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Table 3 Summary of the major findings on the materials of the Ruby Slippers found through analysis by µ-XRF and µ-FTIR, with notes on PLM and HPLC–DAD–MS findings

From: Materials characterization of the Ruby Slippers from the 1939 classic film, The Wizard of Oz

Materials analyzed µ-XRF µ-FTIR Materials identification and notes
Sequins
 Detached sequin 1 Major: Zn, S, Ca, Cl Minor: Fe, Ag Trace: P? Protein core (3306, 1644, 1539 cm−1) Cellulose nitrate coating (1644, 1278, 1065, 841 cm−1) Protein-based core with red cellulose nitrate coating A thin silver layer between the core and coating. The main red colorant in the cellulose nitrate coating was identified as Rhodamine B by HPLC-DAD-MS. This finding explains the chlorine detected by µ-XRF
 Detached sequin 2   Protein core (3304, 1644, 1543, 1240 cm−1) Cellulose nitrate coating (1650, 1280, 1162, 1073, 841, and 753 cm−1) Protein-based core with red cellulose nitrate coating (See “Adhesives”—for identification of adhesive residue on detached sequin 2)
 Attached sequin, p.l. side near heel, p.l shoe Major: Cl, Zn Minor: S, Ca, Fe Trace: K, P? Protein core (1644, 1543, 1240, 3304 cm−1) Cellulose nitrate coating (1650, 1280, 1073, 841 cm−1) Protein-based core with red cellulose nitrate coating. Red colorant could not be identified by FTIR
Prong settings
 Prong, right side near center, p.r. shoe Major: Cu, Zn Minor: S, Fe, Ag Trace: Cl, Mn, Hg, Ca   Brass
 Prong with red coating, p.r. shoe Major: Cu, Zn Minor: Fe Trace: Cl, Mn, Ca, Ti, Ag, Pb? Cellulose nitrate coating (1649, 1281, 1072, 845, 751 cm−1) Brass Red coating is cellulose nitrate based The red colorant could not be characterized.
 Prong, p.l. shoe Major: Cu, Zn Minor: S, Fe, Ag Trace: Cl, Mn, Ca   Brass
 Prong, p.l. shoe Major: Cu, Zn Minor: Fe, Pb, Se, Ca, K, Si Trace: Ba, Mn   Brass Note that minor and trace elements in µ-XRF data probably originate from the nearby red stone held by the prong setting
Beads and rhinestones
 Large red bead, p.r. side, p.r. shoe Major: Zn, Si, K Minor: Fe, Se Trace: As, Cd?, Rb?   Potash-silica glass (type 1, Selenium ruby glass)
 Red bugle bead, p.l. side, p.r. shoe Major: Zn, Si, K, Ca Minor: Fe, Se Trace: Cu, As, Cd, Rb   Potash–lime–silica glass (type 2, Selenium ruby glass)
 Red stone, p.l. side, p.r. shoe Major: Zn, Si, K, Ca Minor: Fe, As, Se Trace: Rb, Ba?, Cd?, Pb?   Potash–lime–silica glass (type 2, Selenium ruby glass)
 Red stone. upper p.l. corner, p.r. shoe Major: Zn, Si, K, Ca Minor: Fe, As, Se Trace: Ba, Cu, Rb, Pb?   Potash–lime–silica glass (type 2, Selenium ruby glass)
 Red stone, upper p.r. corner, p.r. shoe Major: Zn, Si, K, Ca Minor: Fe, As, Se Trace: Cu?, Rb?   Potash–lime–silica glass (type 2, Selenium ruby glass)
 Colorless stone, p.l. upper corner, p.r. shoe Major: Pb, K, Ca Minor: Si, Fe, Zn, As, Cu, Ba Trace: –   Lead–potash–lime–silica glass (type 3)
 Red coating on colorless stone, upper p.r. corner, p.r. shoe Major: Pb, K, Ca Minor: Si, Ba, Fe, Cu, Zn Trace: – Cellulose nitrate (1649, 1281, 1072, 845, 751 cm−1) Lead–potash–lime–silica glass (type 3) The red coating is cellulose nitrate based The red colorant could not be characterized
 Large red bead, p.r. side, p.l. shoe Major: Si, K, Zn Minor: Cd, Fe, Se Trace: Ca As/Pb, Rb, Ti?   Potash–silica glass (type 1, Selenium ruby glass)
 Large red central bead, p.l. shoe Major: Si, K, Ca, Zn Minor: As, Ba, Se, Fe Trace: Cd, Mn, Rb, Pb?   Potash–lime–silica glass (type 2, Selenium ruby glass)
 Red bugle bead from p.r. side, p.l. shoe Major: Zn, Si, K, Ca Minor: Se, Cd Trace: Fe, As/Pb   Potash–lime–silica glass (type 2, Selenium ruby glass)
Paints
 Red paint on sole near arch, p.r. shoe Major: Cd, Ba, Se Minor: S Trace: Fe, Cu, Zn, As/Pb, Sr Cellulose nitrate (1659, 1280, 842 cm−1), alkyd (1728, 2934, 2870 cm−1), barium sulfate (1117, 1074, 983 cm−1) Cadmium red lithopone pigment; cellulose nitrate-alkyd formulation
