High temp

[danelaw]

Hi, can anyone recommend a fine clay that can withstand extreme heat? It's for casting metal artifacts, i thought this would be the section on the forum with the most knowledge of clays, thanks

[potpartner]

What temperature are we talking?

I dont know anything about casting metal but i guess that the heat shock would be 'instant' when the moulton metal hits the mould..... so thermal shock would be the issue and a smooth clay would be less able to tolerate that shock than a grogged clay..( I'm assuming that it is 'fired clay' mould you want to utilise....your not contemplating using unfired clay for a mould ?)


Fireclays are super resiliant but 'rough'

[Daesul]

I did some metal casting - if you are thinking of using clay to make a crucible to melt the metal in, I think Ivanhoe might be best. It's highly grogged and resists themal shock well.

But if you are talking about the moulds themselves, we didn't use clay for that - we used kiln bricks, which we carved the shapes into. Kiln bricks are very soft and heat resistant and make fantastic moulds. I cast a sword, axe heads and some pieces of jewellery using these.

Basically, you carve your shape in the brick, then rub the brick dust created from the carving onto the inside of the mould to make it smooth.

[lockettpots]

You may find this useful

http://web.comhem.se/vikingbronze/casting.htm

Towards the end of the article there are some details of crucibles and moulds using a clay/sand mix.

John

[danelaw]

Thanks for the replies

[toronsmith]

Well it's not necessary that the temp is always high enough to be of concern. A few more degrees could become an issue. His body is generating a temp, most likely in an attempt to fight of infection, so don't try and supress the fever. Instead, let it run its course..