Can I make fireclay from raw materials, suitable build my inner dome

[wilgaburra]

Having trouble sourcing commercially available material, I am wondering if I can make my own fireclay. I can get wild clay, hydrated lime, a variety of sands locally.
Does anyone have a recipe?
I've read that ground firebrick grog can be added but, I cant get that easily, so I'm wondering if I could substitute ground pumice for that.

[Hattori-Hanzo]

Have a look in the "finding building materials" sub forum for possible leads to clay in your area.

As i understand any powdered clay will work in home brew. At the time I could not find fire clay either so went with a HV ball clay.

I believe pumice is an insulator so maybe not recommended for the main dome of the oven though I'm not 100% sure on that.

You can make your own powdered clay but it involves a lot of work, the cost of a bag of powdered clay is so little I doubt it would be worth the effort.

[wilgaburra]

Thanks Hattori-Hanzo,
I can get ball clay from my potter neighbour, but I think is not powdered and is fairly old. My thought with the pumice was, if ground fine enough would lose some of the insulating properties but still have the alumina/silica components.

[david s]

Talk to your potter friend, he no doubt uses powdered clay for his glazes and will tell you who supplies him. Get the cheapest you can find, but avoid Bentonite as its extremely small particles lead to excessive shrinkage that you don't want. Fire clay to a builder is any cheap clay added to make mortar more sticky. Fire clay to a potter is a high alumina clay, expensive and highly resistant to really high temperatures. Don't ask your potter friend for fire clay.

[wilgaburra]

Thanks for the advice David.
I picked up half a ute load of wild clay where a local road was graded the other day with colours ranging from white to pale orange, it seems pretty clean, and I got a free load of washed Sydney sand from a builder who ordered too much. I read somewhere about puddling in 2:1 Sand to clay. Do you think it would be worth me trying to make a fire clay from this and if so is there anything else you would add?
I figure I could possibly use it for my outer dome if not the inner one. Otherwise I'm sure the kids could have fun with it.

[david s]

2 sand to 1 clay throw it onto the middle of a tarp and water it down then start squishing with gum boots or bare feet, add some straw for reinforcing. Lift the corners occasionally to roll the mix back into the middle. If you can organise some female company and alcohol it can be a fun time.

[wilgaburra]

Sounds like fun - things could get a bit slippery. Would the straw reinforcing be OK in the inner dome?
I read somewhere that it would burn out leaving air pockets. What about brickies lime, would that help glue it together?

[david s]

Normally the straw is used throughout the inner layer, but you could omitt it for the first inch of thickness.