Training Maintenance of Art Nouveau - 3 (16 People)

Training "Maintenance of Art Nouveau - 3" (16 people) Ljubljana - 13 to 17 September 2004

Limewash

1 B. – LIMEWASH

B.1. - MATERIALS P. 3-5 B.1.1. - BINDERS B.1.1.1. - Non-hydraulic lime paste B.1.1.2. - Non-hydraulic lime powder B.1.1.3. - Natural Hydraulic lime B.1.2. - WATER B.1.3. - PIGMENTS B.1.3.1. - Natural earth pigments or ochre types B.1.3.2. - oxides

B.2. - LIMEWASH IMPLEMENTATION P. 6-12 B.2.1. - Preparing the wash B.2.1.1. - Liming B.2.1.2. - Limewash B.2.1.3. - Aqua fortis or lime tempera B.2.1.4. - Finishing B.2.1.5. - Choosing the wash B.2.2. - ADDITIVES B.2.3. - STABILIZATION B.2.4. - IMPLEMENTATION B.2.4.1. - Tools B.2.4.2. - The nature of the surface B.2.4.3. - Conditions for implementation B.2.4.4. - Limewash application B.2.5. - "FRESCO" TECHNIQUE B.2.5.1. - Principle B.2.5.2. - The surface B.2.5.3. - Implementation B.2.6. - SYNTHETICAL DATA SHEET

B.3. - LIMEWASH PATHOLOGY P. 12-15 B.3.1. - INTRODUCTION - observation of pathologies B.3.2. - LIMEWASH IMPLEMENTATION PATHOLOGY B.3.3. - AGEING PATHOLOGY

BIBLIOGRAPHY P. 16

2 B. - LIMEWASH

INTRODUCTION

When dealing with limewash, it is necessary to study binders (cf mortar E2).

Reminder: Traditional binders are distinguished according to type: - Mineral: raw clay, common lime, plaster - Organic: plant sap, resin and gum, oils, waxes, blood, softeners or tempera (with glue, egg, milk, casein)

Today’s generation of wash binders can be classified in a new category: - Synthetic: silicate, vinyl, acryl, alkyde

Concerning renderings, a limewash has two purposes: 1 Protect the facing (stone, brick, rendering) by covering the mineral surface with a layer of pure binding material. This layer of binding material, slightly soluble with water, is renewed periodically. 2 Aspect: whether intentional or not, the application of a whitewash, (plaster, or white clay) colours the facing white. Inside, especially when lighting is restricted or sparse, its reflective role is also appealing. According to the time and country, adding pigments has always made it possible to render colour within a specific range, linked to availability in mineral and culture.

3 B.1. - MATERIALS

B.1.1 - BINDING MATERIALS (BINDERS) (see: mortars E2)

B.1.1.1 - Non-hydraulic lime paste: Non-hydraulic lime paste is made from industrially or hand slaked quicklime (slake = disintegration of lime by treatment with water.), using a great volume of water. The lime must be sieved to remove the "grappiers" (over or under fired chunks). It can be preserved as a long time as it is in water and carbon dioxide free. It is preferable to slake it ahead of time to be certain to avoid non-slaked elements that could cause detrimental effects. The lime paste must be thinned to suitable fluidity, to the point where it can be applied with a brush. The disadvantage of lime paste is that dose colouring and additives are calculated through weighing, because water amounts tend to vary a lot. The old name for this type of lime is: XAN - natural air drying lime, but the name is not standardized. It constitutes a high-grade non- hydraulic lime thanks to its colloidal characteristics and low level of carbonation after slaking.

B.1.1.2. - Non-hydraulic lime powder: Non-hydraulic lime powder is quicklime that has been slaked industrially, through a sprinkling process using one tenth of its weight with water. Mixed with water, it keeps as long as it is submerged. When carbonated, this type of lime remains slightly soluble with water. Non-hydraulic lime paste, for its part, hardens through a carbon dioxide fixation process called carbonation. As it is measurable in weight and volume, it is possible to calculate colouring and additives.

