (KSR 3). In both cases the sample area was
about lcm sq. The samples were intended to contain all components that might
contaminate a sample taken after testing, this included pigment, calcium carbonate,
surface dirt and in the case of KSR 1 the wax coating. Gel tests were carried out on both areas with gel 7, as this had been the most successful gel on the site tests, and
cleared with xylene and water. Similar samples were then taken on the waxed (KSR
2) and unwaxed areas (KSR 4) after testing. In the latter case small amounts of wax were removed from the interstices around the edge of the gel test area, as it was important to establish whether residues were left in the coating itself.
FTIR analysis was then carried out on all four samples as well as on samples of
Carbopol 940 and Ethomeen C-12, the non-volatile components of the gel.89 None of the diagnostic frequencies of the Carbopol or the Ethomeen could be seen on either spectra obtained from the after cleaning samples (KSR 2 and KSR4) however in some cases this could be due to masking by another peak. This result is encouraging, but as it is in effect uncalibrated it does not mean that the residues are definitely not present. It would be necessary to conduct a series of tests to obtain an
88 Appendix 1. 89 Appendix 5. -47-
internal standardisation for these results to show positively that the samples contained no residue from the gel.90 Further analysis to establish the presence of residues could be carried out using secondary ion mass spectroscopy which would prove more sensitive for low concentrations than the FTIR.
11. Conclusions and Further Research.
It appears that the use of a gelling medium contains, and, in effect, enhances the action of a particular solvent in terms of the amount of the solute dissolved over a given period of time. This is apparently due to the gelling medium reducing the speed of evaporation of the solvent thus allowing it a longer and more intimate period of contact with the solute. The gel medium will therefore have a greater effect enhancing the action of highly volatile solvents, than those with relatively low rates of evaporation which would, in their free state, remain in contact with the
solute for a longer period of time.91 This enables one to use a relatively inefficient
solvent in a gel to perform the work of a 'stronger' free solvent. Therefore a
material only partially soluble in a certain solvent could more efficiently be
dissolved using the same solvent in a gel system. This reduces the risk to other
materials with similar solubility parameters to the desired solute that may be
effected by the use of a 'stronger' free solvent that may traditionally have been used
to remove the main solute. The results of this and earlier work demonstrate that it is
90 A series of tests could be carried out decreasing the volume of the gel in a standard sample until it no longer registered on the FTIR. This would establish a base-line for the detection of residues which could be related to the results obtained in the present tests. 91 To verify such an hypothesis a series of tests could be undertaken with two solvents of similar solvency parameters but different rates of evaporation. Both solvents would be applied first in their free state and then in a gel for a set period of time. The resulting dissolution of the solute could then be measured for both tests in terms of how much material had been removed and the results compared to establish in terms of percentage gain ('gain' would be considered to be an increase in the material removed from the solute), whether the highly volatile solvent had increased its effect more that the low volatility solvent. -48-
possible to produce a variety of gels with a wide range of solvents, both polar and non-polar, allowing extreme flexibility and the adaptation a particular gel to deal with a specific problem.
The health and safety implications are clear. The gels system by reducing the evaporation of the solvents reduces the volume of solvent released into the air in contact with the conservator. The choice presented by the wider range of solvents available in a gel system able to dissolve the same material also allows the use of less toxic solvents.
Empirical observations made during the gel tests at Holcot using an intervention layer give a further important insight into the working method of the gels. It appears that rather than completely dissolving the wax and absorbing it into the body of the material, the gel is simply swelling it to a high degree, and the mechanical action of the swab is removing the wax in its swollen state from the active interface between gel and coating. It is clear then that mechanical action although significantly less than that involved in traditional solvent cleaning is an integral part of the solvent gel
cleaning process, not only removing the swollen material from the surface, but also replacing the gel at the interface with a fresh solvent-laden gel enabling the process
to continue. Surface characterisation of cleaned areas with SEM, suggests that the
action of the gels is one of thinning the coating from the surface down rather than swelling and dissolution as might occur with the use of free solvents. The effect of
this is to allow far greater control to be exercised over the level of cleaning.
Although many of the results of this project are encouraging in regard to the use of
solvent gels for the cleaning of wall paintings, it must be regarded as part of a larger
long-term study. There are a number of areas which require further and more
detailed investigation. Most important among these is the clearance of the gels
discussed above in section 10. From SEM characterisation it is apparent that there
are no sizable residues of the cleaning reagent deposited on the surface of the -49-
samples after clearance. However, it is necessary to establish by more specific analysis, before the gels are used on any scale, that all the non-volatile material is being removed. The analytical techniques most likely to identify the presence of very small concentrations of the cleaning materials are gas chromatography with mass spectrometry (GCMS).92
The effect of solvent gels on the paint layer is an area that has not been extensively examined in the scope of this work, primeraly due to the nature of the particular paintings tested. In two cases, there appeared to be no organic component in the paint layer that would be effected by the gel, while in the third (Westminster Abbey) the vulnerable paint layers were protected by the presence of the resin layer beneath the wax that proved to be insoluble in the gels. Due to the nature of the solvents contained in the gels, there is clearly a potential risk to certain organic components that occur in many wall paintings. Further investigation should be specifically aimed at examining such effects in order to establish more exactly the action of the gels on such vulnerable materials.
A third area which requires further research is the effect that surfactants have on the solubility parameters of certain solvents. The use of a surfactant allows a polar solvent such as water to dissolve a non-polar material upon which, without the surfactant, it would have no effect. It appears probable that this effect would occur to a greater or lesser extent with all solvents combined with a surfactant. In theory this could radically alter the accepted solvency parameters. As the gels discussed in this project all contain a certain amount of material with surfactant properties, the solvency parameters calculated in the standard manner may be affected in a way that has not been predicted.
The use of solvent gels for removing wax coatings from wall painting clearly has
92 Burnstock and White 1990. -50-
advantages over some of the 'traditional' methods. Most importantly it allows a far greater control over the solvent parameters of the system, in effect making the whole process more specific to the individual material to be removed thereby reducing the risk to other soluble materials in the painting. The reduction in the rate of evaporation of the solvents included in the gel is without doubt advantageous in terms of health and safety to the conservator, as is the possibility of using less toxic solvents in some cases. Further tests are necessary before these solvent gels can be widely used, however the results to date show that they can be successfully employed in certain cases. -51-
12.0 BIBLIOGRAPHY
Baker, E. 1964, 'Wallpaintings in the Holy Sepulchre Chapel.', Winchester Cathedral Record, pp. 10-12.
Baker, E. and Baker R. 1967, 'Paintings in the Chapel of the Holy Sepulchre.', Winchester Cathedral Record, pp.21-25.
Baker, E. 1970, 'The Holy Sepulchre Chapel, Winchester Cathedral.', Winchester Cathedral Record, pp.29-31.
Ballantyne, A. et al. 1988, "The problems of dewaxing', Preprints for the UKIC 30th anniversary conference. London, pp.135-41.
Bellamy, L. J. 1975, The Infrared Spectra of Complex Molicules. London.
Burnstock, A. and White, R. 1990, 'The effects of selected solvents and soaps on a simulated canvas painting.'Cleaning. Retouching and Coatings. (Preprints of the the contributions to the Brussels Congress) IIC, London.
Cather, S. & Howard, H. 1986, 'The use of wax-resin preservatives on English medieval wall paintings: rationale and consequences', Case studies in the conservation of stone and wall paintings (Preprints of the IIC Bologna Congress), pp.48-53.
Central Council for the Care of Churches. 1959, The Conservation of English Wallpaintings. being a report of a Committee set up by the Central Council for the Care of Churches and the Society for the Protection of Aincient Buildings. London.
Church, A. H. 1901, The Chemistry of paintis and painting. London.
Church, A. H. 1904, Treatment of decayed stonework in the Chapter House of Westminster Abbey. London.
Courtauld Institute of Art, Conservation of Wall Painting Department, 1990. 'Chapel of Our Lady Undercroft, Canterbury Cathedral. Report on Cleaning Tests on the Vault and Screen', Unpublished.
Derrick, M. 1989, 'Fourier Transform Infrared Spectral analysis of natural resins used in furnature varnishes.' J.A.I.C. 28. pp.43-56.
Eastlake, C. L. 1847, Materials for a History of oil painting. London.
Fletcher, K. 1988, 'The practical use of some flourescent dyes in the characterisation of varnish layers in cross-section and the subsequent cleaning of some paintings using the methods developed by Richard Wolbers', Unpublished, Courtauld Institute. -52-
Getty Conservation Institute. 1991, Methods in Scientific Examination of Works of Art: Infrared Microspectroscopv.
Goodrich, B. F., CAROPOL Water Soluble Resins. Technical data. Ohio.
Hedley, G. 1980, 'Solubility parameters and varnish removal; a survey.' The Conservator 4, pp. 12-28.
Hedley, G. et al. 1990, 'A study of the mechanical and surface properties of oil paint films treated with organic solvents and water.'Cleaning. Retouching and Coatings. (Preprints of the the contributions to the Brussels Congress, 3-7 September, 1990.) IIC, London.
