I have made about 60 to 70 natural leather dyes, and here is some detailed information on what I have learned.   1. The best mordant for dyeing leather with a vegetable dye is potassium alum. Don't use too much, 5 grams dissolved in 100 ml of water is adequate. Apply only one or two coats of this mordant solution, and then allow to dry before dyeing. (The following vegetable dyes do not require a mordant: indigo, lac, walnut, woad.)   2. The foll