Douglas et al. Herit Sci (2018) 6:49 https://doi.org/10.1186/s40494-018-0214-1

RESEARCH ARTICLE Open Access Materials characterization of the Ruby Slippers from the 1939 classic flm, The Wizard of Janet G. Douglas1, Gwénaëlle Kavich1*, Chika Mori2, Dawn Wallace3 and Richard Barden3

Abstract This article presents a comprehensive materials characterization of a pair of Ruby Slippers used in the 1939 classic flm The , which has been one of the most popular objects on exhibition at Smithsonian’s National Museum of American History (NMAH) since it entered the collection in 1979. The shoes have been on almost constant display with few instances for study during its time at NMAH, and they remain one of the most visited objects within the museum. Plans for an upcoming permanent exhibit, and visible deterioration of the decades-old shoes, led to the present study, which the frst phase of a major efort to preserve this iconic item of cultural heritage for future generations to enjoy. Materials characterization was used to determine the composition of construction materials and condition of the Ruby Slippers to help plan for the optimal environmental conditions for continued display. The current study is also viewed as a valuable opportunity to learn about the original construction and subsequent history of the Ruby Slippers to inform and enrich NMAH’s curatorial research, public programs, and media initiatives. Analyti- cal methods used to characterize the shoes’ components include micro-X-ray fuorescence spectroscopy (µ-XRF), micro-Fourier transform infrared spectroscopy (µ-FTIR), polarized light microscopy (PLM), and high-performance liquid chromatography–diode array detector–mass spectrometry (HPLC–DAD–MS). Keywords: Ruby Slippers, Sequins, Gelatin, Cellulose nitrate, Rhodamine B, Materials characterization, Technical study

Introduction Te Ruby Slippers were designed by Gilbert Adrian, Te classic 1939 flm Te Wizard of Oz is a fantasy tale the chief costume designer for Metro-Goldwyn-Mayer about Gale (a farm girl played by Judy Studios (MGM) from 1928 to 1941 [1]. Te flm’s cos- Garland), and her journey through the magical Land of tume designers altered commercial pump-style shoes Oz. Te flm is based on the 1900 novel Te Wonderful by dyeing them red, attaching red netting covered with Wizard of Oz by L. Frank Baum (1856–1919). Te Smith- red sequins to the exterior fabric and heels, and attach- sonian’s Ruby Slippers (Accession No. 1979.1230) were ing beaded bows on the center of the toes. Several sets of donated anonymously to the National Museum of Amer- Slippers were made for the flm, a common practice with ican History (NMAH) in 1979 and have been on display important costumes and props. Tese items can get dam- almost continuously since that time. Te Ruby Slippers aged during flming or may be adapted for certain uses are treasured by museum visitors from across the United and scenes during production. Te Ruby Slippers were States and around the world, and will be featured in a likely worn by Garland in the dance scenes, because the new exhibit, Ruby Slippers and American Culture Dis- felt glued on the soles is said to have mufed the sound of plays, in October 2018. her dancing footsteps on the wooden . Te Ruby Slippers were warehoused among other Te Wizard of Oz costumes and props in Los Angeles *Correspondence: [email protected] by MGM until they were rediscovered in 1970 [1]. No 1 Museum Conservation Institute, , Suitland, MD, USA information is available on the environmental condi- Full list of author information is available at the end of the article tions under which the shoes were stored before they

© Smithsonian Institution 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Douglas et al. Herit Sci (2018) 6:49 Page 2 of 25

came to NMAH, but it is unlikely that they were con- sistently stored in a climate-controlled environment. QuarterQuarterh heeleell liningsinings vary in shape While on display at the museum, however, the shoes have always been under controlled museum-level conditions of relative humidity, temperature, and light conditions. Interior manufacturingmanufacturing Between 40 years of unknown history and being on dis- marks do notnot matcmatch play for almost another forty, signifcant deterioration is clearly visible. Obvious examples include discolored and dull sequins, cracks in the sequins’ red coating, and fad- ing of the dyed netting. Te shoes’ composite materials may react diferently depending on environmental condi- tions and their degree of deterioration. An understanding of the materials present, the construction of the shoes, and their current condition was needed to support a long-term conservation strategy. In 2016 NMAH staf requested Smithsonian scientists to conduct a materials characterization survey to serve Throat is lowerlowera andnd widerwider as a foundation for their planned Kickstarter campaign on thethep p.r..r.sshoe,hoe, comparedcompared to thethep p.l..l.sshoehoe (see: https​://www.kicks​tarte​r.com/proje​cts/smith​sonia​ Fig. 1 Dorothy’s Ruby Slippers (NMAH, Accession No. 1979.1230; n/conse​rve-dorot​hys-ruby-slipp​ers) to generate funding each shoe is 12.70 cm 7.62 cm 24.13 cm). Physical diferences × × for research into the future conservation and preserva- between the shoes indicate they are not a matched pair. Ruby tion of the Ruby Slippers in preparation for the upcom- Slippers from The Wizard of Oz used courtesy of Warner Bros. ing exhibition. Te main purpose was to characterize the Entertainment Inc. TM and © Turner Entertainment Co. Ruby Slipper’s materials and their condition, as well as posit mechanisms of deterioration. Te fndings helped plan the Kickstarter research and informed decisions in selecting the most appropriate exhibition conditions for 2. Te shoe was dyed red by the flm’s costumer design- their continued display such as relative humidity, and ers. temperature. Other issues currently being addressed 3. A template of the shoe’s upper was cut out of a red through the Kickstarter research include whether an fne-mesh netting, to which red sequins was sewn. anoxic or low oxygen environment would be appropriate, 4. Te sequined netting was then sewn to the faille of and the efects of light levels and spectral quality for their the shoe including the upper and heel. continued display. 5. Te bows were handcrafted out of a stif, loose weave Te materials characterization phase is also viewed as red fabric support covered in the same red mesh, to a valuable opportunity to learn about the original con- which red beads and rhinestones (referred to here as struction and subsequent history of the Ruby Slippers to “stones”) were attached. Te beads (three large rec- inform and enrich NMAH’s curatorial research, public tangular and many bugle) were sewn directly to the programs, and media initiatives. bow, while the stones were held by prong settings which are sewn to the bow. Te fnished bow is sewn Materials at the top center of the vamp. Shoe parts referred to in this study include the heel, 6. Te sole was painted red, presumably to complete insole, quarter lining, sole, throat, upper, and vamp.1 the red appearance over the entire shoe. Each shoe is similarly constructed as described below: 7. A layer of orange felt was glued to the shoe’s sole pre- sumably to dampen the sound during dancing. Te 1. A commercial pump-style shoe with a decorative p.r. shoe has an additional layer of orange felt glued faille fnish was purchased. over the frst.

