AS OF 2021, I AM NO LONGER USING VINEGAROON.
Vinegaroon is an ancient method for turning vegetable tanned leather black. It is a solution of iron and vinegar that reacts with the tannins that are present in the leather, changing the chemical composition of the leather. This is difference between vinegaroon and dye: rather than coloring the surface of the leather, like dye, vinegaroon penetrates the leather and changes the chemical composition.
Unfortunately, the process is quite finicky and in some cases, it resulted in a weakened leather. Although I love the history and think it is important to preserve the knowledge of this process, I am no longer using vinegaroon. I would rather be able to offer consistently high quality items using other eco-friendly, water-based dyes.