Liftoff of metal wires requires soaking the wafer in solvents to “lift off” the unwanted metal. This is a common technique in research, because it is so simple, but liftoff is not usually used in production since there are more reliable and less messy ways of patterning wires. Acetone is a common solvent used for dissolving resist, and it becomes more effective if you heat it. But it also becomes explosive if you heat it! So if someone tells you to boil the acetone, tell them no- that’s foolish and unsafe. Instead, use warm NMP, which can be heated up to 150C without becoming dangerously explosive. (If you heat NMP above 200C it becomes acidic. Isn’t that strange?)