When resin additives are used, the wash is usable up to one-day max. Name: C.l (Calcic Lime) Volume mass : Weight = 0,5 (one litre of C.L. weighs 0,500 kg) Volume Brightness 0,85 French Production Standards: C.L. or D.L. NFP 15311

B.1.1.3. - Natural Hydraulic Lime This type of lime is obtained from limestone containing 5 to 20 % clay. It ranges from white to whitish and is usually found in powder form. When lixed with water, lime stays plastic and supple for approximately 5 hours (according to temperature and humidity) it hardens with water through crystallization (approximately 30 % of carbonation and 70 % of crystallization). Insoluble.

Name: NHL (Natural Hydraulic Lime) Volume mass: 0,8 (one litre of NHL weighs 0,8 KG). Brightness: Variable according to the limestone used, weaker than that of C.L. French Production Standards: NHL 2/3,5/5:NFP 15311

·The choice of a binding material : is made according to several criteria: -brightness: (CL = 0,85; NHL < 0,75) -characteristics of the surface rendering: one seeks good mechanical cling as well as good chemical cling (ionic) - It is best to choose a lime which is of a comparable nature to the rendering. -Conditions for implementation: certain elements must be taken into account: rain, outside temperature, wind, sun, building site schedules and delays, (C.L. is sensitive to poor application conditions for a quite longer period than others).

B.1.2. - WATER plays three roles: It makes the limewash soft and plastic, and is used as a catalyst. When C.L. is used, evaporation activates carbonation (carbon dioxide transforms water into carbonic acid; the CO² then fixes onto the calcium hydroxide), triggering crystallization in the case of a hydraulic lime.

4 B.1.3. – PIGMENTS are the aggregates used with whitewash. They must be compatible with the alkalinity of lime. Their role is to produce colour. We can distinguish natural pigments (Earth based or ochres) from artificial pigments (metallic oxides).

B.1.3.1. - Natural earth or ochre types come mainly from kaolinite and the gorthite. Their colouring capacity is weaker than that of oxides. They diffuse easily in limewash and are more easily fixed.

The earths often used with lime are: 1 yellow ochre 2 red ochre (today calcinated ochre yellow) 3 Raw Sienna 4 Burned Sienna 5 Natural Umber 6 Burnt Umber 7 Ivory black; or bone, fish, mineral, vine black.

B.1.3.2. – Oxides : Oxides are manufactured industrially: they use metals and are more difficult to implement with limewash (diffusion, lime fixing, pigment permanence).

Use (late XIXth and XXth centuries) is more typical of recent façades and decoration.

The main oxides used with limewash are: 8 green oxide (chromium oxide, copper sulfate), 9 red oxide (iron oxide), 10 yellow oxide (iron oxide), 11 ultramarine blue (GUIMET blue).

Earths and oxides are miscible without any side effects. The tones of oxides are colder than that of earth or ochre but can enhance colour when used in small quantity. Density varies according to the pigments chosen.

5 B.2. - LIMEWASH IMPLEMENTATION

B.2.1. - PREPARING THE WASH

 WATER / LIME DOSE RATIO Water plays an essential role in giving limewash plasticity for application. The water/lime dose ratio depends on the texture sought. The lower the volume of water compared to the volume of lime, the thicker the whitewash. The fluidity ratio of a limewash modifies its aspect. It is related to the lime and pigment / water ratio. Lime milk has masking properties, it "fills the pores". When the wash is rather fluid, the colouring effect is more aquarelle-like.

The quantity of lime and water necessary for the preparation of the milky whitewash is shown below.

Type of limewash Liming Wash Aqua fortis Patina Dose ratio (volume)

Lime powder 1 1 1 1

Water 1 2 to 3 4 to 6 10 to 20

B.2.1.1. - Liming The purpose of liming is mainly maintenance and constitutes an antiseptic measure. When thick, liming masks; brush strokes are then apparent (“rope effect”).