As observed by NMAH’s staf prior to our study, the 1 Basic defnitions of shoe parts are as follows: heel—the part of the sole Ruby Slippers are comprised of two shoes from difer- that raises the rear of the shoe in relation to the front; insole—the inner fat ent pairs, as evidenced by some visual diferences (Fig. 1). bed of the shoe on which the foot rests; quarter lining—a covering applied Te shoes difer in the shape of the quarter linings, inte- to the inner rear and sides of the shoe; sole—the entire part of the shoe below the wearer’s foot; throat—upper middle portion of the shoe, upper— rior manufacturing marks, and the height of the throat. the part of a shoe that cover the toes, the top and sides of the foot, and the Te proper right (p.r.) shoe’s quarter lining is “V” shaped, back of the heel; vamp—the section of upper that covers the forefoot. Douglas et al. Herit Sci (2018) 6:49 Page 3 of 25

while the proper left (p.l.) shoe’s quarter lining has an Polarized light microscopy (PLM) “hourglass” shape. Te interior manufacturing mark A polarized light microscope (Nikon Eclipse E600, Tokyo, of the p.l. shoe is stamped with the model number “5 C Japan) coupled with a SPOT Pursuit Peltier cooled cam- 11869 D536”, while the p.r. shoe insole is stamped with era with 1.4 mega pixel resolution was used for fber a diferent model number, “5 BC 152504” and “INNES identifcation. Each fber sample was extracted using fne SHOE CO., LOS ANGELES, PASADENA & HOLLY- tweezers under magnifcation and placed with distilled WOOD”. Te throat of the p.l. shoe appears larger and water on a glass microscope slide with coverslip. Tis rises higher on the foot than that of the p.r. shoe. Finally, process provided temporary slide mounts that allowed the p.r. shoe is 3 mm longer than the p.l. shoe. sample reuse should further analysis by other methods be Possible later repairs were made on the p.r. shoe, desired. Te PLM samples were studied by comparison including the replacement of red stones with colorless to bleached spun silk, cotton, and wool fber references ones that are painted red. We might expect this type of from Testfabrics, Pittston, PA, USA (see: http://www.testf​ mechanical damage to be present since the Ruby Slippers abric​.com). Fiber identifcation was based on the obser- were probably heavily used during the flming. Docu- vation of the fber structure and diameter, with consulta- mentation of these later amendments to the shoes help tion of reference literature [2–6]. conservators understand change over time, and hence, more about their use as costume props. High‑performance liquid chromatography–diode array detector–mass spectrometry (HPLC–DAD–MS) Analytical methods Dye analysis was performed using a HPLC–DAD–MS Te materials analysis survey was carried out using the (Shimadzu LCMS-2020, Japan) with an automatic injec- non-invasive and minimally-invasive analytical methods tor, gradient pump, and column oven. Separation of as described below to optimize characterization of the colorants was performed on a ­Phenomenox® Luna C18 broad range of materials present on the shoes within the reversed phase column (2 mm dia. × 150 mm long; 3-µm scope and time frame of the study. Because the Slippers particle size), operated at a fow rate of 0.18 mL/min. are not a matched pair, materials from each shoe were Columns were eluted with acetonitrile–water gradients analyzed when possible. containing 0.1% formic acid. An extracted micro-sample of the red coating on detached sequin 1 was dissolved Micro‑X‑ray fuorescence spectroscopy (µ‑XRF) in 50 µL 100% MeOH and pipetted to a 1.5 mL plastic Te µ-XRF instrument (Bruker Artax 800, Berlin, Ger- tube. After purifcation, the mixture was frozen using liq- many), a micro-focus version of an x-ray fuorescence uid nitrogen and evaporated under vacuum to decrease spectrometer with an open-architecture air-path, was volume to 35 µL. Te HPLC–DAD–MS data analysis used to study many components of the Slippers. It is was carried out using LabSolution software ver. 5.1.1, composed of a Rhodium X-ray tube with a poly-capillary and detection was done in both negative and positive ion lens beam focus (beam diameter approx. 100 µm), and an modes. XFlash silicon drift detector (SDD). Measurements were taken using an excitation voltage of 45 kV, a beam current Results of 200 µA, and a 30 s live time. Sampling locations and analysis Non-invasive analysis locations for µ-XRF and sampling Micro‑Fourier transform infrared spectroscopy (µ‑FTIR) locations for µ-FTIR are shown for the shoes in Figs. 2 Te µ-FTIR spectrometer (Termo Nicolet 6700, Madi- and 3. Another technique, HPLC–DAD–MS was used son, WI, USA) was used to study organic materials on for red dye analysis on detached sequin 1. the shoes. It is equipped with an infrared light in the Because µ-XRF is quick and non-invasive, this tech- mid-infrared region (wavelengths from 2.5 to 20 µm, nique was used on most materials including sequins, −1 frequencies between 4000 and 650 cm ), a Continuum prong settings, beads and rhinestones, red paint, felt, microscope, and a MTC-A detector. Each spectrum was and heel materials. Elemental determinations were −1 collected for 64 scans at a resolution of 4 cm . Samples qualitative rather than quantitative: major, minor, were placed and fattened using a diamond cell before and trace designations were estimated to approximate examination in transmission mode, and spectra were the relative intensity of the signal for each element. processed using the OMNIC software v.8.3. Micro-FTIR Micro-FTIR analysis focused on characterization of spectra were identifed using the Infrared and Raman the two detached sequins, various fbers, red paint on Users Group (IRUG) reference libraries, the HR Hummel the soles, adhesive residues, and a red coating found in Polymer and Additives library, and the ASTER mineral library. Douglas et al. Herit Sci (2018) 6:49 Page 4 of 25

Proper right shoe

µ-XRF and µ-FTIR Detached sequin 1

µ-FTIR Detached sequin 2

µ-XRF µ-XRF Colorless stone, Colorless stone, upper p.r. upper p.l. corner corner µ-XRF µ-FTIR Red stone, Red coang on upper p.l. corner colorless stone µ-XRF µ-XRF Red stone, p.l Red stone, side upper p.r. corner µ-XRF Red bugle bead, µ-XRF µ-XRF µ-XRF p.l. side Large red bead, Prong, p.r. side Prong with red coang, p.r. side near center p.r. side near center µ-FTIR µ-FTIR µ-XRF Clear, so adhesive Glossy adhesive, Red paint on sole on heel, between near sole near orange felt sole and shoe

µ-XRF and µ-FTIR Orange felt on central sole µ-XRF Heel nail

µ-FTIR µ-XRF and µ- µ-FTIR µ-XRF Adhesive between FTIR Outsole adhesive Brown heel inner and outer Red paint on (between sole and material orange felt sole near arch shoe) Fig. 2 µ-XRF and µ-FTIR sampling locations on the proper right (p.r.) shoe of the Ruby Slippers. (Some fber sample locations not shown). Ruby Slippers from The Wizard of Oz used courtesy of Warner Bros. Entertainment Inc. TM and © Turner Entertainment Co.

small areas of the bows. PLM was used on textiles and Materials characterization threads to identify fber content. Te following discus- Beads and rhinestones on the bows sion presents the research fndings, and the full results Te µ-XRF analysis of the various glass beads and stones of the materials characterization are summarized in on both bows was used to determine if materials were Appendix (Table 3). identical on both shoes and distinguish original beads and stones from repair materials. Tree types of glass Douglas et al. Herit Sci (2018) 6:49 Page 5 of 25

Proper le shoe

µ-XRF µ-XRF Prong Prong

µ-XRF Large red bead, p.r. side

µ-XRF Red bugle bead, p.r. side

µ-XRF Large red central bead

µ-FTIR µ-XRF µ-XRF and µ-FTIR Adhesive between Red paint on sole Aached sequin, orange felt and sole near orange felt p. l. side near heel

