One method for restoring historical leather objects is treatment with glycerin or linseed oil, often without sufficient preliminary cleaning. Linseed oil must be avoided, if the leather is to be examined further. The author's method is to remove as much foreign matter as possible, then to oxidize putrescible organic matter by oxidation with permanganate, followed by treatment with sodium bisulfite to reduce excess permanganate. If the leather is very fragile, foreign matter is removed by treating the object first with a solution of sodium bicarbonate, then, without washing, with dilute hydrochloric acid. The evolved carbon dioxide removes dirt. Curled or twisted, brittle leather pieces aretreated with warm moist air at 40°C until they can be cleaned as above. The tannin has changed so that little soluble matter is lost during the above treatments. Determining the nature of the leather is a difficult problem, unless a hair can be found. The grain is often destroyed. The tannin does not give the normal color reactions. Paper chromatography offers some promise.