Explainers, Sal and Lianna, led us in a bubble prints training this year. They set up long tupperware containers with different bubble/color mixtures. We each had our own straws and blew bubbles in the containers. (I was reliving the days of blowing bubbles into my carton of chocolate milk!) We laid blank index cards over the bubbles and they “popped” into amazing prints (or we scooped them up to sit on top of the cards until they popped). Lots of experimentation and variations!
As for color, I think they used a water-based tempura paint instead of food coloring. l liked the other bubble prints post that suggested using graph paper, sounds like a nice way to make comparisons and take measurements!