I wash everything. Batiks bleed and cotton fabric shrinks. I have found that my fabric has been shrinking a lot WOF this is how the jellly rolls are cut, so I always wash mine. Just fill your sink with warm, almost hot, water, add a few drops of liquid washing machine detergent and swish them around for a while. I rinse well with cool water, then spin them in a salad spinner, about 10 strips at a time. Then I let them air dry till almost dry and iron. If I'm going to cut them into triangles, I'll hit them with spray starch. As one poster said, they shrink like crazy. I wonder how a quilt would look with all the shrinkage only going in one direction? As far as the batiks are concerned, you want to at least test to make sure they don't bleed.