I decided to try the Spin Swirl Challenge one more time. After asking a few questions in the forum, I learned that low water soap batter will stay fluid longer, giving one more time for colouring and swirling. So, I used a suggested recipe, reduced the water to lye ratio and tried again.
It turned out much better! However.... yes, there's a however... I decided to add a little titanium dioxide, dispersed in water, to one third of the batter. I shouldn't have been surprised but I was - the added water instantly thickened up the batter to plopping consistency. I abandoned it.
It seems so counterintuitive, doesn't it? Usually, adding water will thin things down. With soap batter, the added liquid seems to force the batter to thicken. I'm not sure I understand why that is but it has definitely been a learning experience.
So, because I'm happy with my third attempt (generally speaking), I can show you Attempt #2.