Tools of Cultural Heritage Science

bulletin cover story Credit: Stephanie Jewell

ultural heritage science—sometimes XRF analysis in the Science Laboratory at the Walters Art referred to as conservation sci- Museum in Baltimore, Md., of blue and rare violet Montana C sapphires in the Iris Corsage Ornament (WAM No. 57.939). ence—is the scientific study of the materials Tiffany and Company produced the piece for the 1900 associated with art and archaeology, including Exposition Universelle in Paris, France. objects that can be moved and objects that must be studied on-site. Cultural heritage scientists study a wide range of materials that can include metals and corrosion products; textiles and dyes; mineral and organic pigments; gems; composite biomaterials, such as leather, vel- lum, parchment, and wood; paper and papy- Discovering the material rus; natural and synthetic polymers; and even biofilms and biodeterioration. Perhaps the secrets of art: Tools of materials of greatest interest to the American Ceramic Society community would include cultural heritage science fired ceramics, glazes, adobe, enamels, mortar, glasses, and ceramic nanocoatings. By Glenn Alan Gates Cultural heritage scientists apply their unique skills in art museums, universities, and regional or national centers for the conservation of art or to landmarks, such as archaeo- Conservation scientists use familiar characterization logical sites or architectural buildings. This highly interdis- tools to discover the materials science secrets of art and ciplinary profession requires expertise in physical sciences (chemistry, physics, biology, geology, and material science), archaeological objects. forensics, humanities (art history, archaeology, archaeometry, art conservation, ethics, and history), engineering, computer science, and economics. Therefore, collaborations are criti- cal to success, and particularly strong working relationships

20 www.ceramics.org | American Ceramic Society Bulletin, Vol. 93, No. 7 based onepsilon-phase iron(II)oxide, ε-Fe fur” materials glazes yieldimprovedmagnetic of1,000-year-oldWill thestudy Asian “hare’s identification using X-rayfluorescence identification elemental X-radiography, and (CT), tomography (IR). Computed infrared ultraviolet (UV)or that include could possibly radiation various formsof with usually astereomicroscope,and visual examination, These include tools first. analytical nondestructive investigation. scientists Therefore, use analytical an visually impacted—during should notbeconsumed—or cious and artwork ispre- is verylimitedbecause ing with art. Sampling art a workof when work- challenges unique faces investigation, thescientist sparks an it. make to or whatwasused made technology how it art todeterminewas a workof to reverseengineer a scientist is asked attribution. with ofSometimes, the date for theobject’sfabricationareconsistent to confirmthat the materialsused asked object, ascientist to acquireanmight be art museumplans authenticity. an of If questions tists toaddress may beasked this be prevented?”Alternatively,scien- from? Why is this happening? Howcan entists: “What is it?it Where didcome sci artwork, museumcuratorsmayask a ceramic appear on tals spontaneously if crys- For example, day. the following explorer an or even detective thenext, a day, one particular doctor issue—a artwork ora an stances surrounding the circum on various rolesdepending community. heritage science Division Science supports the cultural Conservation and Art, Archaeology, established Within therecently ACerS, curators. conservators and exist between American CeramicSocietyBulletin, Vol.93,No. 7|www.ceramics.org Transferring culturalheritagescience studiestomaterialssciencetoday Regardless of the questionthat of Regardless Cultural heritagescientists assume 2 O 3 ? Credit: Susan Tobin; WAM - - storage? storage? improved glassfor futureradioactivewaste inFranceproduced 500years ago result in ofenamels Might studiesofthedeterioration these techniques make use of fixed abra- fixed of use these techniquesmake although imitate production, ancient collectors withobjectsthat carved jade cottage industries alsosupply Modern variably irregularly andsizedmarks. ated abrasives that extensively usingloosecre- American societiescarvedjade Ancient authenticity. inform questionsof can techniques and modern and ancient that evidence helps distinguish between from theAmericasprovide carved jade tool marksfromabrasiveson example, For examination. such an stereomicroscope canenhance optical an art, and a workof of examination step forany as thepreliminary look a close cultural heritagesleuthobtains Similarly, ing glassready.a Holmes alwayshasamagnify- stereomicroscopy Revealing toolmarkswith Baltimore, Md. in the WaltersArtMuseum investigations artworkfrom of using asexamplesanalytical by culturalheritagescientists, ized characterizationtoolsused highlight the special- some of copy (FTIR).This article will spectros- transform infrared Fourier and (XRD), diffraction X-ray spectroscopy (SEM-EDS), microscopy–energy dispersive electron scanning use routinely appropriate, scientists deemed When samplingartis a workof applied without sampling. that be heritage sciencecan cultural are toolsof (XRF) also The ultimatesleuthSherlock

