I used Seta Color fabric paint from Dharma Trading Company. I chose to leave the cotton dry before painting the fabric. I plopped a couple of ice cubes directly onto the fabric with large salt crystals sprinkled around.
The fabric was placed in the sun... I had no idea what would happen!
Ah... the magic is complete!
What interesting results! The ice cubes seemed to push the paint out causing some fun migrating of colors and the salt captured some of the paint creating spots.
Why don't you give it a try and let me know how your fabric turned out!
The "Ice Cube" fabric is for sale; please click on the Hand Painted and Hand Dyed Fabric Tab at the top of the page!