H.M.Office of Works, 1929, 'Methods of preserving mural paintings in the Chapter House of Westminster Abbey/ The Museums Journal, vol.28, no.12.
Horie, C. V. 1987, Materials for Conservation. London.
Howard, H. 1988, 'Blue Pigments in English Medieval wall paintings', Unpublished, Courtauld Institute.
Hluvko, S. 1991, 'Red Pigments in English Medieval Wall Paintings', Unpublished, Courtauld Institute.
Keyser, C. E. 1883, List of Buildings...having Mural...Decorations. London.
Low, M. J. D and Baer, N. S. 1977, 'Application of Infrared Fourier Transform Spectroscopy to problems in Conservation. I. General Principles', Studies in Conservation. 22.
Macregor, E.A ,Greenwood, C.T, 1980, Polymers in nature. London.
Meilunas, R.J, Bentsen J.G. and Steinberg A. 1990, 'Analysis of aged paint binders by FTIR spectroscopy'.Studies in Conservation. 35. pp.33-51.
Mills, J. and White, R. 1987, The Organic Chemistry of Museum Objects. London.
Mora, L., Mora, P. and Philippot, P., 1984, Conservation of Wall Paintings. London.
Newman, R. 1980, 'Some applications of Infrared spectroscopy in the examination of painting materials', J.A.I.C.. 19. pp.42-62.
Noppen, J. G. 1932, 'The Westminster Apocalypse and its source.' The Burlington Magazine. Vol.61, pp.146-159.
Oakeshott, W. 1981, 'The Paintings of the Holy Sepulcre Chapel' Winchester Cathedral Record, pp. 10-15.
Park, D. 1980, 'The wall paintings of the Holy Sepulchre Chapel' Medieval Art and -53-
Architecture at Winchester Chathedral. (British Archiological Assosiation Conference Transactions), pp.38-62.
Perry lithgow Partnership, 1983, Report on the wall painting in Holcot church. Unpublished report.
Scott, G. G. 1861, Gleanings from Westminster Abbev. London.
Scott, G. G. 1863, Gleanings from Westminster Abbev. London.
Southall, A. 1988, 'New approach to cleaning painted surfaces', Conservation News .37. pp.43-44.
Southhall, A. 1989, 'Wolbers'cleaning methods', Conservation news .38. pp.12-13.
Southall, A. 1990, 'Detergents Soaps Surfactants' Dirt and Pictures Separated. Preprints for the UKIC conference, pp.29-34.
Tristram, E. W. 1926, 'Note on the uncovering and preservation of ancient mural paintings', Victoria and Albert Museum.
Tristram, E. W. 1944, English Medieval Wall Paintings: The 12th Century. Oxford.
Tristram, E. W. 1950, English Medieval Wall Paintings: The 13th Century. Oxford
Tristram, E. W. 1955, English Medieval Wall Paintings: The 14th Century. London.
Turner, B. 1985, 'The patronage of John of Northampton. Further studies of the wall paintings in the Westminster Chapter House.' Journal of the British Archeologists Assosiation. Vol.138, pp.89-101.
Van't Ehrnreich, E. H. 1970, 'Infrared Microspectroscopy for the analysis of old painting materials.'Studies in Conservation, 15.
Waller, J. G. 1873, 'On the paintings in the Chapter House, Westminster.' Tranactions of the London and Middlesex Archaeological Society. 4.
Wolbers, R. and Landrey, G. 1987, 'The use of direct flourescent dyes for the characterisation of binding media in cross sectional examination.' A.I.C. Preprints . pp. 168-202.
Wolbers, R. 1990A, 'A radio-isotropic assey for the direct measurement of cleaning material on a paint film.'Cleaning. Retouching and Coatings. (Preprints of the the contributions to the Brussels Congress)
Wolbers, R. 1990B, 'Notes for the Workshop on new methods in the Cleaning of Paintings.' The Getty Conservation Institute. (Unpublished). Appendix 1
Recipes for wax and wax resin preservatives advocated bv Professors Church and Tristram.
A. H. Church. Published in Keyser (1883, xciii), A. H. Church. Published in Church (1901:122 and described as a 'preservative'. 323-24), described as a 'preservative and medium'. 2 oz. by weight pure white beeswax. 12 oz. of spike or non 6 oz. by measure oil of spike -refinable oil of turpentine. lavender or oil of orange peel. 4 oz. by weight paraffin wax 10 oz. picture copal varnish. (melting point 58-62C) or of 26 oz. freshly distilled ceresin or a mixture of these. spirits of turpentine. 20 oz. 'picture' copal- Preparation; Melt beeswax, pour into the oil of spike; varnish or 16 oz. oil-copal warm until clear, then add copal and turpentine. varnish (containing a Application; warm with 'broad flat soft brush' or, if sufficiency of oil). colour 'easily detached, with spray. Preparation; Warm oil of spike over boiling water, add wax and mix thoroughly at 80C; add copal slowly mixing constantly. Application; Diluted with spirits of turpentine or toluene. Gambler-Parry. 'Simplified* by Church and published in Church (1901:123), described as a 'medium*. 8 oz. oil of spike. 2 oz. by weight elemi. E. W. Tristram, published in Tristram 1926, 2 oz. oil of turpentine. described as a 'preservative'. 4 oz. by weight pure white wax. 1 part beeswax. 20 oz. by measure 'picture'- 6 parts by volume rectified spirits copal varnish or 16 oz. oil- of turpentine. copal varnish. 1% Unseed oil. Preparation; Warm oil of spike over water to 80C, Preparation; Melt the beeswax and add the other add elemi and shake until dissolved; filter warm ingredients. solution; heat oil of turpentine over water to 80C; Application; lightly with a brush or, if the surface is mix thoroughly; heat over water to 80C, add melted 'too friable', dilute with more turpentine and spray wax; shake thoroughly; add varnish with constant on. Polish lightly with a rag two or three times during agitation; allow water to boil under the mixture for 5 the following fortnight. minutes, remove, dry and cool. Appendix 2
Solvent gels formulae1
1. 2. Xylene 50ml Xylene 50ml H2O lml H2O lml Carbopol 940 lg Carbopol 940 lg Ethomeen C-12 7.5ml Ethomeen C-12 7.5ml Propan-2-ol 10ml Propan-2-ol 10ml 69/9.3/21.72 76/7.2/16.8
3. 4. White Spirit 50ml White Spirit 50ml H2O lml H2O lml Carbopol 934 lg Carbopol 934 lg Ethomeen C-12 6ml Ethomeen C-12 6ml Propan-2-ol 30ml Propan-2-ol 15ml 71.6/9.3/19.1 Xylene 10ml 79.3/6.9/13.8
5. 6. White Spirit 50ml White Spirit 50ml H2O 2.5ml H2O lml Carbopol 934 lg Carbopol 934 lg Ethomeen C-12 6.5ml Ethomeen C-12 6.5ml Propan-2-ol 15ml Propan-2-ol 15ml Acetone 10ml 78.7/7.2/14.1 74.5/10.5/15
7. 8. Xylene 50ml Xylene 50ml H20 5ml H2O 5ml Carbopol 940 lg Carbopol 940 lg Ethomeen C-12 7.5ml Ethmeen C12 7.5ml Propan-2-ol 10ml Propan-2-ol 10ml Acetone 20ml Benzyl Alcohol 20ml 68.7/13.4/17.9 69/9.4/21.6
9. 10. White Spirit 50ml White Spirit 50ml H2O lml H2O lml Carbopol 940 lg Carbopol 940 lg Ethomeen C-12 7ml Ethomeen C-12 7ml Propan-2-ol 20ml Propan-2-ol 10ml 76/8/16 Acetone 10ml 76.9/10/13.1
11. 12. White Spirit 50ml White Spirit 50ml H2O lml H2O lml Carbopol 940 lg Carbopol 940 lg Ethomeen C-12 9ml Ethomeen C-12 7ml Propan-2-ol 15ml Propan-2-ol 10ml 10ml Acetone 20ml Benzyl Alcohol 71.2/13.1/15.7 77/7.7/15.3
1 All solvents used were GPR quality except for the White Spirit which was manufactured by Langlow products Ltd. with an aromatic content of 15-25% v/v. * Solveny parameters: dispersion/ dipolar/ hydrogen bonding. Appendix 3
Teas Chart showing the solvency parameters of the most effective solvent gels in relation to the solubility region of beeswax.
10 20 30 40 50 . 60 70 80 Dipolar force
Solubility region of beeswax (Horie 1987) Appendix 4
Solvent Gel Tests. Summary of results reported in the proformas.
Holcot Church.
