On Friday, 18 October 2019 14:22:38 UTC+1, wrote:

The mixture you are using is liquid at/below the boiling point of water, correct?

Blue-Board insulation is fire-rated and easily carved to fit.

but is insulation

Balsa wood is easily carved, but not fire-rated.

no, though in fairness nor is wax or rosin. Low density may prove a pain

Dried (heated until completely dry) Bar-sand is cheap, but heavy relative to blue-board or balsa. It is also not electrically conductive, fireproof and may also be mixed directly into the potting mixture.

yup. Pebbles also work, but heat it & sand to a bit over 100C before use. The traditional packing in pre-war wax-filled kit was card. Not fire rated, and makes a good wick. Not dampproof either.


NT