Credit: WAM ment asurfacepreparedusinglooseabrasives. cone impressionfromCrocodileat40xclearlydocu- long photomicrograph.(c)RTIand(d)SEMofsili- ficult todiscernonCrocodile’ssurfaceinthis10-mm- Bourne Foundation,2013.(b)Toolmarksaredif- and attributedtoancientCostaRica;giftofJohnG. (15.7 cmhigh)carvedinAtlanticWatershed-style Crocodile EffigyPendant(WAMNo.2009.20.273) Figure 1.Authenticallyancientornot?(a)Jade (a)

Credit: Susan Tobin; WAM tor performance? nide pigmentsresult insuperiorsemiconduc- nisms of100-year-old cadmiumsulfo-sele- mecha- Can understandingthedegradation regularly spaced parallel lines. regularly spaced sives that marksappearingasfine, leave algorithms to capture micrometer-scale technique thatcomputer mentation uses mial texturemapping, is aphoto-docu to aspolyno referred (RTI). RTI,once imaging transformation reflectance and stereomicroscopy, SEM, including ods, using severalimaging inspected meth were the surface silicone moldsof and tool marks artifact (Figure1),surface During a recent study of a jade of During arecentstudy (d) (c) (b) 1

Credit: Susan Tobin; WAM - - - 21

Credit: Susan Tobin; WAM Discovering the material secrets of art: Tools of cultural heritage science detail, texture, and even color of surfac- lotus blossoms are made from es.2 This study confirmed authenticity of a different material that is not the artifact and showed that lower-cost steatite, but probably Egyptian RTI provides comparable results to tradi- faience—a partially sintered tional, but expensive, SEM imaging. quartz-containing ceramic with surface vitrification. Under UV Illuminating art with UV and IR radiation (Figure 2(d)), the fluo- Various types of illumination are rescent remnants of a glaze on (a) (b) central to the toolkit used to investigate top of the steatite were clearly art. Generally considered nondestruc- visible in the recesses and inter- tive during the short exposure times of stices of the incised lines and an examination, UV and IR can reveal suggested the steatite was fired, or differentiate many materials that the probably to harden the nor- unaided eye cannot. For example, Figure mally soft stone substrate and 2 illustrates an inlaid steatite (or “soap- set the glaze. stone”) Egyptian Pectoral with Scarab from (c) (d) 1292–1070 B.C. The pigment known Peering inside—CT scan- Credit: Susan Tobin; WAM as “Egyptian blue” is a synthetic calcium ning and X-radiography Figure 2. (a) Under normal light, this steatite Egyptian copper silicate compound with a charac- Examining an artwork’s Pectoral with Scarab (WAM No. 42.91) (9.5 cm high) teristic bright-white visible-light-induced interior often is instructive for from 1292–1070 B.C. shows many colored inlays. (b) IR fluorescence.3 Egyptian blue is one of determining how an object was Using visible-light-induced IR fluorescence, Egyptian few artists’ pigments with an end-of-use made, but it is very difficult blue pigment appears bright white. (c) Reflected IR date. Although Egyptians used it from or sometimes impossible to easily distinguishes Egyptian faience (white) from the at least 2500 B.C., the method for mak- achieve. X-radiography can help steatite (gunmetal gray). (d) Remnants of glaze, which are preserved primarily in the recesses and interstices ing it appears to have been lost around discover how an object was of incised lines, appear bright-white under UV. the fall of the Roman Empire, A.D. made with details regarding its 400. Therefore, the presence of Egyptian construction or use. For example, it tal plate). CT scanning compiles X-ray blue pigment indicates a paint created can reveal joins or points of attachment images obtained in thin sub-millimeter- in ancient times, as opposed to a more that are not visible to the eye. It also or even micrometer-thick slices. As a modern restoration that might have been can show the contents of internal cavi- result, CT scan images may be easier to applied to enhance the value of an object ties of hollow objects, which provide interpret. In the case of the 2,000-year- for sale. clues to how the civilization used them. old ceramic figure from ancient West At the lower edge of the pectoral, An X-radiograph records variations Mexico (Figure 3), X-radiographs sug- the register of stylized lotus blossoms in density, with greater densities appear- gest that the head, body, and legs were retains four of the original shield-shaped ing lighter because of absorption of hand-built, but it was difficult to clearly inlays that appear indistinguishable from X-rays. Although it is an incredibly use- discern just how. A CT scan allowed the steatite support under normal light ful tool for many artifacts, interpreting a clear view of the interior walls, mak- (Figure 2(a)). Vsible-light-induced IR an X-radiograph can be quite complicat- ing it apparent that overlapping slabs fluorescence (Figure 2(b)) indicated that ed, because it records the density varia- of clay were used to create the figure. these regions contained Egyptian blue tions of a three-dimensional object onto Additionally, it appears that the legs, pigment. However, reflected IR (Figure a two-dimensional surface (formerly torso, and head were created separately 2(c)) clearly showed that these stylized film, but more commonly today a digi- and then joined.4