Test Gel Clearing Application Intev. Cleaning Effect, no. no.1 Method.2 Time.3 layer.4 wax layer only.5 Sample.6
1. 7. Xylene/H20 10/30 + + + HO8/565 & HO8b/566 2. 7. Xylene/H20 20/60 + + + + HO9/567 & HO9b/568 3. 8. Xylene/H20 15/60 + + 4. 2. Xylene/H20 15/90 + + + HO10/568 5. 9. WS/H20 20/120 + + + 6. 7. Xylene/H20 10/60 * ++ HOll/569 7. 7. Xylene/H20 10/60 * + + + + HO12/570
Tests 6. and 7. took place on the same area.
Holv Sepulchre Chapel. Winchester Cathedral.
1. 7. Xylene/H20 10/60 2. 7. Xylene/H20 10/60 + + + + HS7/571 3. 8. Xylene/H20 10/90 4. 11. WS/H20 10/90 + HS8/572 5. 1. Xylene/H20 10/90
Tests 1. and 2. took place on the same area.
Westminster Abbey Chapter House
+ + + WA8/558 & WA9/559 1. 7. Xylene/H20 15/90 2. 7. Xylene/H20 0/120 + + + + WA13/563 3. 7. Xylene/H20 15/120 4. 1. Xylene/H20 15/90 5. 1. Xylene/H20 15/90 + + + WA1O/56O 6. 11. WS/H20 15/120 + + +
Tests 4. and 5. took place on the same area.
1 Appendix Proformae 2 Solvent followed by water, both with cotton wool swab. 3 Static/agitation time in seconds. 4 Intervention layer of Japanese tissue. 5 Key: + Little or no effect. + + Limited effect. + + + Partial wax removal. + + + + Substatial level of cleaning. + + + + + Complete removal of wax layer. 6 Samples HO8/565 and HO9/567 were taken before clearance with water. Samples HO8b/566 and HO9b/568 were taken after both xylene and water clearance was carried out. Appendix 5
Fourier Transform Infrared Spectra.
All spectra were carried out on a Perkin Elmer 1710 FTIR in diffuse reflectance mode. All spectra have undergone conversion to Kubalka-Munk units.
Fig.l. Holcot Church. Sample HO2. Waxy surface coating. (KMHO2)
NAX=1.48 T
fHff=8.32 T
3566 3860 2598 2698 1568 CH-1 1888
Fig.2. Holy Sepulchre Chapel, Winchester Cathedral. Sample HS3. Waxy surface coating. (KHS3A)
-1728
1888 CH-1 588 II
Fig.3.WestminsterAbbeyChapterHouse.SampleWA3B.Waxysurfacecoating. (KWA3B)
s MftX=2.73T u
i *rli *l
-v,
*/ v\
I
/\
!niN=e.32
1588 CIM 1888 4*88 3538 2508 2999
Fig.4.WestminsterAbbeyChapterHouse.SampleWA2B.Lowerresinouslayer. (KWA2B)
=i.37T
1588 Cil-t ■839 3588 3888 2589 2988 Ill
Fig.5. Clearance test model. Sample SRI. Wax coating on panel before testing. (KSRl)
IM=7.07 T
11111=9.32 T
4909 3560 3660 2560 2090 1500 1096 Cll-l
Fig.6.Clearance test model. Sample SR2. Residues of wax coating after testing. (KSR2)
6 3
4000 3586 3086 2590 2860 1586 1690 Cll-l 568 IV
Fig.7. Clearance test model. Sample SR3. Paint surface before testing. (KSR3)
<=4,48 T
11111=9.32 T
4988 3589 3088 2588 2889 1508 16130 Cll-l 500
Fig.8. Clearance test model. Sample SR4. Paint surface after testing. (KSR4)
3588 3908 2509 2888 1588 1088 CIH 599 Fig.9.BDHBeeswax,white.(Prod.33017)(KMBW3)
4888 35
Fig.10.EthomeenC-12(KC12)
HIN=B.32T -^ r
4808 3588 VI
Fig.7. Carbopol 940 (KC940) Appendix 6
Nitromors Paint Stripper
'Nitromors' is produced by Henkel Home Improvements and Adhesive Products.
'Nitromors Original' was introduced in the 1940s, and the formula has remained almost unchanged until the 1980s. The basic gelling agent is a small amount of cellulose acetate
and paraffin wax. The solvents were dimethylchloride and methanol. There was no
surfactant or base included, and it was washable with white spirit or IMS.
Water washable Nitromors was introduced in the 1960s. The gelling agent in this case were
paraffin wax and methyl cellulose, CELACOL MMPR1, (approximately 1.2% methyl per
glucose unit) and was produced by Courtaulds Ltd. The main solvents, as with the earlier
version, were dimethylchloride and methanol. Until the 1970s a non-ionic surfactant was
included. In the 1980s this was substituted with an anionic surfactant. In 1987 this was
replaced by a carboxylic acid amine salt (with one end neutralised and the other not). At
this date also the dimethylchloride was reduced in favor of the methanol. Borax nitrite was
also included as a corrosion inhibiter. This was recently replaced by a different corrosion
inhibiter, the nature of which is proprietary information.
Due to the very low water content of the product, the pH value is of limited significance.
However in British Standard Tests Nitromors was found to be not more basic than 5ml of
0.1m HC1 per 20g H2O, and its acidity was low enough not to react with methyl red
indicator. In their own titration tests at a concentration of 10% in water the manufacturers
gave a figure of pH 9.
(pers.comm. Mr Andrew Wood, Chemist at Henkel Home Improvements and Adhesive
Products.) Appendix 7
Solvent Gel Tests Carried out in the
Chapel Of Our lady Undercroft, Canterbury Cathedral.
The first Carbopol solvent gel tests carried out on wall paintings by the Courtauld
Institute were undertaken in 1990 in collaboration with the Canterbury Cathedral
Wallpaintings Workshop, on the painted vault of the Chapel of Our Lady
Undercroft. The aim in this case was to produce a gel that would dissolve the thin waxy coating applied by earlier restorers so that the more complex problem of a dirt layer, which lay directly over the paint surface, could be removed. The gels developed for the work at Canterbury contained relatively polar solvents and therefore an aqueous-based gelling system could be used. Two amines were tested to neutralise the Carbopol, Trietanolamine (TEA) and Ethomeen C/25 . The
Ethomeen C-25 (Polyoxyethylene(15)cocoamine) has cationic surfactant properties with an HLB value of 19. Both achieved the necessary level of neutralisation (PH 7 to 7.5) at acceptable percentage volumes, however due to the possible complications in the clearance of a surfactant from the painting surface, the TEA was used in the final formulation. (Courtauld Institute Report, 1990). CIA/ GCI Conservation of Wall Paintings Department. 1990-1991
An investigation into the use ofsolvent gels for the removal of wax-based coatings on Wall Paintings. Tobit Curteis
Sample nos. Accession nos. 531 - 533 & 565 - 570 HOI - HOI 2
County. Nor thamptonshire. Position of painting.
Village/Town. North wall of the North aisle. Holco t.
Name of Building. Dimensions of Painting.
St. Mary and All Saints 54 ft. long by 12 ft. high. Church, Holcot. Subject. There are a number of subjects depicted. Tristram identifies among others Name/Address of Custodian. a martyrdom of St.Thomas of Canterbury. Rev. A.J.Watkins The test area was on the lower tier of The Vicarage, Station road, subjects, in the area of six standing Brixworth, Northants. Apostles. NN6 9DF. Attribution & Date. Permission granted. 28.1.91 Early 14th Century.
Date. 18.2.91 Sampled by. Tobit Curteis.
Previous Recorded Surface Treatments
Date. Pre. 1950 1983
Conservator. E.W.Tristram. ? The Perry Lithgow Partnership.
Method An examination was made of all the employed. All paintings in paintings in the church but the church were conservation work was only carried coated with a out on those in the south aisle (west preservative treatment wall). The wax and possibly resin of a wax based coatings on this area of painting was mater iJal. removed with Nitromors and methyl chloride. Old repairs were replaced with lime mortar fills, and the area made sound.
Area North aisle. South aisle, west wall. Treated. South aisle,
Location of The Perry Lithgow Partnership records. None.
None. samples None & location. Sheet no.2 Area Sampled (before testing) stratieraDhv 1# Stone/rubble substrate. 2. Single layer of plaster. 3. Limewash ^ p y' ground. 4. Pigment layer. 5. Waxy coating with thick deposits of ambient dirt. In some areas there is the remains of a limewash layer between the paint, layer and the wav. Possible technique. Probably a mixture of lime and organic secco binder.
General Variable. Some areas are very sound, but there are also extensive condition. areas of decohesion and resulting flaking in the paint layer. The Whole painting is covered by a thick layer of surface dirt.
Appearance& yellowy translucent amorphous material homogeniously coating the distribution whole area of the painting. Relatively thick for such a wax layer. ofsurfaces In many cases it fills old losses, however there are a number of coatings. recent losses that penetrate the wax coating.
UV Homogeneous fluorescence with a greenish tinge over the entire area examination. of the coating. Losses stood out clearly through their non-fluorescence.
Positionof A11 sampies were taken in the area of the'knife'of the standing samples. figure second from the right.