µ-XRF Heel nail µ-XRF andµ-FTIR µ-XRF and µ-FTIR µ-FTIR Orange felt near Red paint on sole Glossy adhesive edge near arch near sole Fig. 3 µ-XRF and µ-FTIR sampling locations on the proper left (p.l.) shoe of the Ruby Slippers. (Some fber sample locations not shown). Ruby Slippers from The Wizard of Oz used courtesy of Warner Bros. Entertainment Inc. TM and © Turner Entertainment Co.

were identifed as shown in Fig. 4 and described as of the bow on both shoes. Major elements are zinc, sili- follows: con, and potassium, while minor elements are iron and selenium. Cadmium is present as a trace. Te type 1 glass Type 1 glass (potash–silica glass, ­K2O–SiO2) Tis type of is consistent with recipes to produce selenium ruby glass glass was found on the large ruby red bead in the center [6], where substantial amount of zinc oxide along with Douglas et al. Herit Sci (2018) 6:49 Page 6 of 25

Fig. 4 μ-XRF spectra illustrating three glass compositions identifed on the bow of the p.r. shoe. Type 1: potash–silica glass, K­ 2O–SiO2 (large red bead, p.r. side), Type 2 glass: potash–lime–silica glass, ­K2O–CaO–SiO2 (red bugle bead, p.l. side); and Type 3 glass: lead–potash–lime–silica glass, PbO–K2O–CaO–SiO2) (colorless stone, upper p.l. corner) selenium and cadmium sulfdes are used to obtain an barium as minor elements. Tese stones are colorless, intense ruby color. and have no selenium and cadmium content as found in types 1 and 2 glasses. Te replacement stones appear to Type 2 glass (potash–lime–silica glass, ­K2O–CaO– have been covered with a red coating, identifed as cel- SiO2) Tis type of glass is similar to the type 1 with the lulose nitrate by µ-FTIR. Te diference in stone color addition of calcium, probably lime delivered. It was found and composition compared to glass types 1 and 2, along on the bugle beads as well as the red stones on both shoes. with the red coating confrmed that these stones were Small diferences in arsenic content shows potential for replacements and painted red to match the original diferentiating between the bugle beads with a slightly stones. Similar colorless stones were not found on the lower amount and the red stones with a slightly higher p.l. shoe. amount. Slightly higher arsenic amounts are consistent in Micro-XRF analysis of the prong settings holding the red stones. Similar to the type 1 glass, the elemental the stones showed that they are primarily composed composition of the type 2 glass indicates additions of zinc of copper (Cu) and zinc (Zn) with various other minor oxide, selenium and cadmium sulfdes which may have and trace elements. Tis fnding is consistent with the been used to obtain the ruby color. fact that as a non-precious alloy, brass was often used in costume jewelry during the early twentieth century. Type 3 glass (lead–potash–lime–silica glass, PbO–K2O– Based on visual inspection and compositional analy- CaO–SiO2) Tis type of glass was found on a few sis of the beads, stones, and metal prong settings, the colorless replacement stones on the bow from the p.r. bows of each shoe were similarly constructed using the shoe. It contains lead, potassium and calcium as major same glass and brass materials. Slight variations in each elements, and silicon, iron, zinc, arsenic, copper, and Douglas et al. Herit Sci (2018) 6:49 Page 7 of 25

Fig. 5 µ-FTIR spectrum from the core of the detached sequin 2, consistent with the presence of protein (IRUG reference spectrum ISR00018). This composition suggests the sequins are made of gelatin

bow’s shape and size can be attributed to their hand- at 1650 and 1280 cm−1, but also strong peaks at 1073 and crafted construction. 841 cm−1 (Fig. 6). A peak at around 1715 cm−1 may be associated with the carbonyl of a plasticizer. Detached sequins 1 and 2 A sample of red cellulose nitrate coating taken from Two detached sequins, both likely from the p.r. shoe, detached sequin 1 showed three colorant peaks in the were examined by µ-FTIR, as well as a sequin still HPLC–DAD–MS chromatogram detected at 550 nm attached to the p.l. shoe. From the p.r. shoe, detached (Fig. 7). Te data suggest that the three compounds likely sequin 1 is in a relatively good condition, while detached have related molecular structures based on their simi- sequin 2 has cracks and losses of its red coating. Results lar UV–Visible spectra and mass. Mass data indicates are consistent with the presence of a protein-based core that these structures likely difer by one (or two) ethyl (– (most likely gelatin) laminated on both sides with a thin CH2CH3) or two (or four) methyl (–CH3) groups, which layer of cellulose nitrate. Te fndings are in agreement could be related to the colorant and its degradation prod- with known compositions of gelatin-based sequins of ucts and/or impurities. Based on mass and UV–Visible similar age reported in the literature [7–10]. spectrum, Peak 3 can be attributed to the red dye Rho- Figure 5 reports the µ-FTIR spectrum of detached damine B. Figure 8 shows similar data for Rhodamine B sequin 2’s core and shows characteristic vibrational bands extracted from a historic reference dye sample (textile consistent with protein (amide I and amide II bands at sample #74, sheet No. 13, see: [11]). 1 1 1644 and 1543 cm− respectively, amide III at 1240 cm− , Te data for the textile sample #74 was found to be the 1 and amide A or N–H stretching around 3304 cm− ). Te same as for the red colorant extracted from detached µ-FTIR spectrum of the red coating on detached sequin sequin 1 from the Ruby Slippers. Te HPLC–DAD–MS 2 shows characteristic features associated with the pres- peaks of the sequin’s red colorant had similar retention ence of cellulose nitrate (strong nitrate group absorptions times and UV–Visible spectra of three peaks detected Douglas et al. Herit Sci (2018) 6:49 Page 8 of 25

Fig. 6 µ-FTIR spectrum from the red coating on detached sequin 2, consistent with the presence of cellulose nitrate (IRUG reference spectrum ISR00066)

compared to this reference sample. Molecular masses of mass is consistent with those found for peaks 1 and 2. A the compounds in the sequin’s red coating matched those possible explanation for the presence of peaks 1 and 2 is of the Rhodamine B reference. that they are by-products remaining from the manufac- Te red colorant from detached sequin 1 was also turing process of Rhodamine B dye, such as the starting compared with a mid-twentieth century chemical-grade material N,N-diethyl-m-aminophenol [12] or an impurity Rhodamine B reference manufactured by Allied Chemi- such as N-ethyl-m-aminophenol. Alternatively, peaks 1 cal and Dye Corporation, National Aniline Division. and 2 may arise from photo-oxidation of pure Rhoda- Te Allied Chemical Rhodamine B reference showed mine B, as described recently by Sabatini et al. [13]. Te the same HPLC elution time, absorption spectrum, and fact that peaks 1 and 2 are much smaller in Fig. 8 com- molecular mass as the sequin’s peak 3. However, peaks 1 pared to Fig. 7 is consistent with the idea that the textile and 2 were not observed in the Allied Chemical sample. sample #74, having been kept in a book away from light Tis fnding suggests that the Rhodamine B used for the and air, may have undergone less photo-oxidation than red sequin coating may have been made by a diferent detached sequin 1. company, and/or at a time when pure starting materials Detached sequin 1 was found to contain a minor were not used to produce the dye. Regardless, the ana- amount of silver (Ag) by µ-XRF. Historically, some manu- lytical data indicate that the red colorant used for the facturers used thin metallic coating (gold, silver, or alu- sequins of the Ruby Slippers is Rhodamine B. minum) laminated with other structural layers of sequins We further hypothesize that the presence of peaks [8], presumably to enhance refective efects. Te silver 1 and 2 can be explained by examining the structure of content was slightly higher on one side than the other Rhodamine B (Fig. 9). If a single ethyl (–CH2CH3) group suggesting a silver-rich layer between the protein-based is missing, the molecular mass would be 415 Da; if two core and the cellulose nitrate coating on only one side. are missing, the mass would be 387 Da. Te molecular Figure 10 shows the extremely thin and fragile silver Douglas et al. Herit Sci (2018) 6:49 Page 9 of 25

