How to avoid streaming dye when making racoon tails?

Well, when making coon tails, my colored dye, always seems to stream in to the blonde parts, where it isn't supposed to be. So the blonde streaks get all grayishwell, how could i avoid this? i taped them, but the dye ran under the tape? and I am holding them horizontally when washing them out! heeelp! :)How to avoid streaming dye when making racoon tails?
Use aluminum foil but don't fold it