FACT SHEET, September 4, 2018

The Science Behind the Slippers That Helped the F.B.I. Identify The Missing Pair

In April 2017, the National Museum of American History took its pair of Ruby Slippers from the American classic The Wizard of Oz off display to begin an extensive research and conservation project. The shoes, made in 1938 for the movie that premiered a year later, are now 80 years old. The work was necessary to preserve the shoes for future generations to see.


Several pairs of Ruby Slippers were made for the movie, a common practice with movie props. The museum’s Ruby Slippers are a mismatched pair, indicated by the use of different base shoes and markings that read ‘#1Judy Garland’ on the right shoe and ‘#6 Judy Garland’ on the left. The shoes themselves were styled from commercially available leather pumps made by the Innes Shoe Co. The white silk faille was dyed red. To create the shimmering red hue of the slippers, dark red sequins were stitched with un-dyed white cotton thread to “templates” made of red silk netting in the shape of the upper part of the shoe and heel. These templates were then overlaid onto the shoes and attached with red silk thread. The bows were made from stiff cotton fabric cut into a butterfly shape and covered with the same red silk netting. They were then adorned with three large rectangular beads surrounded by red glass bugle beads and edged in rhinestones set in silver colored brass prongs that have now turned black. The soles and heels of the shoes were painted red and orange felt was glued to the soles to muffle Garland’s footsteps as she danced on the yellow brick road.

Similarities Between the Smithsonian and the Recovered Pair of Ruby Slippers

Research and conservation of the Smithsonian slippers confirmed that its two shoes are from different pairs as there are a number of differences between the individual shoes. These findings helped conservators compare them with the slippers retrieved by the FBI as possibly the pair stolen in 2005 while on loan to the Judy Garland Museum. The two “pairs” appear to have been switched at some point, so that the Smithsonian has a right shoe (labeled #1) from one set and the left (labeled #6) from another. The recovered pair is the opposite, with the left and right shoes matching up respectively to the Smithsonian’s mismatched pair.
The heel of the Smithsonian’s right shoe is more slender and contains a heel cap. It also has a tighter silk faille weave. The inner heel grips on the panels on the back of each Smithsonian shoe differ and the manufacturer’s markings are different, with the right slipper being size 5C and the left size 5BC. The orange felt on the bottom of the left shoe is much dirtier, and the felt on the bottom of the right shoe appears to be a replacement layer of felt, indicated by remnants of orange fibers suspended in adhesive on the sole that were found during the conservation process. The right shoe also shows much more damage and wear. The construction of the bows on each shoe is also visibly different – the right bow extends further out over the edge of the slipper and its bugle beads are hexagonal instead of cylindrical like on the left slipper. The right bow also shows several signs of repair with varying threads securing loose or missing beads, a large tear that almost completely bisects the bow and clear beads painted red to replace lost rhinestones. On the retrieved pair, the inside labeling on one shoe appears to have been removed and the other is too faded to determine what it may have said. However, the shoe manufacturing numbers correspond so that the Smithsonian left shoe would go with the recovered right shoe and vice versa. The interior “v” shaped heel panel on the Smithsonian’s right shoe matches the heel panel on the left recovered pair. There is also a “telltale” bead. It is a clear bead painted red that was found on the retrieved pair’s left shoe. The museum’s pair also has similar clear beads that were painted red, most likely done as a repair to the bow. In addition, museum and Smithsonian scientists at the Museum Conservation Institute did analyze the materials from the retrieved pair, compared them to previous findings, and confirmed that the sequins are consistent with manufacturing practices of the 1930s.
More than a dozen experts formed the conservation team working on the Ruby Slippers, including a curator and two conservators from the National Museum of American History.
More than 300 images of the Ruby Slippers were taken to document their condition and treatment, including the use of UV fluorescence lights and a Hirox digital microscope for extreme close-ups. Nine analytical techniques were used to identify the materials, including Micro-X-ray fluorescence spectroscopy with Artax (µ-XRF), handheld µ-XRF with Bruker Tracer, micro-Fourier transform infrared spectroscopy (µ-FTIR), polarized light microscopy (PLM) and scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM/EDS), solid phase micro-extraction gas chromatography/ mass spectrometry (SPME-GC/MS), high performance liquid chromatography - diode array detector – mass spectrometer (HPLC-DAD-MS), photospectometry, microfading, and Raman spectroscopy.
Analysis identified at least 20 materials within the shoes, including leather, gelatin, silver, cellulose nitrate dyed with Rhodamine B, silk and cotton threads used to sew the sequins on, silk faille for the shoes, and silk netting for the sequins and bows, ferrous nails, wool felt, paint, resin adhesive, three types of glass beads colored red with selenium and cadmium sulfide, brass, wood, cork, and PVA adhesive. Small traces of silver were found on the bead prongs, which indicates a plating on the metals and explains the bright white appearance of the metal in the film. The red paint used to color the soles and heels of the shoes was identified as cadmium red lithapone pigment in a medium containing cellulose nitrate and an alkyd.
There are an estimated 2,400 sequins on each shoe with two loose sequins from unknown locations on the right one. Samples from these loose sequins revealed that the sequins have a gelatin core with a cellulose nitrate coating, appropriate for sequins made in the late 1930s. A thin layer of silver underneath one side of the cellulose nitrate was also discovered. This layer aided in reflecting light and intensifying color. After further research and testing on the sequins, the team discovered the cellulose nitrate was mixed with high concentrations of Rhodamine B, usually a bluish pink color, to create the iconic ruby hue. The sequins on the toes have visible fading, cracks and loss of coating, most likely due to the intense heat from the lights used during Technicolor filming. But the sequins on the sides and back of the slippers are still vibrant.
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Laura Duff
(202) 633-3129