Primitive Clay Based Refractory Mix

[apexmateria]

I'd like to use a mix for my forge with clay as the main ingredient. Anyone have experience making a mix like this?

Quote

50% clay 10% wood ash 40% soil / aeration material

Instead of soil I was thinking of using dry, hollow, straw-like material chopped into small pieces. That would create lots of air pockets in the clay.

 

[Irondragon Forge ClayWorks]

You would basically be making adobe, fine in a fireplace or coal forge, but it will not stand up to the thermal cycling as a flame face or insulation of a propane forge. Might make ok doors.

[ThomasPowers]

Not nearly as insulative as modern refractories; fine for solid fuel forges that have BTUs to burn; but end up costing a lot more to run in a gas forge.  Is this an experiment or does spending extra money for a poorer material not concern you? 

(Usually when I get this question it's associated with "I don't have much money and so I think that by saving US$20 on refractory and spending US$200 more in fuel I am saving money!")

[apexmateria]

Very good points, I didn't consider fuel costs, insulative performance, or how well it will hold up to a flame.

I think I'll buy some bricks / refractory mix and make my own and do a comparison. I'm just really curious about the performance of the primitive mix.

[ThomasPowers]

Well "primitive" forges were not gas forges and so mixes empirically developed for non-gas forges may not be suitable for gas forges.

I know for solid fuel forges just a bed of ash has been used as the firepot.  You dampen the ash and form it in a bowl and start your forge fire.

Refractories have historically been a problem; Huntsman had great difficulties with refractories as he was working with the nascent cast steel industry. Dr Feuerbach's thesis on crucible steel has a lot of analysis of how the crucibles were made and what they were made from. (Including using old crucibles for grog!)

Chemical activity goes up as temperatures rise and things can act very oddly.  I remember how strange it was when I accidentally "boiled" some terracotta trying to improvise an enameling kiln from my forge using a clay pot.  I now know that terracotta is a relatively low temp clay...