Figure 3. (a) Standing Female (a) (b) (c) Figure (WAM No. 2009.20.62) (38.5 cm high) from Nayarit in ancient West Mexico (Lagunillas “C” type) was produced between 300 B.C. and A.D. 200 from bur- nished, slip-painted earthenware; gift of John Bourne, 2009. (b) X-radiograph and (c) CT scan of the figure show joins, suggesting that sections were created separately then affixed to one another. Credit: U. of Maryland Medical Center Credit: Susan Tobin; WAM Credit: Susan Tobin; WAM

22 www.ceramics.org | American Ceramic Society Bulletin, Vol. 93, No. 7 Discovering materials interactions grant through the Institute of Museum with FTIR and Library Services to retrofit exhibition FTIR can be extremely useful to iden- cases. This included replacing fabrics in tify materials by providing information cases with paint to diminish exposure of regarding how elements are combined. In objects to pollutants. This project resulted the instance of the ceramic Mycenaean in a change of protocol and materials for Jug in Figure 6(a), FTIR helped answer all new case construction. In this way, important questions about the appear- materials studies informed materials ance of a crystalline growth on the inte- selection decisions regarding exhibit con- rior rim of this low-fired ceramic vessel struction to best preserve collections of (Figure 6(b)). The crystals appeared while cultural heritage for the future. the object was on display, and museum conservators knew the crystals were not Deterioration or artistic design—