Preparation 1 volume of powder lime in 1 volume of water Mix well (can be mixed with a very fine aggregate).

B.2.1.2. - Limewash A limewash doesn’t produce any “rope effect” but masks the texture of the surface.

Preparation: Pour the lime, whip energetically in a container adapted to the total final amount of limewash prepared. The mixture must be stirred extensively till it becomes homogeneous. If unstable and contains sediments, one must stir before each new stroke to ensure a good result - 1 volume of lime for 2 volumes of water.

Colouring: The pigments incorporated in the wash colour the mixture more or less, whether natural earth or oxides are used, and according to the quantities used. The guidingline is as follows: the pigment concentration in a limewash is determined by weighing a given percentage of pigment/lime ratio. The lime weight is determined by multiplying volume by density.

E.g.: for 20 litres of C.L. wash with 5 % of Raw Sienna, we use:

20 litres of water, 10 litres of C.L. (density 0,5 = 5 kg C.L.)

We thus obtain: 5 kg X 5 % = 0,250 kg of Raw Sienna added to the basic whitewash.

Washes saturate at 25 % of lime weight for Earth or Ochre and at 15 % of lime weight for oxides. B.2.1.3. - Aqua fortis (highly diluted lime) or lime tempera Preparation Same conditions as for a wash. The volume lime / water ratio is 1 to 5. - 1 volume of lime for 5 volumes of water.

6 Colouring As lime tempera contains 2.5 times more water than wash, this leads to two effects: 1 it is thinner and the colouring is more transparent, aquarelle-like. 2 As opposed to wash, we can to add a more significant percentage of pigment without thickening the liquid much (by adding fine aggregates); the saturation point of colouring is 65 % earth and 35 % oxides / lime ratio.

Beyond those levels, adding either oxides or ochres no longer generates any colouring effect; thickening the liquid just adds load to the preparation.

Whitewash (milk lime) is used to paint FRESCO (the fine layer can to be fixed by the surface).

Compared to a wash, the aqua fortis technique contains proportionally half as much lime.

B.2.1.4. - Finishing Finishing is used to give new stones a homogeneous weathered or worn effect during a restoration (rehabilitation) campaign or a partial rendering renewal. Preparation Same conditions as wash and aqua fortis. The lime/water ratio is 1 volume for 20 volumes - 1 volume of lime for 20 volumes of water. Colouring One can add up to 95 % of lime weight with earths and 55 % with oxides to reach colour saturation.

B.2.1.5. - Choosing the wash Choosing the type of limewash Choice is determined by the results sought: "filled" aspect or not, intense colours or not...

Type of limewash Selection Criteria Liming On stone masonry, rendering and mouldings and profiles. Very thick aspect, rustic application (large brush). Generally white, sanitary purpose. Dry technique

Wash On rendered facing, mouldings and profiles. Masking aspect, thick, twisted (rope-like brush) marks. Low saturated colours. Dry technique

Aqua fortis (lime tempera) On rendered facing, stone. Aquarelle-like aspect (flat and round brushes). Possible vivid colours, strongly concentrated. Dry technique and FRESCO .

Patinate On mouldings and stone. Great transparency, enhances the texture of a surface (sponge brushes). Evens out areas and weathers the facing. Dry technique and FRESCO .

It is generally possible to use intermediate lime/water ratios. This is neither fixed nor limited.

B.2.2 - ADDITIVES

Limewash techniques are relatively inexpensive and are traditionally used in the decoration of old constructions, in the same way as rendering techniques. The quality of the results is related to proper implementation conditions.

These techniques were mastered by the ancients: for centuries, these experts used pragmatism and built up experience to improve lime techniques, using various binders and additives (egg, oil added during the slaking of lime, alum salt...).

