I wasted a couple of sheets of plastic before I could
judge the right time to remove frame from the oven.
temperature was set to 260C gasmark 5 and the frame placed
in oven supported at either end
on 4x2 wooden
As the sheet heats up it will
sag under its own
The amount of sag
required depends on the thickness of
the sheet so experimentation is required.
In my case the
right amount of sag was almost equal to the height of the