The polystyrene frames have only a 65 ºC (149 ºF) maximum temperature resistance. At the same time, the polystyrene frames stay straight well in use. Experience has shown that polystyrene doesn’t absorb hydrocarbon from wax, and that is why it doesn’t bend over the years.
We recommend the temperature of the wax to be at 60 degrees Celsius when waxing the frames (right at the point when the wax melts).
Second, avoid use of a paint roller to wax the frames. The roller, in addition to high wax temperature, could cause the frames to bend. This is because you apply pressure with the roller and due to the pressure and the temperature the plastic bends and then “remembers” this position and stays there. Even if you apply the same pressure from the other side, the plastic is already deformed due to high temperature.
A safer way to wax the frames is to dive them in a tank with the melted wax. This way no pressure is applied from both sides and a bit of higher temperature can also be used when waxing the frames.