This
was fun! Thanks, Rik. I do feel sheepish to receive a coveted tip-of-the-hat, since I took my shot only after clues were disclosed that braver people postulated without.
Not water soluble--so likely not a carbohydrate; not soluble in degreasers--so likely not a lipid. For common household liquids, that leaves proteins as a prime suspect. And proteins tend to be long, intricate chains that fold and twist together when perturbed by mechanical, chemical, or kinetic means. These twisted proteinaceous structures can be very durable.
It would be interesting to film the development of the funnel-shaped formations you documented, and to observe their formation in skim vs. two-percent milk. I'd suspect that the funnel shapes form around spots from which bubbles percolate upward; since there is a phase-change going on there, lots of opportunity should exist at these points for messing with proteins. And I'd suspect that the presence or absence of lipids (skim vs. two percent butterfat milk) would at most be an influencing factor, rather than something substantially incorporated into the resulting structures. But who knows, without testing?
Rik, much fun!
Wim, if I've managed to stumble on an answer more quickly than one of the wittiest and most insightful artists whose work includes the macro realm, I'll bask in a swelled head for a day or two--probably inappropriately, but thank you for it anyway!
Harold, you're caramelizing them, right?
Cheers,
--Chris