Nowadays, when necessary, modern materials are added to improve the quality of limewash with additives. (see table hereafter)

Whether traditional or contemporary, additives, though they can improve certain characteristics, can transform others: casein, synthetic resins or linseed oil improve the quality of limewash, as complementary binders. They however tend to reduce porosity. ADDITIVES

Restrictions and Role Additives Effects Dose ratio disadvantages Especially useful with non-hydraulic Carbonation Alum Salt of or helps lime fix Between 2,5 to 10 % limes. Do not mix in enhancers Potassium alum carbon dioxide. of lime weight. advance, with a resin. Makes limewash less permeable to steam or water. If Complementary one layer is synthetic resin binding material. stabilized, the According to needs. emulsion. Casein Fix the pigments following layer is 1 to 10 % maximum Stabilizer or with lime. which are not fixed stabilized too. of the load which is complementary Traditional organic by lime (excess Loss of mattness to be fixed. 1cc for binding material binders (blood, egg, pigment, poor and porosity. Loss 1litre water No oil). hardening of matt finish and longer used today conditions...). porosity. Turns yellow with time. Variable quality (non durable product). Makes the wash (milk lime) more Less common 1 cap measure per fluid and flowing. Fat soap Teepol whitewash. When 50 litreswater. See Wetting agent Better dispersion of Thinning concrete in excess, makes manufacturer user’s pigments. limewash foam. manual. Eliminates oxide “rocket" filaments. improve water Do not use in very retaining (against cold or wet weather Methylcellulose fast desiccation). and on water 5-6 grs for 1 litre of (wallpaper glue, Improves water retainer saturated surfaces. water (maximum Methylan, Quelyd mechanical stability. Dose ratio according dose ratio) types...). Used in case of: to application Wind, heat, sun, conditions. absorbent surface.

8 B.2.3. - STABILIZATION

The quality of a limewash depends on the quality of carbonation for non-hydraulic lime as well as hardening conditions for natural hydraulic limes. The carbonation and/or the hydraulic hardening are increased by water; in the case of air limes this fixes the carbon dioxide in the air, triggering carbonation; it is thus necessary to have sufficient supplies of water. Limewash and lime milk are, by nature, thin layers, (film-like) and have little hydrometric inertia.

A good process consists in: 1 making the mixture of water and lime, using a determined ratio, according to the effect sought. 2 adding the necessary pigments. 3 diluting the mixture with water to obtain a white base fluidity, before adding pigment, thus thickening the whitewash.

In the case of porous surfaces (non-hydraulic lime rendering, natural hydraulic lime, plaster and lime, soft limestone, mud or terracotta), and perfect application conditions (abundant wetting of the surface, good climatic condition limiting evaporation at the beginning of hardening, 2 to 3 days) it is possible to obtain quality limewash, even when richly pigmented, and applied dry.

In the case of less optimal surfaces (rendering with hybrid mortar...) or poor application conditions (wind, heat...) complementary binders may prove necessary, whatever the quantity of pigment.

Excessive quantities of pigments are detrimental to the final reaction of a coloured whitewash. In this case, it can prove necessary to use an additive (binding material of another nature). This is particularly applicable when the amounts reach 20 % of earth or ochre, or 10 % of oxide.

Limewash additives can be determined on a basis of 0 to 10 % maximum in stabilizing material, in aqueous dispersion, (beyond this percentage, the wash is regarded as organic paint), of the total mass fixed.

Two cases can occur: 4 if the surface is good quality (good humidification, porous surface with sufficient mechanical cling) and if the conditions for application are good (no wind, no excessive sun, no hot weather) the mass to be fixed includes only those pigments that are not fixed by the lime. 5 if the surface is not the most appropriate or application conditions are poor, the mass which is to be fixed can be the lime and the pigments.

Additives have been used since time immemorial: ox blood, linseed oil... to solve the pigment fixing issue. These additives, though they stabilize excess pigments, result in a loss or reduced porosity of the surface, as do contemporary additives containing vinyl, acryl...

