Someone said I was waiting too long on this so....Steel wool in a glass jar, weight it down to prevent floating (so it doesn't rust), and cover with vinegar. This time I waited only 8-10 hours and the vinegar was still clear as a bell but when I dabbed it on tanned leather, turned black right away. You don't want any rust so I removed the steel wool but the mixture seemed to keep darkening, black, not rust colored. After a day I tried it again, still worked but the 8-10 hour stuff seemed to work better. Just passing along my experi3ence.