I love your pipe divider swirl! That's what I did yesterday, too, and my results were... less than stellar. I may go back to just swirling colors on the top, which usually turns out very well for me (and it requires NO MATH)s
Your 'and it requires no math' statement has given me some anxiety!
Am I supposed to math using this technique?? I just eyeball it when I separate a batch for a given design and ultimately end up with too much of one colour or not enough of another. It's a area that I tend to learn from my mistakes.
Having said all that, I love the technique and love being able to see the design as it develops.