once you can see the fingers form you are on the way, they accelerate as there is less and less stuck to unstuck surface. The key as you can see is not to hurry it up, that's when glass breaks. I would also recommend you allow the tube to cool slowly, maybe put it out of direct sunlight. I dont think it would be a good idea to take the hot tube directly into a aircondioned house and esp not to wipe it down with any liquids until its at ambient temp.