Credit: Susan Tobin; WAM part of the jug’s archaeological history. XRD and SEM Figure 4. XRF analyzes elemental differ- Indeed, the crystals actually were forc- Determining if the appearance of an ences between blue and violet Montana ing their way through the ancient slip- artwork results from its history and merits (or Yogo Gulch) sapphires used to form decorated surface, causing damage to the preservation or if its appearance is a prod- the petals of the Iris Corsage Ornament. object, as observed with an optical micro- uct of decomposition or deterioration is scope (Figure 6(c)). not always as obvious as in the preceding Identifying chemical The spectrum of an FTIR analysis case. For example, conservators noticed elements—XRF conducted through a microscope in trans- the presence of a white crystalline mate- Some consider XRF the most pow- mission mode, with a microsample com- rial on the surface of the Venetian glass erful nondestructive analytical tool pressed between diamond plates, identi- Ewer (Figure 7(a) and (b)) while preparing in the arsenal of the cultural heritage fied the crystals as a hydrated calcium it for exhibition. Because this artwork was scientist. During the past 50 years, XRF acetate compound.6 Organic acids in the created in the late 19th or early 20th centu- has helped build a rich database of the form of acetates and formates from exhi- ry with the intention of appearing ancient elemental compositions of artwork sur- bition materials can be a serious pollution or antique, the question arose whether faces. In very dense materials, such as problem in the museum environment. the accretion indicated an unstable glass gold-based materials, XRF can identify Potential polluting organic materials composition or if it was evidence of the elements to a depth of 25 μm below the include wood (particularly oak) and wood “antiquing” process used by the creator surface. In less dense materials, XRF products, fabrics, and adhesives. In this and, therefore, ought to be preserved as can identify elements several hundred case, the analytical results led to a federal part of the object’s history. micrometers deep—sometimes at parts- per-million concentrations. Historically, (a) (c) XRF instrumentation used for art analysis was comparatively bulky or had to be used in a lead-lined room, which required transportation of artwork to the analytical instrument. This is not an issue when the object is small and portable, such as the Tiffany Iris Corsage Ornament pictured in Figure 4. Many objects worth studying are not so easily moved. During the past decade, (b) portable XRF instrumentation has come of age to allow routine, on-site analysis of monumental artifacts that cannot be moved. For example, certain sections of the life-sized, wall-mounted Adam and Eve glazed terracotta relief shown in Figure 5 were suspected of being resto- rations (Figure 5(c)). Using a portable Credit: Susan Tobin; WAM instrument, XRF analysis distinguished original Renaissance parts from later Figure 5. (a) and (b) A portable XRF spectrometer analyzed the glazed surface of the Adam and Eve restoration additions based on elemental life-sized (WAM No. 27.219) (280 cm high) created by Giovanni della 5 Robbia in Italy circa 1515. (c) The red shadowing indicates areas of suspected restora- differences in the glazed surfaces. tions, which were confirmed by XRF.

American Ceramic Society Bulletin, Vol. 93, No. 7 | www.ceramics.org 23 Discovering the material secrets of art: Tools of cultural heritage science

(a) (b) (c) Figure 6. (a) Long-Beaked Jug (WAM No. 48.2098) (27 cm high) from Mycenae, circa 1425 B.C.; museum purchase in 1957. (b) Top view shows growth of new, unknown crystals in jug opening. (c) This microscopic image of the 0.5-mm-wide crystals in-situ shows deterioration of the ceramic body from volume expansion during crystallization

Credit: Susan Tobin; WAM of hydrated calcium acetate.