Possible anomalies of area sampled. Sample H07 was taken through the coating in an area where limewash remained over the red pigment layer. During sampling the coating and limewash separated from the red original surface layer.
ftvpe & area) Tne area of tne tests wax recorded in both general and macro with Kyv ' Ilford FP4 (black & white) and with Agfachrome CT100 (transparencies).
Comments.
The presence of areas of limewash between the waxy coating and the paint surface suggests that this area was uncovered in an early restoration of the paintings. Preliminary examination shows little or no dirt on the original surface beneath the coating, suggesting that it was coated soon after it was uncovered (maybe even in the same campaign). There appear to be large area still to be uncovered on this wall, and there also appear to be areas of palimcest. Sheet no. Position of Samples
Site. Holco t Chur ch Date. 18.2.91 Sheet no.
Sample Reference
Sample Accesion Type of Date. number. number. analysis.
HOI Sample damaged.
H02 *** FTIR 19.2.91
H03 *** FTIR 19.2.91
H04 531 X-Section/SEM 18.2.91
H05 Sample damaged.
H06 532 X-Section 18.2.91
H07 . 533 X-Section 18.2.91
H08 565 X-Section 18.2.91
HO8b 566 XSection 18.2.91
H09 567 X-Section/SEM 18.2.91 Sheet no. Solvent Parameter Tests
Site. Holcot Church Date. 18.2.91
Method/Time Solvent. of application. Result.
Xylene Swab substantial amount of the coating is removed.
Xylene 2 Swab Cleaning action is a little quicker than above IMS 1 and a greater part of the coating is removed.
Xylene 1 Swab Action is slower but cleaning is more IMS 1 thorough than above. Curious result!
Xylene 2 Swab Greatly reduced and far slower cleaning IMS 2 action. Acetone 1 "
Acetone Swab No apparent effect.
Acetone 1 Swab Strong and relatively fast cleaning action. Xylene 1
Acetone 1 Swab more effective than the above in terms of both Xylene 2 speed of action and amount of material removed from the surface. Possibly too fast for safe cleaning.
WS Swab No apparent effect.
FURTHER TEST OVERLEAF
Conclusions
The coating was clearly very soluble in a range of solvents particularly in a mixture of aromatics. It was surprising that it appeared to be soluble in white spirit in its^pure form considering that the WS used in the tests had an aromatic content of 15-25% vol/vol. Combinations of xylene and acetone appeared to have the greatest effect on the coating. With the exception of the WS result the test results are consistent with the coating consisting mostly of beeswax. Sheet no. Solvent Parameter Tests
Site. Holcot Chur ch Date. 18.2.9 1
Method/Time Solvent. of application. Result.
Propan-2-ol 1 Swab Slow action but the cleaning; effect appears WS 4 relatively thorough.
H2O Swab No effect.
Propan-2-ol Swab Very limited effect.
Propan-2-ol 1 Swab Some limited effect. Better than 100% P-2-ol Acetone 1
Triton X-100 1 Swab Reasonable speed and depth of action. Xylene 3 H2O 5 (Clearance was carried out by swabbing with both Xylene and H2O).
Conclusions Sheet no Sample Analysis Before Gel Tests
Sample no. HO 2 Accession no. ***** Date. 19.2.91
Hot Stage Examination.
Temp. Observations.
30C White/yellow amorphous translucent material with inclusions of dirt and white crystalline material.
65C Body of material begins to melt.
65C Majority of material melts.
67C The melted material flows free from the white crystalline matrix (calcium carbonate from the painting?)
>100C No further change.
Conclusions.
It appears possible that the majority of the material is wax, possibly beeswax, contaminated with a mixture of surface dirt and calcium carbonate from the surface of the painting.
Sample no. H03 Accession no. ***** Date. 19.2.91
Hot Stage Examination.
Temp. Observations.
30C As for H02.
64C The majority of the material begins to melt.
66C Waxy material flows free from the white crystalline matrix.
>100C No further change.
Conclusions.
The two samples were both taken from the edge of a loss where the coating had gathered in a thick mass. The slight difference in their action under TMA might be explained by the varying levels of contamination in each sample, as well as the different thickness of each sample. Sheet no Sample Analvsis Before Gel Tests
Sample no. HO 3 Accession no. Date. 19.2.91
Hot Stage Examination.
Temp. Observations.
30C As for HO2.
64C The majority of the material begins to melt.
66C Waxy material flows free from the white crystalline matrix.
>100C No further change.
Conclusions.
The two samples were both taken from the edge of a loss where the coating had gathered in a thick mass. The slight difference in their action under TMA might be explained by the varying levels of contamination in each sample, as well as the different thickness of each sample.
F.T.I.R.
Notable Absorbtion Peaks Interpretation.
Conclusions. Sheet no X-Section Examination Before Gel Tests
Sample no. HO 7 Accession no. 533 Date. IS.2.91
Examination Unmounted,
Surface. The surface consists of a course red pigment and is not coated with the wax layer as this separated in the sampling procedure.
Stratigraphy. Red pigment layer over a white crystalline ground with inclusions of a course yellow pigment.
Examination Mounted Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. Film nos. 100/200
Comments.
1. Red crystalline pigment, possibly red ochre. The pigment layer is not bound by calcium carbonate so there is probably a secco medium present. This is not visible at mag. x400.
2. White crystalline matrix (calcium carbonate).
3. Small red and yellow crystalline pigment particles
Photographic records of this sample appear to have a translucent coating on the surface. This is in fact due to the polyester mounting resin, and not a wax or resin coating. Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HO? Accession no. 533 Date. 18.2.91
Graphic record of sample.
Photography: Film Type. ##### Mag.no. Filmnos.
Comments.
1. Very little fluorescence from this layer although the reel colour could clearly be seen under UV.
2. Bright whitish fluorescence
Staining
Type. Acid Fuchsin 2% vol/vol in H20. Rinsed with H20.
Results. A weak stain was seen in the upper half of layer 2 of the sample. No stain was apparent in the pigment layer probably due to the red pigment disguising the light pink stain. The conclusion would appear to be that there if some proteinous material included in the limewash as and additional binder. This may imply that the binder for the pigment layer is also a protein. Sheet no. Solvent Gel Tests
Site. Holcot Church Date. 8 .3 .9 1
Method/Time Solvent gel. of application. Result.
1/ 7 Swab, 10/30. Cleaning action appears to be quite effective and fast, especially towards the centre of the test area. Clearance: xylene/H20. Samples: HO8a/HO8b
2/ 7. Swab, 20/60. Action similar to test 1, but proportionally more coating is removed, due to the extended time period. Fairly good level of cleaning. Clearance: xylene/H20. Sample: HO9.
3/ 8. Swab, 15/60. Slower action than above. Coating appeared to be thinned but to a lesser extent. Clearance: xylene/H20.
4/ 2. Swab, 15/90. Relatively good action with partial removal of the coating. Clearance: xylene/H20. Sample. HO10.
5/ 9. Swab, 20/120. Slow cleaning action but a homogeneous thinning action. Less than test 2. Clearance: white spirit/H2O
FURTHER TESTS OVERLEAF
Conclusions
Test 2 and 6/7 appeared to give the most satisfactory levels of cleaning with virtually all the coating being removed. Under UV illumination this also appeared to be the case. In niether case did there appear to be any surface damage caused by mechanical action.
It seems likely that the clearing procedure is actually responsible for a substantial amount of the cleaning action.
(Samples HO11 & HO12 were taken from an area that may have lost its surface layer due to earlier damage.)
The surface temperature of the wall at the time of the tests was 8C. The ambient temperature was 12.5C and the RH was 7 7%. Sheet no. Solvent Gel Tests
Holcot Church 8 .3 .9 1 Site. Date.
Method/Time Solvent gel. of application. Result.
6/ 7. Swab, 10/60. The gel swells the surface coating but Intervention does not remove it. Removal takes layer. place during clearance when the vulnerable, swollen material is lifted off by the swab. Clearance: xylene/H2O. Sample: HO11
7/ Swab, 10/60 Similar action to the above. Overall Intervention cleaning effect on the area after two layer. tests is similar to test 2. Clearance:xylene/H2O. Sample: HO12.
(Tests 6 & 7 took place over the same area.)
Conclusions Sheet no X-Section Examination Before Gel Tests
Accession no. Date. Sample no. HO 4 531 18.2.91
Examination Unmounted.
Surface. Surface dust over a thin waxy coating.
Stratigraphy.
Surface dust, waxy costing, red pigment layer, white crystaline substrate.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. Film nos. X100/X200
Comments.
1. Fine white surface 'dust' in some areas. 2. Thick yellowy translucent coating. 3. Pigment layer. Fine red crystalline particles. 4. Possibly a ground layer separate from 5. but interface is very indistinct. 5. White crystalline matrix, dense and homogeneous. 6. Single red crystals. 7. Two large dark red/black crystals. Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HO4 531 Accession no. Date. 18.2.91
Graphic record of sample.
Photography: Film Type. Ektachrome 6 4 Mag.no. xlOO Filmnos.
