Les Crimp on fri 4 aug 00
Hi All -=20
I have a little problem I could use some advice for.
I have 10 x 5 gal. pails of reclaimed ^6 clay. I want to convert this =
clay to a high fire clay for my wood-fired kiln.
Can anybody out there help with a suggested recipe? The clay is very =
moist in the pails and I have the use of a clay mixer to add the =
ingredients I will need. I need to know the best ingredients to add and =
in what quantities. I am assuming I must add fire clay but I don't know =
which one to use and any other ingredients that will make it work for =
TIA for any help you can give.
Les Crimp in Nanoose Bay, B.C. (Vancouver Island)
Paul Taylor on sat 5 aug 00
So you are looking at a half ton of wet cone six clay.
The clay you have may well fire to cone nine well especially if it has
little or no Iron in it, so cheque that out first.
If I had more info I could be specific. No way would Any body dare make a
certain judgment as what to add with out at least the formula of the clay.
Then you have to work out the dry weight of the clay and the dry weight of
the additives to do the adjustment accurately. Even then I would only
consider it a guess and would not give any guarantee that it would work. Of
course you can make a guess and try your luck keep adding china clay and
fierclay until you are satisfied . Glazes are fixed with more certainty.
I am presuming you are new to the technology of ceramics even if you are
not new to pottery.
Because of the strange irony is, that the more able and confident you
are to do the conversion the greater likelihood of your certainty that it
is not worth doing.
To go the other way is easier. You just add enough spar that's handy to
bring down the maturing temperature and if you are oxidizing a bit of red
earthen ware . But to bring the maturing temp up you have to add a lot of
china clay and fire clay and some times this does not work even if you
seemingly have the right amounts.
If there is a red clay mixed in the cone six body I would defiantly not
bother . Iron is a great flux in reduction (wood firing). Lots of stoneware
bodies have iron in them but in small lumps that burn to speckles. If the
iron was in finer form the stoneware would not be as reliable. In reduction
reduced iron seems to encourage bloating or maybe irony stone wares have a
lot of carbon in them but after 2 percent you are risking it after cone9 .
It will be difficult to get consistency you may get it right with the
first bucket but with the second not so lucky. You will have to mix the
whole lot together hours of work, which could be used making pots with out
the uncertainty . There is so much to get right in pottery with out taking
risks with a clay that has probably been doctored to fire at cone six and
nursed back to cone nine by you.
And then you end up with glaze fit problems. In a clay you are only using
temporarily. It is probably not worth it just for that reason alone .
I have lots of different clays in storage. Bag it up and store it well:
it can only improve - if it does not dry out. One day in the future you will
be looking for some cone six clay.
I had a quarter tone of fire clay it had so much carbon in it it could
have fired it's self. It was hopeless even mixed in with stoneware I made
decorative planters out of it for my lady and for friends. Because of the
lack of the usual angst of having to sell them some very nice pots were
made, and I have put them on the webb site, which I will have on the server
soon as I am able - God willing.
-- Regards Paul Taylor.
Westport Pottery, Liscarney, County Mayo. Ireland.
Ps to all. Please paragraph your posts and put a blank line in between the
paragraphs. I have great difficulty reading large blocks of type from a
Firstly a half ton of clay costs a lot
> From: Les Crimp
> Reply-To: Ceramic Arts Discussion List
> Date: Fri, 4 Aug 2000 10:56:16 -0700
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Making High Fire Clay
> Hi All -
> I have a little problem I could use some advice for.
> I have 10 x 5 gal. pails of reclaimed ^6 clay. I want to convert this clay to
> a high fire clay for my wood-fired kiln.
> Can anybody out there help with a suggested recipe? The clay is very moist in
> the pails and I have the use of a clay mixer to add the ingredients I will
> need. I need to know the best ingredients to add and in what quantities. I
> am assuming I must add fire clay but I don't know which one to use and any
> other ingredients that will make it work for me.
> TIA for any help you can give.
> Les Crimp in Nanoose Bay, B.C. (Vancouver Island)
> Send postings to email@example.com
> You may look at the archives for the list or change your subscription
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iandol on sun 6 aug 00
It is probable that you can convert your cone 6 clay to a higher =
maturity by adding a proportion of Kaolin and/or Ball Clay. Kaolin would =
absorb some of the excess fluxing material and Ball Clay would preserve =
the plasticity. Fire clay may be problematic. Often the refractoriness =
of this substance is due to a high silica content and this can impose =
it=92s own suit of problems. Perhaps Ron Roy can confirm this opinion.
Ron Roy on mon 7 aug 00
It would be simple if you needed a cone 8 clay - just mix equal parts with
a cone 10 clay.
If you had the recipe for the cone 6 clay I could do it easy - just a
matter of keeping the plastic to non plastic ratio the same and adding
enough refractories to raise the maturing temperature. Don't use silica -
too much cristobalite generated in those long wood fires. I would suggest
taking 10 pounds (wet) and adding (wedging in) fire clay (Hawthorne) and
100m Kyanite till you see some aborbency at cone 10. Just keep track of how
much you add.
If you want to get there faster use some EPK with the fire clay.
If you need to know how to check the vitrification let me know.
As someone said - it seems like a lot of work for something that worth 20
cents a pound.
>I have a little problem I could use some advice for.
>I have 10 x 5 gal. pails of reclaimed ^6 clay. I want to convert this
>clay to a high fire clay for my wood-fired kiln.
>Can anybody out there help with a suggested recipe? The clay is very
>moist in the pails and I have the use of a clay mixer to add the
>ingredients I will need. I need to know the best ingredients to add and
>in what quantities. I am assuming I must add fire clay but I don't know
>which one to use and any other ingredients that will make it work for me.
93 Pegasus Trail