XRD analysis identified the accretion of the maker’s antiquing technique, revealed the Walters and the Dumbarton as malladrite, a sodium fluorosilicate. thus it was preserved.7 ceramics were of the same compositional This mineral occurs in the vicinity of group, providing strong evidence of a Italian volcanoes, including Mount Teasing out provenance with neu- substantial connection to the Byzantine Vesuvius, near where the object was tron activation analysis capital for the Walters tiles.8 created in Venice. However, the ques- Sometimes the scientific study of art- tion remained whether the object itself work materials helps inform the history Work in-progress: Examining a was decomposing. Extracting a small or origin of an unprovenanced, undocu- pigment particle with FIB and TEM sample that included the glass and the mented artwork. Such was the case for Perhaps one of the most exciting accretion for SEM-EDS analysis showed a vast collection of more than 1,000 opportunities for materials analysis in with certainty that the white material Byzantine ceramic tiles and tile fragments cultural heritage science occurs when a had been applied, because fluorine was that were purchased as a group by the conservator observes something unusual detected only in the accretion, not in Walters in 1956 from an art dealer. This in an artwork, such as a material beyond the underlying glass substrate (Figure dealer purchased the collection at the common experience. Determining what 7(c) and (d)). In this case, material anal- Istanbul Bazaar, so little information it is, or simply knowing more about it, ysis informed the proper conservation existed about the context or geographical provides potential lessons about the of the object during its preparation for origin of this important collection of figu- artwork or its materials. This situation exhibition—the accretion was evidence rative and decorative tiles. Made approxi- occurred at the Walters with the observa- mately 1,000 years ago, such tiles (a) (b) are rare and likely served as deco- (a) rative schemes for the interior of small chapels or sacred spaces. A similar group of tiles of known provenance in the col- (c) lection at Dumbarton Oaks (Washington, D.C.) was excavated by M. Ramazanoglu from a site in Constantinople, the Byzantine capital known today as Istanbul, Turkey. The Walters tiles appeared (b) (d) to be similar but differed in sig- nificant ways. Therefore, scientists compared trace element compositions of the ceramic bodies to try to establish a secure connection Credit: Susan Tobin; WAM to the Byzantine capital. Drilled Figure 7. (a) Italian glass Ewer (WAM No. samples from the ceramic body of 47.339) (17.6 cm high) by Salviati and Co., the Walters tile fragments were Credit: Susan Tobin; WAM produced in the late 19th or early 20th century to mimic the style and appearance of ancient glass. compared with Dumbarton tile Figure 8. (a) Painted icon wall tile of St. (b) Neck detail shows white encrustation on the fragments using neutron activation Nicholas (WAM No. 48.2086) (15 cm glass. (c) Backscattered electron image of a sam- analysis (Figure 8). high) from Byzantium, 10th century; muse- ple from the surface shows the polygon shape Cluster analyses of the neutron um purchase in 1956 and partial gift of of surface encrustations. (d) Energy-dispersive activation results for 53 major, Robert E. Hecht Jr., 1957. (b) Fragment of map of fluorine (green) and silicon (red) shows minor, and trace elements at Byzantine tile (WAM No. 48.2086 CV2) analyzed by neutron activation analysis. fluorine located in the encrustation but not in the parts-per-million concentrations underlying glass.

24 www.ceramics.org | American Ceramic Society Bulletin, Vol. 93, No. 7 (a) (b) (d) (e)

the afterlife of the individual portrayed (Figures 9(b) and (c)). To identify this material, conservators removed a tiny sample of the unusual purple paint, Credit: Jatuporn Burns and Yaqiao Wu Credit: Susan Tobin; WAM retrieving a single particle about 20 μm (f) in diameter for analysis—too small for (c) XRD and susceptible to damage or burn- ing during Raman analysis. The single particle was mailed to Darryl Butt, distinguished material science and engineering professor at Boise State University (Idaho). His team manipulated