Comments.
1. light white fluorescence clearly different from 2. 2. Thick layer fluorescing dark blue/ yellow. 4. & 5. Both fluoresce bright white. Distinction between the two is made no more apparent in UV.
Type.
Results. Sheet no X-Section Examination Before Gel Tests
Sample no. HO 6 Accession no. 5 3 2 Date. 18.2.91
Examination Unmounted.
Waxy coating with small areas of surface dust (extends around the edge of the sample.
Stratigraphy.
Waxy coating over simple white crystalline mass.
Examination Mounted Normal Light. (Tunosten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160. Mag.no. xlOO Film nos.
Comments.
HO6 was taken from the edge of an old (pre-wax) loss therefore the wax has continued around the edge, and beneath the sample.
1. Yellowy translucent coating. 2. White crystalline matrix. 3. White crystalline disruption within wax. 4. Red particle. 5. Large red/black particle. Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HO6 Accession no. 532 Date. 18.2.91
Graphic record of samnle.
Photography: Film Type. Ektachrome 6 4Mag.no. xlOO Fihn nos.
Comments.
1. Dark yellowy/blue layer, with littlff apparent surface dirt 2. White bright flourescence..
Stainint
Type.
Results. Sheet no X-Section Examination After Gel Tests
Sample no. H08 Accession no. 5^5 Date. 20.3.91
Examination Unmounted.
Surface. White crystalline surface with small inclusions of dirt particles, and possible pigment particles.
raigrapy. Apparentiy Hmewash layer over a limewash ground.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. xl00/x200 Film nos.
Comments.
1. White crystalline layer with small inclusions of pigment particles.
2. Second white crystalline layer, apparently slightly more pigmented than 1.
3. Course pigment particle.
There does not appear to be any residues of the wax on the surface of the sample and no physical or mechanical damage is apparent. Sheet no X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HO 8 Accession no. 5 6 5 Date. 20.3.91
Graphic record of sample.
Photography. Film Type. Mag.no. Film nos.
Comments.
Layers 1 and 2 fluoresce with a similar bright whitish fluorescence, but there is a clear distinction between the two which is less apparent in visible light. There is no evidence of any remaining wax coating on the surface of the sample.
Staining
Type.
Results. Sheet no X-Section Examination After Gel Tests
Sample no. HO8ta Accession no. 5 g g Date- 20.3.91
Examination Unmounted,
Surface. White crystalline surface with dark inclusions, probably mixture of dirt and pigment.
Stratigraphy. White lime layer over tinted lime background.
Examination Mounted Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fug i chrome 160 Mag.no. xl00/x200 Film nos.
Comments.
1. white crystalline surface layer with pigment particles
2. White crystalline layer tinted with yellow and red (ochre?) particles. Sheet no X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HO8b Accession no. 5 6 6 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
Layers 1 and 2 fluoresce in a similar bright way but the separation between the two is apparent.
Staining
Type.
Results. Sheet no X-Section Examination After Gel Tests
Sample no. HO 9 Accession no. ^ 6 ? Date. 20-3.91
Examination Unmounted.
Surface. White crystalline layer with inclusions of yellow pigment particles. Some areas of waxy material on surface.
Stratigraphy. Yellow tinted white crystalline layer over similar background layer.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. xlOO/x2OO Film nos.
Comments.
1. Fine translucent waxy layer broken in some places.
2. White crystalline layer with inclusions of yellow (ochre?) pigment particles.
3. Dirt particles.
4. White crystalline layer with further inclusions of yellow pigment particles. Sheet no X-Section Examination Mounted After Gel Tests
UV Source
HO9 c /• n 20.3.91 Sample no. Accession no. Date.
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Very little fluorescence from this layer, but clearly visible against the layers below.
Layers 2 and 3 fluoresce in a similar way.
Type.
Results. Sheet no X-Section Examination After Gel Tests
Sample no. HO 10 Accession no. 55s Date. 20.3.91
Examination Unmounted.
Surface. Clear waxy surface with inclusions of red particles.
Stratigraphy. Waxy coating over a whitish crystalline layer, lower layer has greater amount of yellow pigment particles than that above.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
5.
Photography: Film Type Fug i c h r ome i 6 0 Mag.no. xl00/x200 Film nos.
Comments.
1. Thin waxy layer.
2. white surface layer. Very indistinct separation between layers 2 and 3.
3. White crystalline layer with yellow and red pigment par tides.
4. Large yellow crystalline pigment particle.
5. Small red particles. Sheet no X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HO 10 Accession no. 5 6 8 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Very little fluorescence. Similar fluorescence from 2 and 3. The interface between the two is not clear in this sample.
Staining
Type.
Results. Sheet no X-Section Examination After Gel Tests
• ^ fi 9 Sample no. HOI 1 Accession no. Date. 20.3.9 1
Examination Unmounted,
Surface. Surface appears waxy.
Stratigraphy. Fine waxy coating on the surface over white crystalline layer tinted with red and yellow pigment particles.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fug i ch r ome 1 6 0 Mag.no. xlOO/x2OO Film nos.
Comments.
1. Very fine waxy layer,
2. White crystalline layer (apparently single) with inclusions of pigment particles.
3. Yellow and red (ochre?) particles. Sheet no X-Section Examination Mounted Alter Gel Tests
UV Source
Sample no. HO11 Accession no. 569 Dale- 20.3.91
Graphic record of sample.
Photography: Film Type. FUm nos. ^4* ^a ^^ ^^ ^^ Mag.no.
Comments.
1. little or no visible fluorescence.
2. Apparently only a single layer. Fluorescence is quite bright.
Staining
Type.
Results. Sheet no X-Section Examination After Gel Tests
Sample no. HO12 Accession no. 570 Date. 20.3.91
Examination Unmounted.
Surface. Areas of waxy material over white crystalline surface.
Stratigraphy.
Broken waxy coating over white crystalline layer with red and yellow particles.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 M ag.no. x200 Film nos.
Comments.
1. Broken area of fine waxy coating.
2. White crystalline matrix.
3. Small yellow crystalline particles
4. Large white particle. Sheet no X-Section Exaihination Mounted After Gel Tests
UV Source
Sample no. HO12 Accession no. 5 7 0 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Little or no fluorescence.
2. Single brightly fluorescing layer.
Staining
Type.
Results. Sheet no. Posilioii of Samples
Site. llolco t Chui ell Dale. S - 2 . 9 1 CIA/ GCI Conservation of Wall Paintings Department. 1990-1991
An investigation into the use ofsolvent gels for the removal of wax-based coatings on Wall Paintings. Tobit Curteis
Sample nos. Accession nos. HS1 - HS8 528 -530, 571 - 572
County. Hampshire. Position of painting.
Village/Town. Winchester. South wall, West bay.
Name of Building. Dimensions of Painting.
Winchester Cathedral. Holy Sepulchre Chapel
Subject.
Resurrection of the dead Name/Address of Custodian.
John Harclachre. Cathedral Office. Winchester Cathedral
Attribution & Date. Jl 1 1 L> i LOU Permission granted. 12.2.91
Date. 13.:2.91 Sampled by. Tobit Cur teis •
Previous Recorded Surface Treatments
Date. Pre . 1900 C 1900-1950 c. 1959 -1970
Conservator, Unknown. E.W.Tristram ? The Eve Baker Trust
Method employed. An area of 13th century painting on the west side An unidentified material A coating of was removed to reveal the possibly copal varnish wax preservative 12th century trumpeting was applied to the was applied to angel (previously surface of the painting. the paint surface, untreated). The east side over the of the painting was previous coating:. cleaned possibly with Nitromors paint stripper.
Area Eastern section Treated. Same area as the Tne wnoie area of the of the painting previous treatment, painting.
Location of records. None None The Eve Baker Trust
Previous samples None None None & location. Sheet no.2 Area Sampled (before testing)
Apparent lt stone substrate. 2. Rough plaster. 3. Possibly a fine stratigraphy. layer of plaster in some areas only. 4. Limewash ground. 5.Underdrawing. 6. Limewash layer. 7.Paint layer. 8. Surface coatings.
Possible Calcium Carbonate binder. (Limewash). technique.
General Paint surface heavily abraded in many areas. Some areas of condition. active deterioration with severe flaking.
Appearance & Surface coatings only apparent on the eastern side of the distribution painting. Dark material with some form of surface residue of surfaces and considerable surface dirt. coatings.
UV Homogeneous distribution of slightly fluorescing coating examination. on the eastern side of the painting. The residue on the surface fluoresces a lighter green than the body of the coating
Positionof Central area of the painting close to the central and samples. right hand angles descending from the cloud to rescue the souls of the dead.
Possible anomalies In order to take samples of the most suitable areas of of area sampled. the coating some samples were taken from areas of red background while others were taken from areas of red.
Photography: The whole area of the painting was recorded in general and (type&area) in macro with both Ilford FP4 (black & white) and Agrachrome CT100 (transparencies).
Comments.
