As long as required. I put a hook in the end of a coat hanger slide the part on the hanger and put in dye. Do not put more than one part per hanger. Parts will not dye where they touch. Pull them out after a while and check the color, as often as needed. I rinse the parts with cold water when done so the dye does not streak or get all over everything. It can get real messy if you are not careful.