Credit: Jatuporn Burns and Yaqiao Wu the particle with an eyelash for SEM–EDS Figure 9. (a) Portrait of a Bearded Man (WAM No. 32.6) (40 cm high) is an encaustic analysis and confirmed the presence on wood Roman-Egyptian mummy portrait circa A.D. 170. (b) Detail of lower right side of chromium. Subsequently, he used a of portrait showing original mummification residues on top of sparkly purple paint. (c) focused ion beam (Figure 9(d)) to create Detail of gemlike particles with a millimeter-scale bar. (d) Focused ion-beam slices of a thin sections of the particle for analysis purple paint particle. (e) Purple paint under UV radiation shows characteristic orange using transmission electron microscopy fluorescence of an organic lake pigment. (f) TEM micrograph of the pigment's interior, (TEM). The results showed that the inte- including a light gray matrix, black irregularly-shaped spherical parrticles, and needle- rior of the particle contained an organic shaped particles rich in aluminum. phase rich in aluminum, potassium, and tion of unusual purple, gemlike particles Usually, chromium indicates a modern sulfur, with small amounts of iron. embedded in paint used for the Portrait pigment because it was not used exten- Although this examination is a work of a Bearded Man mummy portrait, pro- sively as an intentional coloring agent in progress, these findings are consistent duced in Egypt around A.D. 170 (Figure until after the element’s “discovery” in with the use of a lake pigment, corrobo- 9(a)). The purple paint was used for 1797. However, resinous residues of the rating initial findings using ultraviolet the figure's clavi, a fashion element on original mummification process covered radiation that revealed the characteristic the shoulder of a toga used to indicate the purple paint, confirming that the orange fluorescence of a lake pigment senatorial or equestrian aristocratic rank unusual purple pigment particles were (Figure 9(e)). Lake pigments are cre- (and from which today’s word clavicle, ancient, not modern. Given the gem- ated by affixing an organic dye onto an meaning shoulder bone, comes). like appearance, it was suggested that inorganic substrate, usually using a poly- Elemental analysis of the unusual semiprecious stones, perhaps ground-up valent metal ion as a mordant that joins purple particles using XRF revealed garnets or spinels, were mixed into the them. Structurally, lake pigments are the presence of chromium and iron. paint to enhance the perceived status in poorly understood. However, the TEM Glossary of tools for discovery in conservation science Stereomicroscopya X-radiographyg that are difficult to access and some subsurface features. Stereomicroscopy views objects through a two-eyepiece X-ray imaging reveals structure based on specimen density Transmission electron microscopyh optical microscope, or stereomicroscope. The technique variations. Higher-density regions appear more white on a High-energy electrons image ultrathin samples at resolutions images samples in three dimensions and is especially useful grayscale image, and voids appear black on the image. of 1 to 2 Å. In diffraction mode, TEM provides crystallographic for characterizing depth and contrast detail. X-ray diffractometryh orientation data, and, similar to SEM-EDS, can provide im- Reflectance transformation imagingb Crystal lattice planes diffract incident X-rays, which interfere ages based on elemental contrast. RTI photographs surface shape and color. Applying compu- with each other constructively to generate a spectrum of tational methods enables lighting of the sample from any peaks that is characteristic for a given material. References (accessed 8/11/2014) direction as well as enhancing shape and color features. Fourier transform infrared radiation analysisi ahttp://www.nikonsmallworld.com/techniques/main/ Ultraviolet and infrared illuminationc,d Infrared radiation transmitted through a specimen creates a stereomicroscopy Ultraviolet light wavelengths range from 400 to 10 nm, which spectrum unique to the molecular structure of the material. bhttp://culturalheritageimaging.org/Technologies/RTI/ is shorter than visible light and longer than X-rays. Infrared Scanning electron microscopy (with BSE and EDS)j wavelengths are longer than visible light and range from 700 High-energy electrons interact with solid samples to provide chttp://en.wikipedia.org/wiki/Ultraviolet to 1 mm. images of surface morphology. Elastic collisions between dhttp://en.wikipedia.org/wiki/Infrared 3 Visible-induced luminescence the electron beam and the sample emit backscattered ehttp://archaeometry.missouri.edu/xrf_overview.html Images based on the reflective properties of luminescent electrons (BSE) to create high-resolution composition maps. fhttp://en.wikipedia.org/wiki/X-ray_computed_tomography surfaces in the near-infrared range (800–1,700 nm) aid the Energy-dispersive X-ray spectroscopy (EDS) captures emitted spatial characterization of historical blue pigments. X-rays, which can be correlated to characteristic elements for ghttp://www.vam.ac.uk/content/journals/research-journal/ issue-03/x-radiography-as-a-tool-to-examine-the-making- X-ray fluorescence spectroscopye compositional analysis. and-remaking-of-historic-quilts/ An external energy source, such as a high-energy electron Neutron activation analysisk beam or X-ray, excites individual atoms, which emit X-ray NAA measures characteristic radiation from radionuclides hhttp://www.eag.com/mc photons with characteristic wavelengths. The characteristic that results from neutron irradiation of the specimen and ihttp://mmrc.caltech.edu/FTIR/FTIRintro.pdf wavelength identifies elements present, and the number of provides qualitative as well as quantitative element analysis. jhttp://serc.carleton.edu/research_education/geochemsheets/ photons determines the proportion. Focused ion-beam spectroscopyh techniques/SEM.html f Computed tomography Commonly used to precision cut small samples, the focused khttp://www-pub.iaea.org/MTCD/publications/PDF/te_1215_ CT involves digital construction of a three-dimensional image ion-beam instrument can image samples by detecting elec- prn.pdf of an object’s interior from a series of two-dimensional trons emitted from the ion beam’s interaction with the mate- scans, usually generated by X-ray irradiation. rial. The technique allows characterization of small features