Fig. 7 HPLC–DAD–MS analysis results for the red colorant from detached sequin 1. a Chromatogram showing three peaks, 1, 2 and 3; b–d UV– Visible spectra of peaks 1, 2 and 3, respectively

Fig. 8 HPLC–DAD–MS analysis results for Rhodamine B in textile sample #74, sheet No. 13 [11]. a Chromatogram showing three peaks, 1, 2 and 3; b–d UV–Visible spectra of peaks 1, 2 and 3, respectively Douglas et al. Herit Sci (2018) 6:49 Page 10 of 25

Red paint on the shoe soles Te µ-XRF analysis of red paint on the soles of both shoes shows the presence of cadmium, selenium, bar- ium, and sulfur. Tese elements are consistent with the colorant cadmium red lithopone, a mixture of cadmium sulfo-selenide co-precipitated with barium sulfate [14] (Fig. 11). Te red paint on the p.l. shoe also contains a minor amount of zinc, suggesting the presence of a small amount of zinc oxide from the inclusion of zinc white in the paint formulation. A µ-FTIR spectrum of the red paint from the sole of Fig. 9 Molecular structure of Rhodamine B (modifed from [12]). the p.r. shoe is shown in Fig. 12, indicates that the paint Dotted rectangles indicate ethyl (–CH2CH3) groups, some of which formulation is based on cellulose nitrate; the spectrum may be missing in the red colorant found in the thin red coating on for the red paint from the p.l. shoe provided the same detached sequin 1 result. Historically, paints containing cellulose nitrate were mixed with other resins to provide higher gloss [15]. Te presence of an alkyd is also suggested due by a more intense carbonyl peak at 1728 cm−1 and character- istic C–H stretching at 2934 and 2870 cm−1. In addition, the increased intensities in the fngerprint region peaks at 1117 and 1074 cm−1 with shoulder peaks at 1181 and 983 cm−1 suggest the presence of barium sulfate. Micro- XRF analysis of the sole detected barium, selenium, cad- mium, and sulfur as the major elements; consistent with 0.5 mm cadmium red lithopone as the red pigment and barium Detached sequin 1- reflecve side sulfate as a fller.

Adhesives Several adhesives were sampled, including those on detached sequin 2 and on the soles and felt of both shoes. Polyvinyl acetate (PVAc), cellulose nitrate (with camphor plasticizer), poly(ethyl acrylate), and natural resin were 0.5 mm identifed. Te results of the µ-FTIR analysis of these Detached sequin 1 -ma side adhesives are summarized in Appendix (Table 3). As shown in Fig. 13, the µ-FTIR spectrum of the adhe- Cellulose nitrate (Rhodamine B) sive residue collected on detached sequin 2 has spec- Silver troscopic similarities with polyvinyl acetate (PVAc) −1 Protein (carbonyl C=O stretching at 1736 cm , C–H asymmet- ric deformation at 1434 and 1373 cm−1, and the C–O stretching at 1240 cm−1). Tis material is likely con- Proposed layered structureofthe sequins tamination by an adhesive residue on the surface of the Fig. 10 Detached sequin 1 (5 cm 0.2 mm). Top: Refective side, and sequin. PVAc was also found in the adhesives sampled— × a detail showing the presence of a thin silver layer in areas where the to attach the single piece of felt to the p.l. shoe and the cellulose nitrate/Rhodamine B layer has been lost due to degradation. second felt piece over the frst one on the p.r. shoe. Origi- Center: Matt side, and a detail showing no similar silver layer. Bottom: Schematic diagram of the proposed layered structure of the sequins, nally two separate felt layers were thought to be present where the top side is slightly more refective, and the bottom side on the p.l. shoe, but further examination showed only a is more matt. Ruby Slippers from The Wizard of Oz used courtesy of single piece of felt. Warner Bros. Entertainment Inc. TM and © Turner Entertainment Co. A clear, soft adhesive was seen on the heel of the p.r. shoe between the sole and upper. Tis material is thought layer. In exposed areas on some sequins where the cellu- to be a repair as no similar adhesive was seen elsewhere, lose nitrate has been lost, the silver appears to be covered and because its application runs slightly over on to the with a black silver sulfde tarnish. surface of the commercial-style pump. Te µ-FTIR Douglas et al. Herit Sci (2018) 6:49 Page 11 of 25

Fig. 11 µ-XRF spectrum of red paint on soles of both shoes showing similar composition with minor diferences. The presence of Ba, Se, Cd, and S indicates cadmium red lithopone pigment

spectrum of the adhesive of the sample shows charac- fbers. A summary of the results are given in Table 1, and teristic features that may be associated with poly(ethyl more detailed descriptions and micrographs are given in acrylate) (C–H stretching at 2980, 2937, and 2876 cm−1, Appendix (Table 4). Some of the fber samples were also −1 C=O stretching at 1734 cm , C–H bending at 1448 and studied by µ-FTIR, as summarized in Appendix (Table 3); 1380 cm−1, C–O stretching at 1236 cm−1, C–C stretching this method was found to be complementary in confr- at 1169 and 1096 cm−1, and C–H rocking at 854, 787 and mation of the presence of protein such as found in wool 755 cm−1); see Fig. 15 in Appendix. and silk, and cellulose present in plant material. Note that synthetic materials were not found, as they did not Red coating on a colorless stone and prong setting become widely available until several years after the crea- Micro-FTIR analysis was performed on two similar pale tion of the Ruby Slippers. red coating samples taken from a colorless stone and its PLM study of p.r. shoe red netting and the thread used prong setting at the upper p.r. corner of the bow on the for its attachment showed smooth fbers regular in diam- p.r. shoe. Cellulose nitrate was identifed as the coating eter (average 15 µm). Te morphology indicated identif- (Fig. 16 in Appendix), but the red colorant was not iden- cation as silk, consistent with µ-FTIR data showing bands tifed. Te presence of this red coating confrms that this consistent with protein (Fig. 18 in Appendix). Similar colorless stone was added as a repair and subsequently morphology was found on the p.l. shoe for the red thread painted red to match original stones. holding the netting to the shoe and the faille fabric (weft), with average fber diameters of 13 and 12 µm respec- Thread and textile fbers tively. Te average fber diameter for all four samples is Sampling of thread and textile fbers was limited by the close to those reported for silk of 10–13 µm [2]. availability of loose fbers in order to avoid damage to Four fber samples were identifed as cotton, includ- the shoes. PLM samples were extracted from 11 loose ing thread holding sequins to the netting on the p.r. shoe, Douglas et al. Herit Sci (2018) 6:49 Page 12 of 25

