How to clean stained frosted glass

Hello! I usually soak my stuff in 99% iso and if things are really stuck on, I’ll use a few Q-tips. The end of this bowl that gets heated up stained over time. I can’t for the life of me get it fully clean again. If it was a banger, I’d hit it with my blazer until it all burns off, but that would crack this one. Any advice would be appreciated!