Overheating will sometimes cause bubbles to form inside the acrylic as well as slump. It should be hot enough to just bend without using a lot of force, but a little force should be necessary, it should not just fold too easily, needs a few, (3-5?) pounds of force for about one foot of fold. If you have to go past about 20 pounds per foot, it is not hot enough.

Cell cast acrylic needs the highest temp, continuous cast needs lower temps, extruded needs the lowest. I have seen some extruded that would melt easily in boiling water. If you are using extruded, dip a piece of scrap in boiling water for a bit and then try to bend it. That will give you a good idea on how much temp you will need. I am told that an IR heat gun will not read properly on a shiny surface, but believe that anything stuck on the plastic will leave a mark after reaching folding temperature, so that will not help.

The main difference in the acrylics is the composition. The cell cast is made with mainly polymers with just enough monomer to cover and hold it together. Continuous cast uses more monomer to be able to cast in that method. Extruded has a lot of monomer in order to be forced out of a slot in that manor. Monomer melts at a very low temperature.

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