put vineagar and clean steel wool, or any clean iron, in a glass jar until the wool is gone or a week or so at least, apply it just as any dye. You can stain wood with it also just paint your wood with tea then apply the roon, the black color comes from the chemical reaction between the iron and tannic acid that leather is tanned with. tea also has tannic acid. then folks neutralize the vinegar with baking soda water mix.