How are you doing it? I have a large stainless steel stock pot with a separate insert for cooking that I use. I place it on a electric stove to create the acetone vapor. I normally get the vapor started, give part 5 minutes, check on how it went, touch up needed areas, then do another 5 minute run. So about 10 - 15 minutes if I want it extra smooth. After that I let it sit for 4 - 8 hours and take a knife to clean up edge on where it sits on the ground. I use parchment paper, never use wax paper or foil!