Yesterday, for our art group project, we "tie dyed" t-shirts with colored tissue paper following this tutorial at Make and Takes.
We had the kids get their t-shirts wet in the sink first and wring them out before bringing them back to the studio. I had baskets of bleeding tissue paper pieces set out as well as a spray bottle of water (and later, bowls of water with brushes). I thought that cutting the tissue paper into squares ahead of time would be easier with a group, but in retrospect, I might have the kids tear them just because I think the finished product would look better.
They had fun arranging the tissue paper and spraying or brushing them with water. The bleeding tissue paper dyes the fabric underneath fairly quickly -- some colors quicker than others.
Here, the tissue paper has all been removed and we're using a sponge brush to add the distilled white vinegar. One problem I noticed is that since the shirts were wet the color continued to run even after the tissue paper was removed -- this wasn't much of an issue with the random designs the kids made but was with more specific patterns or designs (one of the moms tried some flowers and dots on onesies). I think the solution would be to dry them quickly after making a design you're satisfied with. OR, maybe to use regular tissue paper rather than bleeding tissue paper (I think the onesie in the original tutorial was made using regular tissue paper).
I set the color by putting them in the dryer (another option is using an iron). As often seems to happen, the colors dried lighter.
The colors even bled through to the backs of the shirts, although not as intensely.
Update: The dye doesn't surve the wash cycle, despite the vinegar. Darn! Not sure if we missed a step or if the project itself is faulty. Back to the drawing board...