9 PIGMENTS SATURATION LIMIT expressed in %, ratio with weight in lime

Rough guideline for Saturation limits

Aqua fortis Liming Wash Patina (tempera) Earth / Ochres 10 % 25 % 65 % 95 % Oxides 5 % 15 % 35 % 55 %

Beyond a certain percentage, adding earth or oxide in the mixture no longer changes colour intensity or vividness. We then speak of colour saturation limit. Exceeding these limits in no way "enhances" colour. On the contrary, an excess amount of pigments thickens the mixture, increasing the load that is to be fixed. This value varies whether one uses earth or oxides.

B.2.4. - IMPLEMENTATION

B.2.4.1. - tools: Lime washes and lime tempera are applied with a wide rectangular brush and a round finishing brush; the patina is applied with a natural sponge or brush. The brush (length: 12 to 15 cm - width: 4 to 5 cm) is a wide rectangular application brush made of natural silk. The fine brush is a round or flat brush with a bevelled edge. It is recommended to have a drill with a mixer nozzle or extension to prepare the whitewash.

B.2.4.2. - nature of the surface: traditional lime washed surfaces are mineral surfaces: stone, terracotta brick, lime renderings, plaster and lime, mud earth. On plaster, chalking and peeling are quite frequent. The reaction also varies according to the geological nature of stones: limewash clings better to basic stones (limestone) with high porosity. Organic paints, wood, contemporary materials (PVC...), plasters and plasterboards are not appropriate surfaces for traditional limewash. (Certain industrial products containing lime with a large amount of resin additives approach the aspect and colour of traditional limewash).

Preparation of the surface: The surface which is to be lime washed must be clean, free of any powdery or farinaceous areas and must have some grading level for appropriate cling (beware of excessively smooth surfaces). The surface must be brushed, dusted and washed. The surface must be humidified before each layer: a dry surface would absorb the water needed for a good hardening of the limewash and cause chalking. On the other hand, too much water on the surface removes part of the clinging and covering capacity of the whitewash. For these reasons, a surface is best wetted the day before. The surface rendering must have finished hardening before application, short of this, loose lime can migrate over the surface and form non aesthetical efflorescence. Note: only the “FRESCO” technique allows for an application of aqua fortis on fresh rendering under strict conditions (see: “FRESCO ”technique, whitewash application).

B.2.4.3. - Conditions for implementation: 1 Conditions are the same as those for traditional lime rendering (cf Renderings - DTU 26-1). 2 limewash is in fact a very fine layer of rendering with a colouring aggregate, which is an impalpable powder. The brush then replaces the trowel. 3 the most favourable seasons for limewash are spring and autumn, like renderings. The main problem is to comply with suitable weather conditions (particularly in façade): 4 minimum temperature of the surface: 5° 5 outside temperature between 5° and 30° 6 no wind or moderate wind; covering with opaque sheeting is possible (but no transparent canvas: this would causing a greenhouse effect) and / or using additives (see water retaining). 7 avoid midday sun (quite desiccation causes chalking).

10 B.2.4.4. - Application of whitewash: 8 On old rendering, when pigment colouring is sought, it is preferable to even out the tone of the façade before colouring; a coating of white limewash over the whole surface is recommended. Limewashing is carried out by crossing layers, finishing vertically (thus easing rainwater run-off). 9 the layer must be applied in one stroke and cover the area stroked by the brush, limewash cannot be spread like an oil-base paint. 10 Avoid wide or strong brush blows. The lime milk must be mixed and smoothened before each dipping to avoid reaching the bottom of the container (bucket) with thick-pigmented material. The bottom deposit (concentration of pigments) must be mixed with the lime regularly between strokes. 11 drying time between the layers of C.L. varies, according to weather conditions, from 1 to 3 days: with NHL, hardening time is approximately 24 hours. 12 When working in successive layers, it is preferable to use increasingly diluted milks. 13 Limewash tones always get lighter after drying. It is difficult to be get a clear idea of the final colour before complete drying: making preliminary samples is highly recommended.

