[Sca-cooks] pottery braziers, cooking in pottery

[wheezul at canby.com]

Might you explain the difference in "cone" in terms of temperatures please?

Thanks,

Katherine

>> Most modern potters fire to cone 5 or 6 which is a stoneware fire. Most
> european
> (or at least English) pottery in period was fired to earthernware
> temperatures,
> cone 05 or 04.  This makes a difference to how a clay body behaves. 
>
> When you fire to stoneware you vitrify, i.e. make the clay glass like.  If
> a
> crack starts in a vitrified body unless there is heavy grog (sand, fired
> clay
> particles or shell) the crack will run through the pot and you get a
> crack.
>
> In earthernware the body is not vitrified, this means that the cracks
> don't tend
> to run very far at all.  Think of it as the difference between a
> terracotta
> planter (you put water in and it leaks through the body) which is
> earthernware
> and a ceramic vase or mug (you put water in and it stays on the inside, no
> weeping) which is stoneware. 
>
> One way to make stoneware more resistant to cracking is to increase the
> amount
> of grog (such as is often found in Raku clay) or to incorporate sand or
> other
> material in.  Something that will "interupt" the crack.
>
> Helewyse
> (another potter).
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