Allen Dick wrote

> I understand that the design is nothing particularly difficult, but I
wonder if
> there is any necessity to use glass on top, or if plastic will work as
well --
> assuming it does not melt.

Plastic does work but most plastics do not have UV inhibitors in them so
they tend to break up into little pieces in a short time.  When I tried a
piece of plastic (many years ago) it worked just as well as glass but broke
up.  Allen in your part of the world, remember to tilt the melter towards
the south (north in our part of the world) at the angle of your latitude, if
that is possible.

Trevor Weatherhead
AUSTRALIA