Bubbling cauldron opinions please

I have been working the idea of having a bubbling cauldron this year and am thinking about what else I need to do. This is just a test run.

http://s6.photobucket.com/albums/y213/kristy510/?action=view&current=050811.flv

I tried with dish soap and got white bubbles even though I had food coloring so that idea was out. I then moved on to other ideas. I settled on flour, water, and food coloring. I like the effect for the most part. I have to thicken up the "soup" a bit, add more coloring, and put a flex hose in it to spread the bubbles around the cauldron.

Is there anything else that you can think of I should try? Also what do you think so far? Thx for your help!