 Red paint on sole, near orange felt, p.r. shoe Major: Ba, Fe, Se Minor: S, Cd, Ca Trace: Cu, Zn, As/Pb   Cadmium red lithopone pigment with possibly iron oxide
 Red paint on sole, near arch, p.l. shoe Major: Cd, Ba, Se Minor: S, Fe, Cu, Zn Trace: Cu, Sr, As/Pb Sr Cellulose nitrate (1659, 1280, 842 cm−1), alkyd (1728, 2934, 2870 cm−1), barium sulfate (1117, 1074, 983 cm−1) Cadmium red lithopone pigment; cellulose nitrate-alkyd formulation
 Red paint on sole, near orange felt, p.l. shoe Major: Cd, Ba, Se Minor: S, Fe, Zn Trace: Cu, As/Pb, Sr   Cadmium red lithopone pigment
Adhesives
 Adhesive on detached sequin 2   Polyvinyl acetate (3541, 2926, 1736, 1373, 1240, 1123, 1022, 947, 793 cm−1) Polyvinyl acetate This material on detached sequin 2 is likely contamination by an adhesive residue
 Outsole adhesive (between sole and shoe), p.r. shoe   Natural resin (2969, 2935, 1716, 1453, 1379 cm−1) Natural resin
 Adhesive between inner and outer orange felt, p.r. shoe   Polyvinyl acetate (1739, 1434, 1373, 1242 cm−1) Polyvinyl acetate
 Clear, soft adhesive on heel, between sole and shoe, p.r. shoe   Poly(ethyl acrylate) (2980, 2937, 2876, 1734, 1448, 1380, 1236, 1169, 1096, 854, 787, 755 cm−1) Poly(ethyl acrylate)
 Glossy adhesive near sole, p.r. shoe   Cellulose nitrate (1650, 1277, 1069, 842 cm−1) Cellulose nitrate
 Glossy adhesive near sole, p.l. shoe   Cellulose nitrate (1650, 1277, 1069, 842 cm−1) Cellulose nitrate
 Adhesive between orange felt and sole, p.l. shoe   Polyvinyl acetate (1739, 1434, 1373, 1242 cm−1) Polyvinyl acetate
Fibers
 Sequin thread, p.r. shoe   Cellulose (3342, 2899, 116, 1115 cm−1) Cotton (identified by PLM)
 Red netting thread, p.r. shoe   Protein (1645, 1519, 1234, 3298 cm−1) Silk, red dyed (identified by PLM). Red dye could not be characterized
 Red thread holding netting to shoe, p.r. shoe   Protein (1645, 1519, 1234, 3298 cm−1) Silk, red dyed (identified by PLM). Red dye could not be characterized
 Orange felt on central sole area, p.r. shoe Major: S, Fe, Zn Minor: Ca, Mn, Cu, Pb, Ba Trace: Cr?, Zr? Protein (1655, 1530, 1235, 3302 cm−1) Wool, orange dyed (identified by PLM) Dye component could not be characterized
 Structural shoe fabric, p.r. shoe    Cotton, possibly mercerized (identified by PLM)
 Sole near arch, p.r. shoe    Leather (identified by PLM)
 Bow support thread, left, p.r. shoe    Cotton (identified by PLM)
 Red thread holding netting to shoe, p.l. shoe   Protein (1645, 1519, 1234, 3298 cm−1) Silk, dyed red (identified by PLM). Red dye could not be characterized
 Sequin thread, p.l. shoe   Cellulose (3342, 2899, 1161, 1115 cm−1) Cotton (identified by PLM)
 Orange felt, near edge, p.l. shoe Major: S, Fe, Zn Minor: Ca, Ba, Mn, Cu, K Trace: Pb, Ti? Protein (1655, 1530, 1235, 3302 cm−1) (thick fiber) Wool, dyed orange; undyed wool, cotton, other fibers present in minor amounts (identified by PLM). Dye could not be characterized
 Decorative silk faille shoe fabric, p.l. shoe    Silk, red dyed (identified by PLM). Dye could not be characterized.
 Red netting thread, p.l. shoe   Protein (1645, 1519, 1234, 3298 cm−1) Silk, red dyed (identified by PLM)
 Fiber materials from heel, p.l. shoe   Cellulose (3347, 2897, 1161, 1113 cm−1) Natural resin (2967, 2935, 1712, 1453 and 1376 cm−1) Cellulose-based fibers coated with natural resin
Heel materials
 Brown heel material, p.r. shoe Major: Fe, Zn Minor: S, K, Ca, Ba, Pb Trace: Si   No identification Some elements found by may be due to nail corrosion
 Heel nail, p.r. shoe Major: Fe Minor: Ca, Mn Trace: S, Zn, Cu, Si, K, Ba, Cr   Iron or steel
 Heel nail, p.l. shoe Major: Fe, Zn Minor: S, Ca Trace: Mn   Galvanized iron or steel
  1. µ-XRF elemental determinations were qualitative rather than quantitative, and the designations of major, minor and trace are estimated. These terms reflect the relative intensity of the signal detected to approximate the relative amounts of each element present