Fig. 12 µ-FTIR spectrum from the sole paint near arch, consistent with the presence of cellulose nitrate (IRUG reference spectrum ISR00039)

sequin thread from the p.l. shoe, the structural shoe fab- determination. Te wool fbers have the surface struc- ric, and the woven bow support fabric. Average fber ture of overlapping scales typical of wool. Average fber diameter ranges from 17 to 23 µm, which is within the widths are 24 µm for the p.r. shoe and 30 µm for the p.l. range for cotton, 1–40 µm [2]. Te cotton fbers of the shoe, well within the reported range for wool, which var- bow’s support thread are more rounded in cross-section ies from 10 to 70 µm depending on the fber type and than is typical for natural cotton, which suggests that the species [2]. cotton was mercerized [16]. Te sequin thread from the Te µ-FTIR spectra of the wool fbers from the orange p.r. shoe was also analyzed by µ-FTIR and found to be felt from the p. l. shoe and the outer orange felt from the composed of cellulose (Fig. 19 in Appendix), supporting p.r. shoe (Fig. 17 in Appendix) show characteristic spec- the identifcation of the thread as cotton by PLM. tral features that may be associated with protein. Tis As previously mentioned, the p.r. shoe has two layers fnding supports the wool identifcation by PLM. of orange felt glued to its sole, while the p.l. shoe has a single layer. No signifcant visual diferences in the felts Soles and heels were apparent otherwise. PLM samples of the orange Analysis on the soles and heels was minimal. A PLM outer felt from both shoes were observed to be composed sample from the sole near the arch was taken from the of a mixture of fber that contains orange-dyed wool as it p.r. shoe. Te fbers were found to be light brown with major component. Minor amounts of other fbers, mostly the average width of 7 µm, which are characteristics con- colorless, were also observed by PLM. Te felt from the sistent with leather. p.l. shoe also contained some undyed wool, which was One heel nail on each shoe was analyzed by µ-XRF. not seen in the felt from the p.r. shoe. Tis fnding sug- Te nail of the p.r. shoe (Fig. 14) had a high iron con- gests the felts for the two shoes may be diferent, but tent, suggesting an iron or steel composition. Te nail the small size of the felt samples prevented conclusive Douglas et al. Herit Sci (2018) 6:49 Page 13 of 25

Fig. 13 µ-FTIR spectrum from the adhesive found on detached sequin 2, consistent with the presence of polyvinyl acetate (IRUG reference spectrum ISR00130)

Table 1 Findings of the PLM fber identifcation study. Additional details are given in Appendix, Table 4 Fiber sample Fiber diameter, µm (n 5) Identifcation = Red netting thread, p.r. shoe 15 Silk (dyed red) Red thread holding netting to shoe, p.r. shoe 15 Silk (dyed red) Red thread holding netting to shoe, p.l. shoe 13 Silk (dyed red) Decorative faille shoe fabric, from weft, p.l. shoe 12 Silk (dyed red) Sequin thread, p.r. shoe 17 Cotton Woven bow support thread, p.r. shoe 22 Cotton Structural shoe fabric, p.r. shoe 23 Cotton (possibly mercerized) Sequin thread from toe, p.l. shoe 18 Cotton Orange felt on central sole area, p.r. shoe 23 (wool, dyed orange) Wool (dyed orange), other fbers Orange felt, near edge, p.l. shoe 30 (wool, dyed orange) Wool (dyed orange); undyed wool, cotton, other fbers Sole near arch, p.r. shoe 7 Leather of the p.l. heel had a relatively higher zinc content and Discussion and conclusions lower iron content, suggesting a galvanized iron or steel Te major fndings from the materials survey of composition. Tis fnding is consistent with the silver NMAH’s Ruby Slippers including both the p.r and color of the nail as observed under magnifcation. p.l. shoes are summarized in Appendix, Table 3. Te Douglas et al. Herit Sci (2018) 6:49 Page 14 of 25

Fig. 14 µ-XRF spectra of heel nails from both shoes. The nail from the p.r. shoe is iron-rich, suggesting it is composed of iron or steel. The nail from the p.l. shoe exhibits relatively lower iron and a signifcant zinc content suggesting a galvanized iron or steel composition. Spectra were normalized

at the rhodium ­Kα1 line

various materials found on the Slippers are consistent been applied as nail polish or hobby paint. Te heel of the with the time of their creation. p.r. heel appears to have been re-glued with a poly(ethyl Prior to the present study, NMAH staf had observed acrylate) adhesive. All of the fndings suggest the Ruby that the Ruby Slippers were from diferent pairs and Slippers were actively used during flming, and likely that they were created in the same manner by adorn- repaired and modifed at that time. ing a commercially available pump-style shoe. Analysis Te black tarnish on the sequins presents a treatment of the red sequins confrmed that the sequins on both challenge because it has dulled the appearance of the shoes are similar in composition and structure (a gelatin Slippers. Minimization of the tarnish is likely to be dif- core with a cellulose nitrate coating), as well as in their fcult if not impossible given the fragility of the outer red method of attachment. Decorations on the bows of each cellulose nitrate layer. A less invasive possibility would be shoe are also largely identical in selenium ruby glass bead to manipulate the sequins so that the maximum number and stone, and brass prong compositions. Some variation of untarnished ones have their refective side facing out- in the bows’ sizes and shapes can be attributed to hand- ward. In any case, further degradation of the silver layer crafted construction. Te orange felt on the bottom of could be reduced by placement of sulfur scavengers in each shoe appears to vary slightly in fber content, as do the display case. adhesives on the shoes. Te standard gallery environment within the museum Areas on the bow of the p.r. shoe are identifed as are 70 °F ± 4 and 45% ± 8 RH, parameters which are safe repairs made using colorless glass stone replacements for most objects and comfortable for visitors. Te Ruby of a lead–potash–lime–silica glass (labeled Type 3). Te Slippers were previously displayed at 30 lux/3 foot-can- replacements were painted to match the originals using dles. Based on the relevant conservation and conser- a red cellulose nitrate-based material, which may have vation science literature [17–29], Table 2 summarizes Douglas et al. Herit Sci (2018) 6:49 Page 15 of 25

Table 2 Preliminary exhibition recommendations for several materials of NMAH’s Ruby Slippers Material Temperature, °F Relative humidity, % Light, lux/foot-candles