When the bottom layer is stabilized with resin, it must be covered with a layer of limewash stabilized in similar ratios, even if the colouring does require this. Remember the saying: "thin carries fatty".

B.2.5. - "FRESCO" TECHNIQUE

B.2.5.1 - Principle: 14 Aqua fortis is applied on fresh rendering, carried out exclusively on non-hydraulic lime when carbonation begins. 15 This technique is close to the fresco technique of fine art painters; it is the opposite of lime techniques on finished dry rendering, known as dry or “secco” techniques.

B.2.5.2. - The surface: 16 The finishing rendering must have sufficiently carbonated so as not to deteriorate with brush strokes. It should not have carbonated excessively, so as to fix the pigments of aqua fortis. 17 The application time of aqua fortis depends on the climatic conditions and can vary from one to two days, maximum. 18 Projecting horizontal friezes favour the use of this technique because the work can then be split into independent panels.

11 B.2.5.3. - Implementation: 19 Making aqua fortis follows the same principles as those used for dry renderings, with an identical process for colouring. 20 Liquid agent and water retaining additives are similar to those used in the dry technique. On the other hand, it is useless of add resin because the rendering fixes the pigments, even when concentrated or saturated. 21 The application is carried out with the same tools as the dry wash technique. This technique implies organizing the task in one day of work, which is to be carried out by a skilled craftsman or a team.

B.2.6. - SYNTHETICAL DATA SHEET

Pigment concentration (%) = UUPigments WeightUU Lime Weight

Lime weight = volume mass x volume of lime Volume mass = 0,5 Volume mass = 0,8 Wash: 60g of C.L. 90 G of NHL

Lime per m² and layer: Aqua fortis: 30g of C.L. 50 G of NHL

B.3 LIMEWASH PATHOLOGY

B.3.1. - INTRODUCTION: Examining pathologies

Limewashing was originally a measure to protect a construction’s facing: whether outside on the façades or inside buildings, its primary role is to protect the rendering, whether lime or earth, stone or brick.

In addition, the inside layer used to play a sanitary role in rural environment, still acknowledged toady, as well as a source of light (brightness and reflective properties (0,85)) at times when light interiors were an issue and light sources limited.

Limewashing maintain (used to maintain) and still preserve areas that undergo (underwent) physical, chemical or organic deterioration.

According to the quality of the construction, from ordinary agricultural constructions to commissioned architectural projects, the protective role of limewash can play yet another role: decoration.

Adding mineral pigments then makes it possible to use one or more colour, as well as to draw courses or decorative patterns...

These limewashes are short-lived layers: they undergo natural aggression, trends, and develop differently according to the rate of maintenance or upkeep, inside or outside exposure, weathering and wearing of the construction.

12 When repairing in a rehabilitation /conservation project, it is essential to bring special attention to in depth observation, not only limited to the surface: this preliminary study guarantees better technical solutions and increases the quality of heritage architecture.

22 history of the building, evolution in time 23 construction environment, in a broad sense: climatic, exposure/angle (orientation)... 24 state of preservation and all deterioration phenomena 25 techniques used and pigments implemented

As facings are constituted by layer upon layer of washes, the preliminary study is to note the successive colours and decorations implemented through the many previous campaigns.

Pathologies and ageing speed are variable, and are related to many parameters:

26 environment 27 maintenance 28 techniques and materials used

Other pathologies related to the implementation can largely accelerate the processes; they should be classified and studied prior to work.