American Ceramic Society Bulletin, Vol. 93, No. 7 | www.ceramics.org 25 Discovering the material secrets of art: Tools of cultural heritage science

laborating with the University ACerS Art, Archaeology, of Maryland and Conservation to explore and develop atomic Science Division layer deposi- The AACS Division mission is to advance the tion (ALD) of scientific understanding of materials found in amorphous alu- ceramic art and to provide information that minum oxide aids in the interpretation and preservation of on silver art to traditional ceramic art and artifacts as well as add an imper- the techniques and technologies used in their ceptible, stable creation. AACS strives to help ACerS members Credit: Ray Phaneuf Credit: Susan Tobin; WAM barrier coating better appreciate the artistic side of ceramics; Figure 10. (a) Amy Marquardt, graduate researcher at the University to reduce tar- work cooperatively with others in the field of Maryland Nanocenter, prepares samples. (b) At their 2013 annual nish. This proj- (e.g., craftspeople, historians, archaeologists, curators, conservators, and conservation sci- meeting, U.S. art conservators compared three 70-year-old silver art ect is funded objects: one with traditional polymeric coating (top), one with the new entists); attract and train the future workforce by the National ceramic ALD coating (middle), and one without coating (bottom). All in this area; stimulate interest and foster inter- of the 27 professional evaluators agreed the new ceramic coating Science actions in this area; reconstruct older ceramic was acceptable for museum exhibition. Foundation. technologies; and improve public understand- Tarnish, or ing and appreciation of ACerS, professional images from this study provide the first- the corrosion of highly polished silver societies, and ceramists and ceramics (artistic ever visualization of the internal struc- surfaces, is a monumental problem for and industrial). For more information, visit ture of an ancient lake pigment (Figure art collections throughout the United www.ceramics.org/divisions/art-division. 9(f)). It remains to be determined if the States and the world. Removing tarnish chromium was intentionally added dur- by polishing in preparation for exhibi- based barrier coatings reduce the reaction ing the creation of the lake pigment, per- tion removes silver metal. In fact, if of silver metal with tarnishing pollutants, haps to modify the hue, or if the occur- a hallmark stamped onto silver to a but they have a lifetime of only 10 to 20 rence is unintentional. XRF analysis of depth of 0.5 mm was cleaned every few years. ALD, a technique developed by a second mummy portrait also detected months, the hallmark would disappear nanotechnology researchers, may prove the presence of chromium in the purple in just more than 40 years.9 The develop- an alternative preservation strategy. The paint, suggesting that a mordant rich in ment of a long-lasting barrier coating to technique is being refined to precision- chromium was favored in ancient Egypt. reduce tarnish, suitable for one-of-a-kind deposit nanometer-thick films of metal silver artifacts, would significantly reduce oxide on silver-metal artifacts to reduce Preserving art for the future the costs and labor devoted to mainte- corrosion (Figure 10). The service life of Besides characterizing artifacts, cul- nance and preservation of silver artwork. the metal oxide coating could be more tural heritage scientists apply materials The standard practice in art conserva- than 100 years, but by mixing getters, science knowledge to appropriately con- tion to reduce silver corrosion is to hand- such as zinc oxide, into the deposited serve artifacts for future study and appre- apply a solvent-based polymeric coating film, the lifetime of the coating may be ciation. To this end, the Walters is col- on artwork—a tedious process. Polymer- extended by many hundreds of years.

