Aceton works quite well for me, with a very clean fabric.
But as I find it very difficult to have a perfectly clean shell, I decided to use those marks in an aesthetic way. This with some other ideas and it makes something quite cool

But I’m using a torch, not oven.
By the way, could anyone give me a quick feedback about the annealing time ? The torch makes a very quick warm up, and I only fire for a 3 or 4 minutes. It then cools down pretty quickly, I’d say the whole process may take 15 minutes. I like the way I work now, and I won’t be able to get an oven before a while, but I’d be curious to know the consequences of such a a controlled and long annealing 🙂