[Milsurplus] Flattening Plastic?

[Kenneth G. Gordon]

> The CRT Graticule is a disc of green plastic and is
> warped.  The plastic has only shrunk slightly if at all.
> There are no cracks, and the plastic is not clouded. The warps
> are basically "waves" about 3/8" and the disc appears to be
> about 1/16" thick.
> 
> Is there any way of flattening the plastic out?

I have used the following method with about a 50% success rate.

Lay the warped piece in a GLASS baking pan, put it in your oven, and 
set the heat no higher than about 150 degrees F.

If you can watch it, take the pan out of the oven just as soon as the 
plastic "relaxes" to flat. If your oven doesn't have a glass door through 
which you can watch it, check it every few minutes.

Let it cool and then remove it from the pan.

If you use any kind of pan other than spotlessly clean glass, the plastic 
will stick to it and it will be nearly impossible to remove without 
damaging it.

Ken W7EKB