One of the Regulars
That sounds like a big problem, looks like you're going to stick with it, let us know how it turns out, I hope you beat this problem. I am not real happy about the surprise problems, it always throws me off. I almost tossed my brown hat into a gallon of denatured alcohol to wash out all of the shellac then start over, the only thing that kept from doing that was how was I going to mark the crown-brim break.I was planning on posting today. It did not help. It just made the dark spot darker. I flipped the hat inside out and started it all over again. The problem was a weird one. It appeared to me that the felt had 4 small flakes of undissolved shellac embedded in the felt. I tried: steam, alcohol to melt and remove them but it did not budge the shellac much, only darkened the felt. I ended up scraping the flakes out with an exacto blade. Never seen undissolved shellac flakes before and never want to see them again.
This was on a western weight felt that I had already blocked inside out, pounced a lot to soften it some. So this is the 3rd blocking on this felt.
Good Luck, I hope you beat this problem.