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the only thing i would add to cassidy's steps is that when you take the disc out of the dye wash it really well in cold water.
for a really simple, cool effect:
drizzle some plain old white glue (like elmer's) over the disc. and allow it to dry completely before you place the disc in the dye. try spirals, stripes, zig-zags, no artistic talent needed. The glue comes off cleanly when you wash the disc.