Homebrew PCBs

You should use mineral wool, it has a significantly higher operating
temperature (750°C).
Theoretically glass wool should suffice with 500°C but it may be
hotter than expected very near the heating elements.

There are also ceramic fiber wools with even better temperature
rating, but much more expensive than the regular building materials.

Mind that you will defeat the thermostat if you insulate the oven.
With cheap ones the bimetallic element sits right behind the dial and
is controlled by guesswork and wishful thinking rather than the actual
oven chamber temperature. But I expect you replaced that long ago
anyway.

The oven may also rely on thermal losses to keep the heat away from
certain parts (plastic etc.). You will use your own judgement to
identify and remedy such problems.

ST

On Sat, Mar 10, 2012 at 7:39 AM, ftkalcevic <frank@...> wrote:
> I'm using it as a general purpose heating oven too (not food).  I was using it to preheat some moulds.  Sitting at 250C, the "Caution Hot Surface" sticker on the top was at 110C.
>