If one wants to avoid using glass in a solar wax melter,
one cannot do better than Dupont Tefzel plastic.

I used it to glaze my main greenhouse here at
Farmageddon, and as a winter replacement for the
screens on my front porch.

The stuff is nearly bullet-proof.  If mounted properly in
a sturdy wooden frame, this plastic (no thicker than
the clear plastic covers that the airlines put on magazines)
can take wind-blown branches, the occasional baseball,
and driving wind and rain without any problem.  My strongest
friend cannot rip Tefzel.  One must cut it with a knife.

As far as long-term weathering goes, I know of a greenhouse
that stood for 15 years on Cape Cod (Massachusetts, USA)
without the Tefzel turning yellow or breaking down in the sunlight.
(At the now-defunct New Alchemy Institute near the town of Woods Hole)

Getting the stuff is a pain, and it is not cheap.  One must order from
DuPont directly, and they really do not like small quantity orders.
But they WILL send any number of 8 1/2-inch by 11-inch "samples"
to anyone who asks, free of charge, and one can make a rather nice
wax melter with just one sample kit from DuPont if one is willing to make
up two or three small double-glazed "windows" using these samples.

        hey, "better living through chemistry" really DID happen  :)

        jim

        farmageddon