This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
Crude neatsfoot oil 5,000 parts
Alcohol, 90 per cent 2,500 parts
Tannin........... 5 parts
Place in a clearing flask, agitate vigorously and allow to stand for 8 days in a warm room with daily repetition of the shaking. Then draw off the spirit of wine on top, rinse again with 1,000 parts of spirit of wine (90 per cent) and place the oil in a temperature of about 53.5° F. Allow to stand in this temperature for at least 6 weeks, protected from the light, and then filter.