The severe abrasion of much of the painting hinders the reading of the central section. This depicts three small but delicately drawn angels descending from a cloud to take up the souls of the dead that can just be discerned at the base of the scene. This abrasion also reviles many areas of the red underdrawing which has been exposed when the black linear painting has been lost. Much of the outline now visible on the large trumpeting angel on the left of the scene is this red underdrawing. The situation is clarified in sample HS6/530 which shows the stratigraphy of the paint layers. Sheet no. Position of Samples
Site. Winchester Cathedral: HSC Date. 13.2.91 Sheet no.
Sample Reference
Sample Accesion Type of Date. number. number. analysis.
HS1 528 X-Section 15.2.91
HS2 Sample damaged.
HS3 *** FTIR 14.2.91
HS4 *** FTIR 14.2.91
HS5 529 X-Section/SEM 15.2.91
HS6 530 X-Section 15.2.91
HS7 " 571 X-Section/SEM 20.3.91
HS8 572 X-Section 20.3.91 Sheet no. Solvent Parameter Tests
Site. Date. Winchester: HSC 13.2.91
Method/Time Solvent. of application. Result.
Xylene. Swab. No apparent effect on the coating.
Xylene 2 Swab. Some effect on the coating. Surface IMS 1 dirt removed but majority of coating remains in tact.
Xylene 1 Swab. Greater cleaning effect than above IMS 1 Surface dirt removed.
Xylene 1 • Swab. Similar/slightly improved cleaning IMS 2 on the above, but coating still Acetone 1 on surface.
Xylene 1 Swab. Slower action with less effect than Acetone 1 that above.
Xylene 2 Swab. Limited slow action. Acetone 2 Propan-2-ol 1
Xylene 5 Swab. Cleaning action appears better than H20 5 (Clearance with above, but seems to rely heavily Triton X-100 1 Swab of Xylene) on mechanical action of clearance.
FURTHER TESTS OVERLEAF
Conclusions
The use of non-polar rather than polar solvents appears to have the greatest effect on the coating, however even when strongly;aroinatic solvents are applied the effect is limited. This suggests that there is a component of the coating that is not readily soluble in standard organic solvents. The inclusion of a surfactant appears to enhance the effect of the solvent mixture on the coating, but even in this case it is not readily dissolved. It is possible that there is are more than one layer of coating on the painting, and that the solvents are working on only a single layer leaving the others more or less untouched. (This may become apparent with X- section analysis or SEM). There is a substantial amount of surface dirt that is readily removable with light mechanical action. Sheet no. Solvent Parameter Tests
Site. Winchester HSC Date> 13.2.91 Cont. . .
Method/Time Solvent. of application. Result.
Xylene 10 Swab. Greater effect than above, but H2O 5 (Clearance with majority of coating remains T X-100 1 swab of Xylene) in tact.
Acetone Swab. No apparent effect.
H20 5 Swab. Limited effect. T X-100 1
Conclusions Sheet no X-Section Examination Before Gel Tests
Sample no. HS1 Accession no. 52s Date. 15.2.91
Examination Unmounted.
Surface. Fine waxy coating and layer of surface dirt over red pigment layer.
Stratigraphy. Waxy coating over red pigment on white crystalline layer.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Ektachrome 64 Ma*no' x2OO/x4OO FlIm nOS"
Comments.
1. Fine dark translucent layer, with areas of surface dirt.
2. Translucent, but material slightly more white and opaque than 1. Very broken.
3. Whitish crystalline later intimately bound with 4.
4. Red pigment particles, apparently bound in the white crystalline matrix that surrounds them.
5. Large void. 6. White crystalline material. Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HS1 Accession no. 5 2 8 Date. 15.2.91
Graphic record of sample.
Photography: Film Type. ***** Mag.no. Filmnos.
Comments.
1. Yellowy fluorescence.
2. Far less fluorescence than the above. Much darker
3. Bright whitish fluorescence.
Stainlm
Type.
Results. Sheet no Samnle Analvsis Before Gel Tests
Sample no. HS3 Accession no. ***** Date. 14.2.91
Hot Stage Examination.
Temp. Observations.
30C Dark whitish amorphous material apparently containing some particles of dirt.
66C Some movement of the sample observed.
68C Most of the sample melts freely.
71C Most of the sample is free flowing. There is a small area of white apparently crystalline residue.
>100C No further change.
Conclusions. Although the melting temperature is marginally than would normally be expected, the majority of the sample may still be beeswax. It could be contaminated with certain materials (the white residue ?) that may disperse the heat, resulting in a higher apparent melting temperature.
Sample no. HS 4 Accession no. ***** Date. 14.2.91
Hot Stage Examination.
Temp. Observations.
30C Dark whitish amorphous material containg particles of dirt, (similar to HS3) .
66C Some melting occurring.
67C Majority of the sample melts at this stage.
68C Majority of the sample is free flowing leaving a residue of a white crystalline material.
>100C No further change.
Conclusions. Conclusions are as for HS3. Sheet no Sample Analvsis Before Gel Tests
Sample no. HS2 Accession no. Date. i 4 . 2 . 9 i
Hot Stage Examination.
Temp. Observations.
30C Fine white papery material with a fiberous celluJoser texture.
235C Some apparent movement in fibrous matrix.
245C Small voids opening in sample.
267C Larger voids developing and areas beginning to darken.
272C Whole sample undergoes slow darkening.
300C Whole sample now uniformly darkened.
Conclusions. Charring appears to be occurring above 2 50C therefore possibly some form of cellulose material
F.T.I.R.
Notable Absorbtion Peaks Interpretation.
Conclusions. Sheet no X-Section Examination Before Gel Tests
Sample no. HS5 Accession no. 5 2 9 Date. 15.2.91
Examination Unmounted.
Surface. Waxy coating with surface dirt over red pigment layer.
Stratigraphy. Waxy coating with surface dirt over red pigment layer White crystalline lower layer.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record or sample.
Photography: Film Type Mag.no. Film nos. Ectachrome 64 X200/X400
Comments.
1. Whitish translucent coating with areas of dirt on the surface.
2. White crystalline? deposits.
3. Large red crystalline particles. Does not appear typical of lime/fresco technique. 4. White crystalline layer. 5. Waxy material. Whitish/brown. Maybe some contamination after sampling. Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HS5 Accession no. 5 2 9 Date. 15.2.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Yellowish fluorescence.
2. No strong fluorescence.
3. Bright white fluorescence. 4. No apparent fluorescence.
Staining
Type.
Results. Sheet no X-Section Examination Before Gel Tests
Sample no. HS6 Accession no. 539 Date- 15.2.91
Examination Unmounted.
Surface. ., . . n . . . Waxy coating over black pigment layer.
Stratigraphy. Waxy coating on top of a black pigment layer intimately bound with white crystalline matrix. Below this is a separate white layer above a layer of red pigment. Below this is a second white crystalline layer.
Examination Mounted Normal Lipht. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Ectachrome 8 4 Mag.no. x200/x400
Comments.
1. Translucent whitish coating.
2. Areas of more opaque translucent material. 3. Corsly ground charcoal black pigment in white crystalline matrix (lime). 4. White crystalline layer.
5. Red (ochre?) pigment layer. Quite pigment thin
6. White crystalline layer. Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HS6 Accession no. ^ ^ 0 Date. 15.2.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Yellowy but fairly weak fluorescence
2. Apparently no fluorescence.
3 & 4. Bright white.
Staining
Type.
Results. Sheet no. Solvent Gel Tests
Site. Winchester . HSC. Date. 1 1 .3 .9 1
Method/Time Solvent gel. of application. Result.
1/ 7. Swab 10/60. Little or no cleaning effect. Clearance: xylene/H2O.
2/ 7. Swab 10/60. no further effect. Clearance: Xylene/H20. Sample: HS7. (Tests 1 & 2 took place over the same area.)
3/ 8. Swab 10/90. Apparently little or no effect. Possible that some gel remaining on the surface after clearance. Clearance: xylene/H20.
4/ 11 Swab. 10/90 No material visibly removed from the surface, but the surface has a shine after cleaning. Maybe due to the removal of surface dirt Clearance: WS/H2O. Sample: HS8.
5/ 1. Swab 10/90. Again no visible cleaning effect. Clearance: xylene/H2O.
Conclusions
There appeared to be almost no effect on the surface coating* suggesting that it is a hard resin with no wax component. Surface dirt is removed and a shine is left on the surface, so it is possible that residues of some material are being removed from the surface. (I.E. the residues of Tristrams wax treatment that had been mostly removed in the 1960s.)
True results will only be apparent under SEM or visible microscopy. The surface temperature of the wall at the time of the tests was 15C The ambient temperature was 16c and the RH was 6 7%. Sheet no. Solvent Gel Tests
Site. Date.
Method/Time Solvent gel. of application. Result.
Conclusions Sheet no X-Section Examination After Gel Tests
Sample no. HS7 Accession no. 571 Date. 20.3.91
Examination Unmounted.
Surface. Fine waxy coating over reel pigment.
Stratigraphy.
