Just last night, I did these for the 1st time. I'd poured 6 diff colored tarts and when I was done, I had some extra left over of one color. The 1st tarts I'd poured were just starting to get a skin on top and I thought, what the hey - I'll pour my leftovers on them. When cooled, they had a perfect division of the two colors, but were just as smooth as could be. Happy accident, considering how I usually have things happen.