buy your vermiculite blocks from a fireplace supplier they are much cheaper!!!

Dunno the cost of things these days, but it may be more economic (unless you are bent on a self-build) to look for a second hand kiln?

I have a Paragon (Sc2, I think), which has been fine for most odd bits I’ve wanted to heat treat.  There are several other makes and different types out there.

Hardening is the easy part for many jobs – heat to red with a gas flame and quench.  Tempering is easy enough, too – up to the maximum temperature of a domestic oven, or colour if you can see it (I cam’t).

Check out lampworking, metal clay, enamelling and other glass hobby sites (such as slumping) for inspiration, maybe?

My kiln has a ‘bead door’ (for lampworking) which has, on occasions, been useful for heating the end of longer items without opening the main door.

DO NOT consider any type of heavy brick, eg those used in night store heaters ! Noel.

I’ll second that!  Ages to heat up – and likely too slow to cool down on a ramped cooling program.  Little or no thermal insulation, either.

I’m not sure, but think the paragon (etc) kilns use both bricks and ceramic fibre/wool for insulation.