Can anyone please tell me how to do the tie-dye effect with icing or color on top of a cake? My grandaughter wants a tie-dye butterfly for her 6th birthday. I have the butterfly shape pan but have no idea how to make that tie-dye look. The napkin with the pattern I want to coordinate with has a spiral tie-dye pattern. (I do not have access to an air brush.) Thanks for any help with this.

If you use a crusting BC you could just put different colored blobs of icing on it, then go back an smooth them together using the paper towel trick..

Or you could use fondant any get a few different colores, put them together and just do not kneed them all the way, gives a great marble/ tye-dye look...

you could always use the spray can color thingies they sell in the grocery store instead of an airbrush. Or you can simply paint on fondant!!

Here is a cake I tried to get the same effect on. It was just for practice so I just used the buttercream colors I had left over. i piped the colors on in a misc. pattern and tried to smooth as best as possible keeping the colors together but seperate. Then I put wax paper on top and smoothed it with my hands as best as possible put it in the freezer for aobut 15 min and then peeled the wax paper off. I wasn't very happy with the outcome but more practice might pay off.
http://www.cakecentral.com/modules.php?name=coppermine&file=displayimage&meta=allby&uname=karebere&cat=0&pos=1