I have gotten other great input on other topics on this forum that I'm grateful for which has helped get me to this point: https://flic.kr/p/q2u427
My riser is fire brick (yellow ones) and old chimney brick (red ones) both salvaged from chimneys, mortared with pottery clay and river sand (about 1:3) because that's what I had available. The base is concrete (to get it above ground level since it's outside) insulated by the following layers above: cored brick, cement board, perlite/clayslip boxed in by cored brick, cored brick, fire brick, and then another layer of fire brick which is the burn tunnel (so about 10" of insulation under the burn tunnel, fingers crossed that's enough to insulate cement).
Tomorrow I go to work cobbing a base on which to set the riser insulation and eventually drum. I'm looking for ideas for how to keep the cob from touching the ground and wicking moisture and cracking the cob? Materials I have: urbanite, cinder blocks, plenty of brick of all kinds, limestone (hoping to save for conductive material in benches), clay chimney flues, plenty of clay mixed with gravel. I have a budget for some river sand I was planning on buying.
Also, this will be my first cobbing experience ever. I was planning on starting with 1:2 clay:sand with some straw mixed in. My clay is dirt that is clay-y, some of which has quite a bit of gravel (probably 1/4-1/5 of the volume). How much of the gravel do I need to pick out? What am I risking by leaving it in?
Also, I sifted some of my dirt of gravel but it's been sitting in water. Is there an easy way to drain the water other than sieves? Can I just dump it out onto my piece of plywood and let it dry out a bit before mixing in river sand? Is this necessary?
Yes I can just play and experiment and I will but any any experienced ideas are welcome