Fine waxy layer over red pigment rich layer. White crystalline lower layer.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record or sample.
Photography: Film Type Ektachrome 6 4 Mag.no. x20 0/x40 0 Film nos.
Comments.
1. Whitish translucent surface coating.
2. Red crystalline pigment rich layer with white white crystalline binder.
3. White crystalline matrix. Sheet no X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HS7 Accession no. Dale. 20.3.91
Graphic record of sample.
Photography: Film Type. * He ** * Mag.no. Film nos.
Comments.
1. Dark yellowy fluorescence.
2. No apparent autofluorescence.
3. Bright white.
Staining
Type.
Results. Sheet no X-Section Examination After Gel Tests
Sample no. HS8 Accession no. 572 Date. 20.3.9 1
Examination Unmounted.
Surface. Waxy surface over white layer.
Stratigraphy.
Fine waxy coating over white crystalline layer with small areas of red pigment. Second white crystalline layer below
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography; Film Type Ektachrome 64 Mag.no. xl00/x200 Film nos.
Comments.
1. Small area of red pigment particles in a white crystalline matrix.
2. Translucent coating.
3. White crystalline layer.
4. Second distinct white crystalline layer.
5. Second area of red pigment. Sheet no X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HS8 Accession no. 5 7 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Weak yellowy fluorescence. 2. and 3. fluoresce in the same bright white fashion* but in UV there is more of deliniation between the two than in normal light.
Staining
Type.
Results. bheet no. Position of Samples
Site. Winchester Cathedral: NSC Date. 13.2.9] Sheet no. Solvent Parameter Tests
Site. W. A. C. H. Date. 23.1.91
Method/Time Solvent. of application. Result.
Xylene 1 Swab Some action apparent, possible Propan- 2-ol 1 swelling of surface coating:, and some material removed. Xylene 2 Swab Marginally better results than above. Propan- 2-ol 2
Xylene 2 Swab Action is less than the above two Propan- 2-ol 1 tests. Apparently certain material is Acetone removed and then action stops.
White s pir it • Swab No apparent action.
White s p i r i t 2 Swab No apparent action. Propan-2-ol 1
White spirit 1 Swab No apparent action. Propan-2-ol 1
Toluene. Swab Some slight effect. Small amount if material is removed, including surface dirt.
Toluene 1 Swab This appeared to have some effect. It Benzyl alcohol 1 was unclear what it was removing but there did appear to be a certain amount, of material absorbed into the swab.
FURTHER TESTS OVERLEAF
Conclusions
The tests indicate that there area large areas where there are two coatings present. One of these, the lower (and earlier) is almost insoluble in solvent mixtures. This is probably the varnish (perhaps copal) applied by Scott. Above this is a second very broken and thin coating. This is probably the v/ax applied by HMG. It is readily soluble in a range of aromatic solvents. In the centre of the picture its is very thin presumably because the majority of it was removed by EH in 1985. Towards the edge of the painting where it is obscured by the pillars this upper waxy layer survives far thicker. It appears that any gel would be aimed at this upper layer only, and an alternative method should be used to tackle the lower layer if this was considered to be desirable. Sheet no. Solvent Parameter Tests
Site. W.A.C.H. Date. 23. 1 .91
Method/Time Solvent of application. Result.
Toluene 2 Swab. The top (waxy) layer dissolves readily Benzyl alcohol 1 but the problem occurs when the second layer is reached. This appears to be insoluble in solvent mixtures. A test with this mixture was carried out in an area where the waxy layer appeared to be directly over the stone substrate Here all the coating was readily removed.
Xylene 2 Swab Very similar in effect to the above Benzyl alcohol 2 test.
Xylene 2. Swab Again very similar to the above two Benzyl alcohol 1 tests. Acetone 1
Conclusions Sheet no Sample Analvsis Before Gel Tests
Sample noWA 1 WAI Accession no. *** * Date. 3 0.1.91
Hot Stage Examination.
Temp. Observations.
30C Dark brown/yellow resinous material, quite hard and brittle, with inclusions of surface dirt.
192C Slight darkening observed.
2 4 8C Darkening observed throughout.
300C Further darkening occurs. Sample now dark brown and opaque.
Conclusions.
Sample possibly consists of a hard resin such as copal.
Sample no. WA2 Accession no. * ** * Date. 3 0.1.91
Hot Stage Examination.
Temp. Observations.
30C Translucent amorphous whitish material, with inclusions of surface dirt and white crystalline material.
58C Some movement occurs.
62C Sample begins to melt.
64C Melting occurs throughout the sample.
68C Material free flowing leaving white crystalline material unaffected.
>100C No further change.
Conclusions. The melting point suggests that the sample consists mostly of a wax, probably beeswax. The white crystalline material is probably a contaminant from the wall. Soluble salts?. Sheet no Sample Analysis Before Gel Tests
Sample no. Accession no. Date.
Hot Stage Examination.
Temp. Observations.
Conclusions.
F.T.I.R.
Notable Absorbtion Peaks Interpretation.
Conclusions. Sheet no X-Section Examination Before Gel Tests
Sample no. WA4 Accession no. 501 Date. 2 8.1.91
Examination Unmounted.
Surface. Thick translucent layer covers surface of the sample. Apparently white layer below.
Stratigraphy. 1. Waxy layer, 2. Resinous layer, 3.Paint Layers containing blue pigment particles. The paint layers appear to be saturated with the waxy material.
Examination Mounted Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Ektachrome 6 4 Mag.no. x100/x200 Film nos-
Comments.
1. Sur face dirt. 2. Thick resinous layer, translucent yellow/brown 3. Carbon black? particles. 4. Small amounts of surface dirt at interface. 5. Translucent coating similar to 2. 6. Disrupted white material. 7. Dark particles-carbon black? 8. Opaque white layer. Broken in places. 9. Further original surface dirt. 10. Original surface? Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. WA4 Accession no. 501 Date. 29. 1 .91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Yellow/green fluorescence. 2. White fluorescence. 3. As above. 4. Dark purple. 5. White disrupted layer. 6. Bright white. 7. Light purple.
Type.
Results. Sheet no X-Section Examination Before Gel Tests
Date. 2 3.1.91 Sample no. Accession no. 5 0
Examination Unmounted.
Surface. Yellowy waxy surface coating with surface dirt
Stratigraphy. 1. Waxy material, 2. resinous material. 3. complex mixture of pigment layers, inc. blue crystalline pigs.
Examination Mounted Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type „, , „ t Mag.no. . Film nos. B v 3 JV Ektachrome 64 xl00/x200
Comments,
1. Yellow brown coating. 2. Surface dirt. 3. Carbon black particles. 4. Disrupted white material. 5. Large dark amorphous lump. 6. Yellow/white crystalline material. 7. Carbon black particles. 8. Yellow crystalline material as in 6. 9. waxy material ? 10. as for 8 Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. WA6 Accession no. Date. 29.1.91
Graphic record of sample.
Photography. Film Type. **** Mag.no. Film nos.
Comments.
A. Fairly solid and coherent. B. Very disrupted and broken.
1. Yellow green. 2. light purple-disrupted. 3. White particles. 4. Dull bluish area. 5. similar to 4. 6. Opaque white with orange tinge. 7. bright white. 8. Dark purple. 9. Darker purple/black. 10. Opaque white.
Staining
Type.
Results. Sheet no X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. WA7 Accession no. ^ 0 4 Date. 29.1.9 1
Graphic record of sample.
Photography: Film Type. * * ** Mag.no. Film nos.
Comments.
1. White- possibly disrupted waxy material 2. Yellow/green. 3. white particles. 4. as for 3 5. opaque white layer. 6. Less opaque white. 7. light purple. S. Opaque white with orange tinge. 9. as above, but orange more intense. 10. disrupted white.
Staining
Type.
Results. Sheet no X-Section Examination Before Gel Tests
Accession no. Date. Sample no. WA7 504 29. 1 .91
Examination Unmounted.
Surface. Thick resinous surface coating.
Stratigraphy. Sample very thin. 1. waxy/resinous coating over 2. white layer containing light blue crystals.
Examination Mounted Normal LichL (Tungsten Source)
Granhic record of sample.
Photography: Film Type Ektachrome 6 4 Mag.no. xl00/x200 Filmnos-
Comments.
1. Sur face dirt. 2. Yellow/brown translucent coating. 3. Carbon black particles? 4. Disrupted white crystalline material. 5. Original surface ?? 6. Surface dirt from above. 7. Opaque crystalline material broken in places. Sheet no. Solvent Gel Tests
Site. W.A.C.H. Date. 13.3.91
Method/Time Solvent gel. of application. Result.
1/ 7. Swab. 15/90. Little apparent cleaning- effect. Surface dirt and small amount of coating: removed. Some small bloom on edge of test. area. Clearance: xylene/H2O. Samples. WA8/WA9
2/ 1. Swab. 15/90. Again little cleaning effect. Also some bloom at edges. Clearance: xylene/H2O.
