Not all of the dye was exhausted so I started another batch in the microwave: 2 minutes on, 2 minutes rest, etc.
Our 20 year old food coloring box with two bottles left:
(NB: I have a separate set of dye equipment for working with dyes that are not food grade. Please, if you think you'd like to dye your own fiber or yarn, do your research first. Never use the same utensils that have come in contact with dye for cooking. Articles on dye safety are your friend.)