Gelatin (sequin core) 50°–65° 35–50a 50–100/5–10 Cellulose nitrate (sequin coating) 40°–50° (or cooler than room temp) 40–50 50/5 Glass (beads and stones) – 40–60 200/20 Paint (sole) 50°–75° 40–60 50–150/5–15b Leather (heel) 65°–70°c 45–50 50/5 Silk, dyed synthetic (thread, fabric) 65°–75°c 45–60 50/5 Cotton, dyed synthetic (thread) 65°–75°c 45–60 50/5 a Dependent on temperature b Estimate based on a cellulose nitrate/alkyd paint composition c Lower temperatures above > 40° are generally not detrimental exhibition recommendations for temperature, relative Abbreviations MCI: Museum Conservation Institute; NMAH: National Museum of American humidity and light exposure ranges for some of the History; µ-XRF: micro-X-ray fuorescence spectrometry; µ-FTIR: micro-Fourier various materials identifed on the Ruby Slippers. Both transform infrared spectrometry; PLM: polarized light microscopy; HPLC– gelatin and cellulose nitrate beneft from cold storage DAD–MS: high-performance liquid chromatography–diode array detector– mass spectrometry; p.r.: proper right; p.l.: proper left. while of display, however the paint, textiles and leather can become desiccated and brittle at low temperatures. Authors’ contributions Although not ideal for the cellulose nitrate coating on DW and RB initiated the investigation and provided conservation and historical expertise. JGD, GK, and CM undertook the analytical study and data the sequins, we conclude that the most acceptable con- interpretation. All authors read and approved the fnal manuscript. ditions for the exhibition of the majority of the mate- rials is 65 °F, 45–50% RH and 30 lux/3 foot-candles. Author details 1 Museum Conservation Institute, Smithsonian Institution, Suitland, MD, Tese parameters incorporate the coolest temperature USA. 2 Freer Gallery of Art/Arthur M. Sackler Gallery, Smithsonian Institution, for the majority of materials, standard RH values, and Washington, DC, USA. 3 National Museum of American History, Smithsonian the conservative light values which have been suc- Institution, Washington, DC, USA. cessfully used at NMAH in the past. Low light values Acknowledgements ensure the minimization of ultraviolet-induced degra- The authors thank Eric Jentsch, Deputy Chair and Curator, Division of Culture dation, a major cause of cellulose nitrate deterioration. and Arts, Ryan Lintelman, Curator of the Entertainment Collection, NMAH for the opportunity to participate in this research. Mary Ballard, Senior Textile Con- Questions remain as to what environmental ranges servator at MCI provided information and consulted on fber identifcation. can be achieved and maintained in the constructed We also thank Robert Koestler, MCI Director, Paula DePriest, Deputy Director, display case, whether an anoxic environment for the Rebecca Kaczkowski, Preventive Conservator, Carol Grissom, Senior Objects Conservator, and Thomas Lam, Physical Scientist, all at MCI for their support exhibition case would be benefcial, as well as other and consultation. Blythe McCarthy, Senior Scientist at the Smithsonian’s Freer logistical and curatorial considerations including costs. Gallery of Art and Arthur M. Sackler Gallery provided consultation on dye Regardless, the current work lays a foundation on analysis. We also thank the Smithsonian’s Museum Conservation Institute for generous support for the project. which to make an informed decision on the basic envi- ronmental conditions for the permanent exhibition of Competing interests the Ruby Slippers at NMAH. The authors declare that they have no competing interests. Materials of the Ruby Slippers were characterized Ethics approval and consent to participate within the limited time frame to accommodate ongo- Not applicable. ing exhibition, and the fndings are being used to pre- pare plans for long-term preservation and exhibition. A Appendix future phase of research is being considered as NMAH curators and conservators evaluate the current results See Tables 3, 4 and Figs. 15, 16, 17, 18, 19. and develop goals for an expanded analysis program. Te current work has also revealed signifcant evidence of the original construction and subsequent history of the Ruby Slippers which promises to enrich our under- standing of this iconic object. Douglas et al. Herit Sci (2018) 6:49 Page 16 of 25 - ”—for identifcation of adhesive residue residue identifcation of adhesive ”—for Adhesives ably originate from the nearby red stone held by the held by stone the nearby red from ably originate setting prong on detached sequin 2) main red colorant in the cellulose nitrate coating was colorant in the cellulose nitrate main red fnd - This identifed as Rhodamine HPLC-DAD-MS. B by ing explains the chlorine µ-XRF by detected FTIR Red colorant could not be identifed by Materials identifcation and notes identifcation Materials Brass based Red coating is cellulose nitrate colorant could not be characterized. red The Brass Brass data prob that minor and trace elements in µ-XRF Note Potash-silica glass (type glass) 1, Selenium ruby Potash-silica Potash–lime–silica glass (typePotash–lime–silica glass) 2, Selenium ruby Potash–lime–silica glass (typePotash–lime–silica glass) 2, Selenium ruby Potash–lime–silica glass (typePotash–lime–silica glass) 2, Selenium ruby Protein-based core with red cellulose nitrate coating cellulose nitrate with red core Protein-based (See “ Protein-based core with red cellulose nitrate coating cellulose nitrate with red core Protein-based The and coating. between the core layer A thin silver coating. cellulose nitrate with red core Protein-based Brass ) ) − 1 − 1 ) ) − 1 − 1 ) − 1 ) − 1 ) − 1 and 753 cm 751 cm - FTIR Cellulose nitrate coating (1644, 1278, 1065, 841 cm nitrate Cellulose µ Protein core (3306, 1644, 1539 cm core Protein Cellulose nitrate coating (1650, 1280, 1162, 1073, 841, nitrate Cellulose coating (1650, 1280, 1073, 841 cm nitrate Cellulose Protein core (3304, 1644, 1543, 1240 cm core Protein Protein core (1644, 1543, 1240, 3304 cm core Protein Cellulose nitrate coating (1649, 1281, 1072, 845, nitrate Cellulose XRF - Major: Cl Zn, S, Ca, Ag Minor: Fe, P? Trace: Major: Zn Cu, Ag Minor: S, Fe, Mn, Cl, Ca Trace: Major: Zn Cu, K, Ca, Se, Si Pb, Minor: Fe, Ba, Mn Trace: Major: Zn, Si, K Se Minor: Fe, Rb? Cd?, As, Trace: Major: Zn, Si, K, Ca Se Minor: Fe, Rb Cd, As, Cu, Trace: Major: Zn, Si, K, Ca Se As, Minor: Fe, Pb? Ba?, Cd?, Rb, Trace: Major: Zn, Si, K, Ca Se As, Minor: Fe, Pb? Rb, Ba, Cu, Trace: Major: Zn Cl, Minor: Fe S, Ca, K, P? Trace: µ Major: Zn Cu, Ag Minor: S, Fe, Mn, Ca Cl, Hg, Trace: Major: Zn Cu, Minor: Fe Pb? Ag, Ti, Mn, Cl, Ca, Trace: Summary of the major fndings on the materials of the Ruby through analysis found Slippers by µ-XRF and µ-FTIR, with