Hi, I tried using white-out a year or two ago, to avoid fusing AS
when fold forming, but I did not like the texture it left on the
inside surfaces after confirming. Maybe you’re using a different
brand that paints on more smoothly? My students and I resolved the
problem by being very careful when annealing to stop as soon as the
Sharpie marker fades to a ghost. The one idea that I did not get
around to trying, that might be worth checking, is “dirtying” the
surface inside the fold with oil. If you like that idea, I’d suggest
starting with an organic, like olive oil, etc., so that the fumes
during annealing would be less toxic—but ventilate nevertheless,
of course.
Cindy