Im doing an 80's theme cake and i want to know how to get the tye dye effect with bc?

i wonder if you could do circles of different colors (start with a solid circle in the center, outline that circle with a band of a different color icing, and so on) and then drag a knife through from the center out?

How about painting stripes in your icing bag with the colors you want before putting in your icing. You should get a good effect that way.

Painting stripes of color length wise in your piping bag works well

I think stripping the bag and then piping it on would look cool but it might be too thick and not smooth on the sides of a cake. But I dont really know how youd get the effect otherwise.

http://www.cakecentral.com/cake-photo_1675485.html

I thought that you were doing cupcakes and the stiping method is great for that,not sure about a cake though.
Here is an image of cupcakes that were tye dyed by some one on the site

I hesitate in posting this because, this was many years ago, before I knew what I should, or shouldn't do, but I did a tye dyed bc cake for my son. He loved it and at the time I thought it was great! I took the regular liquid food colors and basically put them on the top of my cake in the pattern I wanted. Then I took a brush and blended them in a way you would see on a shirt. Now - when I look back at the pictures I cringe, I see (1) that I didn't have my magic line pans then and (2) I didn't cover my board very nicely! But the tye dye effect wasn't bad! Good Luck!! HTH

First I frost the cake, then I pipe a swirl or a circle with tip 18 and zig-zagging. Then I put the next color next to the first and draw another swirl or circle with the new color, keep adding colors and new swirls or circles then I draw a toothpick through the two colors to mix them.

http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1523233

http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=52898

http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1325506