Walters Art Museum celebrates eight decades of art More than two-thirds of the 35,000 objects at the Walters were acquired (Below) The Walters Art Museum introduces Baltimore youngsters to conservation by the Baltimore liquor merchant and railway tycoon, William T. Walters science. Here, Glenn Gates explains how nanotechnology coatings can preserve (1819–1894), and his son, Henry (1848–1931). The elder Walters began silver art and prevent metal loss from traditional, abrasive polishing. opening his home to the public in 1874, a tradition he continued almost annually. The proceeds of these openings, where admission cost 50 cents, were donated to the Baltimore Association for the Improvement in the Condition of the Poor. Following William’s death, Henry continued to build the collection, opening his palazzo-style museum building to the public in 1909. The gallery’s buildings and contents were given to the city of Baltimore when Henry died in 1931. Now known as the Walters Art Museum, it opened as a public institution in 1934. That same year, the Walters hired a staff scientist, becoming the third art museum in the U.S. to do so, after the Fogg at Harvard and the Freer Gallery. The 80th anniversary of the Walters opening will be celebrated with a special exhibition, From Rye to Raphael: The Walters Story, on view at the museum from October 26, 2014. For more information, visit www.thewalters.org. Credit: Susan Tobin; WAM 26 www.ceramics.org | American Ceramic Society Bulletin, Vol. 93, No. 7 Getting involved in cultural involved—learn what you can bring to raphy-based digital imaging techniques for heritage science the study of cultural heritage and what museums”; presented at VAST 2010, The There are many ways to become ancient artifacts may be able to teach 11th International Symposium on Virtual Reality, Archaeology, and Cultural Heritage, involved in cultural heritage science. the modern ceramic engineer. Paris, 2010. The NSF solicited proposals in 2010, 3G. Verri, “The application of visible- 2011, and 2012 under the SCIART and Acknowledgments ALD work was supported by NSF induced luminescence imaging to the CHS programs and now funds unsolic- examination of museum objects”; Proc. SPIE Award No. 1041803. Julie Lauffenburger ited research in the field. Increasingly, 7391, O3A: Optics for Arts, Architecture, art museums feature scientific studies of and Greg Bailey at the Walters greatly and Archaeology II, 739105 (2009). art alongside more traditional stylistic helped with this article, and their assis- doi:10.1117/12.827331 tance is much appreciated. Photography by or art historical presentations. If you 4D. Reents-Budet, “Mesoamerica”; p. 74 in appreciate this, make sure you let the Susan Tobin unless otherwise indicated. Exploring Art of the Ancient Americas. Giles, museum know so that such program- London, 2012. About the author ming can continue. Some major muse- 5G. Bailey, personal communication. Glenn Gates is conservation sci- ums have science laboratories and may 6 entist at the Walters Art Museum in J. Giaccai, Walters Art Museum, Analytical offer volunteer opportunities. Report, 2008. Of course, professional societies, Baltimore, Md., and vice-chair of the 7A. Elliott and J. Giaccai, “The technical such as ACerS, are always a great way to AACS Division of ACerS. Contact at [email protected]. analysis of a glass Ewer by Salviati & Co.,” extend professional networks outside of The Journal of the Walters Art Museum, 70–71, personal areas of expertise. The AACS 133–37 (2012–2013). Division of ACerS is looking for vol- References 8J. Lauffenburger and J. Williams, “Byzantine 1 unteers to help with fundraising, work- J. Lauffenburger, “Approaches to authenti- tiles in the Walters Art Gallery and shop organization, and annual meet- cation”; pp. 198–200 in Exploring Art of the Dumbarton Oaks collections: A comparison ings. For people looking to get into the Ancient Americas. Giles, London, 2012. of technique”; Ch. 5 in Materials Analysis field, graduate and postgraduate edu- 2M. Mudge, C. Schroer, G. Earl, K. Martinez, of Byzantine Pottery. Dumbarton Oaks, cational opportunities in cultural heri- H. Pagi, C. Toler-Franklin, S. Rusinkiewicz, Washington, D.C., 1997. ISBN 0-88402-251-X. tage science continue to increase, with G. Palma, M. Wachowiak, M. Ashley, N. 9D. Stevens, “The effects of fingerprints on programs at Harvard, Northwestern, Matthews, T. Noble, and M. Dellepiane, silver,” V&A Conservation Journal, 59, 12–13 “Principles and practices of robust, photog- and the University of Delaware. Get (2011). n Order today!

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