A comparison of different techniques and materials for the surface cleaning of leather/skin was carried out in the Royal Ontario Museum. The intention was to see whether measurable ill-effects were produced rather than to evaluate the visual efficiency of different treatments. With erasers and drafting powders, the test was whether they contained materials which could tarnish if left behind. Samples were placed in glass jars with strips of silver, copper and lead foil. All tested samples corroded, although one, Skumex, to a markedly lesser degree. This was at variance with CCI results - so batch quality could vary. Soaps, spirit soaps and detergents all tend to raise the pH of leather to an extent where detannage could occur (above pH 6). Saddle soap, Vulpex B30 (alkaline methyl cyclohexyl oleate) and neutral triethanolamine oleate (TEO) soap were considered. The first two are no longer used and the third only sparingly. It is best to make this up, since commercial products are frequently made of alkaline -2 ml. Ethanolamine plus 8 ml. Refined white oleic acid.