These deep sea diver’s boots were made in the 1920s by Siebe Gorman, a company originally based in London, England. They are made with a thick leather boot anchored by a heavy brass sole each weighing 8.2kg (18 lbs). The strap over the vamp is 4cm wide (1 ½”) with 2 narrower straps, 2cm wide (3/4”), that wrap around the ankle and top edge. All components are secured with copper rivets which were covered with waxy green residue.
This residue is caused by fatty acids in the leather and the oil of a leather dressing applied by the previous owner reacting with the copper rivets and creating a metal soap. If left in place, this corrosion byproduct expands, damaging the leather and obscuring the rivets.
The treatment involved removing this residue from the surface of the rivets and the leather. Since copper is easily scratched it was decided to limit the tools for mechanical cleaning to wooden picks and soft micro brushes. The other consideration was to prevent the residue from becoming embedded in the leather so a short length of polyethylene surgical tubing was fitted into the terminal end of a micro nozzle attached to a low suction vacuum. The technique used required some ambidexterity as the cleaning was done with one hand while the other hand held the vacuum nozzle close to the work surface. After the residue was removed the rivets were cleaned with an organic solvent.
This treatment does not stop of development of metal soaps but removing it makes it easier to spot future accumulations. A half pair of the diving boots is now on display in the What’s Their Line? section of the All About Shoes exhibition on the lower level of the museum.