notes on PLM and HPLC–DAD– 3 Detached sequin 1 Prong, p.l. shoe p.l. Prong, Prong, p.l. shoe p.l. Prong, Large red bead, p.r. side, p.r. shoe p.r. side, p.r. bead, red Large Red bugle bead, p.l. side, p.r. shoe p.r. side, p.l. Red bugle bead, Red stone, p.l. side, p.r. shoe p.r. side, p.l. Red stone, Red stone. upper p.l. corner, p.r. shoe p.r. corner, upper p.l. Red stone. Attached sequin, p.l. side near heel, p.l shoe p.l side near heel, sequin, p.l. Attached Detached sequin 2 shoe p.r. right side near center, Prong, Prong with red coating, p.r. shoe p.r. coating, with red Prong Sequins Beads and rhinestones Table MS fndings analyzed Materials Prong settings Prong Douglas et al. Herit Sci (2018) 6:49 Page 17 of 25 formulation formulation oxide tion by an adhesive residue an adhesive tion by Materials identifcation and notes identifcation Materials Potash–lime–silica glass (typePotash–lime–silica glass) 2, Selenium ruby Lead–potash–lime–silica glass (type 3) Cadmium red lithopone pigment; cellulose nitrate-alkyd lithopone pigment; red Cadmium cellulose nitrate-alkyd lithopone pigment; red Cadmium Cadmium red lithopone pigment with possibly iron with possibly iron lithopone pigment red Cadmium lithopone pigment red Cadmium Polyvinyl acetate Polyvinyl material on detached sequin 2 is likelyThis contamina - Poly(ethyl acrylate) Poly(ethyl Polyvinyl acetate Polyvinyl Natural resin Lead–potash–lime–silica glass (type 3) based coating is cellulose nitrate red The colorant could not be characterized red The Potash–silica glass (type glass) 1, Selenium ruby Potash–silica Potash–lime–silica glass (typePotash–lime–silica glass) 2, Selenium ruby Potash–lime–silica glass (typePotash–lime–silica glass) 2, Selenium ruby ) ) − 1 ) − 1 − 1 ), alkyd (1728, ), alkyd (1728, ) − 1 − 1 − 1 ) − 1 ), barium (1117, 1074, sulfate ), barium (1117, 1074, sulfate − 1 − 1 ) ) − 1 − 1 1022, 947, 793 cm 983 cm 983 cm 2934, 2870 cm 2934, 2870 cm 1236, 1169, 1096, 854, 787, 755 cm - FTIR Polyvinyl acetate (3541, 2926, 1736, 1373, 1240, 1123, acetate Polyvinyl Natural resin (2969, 2935, 1716, 1453, 1379 cm Natural resin µ Cellulose nitrate (1649, 1281, 1072, 845, 751 cm nitrate Cellulose Poly(ethyl acrylate) (2980, 2937, 2876, 1734, 1448, 1380, Poly(ethyl Polyvinyl acetate (1739, 1434, 1373, 1242 cm acetate Polyvinyl Cellulose nitrate (1659, 1280, 842 cm nitrate Cellulose Cellulose nitrate (1659, 1280, 842 cm nitrate Cellulose XRF - Major: Zn, Si, K, Ca Se As, Minor: Fe, Rb? Cu?, Trace: Major: Pb, K,Major: Ca Pb, Ba Cu, Zn, As, Minor: Si, Fe, – Trace: Major: Pb, K,Major: Ca Pb, Zn Cu, Minor: Si, Ba, Fe, – Trace: Major: Ba, Fe, Se Major: Ba, Fe, Minor: Ca S, Cd, Zn, As/Pb Cu, Trace: Major: Ba, Se Cd, Zn Minor: S, Fe, Sr As/Pb, Cu, Trace: Major: Ba, Se Cd, Zn Cu, Minor: S, Fe, Sr As/Pb Sr, Cu, Trace: µ Major: Si, K, Zn Se Minor: Fe, Cd, Ti? Rb, As/Pb, Ca Trace: Major: Si, K, Zn Ca, Minor: Fe Ba, Se, As, Mn, Pb? Rb, Cd, Trace: Major: Zn, Si, K, Ca Minor: Cd Se, As/Pb Fe, Trace: Major: Ba, Se Cd, Minor: S Sr Zn, As/Pb, Cu, Fe, Trace: (continued) shoe p.r. shoe p.r. shoe Red stone, upper p.r. corner, p.r. shoe p.r. corner, upper p.r. Red stone, Colorless stone, p.l. upper corner, p.r. shoe p.r. upper corner, p.l. Colorless stone, Red coating on colorless stone, upper p.r. corner, p.r. p.r. corner, upper p.r. Red coating on colorless stone, Red paint on sole, near orange felt, p.r. shoe p.r. near orange felt, Red paint on sole, shoe p.l. near orange felt, Red paint on sole, Red paint on sole, near arch, p.l. shoe p.l. near arch, Red paint on sole, on detached sequin 2 Adhesive Outsole adhesive (between sole and shoe), p.r. shoe (between sole and shoe), p.r. Outsole adhesive Clear, soft adhesive on heel, between sole and shoe, between sole and shoe, soft on heel, adhesive Clear, Adhesive between inner and outer orange felt, p.r. p.r. orange felt, between inner and outer Adhesive Large red bead, p.r. side, p.l. shoe p.l. side, p.r. bead, red Large Large red central bead, p.l. shoe p.l. central bead, red Large Red bugle bead from p.r. side, p.l. shoe p.l. side, p.r. Red bugle bead from Red paint on sole near arch, p.r. shoe p.r. Red paint on sole near arch, Adhesives 3 Table analyzed Materials Paints Douglas et al. Herit Sci (2018) 6:49 Page 18 of 25 characterized characterized could not be characterized characterized PLM). Dye in minor amounts (identifed by present could not be characterized characterized. Materials identifcation and notes identifcation Materials Silk, red dyed (identifed by PLM). Red dye could not be PLM). RedSilk, dye (identifed by dyed red could not be PLM). RedSilk, dye (identifed by dyed red PLM) Dye (identifed by component orange dyed Wool, PLM) (identifed by possibly mercerized Cotton, PLM) (identifed by Leather PLM) (identifed by Cotton could not be PLM). RedSilk, dye (identifed by red dyed other fbers cotton, wool, orange; undyed dyed Wool, PLM). DyeSilk, (identifed by could not be dyed red PLM) Silk, (identifed by dyed red Cotton (identifed by PLM) (identifed by Cotton Cotton (identifed by PLM) (identifed by Cotton Polyvinyl acetate Polyvinyl Cellulose nitrate Cellulose nitrate Cellulose Cellulose-based with natural resin fbers coated No identifcation nail corrosion be due to may by Some elements found Iron or steel Galvanized iron or steel Galvanized iron ) − 1 ) ) ) − 1 − 1 − 1 cm cm cm ) ) ) ) ) ) ) ) (thick fber) ) − 1 − 1 − 1 − 1 − 1 − 1 − 1 − 1 − 1 - FTIR Cellulose nitrate (1650, 1277, 1069, 842 ­ nitrate Cellulose µ Protein (1645, 1519, 1234, 3298 cm Protein (1645, 1519, 1234, 3298 cm Protein (3342, 2899, 1161, 1115 cm Cellulose (1645, 1519, 1234, 3298 cm Protein (3347, 2897, 1161, 1113 cm Cellulose Natural resin (2967, 2935, 1712, 1453 and 1376 cm Natural resin Protein (1645, 1519, 1234, 3298 cm Protein Cellulose (3342, 2899, 116, 1115 cm Cellulose Cellulose nitrate (1650, 1277, 1069, 842 ­ nitrate Cellulose (1739, 1434, 1373, 1242 ­ acetate Polyvinyl Protein (1655, 1530, 1235, 3302 cm Protein Protein (1655, 1530, 1235, 3302 cm Protein XRF - µ Major: S, Fe, Zn Major: S, Fe, Minor: Ba Pb, Mn, Ca, Cu, Cr?, Zr? Trace: Major: S, Fe, Zn Major: S, Fe, Minor: K Ba, Mn, Ca, Cu, Ti? Trace: Pb, Major: Fe, Zn Major: Fe, Minor: S, K, Ba, Pb Ca, Si Trace: Major: Fe Minor: Mn Ca, Si, K, S, Zn, Cu, Ba, Cr Trace: Major: Fe, Zn Major: Fe, Minor: S, Ca Mn Trace: (continued) Glossy adhesive near sole, p.r. shoe p.r. near sole, Glossy adhesive Red thread holding netting to shoe, p.r. shoe p.r. shoe, holding netting to Red thread shoe p.r. on central sole area, Orange felt shoe Structural p.r. shoe fabric, shoe p.r. Sole near arch, shoe support left, Bow p.r. thread, shoe p.l. shoe, holding netting to Red thread shoe p.l. Sequin thread, shoe p.l. silk faille