Below you can see a simplified version of a strip heater. The electricity heats the wire and this heats the piece of plastic above. When the plastic becomes warm you are able to bend it along the heated line.  If the wire gets too hot it will burn the plastic making it bubble on the bend. A good idea is to keep turning the plastic over so that one side does not become hot. Another idea would be to turn the heater down and yet another idea would be to raise the plastic away from the wire a little.

By looking at the diagram opposite you can see that raising the plastic away from the heater makes the heat spread out and a wider strip of the plastic becomes pliable (bendy).This can be useful if you want to bend a large area of plastic rather than just bend it on a line. Once the plastic is hot you need to be able to handle it safely so wearing a pair of thick leather gloves is useful. It is difficult to hold the plastic in shape with your hands whilst it cools, so before heating it is advisable to have a jig ready to fit the plastic in. Above you can see a number of jigs used for making different shapes.