3/ 1. Swab. 15/90. Very similar to the above. Some of the bloom removed. Clearance: xylene/H2O. (Tests 2 & 3 took place over the same area.)
9FOC Swab. 120. Does not appear to have any effect on lower layer. clearance: H2O. (Test 9FOC took place over the area of 3. )
4/ 7. Swab. 0/120. Wax layer directly over stone. Shows good thorough cleaning effect all the way to the stone substrate. Clearance: xylene/H2O.
5/ 7. Swab. 15/120 Good cleaning effect, all the wax appears to be removed. No bloom. Clearance: xylene/H2O. Sample: WAI 3.
Conclusions
It seems clear that even gelled solvents have little or no effect on the lower resionous layer (as was presumed from the solvent parameter tests.) Gel 7. is the most effective for dissolving the upper wax coating, and as there is in effect a barrier layer between the wax layer and the paint surface, there is no danger to the vulnerable organic components of the painting itself. Care must be taken to avoid areas of bloom that sometimes occur. Further examination must be carried out to establish exactly the source of this bloom. Sheet no. Position of Samples
Site. W . A . G . DaLe. 30.1.91
; v
5 Sheet no.
Sample Reference
Sample Acccsion Type of Date. number. number. analysis.
WAI FT I R a 0 . 1 . 9 1 WA2 FT1R 30.1.91 WA3 -f* Site. W. A. C . H . Date. 13.3.91 Method/Time Solvent. of application. Result. A9C Swab. 120. Appears to have some cleaning action on the lower coating, some material dissolved. After clearance a bluish fluorescence could be seen under UV on the area of the test. Some bloom around the edges (removed with mixture of 1/1 acetone/propan-2-ol). Clearance: H20. Sample: WAI 4. 6/ 11. . Swab. 15/120. Test 5 was carried out twice over the same area. On both occasions there was a negligible result. Clearance: WS/H2O. Conclusions Sheet no X-Section Examination After Gel Tests Sample no. WAI 1 Accession no. Date- 13.3.91 Examination Unmounted. Surface. Thick dark resinous layer. Stratigraphy. Thick coating with inclusions of disrupted white material over a white crystalline layer. Examination Mounted Normal Light. (Tungsten Source) Graphic record of sample. Photography: Film Type Mag.no. Film nos. Ektachrome 6 4 xl00/x200 Comments. 1. Dark translucent resinous layer. 2. Dirt and white disrupted material. 3. dense white crystalline layer. 4. Small red crystals. 5. Further disrupted white effluorescence. Sheet no X-Section Examination Mounted Alter Gel Tests UV Source Sample no. WA1 1 Accession no. ^ 6 * Date. 13.3.91 Graphic record of sample. Photography: Film Type. Mag.no. Film nos. 5|C 5C fC 3C Comments. 1. Yellow/green fluorescence. 2. Dull white. 3. Bright white. Staining Type. Results. Sheet no X-Section Examination After Gel Tests Sample no. WAI Accession no. 5 6 2 Date. 13.3.91 Examination Unmounted. Surface. Thick dark resinous coating'. Stratigraphy. The coating lies directly over a red pigment layer on a white ground. Examination Mounted Normal Light (Tungsten Source) Graphic record of sample. Photography: Film Type Ektachrome 64 Mag.no. xlOO/x2O(Film nos. Comments. 1. Light red/white layer. 2. Red orange dense pigment layer. 3. Dark blackish material. 4. and 5. White crystalline material Sheet no X-Section Examination Mounted After Gel Tests UV Source Sample no. WA12 Accession no. 5 6 Date. 13.3.91 Graphic record of sample. Photography: Film Type. Mag.no. Film nos. Comments. 1. Bright white with redish tinge. 2. Orange/red fluorescence-weak. 3. White matrix with orange tinge. 4. Similar to 3. but weaker orange. Type. Results. Sheet no X-Section Examination After Gel Tests Sample no. WA13 Accession no. 563 Date. 13.3.91 Examination Unmounted. Surface. Thick dark resinous layer on surface. Stratigraphy. The coating lies over complex pigment and ground layers. Waxy material is on the bottom of the sample. Examination Mounted Normai Light. (Tungsten Source) Graphic record of sample. Photography: FilmType Ektachrome 64 Mag'no' xl 00/x20rjilmnos' Comments. 1. Translucent dark resinous material. 2. White crystalline material. 3. Dense white crystalline mass. 4. Red pigment layer in white matrix. 5. Waxy material containing large amount of dark material (probably dirt and carbon black). 6. Blue crystals. 7 . Red Crystals. 9. Dense white layer. Sheet no X-Section Exaihination Mounted After Gel Tests UV Source Sample no. WAI 3 Accession no. 553 Date- 13.3.91 Graphic record of sample. Photography: Film Type. Mag.no. Film nos. Comments. 1. Reel/orange weak fluorescence. 2. Orangey fluorescence. 3. Darker than 2, but similar hue. 4. Bright white. Stainint Type. Results. Sheet no X-Section Examination After Gel Tests Sample no. WA14 Accession no. 564 Date. 13.3.91 Examination Unmounted. Surface. Red broken pigment layer. Stratigraphy. Red crystalline pigment layer over white ground. Examination Mounted Normal Light (Tungsten Source) Graphic record of sample. Photography: Film Type Mag.no. Film nos. Ektachrome 64 xlOO/x2OO Comments. 1. Red pigment layer. Crystalline. Uneven and broken in some areas. 2. White crystalline material-loose matrix. 3. Large red particle of pigment ? 4. Blue amorphous crystalline particle. Sheet no X-Section Examination Mounted After Gel Tests UV Source Sample no. WA14 Accession no. 5 g 4 Date. 13.3.91 Graphic record of sample. Photography: Film Type. Mag.no. Film nos. 2|C 3|C 3{C j(C Comments. 1. Pigment layer does not appear to fluoresce, however there appears to be a light white fluorescence above it. Possibly something to do with the mounting medium as there is no layer visible. 2. Bright white with orange tinge. Staining Type. Results. CIA/ GCI Conservation of Wall Paintings Department. 1990-1991 An investigation into the use ofsolvent gels for the removal of wax-based coatings on Wall Paintings. Tobit Curteis Samplenos. WAI-WAI 4 Accession nos. 501-504 560-564 County. London Position of painting. South arcade, Village/Town. central bay. London Name of Building. Dimensions of Painting. 14 3cm. x 2 28cm. Westminster Abbey Chapter House. Subject. Name/Address of Custodian. Apocalypse of St. John. English Heritage. (Mr Jan Keevil) Attribution & Date. Permission granted. 2 1.1.91 Between 13 72 and 1404. Date. 2 3.1.91 Sampledby. Tobit Curteis. Previous Recorded Surface Treatments Date. 1806/36 1901/3 1929 1985 Conservator. G.G.Scott A.H.Church H.M.G. English Heritage. Method IMS 80 %/Propan-2- Baryta water was Beeswax with employed. ol 80% mixture was possibly applied 2% linseed oil to certain areas used to surface No exact account was applied to of the paintings clean the survives, but it the paintings &, including the area paintings in the appears that the driven in with examined for this NW arcade. All paintings were heat. Used as project. No record other paintings Varnished during adhesive and of any surface were surface this period. Consolident. coating applied at cleaned with hot this time. air and cotton wool to remove part of the wax coating. Area Treated AH Paintings ? Unknown All paintings All paintings. Location of CIA/EH EH EH. records. CIA/EH Previous British None None samples Museum. None & location. Sheet no.2 Area Sampled (before testing) Apparent i. stone substrate. 2. White ground 3. In many areas there stratigraphy. also appears to be a red ground. 4. Paint layers (very complex and confused in some areas.) 5. Dark resinous layer. 6. Soft waxy layer. Possible Organic medium of some sort (Oil?). technique. General Bad exfoliation and decohesion in many areas. Stone condition. support is often in v.bad condition resulting in surface damage. Some areas appear to be sound. Appearance & Organic coatings cover the whole painting. Apparently two distribution iayers. Possibly thinned in the 1985 conservation by EH. or sorisccs . Much of the paint surface is consolidated by the surface coaings. coating as it appears to have lost original cohesion. Coating has collected in all damages or lacunae. White/green fluorescence over most of coating. Some examination. repaints appear to show in areas of the hands and face of figures. Two coatings not apparent in UV. Position of All cross sections were taken from the area of the two samples. vscrolls' in the hand of the right hand angel. Two coating samples taken from large lacunae nearby. Possible anomalies The very disrupted nature of the surface/coatings and of area sampled. the varying staratigraphy of the paint layers may make comparison of individual samples difficult. In most cases the surface coatings in which we are interested will be apparent. Photography: All areas were recorded with Ilford FP4 (black & (type & area) white) and with Agfachrome CT100, in both general and macro. Comments. Samples were intended to be as representative of the area as possible, and comparable with other samples from the same area. It was found that the stratigraphy of individual samples varied considerably within very small areas, presumably due to the damaged nature of the paint layer. This made cross-referencing more complex than is normal.