13 REMEDIES / MEASURES

OBSERVATIONS CAUSES MEASURES Chalking Poor Bad conditions of hardening: excessive temperature, Brushing -dusting quality lime, easily exposure to sun, too much wind, therefore quick Humidification and stained (fingermarks) desiccation Rendering-surface insufficiently or repairing Consolidation excessively wet Concentration of pigments poor through application additives (lack of resin in the event of high pigment Restoration concentration) Lime stored too long Rendering (rehabilitation)technique excessively carbonated at the time of limewash ex: Ethyl silicate application (fresco technique) Frozen milk lime Support is incompatible with limewash (plaster, non- mineral surfaces) Separation, peeling Support is incompatible with limewash (plaster; non- Elimination (scraping with mineral surface) Synthetic paint under limewash a spatula) and repairing. layer Waterproof surface rendering In the under-coat, Restoration technique: presence of resin, and no or less resin in the last layer Paraloïd B 72 Peeling by moisture (limewash made waterproof by excessive amounts of resin additives). Risk of peeling is increased by thick whitewash. Efflorescence Rendering and masonry gorged with water before Repairing Precautions: application of limewash, salt migration and deposit take according to cause after drying of the surface Rendering is not dry (drying, dry technique, enough at the time of the limewash application (in delay...), secco technique): migration and deposit of loose lime. Fresco limewash on plaster and lime rendering: application too thick or thickness irregular. Marks from flat or Poor application Support is too absorbent (not wet According to cause: round brushes enough) Insufficient number of layers (2 layers better technique of minimum) application. More water / wetter surface. Additional layer. Cordage Milk lime is too thick (liming) If the twisted (rope-like) aspect is not appropriate, slacken the limewash with water. Wet the surface. Colour tones and Rendering-surface already is a certain shade or Dispersion: -Add liquid st nuance colour (requires a 1 PP PP uniform layer of white). Bad -mix thoroughly -mix pigment dispersion due to faulty preparation of more often and regularly, whitewash. Limewash is not mixed enough during between each brush application process, (deposit in the bucket or stroke container). Application is Support is not absorbent enough (surface rendering Thick limewash More difficult, the wash with artificial binders, stones are cold). Surface is too limewash layers. Wait doesn’t « cling » or wet. until the surface is less cover the surface wet. Poor chromatic Pigments incompatible with lime (lime = base) Repair with a base- resistance resistant pigment. Stains (oil-like · Bad dilution of the resin · Application of a limewash Apply a covering layer. stains) with resin when it’s too cold (the outside temperature, the surface, water and limewash temperatures must be at least 5° C or higher). Micro crackling Application of limewash is too thick (shrinkage of the Application of an extra, binding material when hardening) more liquid layer. B.3.3. - AGEING PATHOLOGY 14 Ageing pathologies are comparable to those of rendering (the main difference concerns the extent and nature of the damages; e.g.: rendering disaggregates into sand grains whereas limewash “flours”).

OBSERVATIONS Gradual disappearing of the surface layer (facing) on surfaces exposed to liquids or water. Surface calcification: calcite deposit or calcining (on non-exposed surfaces).

OBSERVATIONS Separation of the surface layer. Disintegration of the surface layer by salt: water deposit. Change of colour or nuance (darker aspect / wet aspect / slightly pink aspect).

OBSERVATIONS Appearance of various spots, sometimes accompanied by crumbling.

CHEMICAL CAUSES Dissolution of non-hydraulic lime by rainwater (loaded with carbon dioxide or sulphuric gas). Lime dissolved by water and water deposit, by surface evaporation.

PHYSICAL CAUSES Following the calcification of surface, peeling or scaling is caused by a splitting of the crystals under the face layer by strain / retractation (rare). Poor clinging. Crystallization pressure (salt deposit). Hydration pressure (salts changing in volume according to humidity levels). Salt deposit by surface water evaporation. Masonry is too recent (fresh mortar and wet mortar).

BIOLOGICAL CAUSES Development of microorganisms (cryptogams bacteria, algae, mushrooms) can eat up mineral elements.

MEASURES Maintenance of the facing by application of a whitewash (repairing).

MEASURES Application of a limewash (repairing). Restauration (rehabilitation) technique . Fighting against water. Application of a limewash (repairing). Restauration (rehabilitation) technique. extraction of salts. surface consolidation. Fighting against moisture. Application of a whitewash after drying.

MEASURES Brushing. Application of fungicidal products. Fighting against water. Ventilation (when the phenomenon is interior).