ross01@TELUS.NET on wed 18 sep 02
In "Smoke Fired Pottery" by Jane Perryman she covers her pots in "crank
slurry" to act as a resist against the smoke. What is this?
Thanks
Julie
Steve Mills on thu 19 sep 02
Some of the clays available to UK Potters are called Crank Clays, These
are very coarse and are descended from the Coarse Marls (that word
again) used to make Saggars for the old Stoke-on-Trent production Kilns.
They are very popular for Sculptural work, and large hand built pots
etc. The high proportion of Grogs in them make them very resistant to
thermal shock. The Slurry Jane uses made from these clays stays put
during firing, but is relatively easily removed afterwards.
Steve
Bath
UK
In message , ross01@TELUS.NET writes
>In "Smoke Fired Pottery" by Jane Perryman she covers her pots in "crank
>slurry" to act as a resist against the smoke. What is this?
>
>Thanks
>Julie
--
Steve Mills
Bath
UK
Pat Southwood on thu 19 sep 02
Dear Ross,
It is a sloppy paste ( slurry) made from "crank" clay. This is an English
clay, some times called "craft crank" it is a stoneware with a high
proportion of grog added. Usually used for sculptural and garden pot
purposes.
It is used as a resist in smoke firing because it copes with thermal shocks
and knocks off the pots easily after firing as a sort of shell.
If you dont have access to anything like this, add grog (bought from shops,
or finely ground up, fired bits ) to the clay you are using.
I can recommend Jane's workshops from personal experience.
Best Wishes
Pat.
----- Original Message -----
From:
To:
Sent: Wednesday, September 18, 2002 3:50 PM
Subject: What is crank slurry used by Jane Perryman in smoke firing?
> In "Smoke Fired Pottery" by Jane Perryman she covers her pots in "crank
> slurry" to act as a resist against the smoke. What is this?
>
> Thanks
> Julie
>
>
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Janet Kaiser on fri 20 sep 02
A "crank" can be one of several things beyond a crusty, eccentric person or
a type of axle. So from the great holder of 1001 useless facts and tiresome
definitions, here is a little history lesson!
In ceramic terms "crank" was applied to several items of kiln furniture
made of refractory clay in The Potteries (and I presume elsewhere in
England). A crank was any kiln shelf, but especially a small thin one up to
a foot long used to facilitate economic use of kiln space (i.e. fill every
cubic inch).
BTW It was really very funny when I was introduced to this term by our
studio technician... "Pass me a crank, Janet" had me searching around for
an iron bar "thingy"... Why he wanted such a thing, I could not imagine...
Of course I was glared at and once again relegated to "stupid student"
status as he grasped a tiny kiln shelf from the pile... Yes, I am old
enough to remember the days when a car could be "cranked" from the front.
But where was I? Oh yes... to make matters more complicated "crank" was
also the term applied to the kiln furniture used for making tiles... The
vertical holders with pins to hold tiles (or plates) are/were called cranks
and the square posts to hold them up were called "dots". I have no idea if
they are still in use.
Indeed because all kiln shelves or "holders" could be referred to as
cranks, of course the clay they were made from was "crank clay".
To muddy the waters even further, "Crank" is also the trade name of a clay
produced by Potclays, Stoke-on-Trent, England and probably/presumably what
Jane Perryman uses. It used to be rather variable in quality (don't know
how it is these days) but helped to make a more open texture in
thick-walled sculptural work, including coiled pots. It was the first
ready-made commercially produced clay I remember using, which did not need
additional grog wedged in and was a great time saver, even if it was
different from one batch to the next. I do not believe it was at all like
true crank clay, but it was a catchy name to use...
But, "real" crank clay was originally simply a mixture of coarse, grogged,
refractory clay used to make the "cranks" or kiln shelves. So if you are
trying to get or make a similar clay, you will need to aim for high grog
content and low shrinkage rate. A crank slurry would be a thick slip made
from it... Not too thin, because highly grogged clay is not very useful
when really runny.
Hope this helps, rather than confuses the issue?!
Sincerely
Janet Kaiser
The Chapel of Art =95 Capel Celfyddyd
8 Marine Crescent, Criccieth LL52 0EA, Wales, UK
Tel: 01766-523570 URL: http://www.the-coa.org.uk
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