shoe fabric, Decorative shoe p.l. Red netting thread, shoe p.l. heel, materials from Fiber Orange felt, near edge, p.l. shoe p.l. near edge, Orange felt, Red netting thread, p.r. shoe p.r. Red netting thread, Sequin thread, p.r. shoe p.r. Sequin thread, Glossy adhesive near sole, p.l. shoe p.l. near sole, Glossy adhesive shoe p.l. and sole, between orange felt Adhesive Brown heel material, p.r. shoe p.r. heel material, Brown Heel nail, p.r. shoe p.r. Heel nail, Heel nail, p.l. shoe p.l. Heel nail, 3 Table analyzed Materials the approximate detected to of the signal intensity refect terms the relative These estimated. are of major , minor and trace and the designations than quantitative, rather qualitative were determinations elemental µ-XRF present of each element amounts relative Fibers Heel materials Douglas et al. Herit Sci (2018) 6:49 Page 19 of 25 Identifcation Cotton Silk Wool red) Silk (dyed red) Silk (dyed - less; undyed transparent. Occasional dents, constrictions Occasional dents, transparent. and sug - colorless, are Fibers occur in some. swellings undyed gesting they are length. Some changes twist (S or Z) direction be fat to tend observed along fber length. Fibers and color transparent are Fibers and elongated. are Fibers scales characteristicoverlapping of wool. colorless undyed suggesting they are constrictions Occasional dents, transparent. and consistent fbers are The occur in some. swellings been bent due to be have with silk but appear to in the red of twisting of the threads “memory” the color red a uniform dyed are Fibers netting. constrictions Occasional dents, transparent. and dyed are Fibers occur in some flaments. swellings color red a uniform Morphology description Fibers are thin, smooth, uniform in diameter, and in diameter, thin, smooth, uniform are Fibers tubes that twist thin hollow along the are Fibers slightly variable in width, and show are Fibers and in diameter, thin, smooth, uniform are Fibers and in diameter, thin, smooth, uniform are Fibers = 5) Average fber Average µm (n diameter, 13 27 24 15 15 PLM image Results summaryResults study fber of the PLM identifcation Spun silk (Testfabrics reference) 4 Table sample Fiber Wool (Testfabrics reference) Wool Bleached cotton (Testfabrics reference) Bleached cotton shoe p.r. Red netting thread, shoe p.r. shoe, holding netting to Red thread Douglas et al. Herit Sci (2018) 6:49 Page 20 of 25 Identifcation Silk (dyed red) Silk (dyed red) Silk (dyed Cotton Cotton possibly mercerized Cotton, - and transparent. Occasional dents, constrictions Occasional dents, and transparent. are Fibers occur in some flaments. and swellings color red a uniform dyed con - Occasional dents, and transparent. diameter, strictions occur in some flaments. and swellings color red a uniform dyed are Fibers (S or Z) at vari change direction length which may - be fat and elongated. to tend ous intervals. Fibers color and a light brown transparent are Fibers but is been dyed have may suggesting the thread and/or faded altered now (S or Z) at vari change direction length which may - be fat and elongated. to tend ous intervals. Fibers and colorless; undyed transparent are Fibers (S or Z) at vari change direction length which may - be fat and elongated. to tend ous intervals. Fibers Glob and colorless; undyed. transparent are Fibers ules of nearly opaque material on surface of fbers and/or stifener of adhesive be a residue may Morphology description Fibers are thin, smooth, quite uniform in diameter in diameter uniform thin, smooth, quite are Fibers in uniform Individual thin, smooth, quite fbers are with twists along fber tubes, thin hollow are Fibers with twists along fber tubes, thin hollow are Fibers with twists along fber tubes, thin hollow are Fibers = 5) Average fber Average µm (n diameter, 13 12 17 22 23 PLM image (continued) Red thread holding netting to shoe, p.l. shoe p.l. shoe, holding netting to Red thread 4 Table sample Fiber Decorative faille shoe fabric, from weft, p.l. shoe weft, p.l. from faille shoe fabric, Decorative shoe p.r. Sequin thread, shoe support p.r. bow thread, Woven shoe Structural p.r. shoe fabric, Douglas et al. Herit Sci (2018) 6:49 Page 21 of 25 Identifcation Cotton fbers other undyed dyed), (orange Wool other fbers wool, undyed dyed); (orange Wool Leather - - - may change direction (S or Z) at various change direction may intervals; are Fibers be fat and elongated. to fbers tend suggesting the thread and light brown, transparent and/or altered but is now been dyed have may faded interlock with its fbers to which allow istics scales, Other bright orange. uniform other fbers; dyed fb characteristics fbers show Cotton undyed. ers are be may wool other than orange dyed Fibers twists. scrap fber), and/or dust reuse (inferior, “shoddy” the foor duringpicked shoe usage up from be distin - its fbers to which allow istics scales, bright uniform other materials; dyed guished from other than Fibers Other undyed. orange. fbers are reuse (inferior, “shoddy” be may wool orange dyed the from fber adhered scrap fber), and/or foreign foor during shoe usage Morphology description Thin hollow tube, twists tube, along fber length which hollow Thin can be variable character in width but shows Wool can be variable character in width but shows Wool short brown fbers Fine = 5) Average fber Average µm (n diameter, 18 orange dyed) 23 (wool, orange dyed) 30 (wool, 7 PLM image (continued) Sequin thread from toe, p.l. shoe p.l. toe, from Sequin thread 4 Table sample Fiber Orange felt on central sole area, p.r. shoe p.r. on central sole area, Orange felt shoe p.l. near edge, Orange felt, shoe p.r. Sole near arch, Douglas et al. Herit Sci (2018) 6:49 Page 22 of 25

Fig. 15 µ-FTIR spectrum from the clear, soft adhesive on heel, between sole and shoe body, consistent with the presence of poly(ethyl acrylate) (HR Hummel Polymer and Additives reference spectrum #202)

Fig. 16 µ-FTIR spectra from the red coating on a prong and a bead in the upper p.r. corner of the bow on the p.r. shoe. Both are consistent with the presence of cellulose nitrate (IRUG reference spectrum ISR00039) Douglas et al. Herit Sci (2018) 6:49 Page 23 of 25

Fig. 17 µ-FTIR spectra from the orange felt fbers from the outer and inner felts on the sole of the p.l. shoe, and the sole of the p.r. shoe. All are consistent with the presence of protein

Fig. 18 µ-FTIR spectra from the red thread fbers and the red netting fbers from both shoes consistent with the presence of protein Douglas et al. Herit Sci (2018) 6:49 Page 24 of 25

Fig. 19 µ-FTIR spectra from the thread fbers holding the sequins to p.r. shoe and the p.l. shoe consistent with the presence of cellulose

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