Before intervening on a leather object, particularly one made of gut leather, it is necessary to carry out a number of measurements of the leather's chemical and physical properties. On the basis of these results, decisions can be made concerning the required treatment. Measurements required are: pH, fat content, moisture content, sulfate or ammonium content (to determine the effects of air pollutants). Acceptable values and sample size required are; pH values of 3-6, 250 mg; fat content, 3-5%, 0.5 to 5 g. moisture content, 12-15%, 0.5-1 g. A number of other tests can also be carried out to provide supplementary information on technical or art historical aspects. Methods for removing different types of fats and oils using organic solvents, as well as the impregnation of degraded material with synthetic resins have also been studied.