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new post/thread notification: pit firing

updated tue 15 jul 08


Andy Clift on fri 11 jul 08

From: "Claystation Community"
Date: July 11, 2008 11:52:41 AM PDT
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nadesprockett has just posted in the Pit Firing forum of Claystation
Community under the title of Chipping off of a TS slip or just the
fading of a smoke fired pot!.

This thread is located at

Here is the message that has just been posted:
Hi all-
I've just started smoke firing some coil pots I've made and love the
finish I have achieved...
But has anyone ever had chips of the pot break off ??!!

This was an experimental beginning....
I made a large sculptural pot using a raku clay for strength, and made
up a TS slip to put on over burnishing and then burnish again...( the
TS was applied many times and completely covered the grog in the raku

I made the TS from powdered red earthenware clay ( only thing the
suppliers had....)
Bisqued to 900'c in an electric kiln....Smoke fired using newspaper
and kindling......took about maybe 30 mins- so just a light smoking...

All great and fine....
I noticed then, maybe 3 weeks later that what looked like chips ( ie
small pieces) of the actual surface of the pot was coming away! I can
see the bisqued raw raku clay where the TS seems to have literally
fallen off the pot surface!

Is there any way I can stop this from happening?!
Is this because I used an earthenware red clay to make the TS and its
on a raku stoneware body?
Do I need to fire/ smoke it for much longer to make it gel better?

And this leads to another problem!!!
If you smoke fire a burnished coiled pot, with a TS applied ( again
using either red or white earthenware clay powder to make the TS)
Can the smoke marks eventually fade?

I got a shock when I saw that a buff stoneware clay, coiled pot thats
been burnished, ( no TS) the carbon black/ greys/ taupe colours
achieved in the smaoke firing ( again about 20 - 30 mins with
newspaper)have faded dramatically over 3 months...

Is there any way to stop this from happening?

Surely, you could never sell a pot that has the potential to fade?
Thats a money back guarantee from an angry customer!

Has anyone heard of making up a TS slip with porcelain powder ( so it
is stoneware firing...)

As you can see, I'm floundering here....
Any advice, pointers , own experiences , other knowledge would be
greatly appreciated!

I have a chance to put a piece into an exhibition soon, but if theres
fading and chips flying......oh no!

Thanks again

Bonnie Staffel on sun 13 jul 08

Andy Clift

Andy, I have made such an error in my early days of working with smoke
firing and TS. It is my belief that you have applied the TS too thickly. =
only need a very thin wash, maybe only two coats of it., with a polish
between the two coats and after.

As for keeping the smoke pattern from fading, you need to apply a =
sealer. I
used to use Future, an acrylic floor polish. However, I didn't like the =
shine that was left on the pot. Through another potter, I found the =
called WeldBond originally made in Canada. However it is now =
manufactured in
the US and you can find it in some home shops, like Home Depot. You can
probably also find it on the Internet. =20
185 Weldbond 8 OZ Bonding Adhesive Bonds Almost Anything FRANK T ...=20
Weldbond, 8 OZ, Bonding Adhesive, Bonds Almost Anything, Bonds Metal,
Styrofoam, ... Dries Clear, Can Be Reduce With Water To Seal Porous
Surfaces....The plastic bottle is red with white and green additions, 8 =
is really cheap.
I cut it with water to make a wash that looks like skimmed milk. Only =
a bit and the bottle lasts a long time, depending upon how many pots you
plan to seal. It is also non toxic and be sure to wipe up the drips. I
apply it with a sponge brush. I have coated the inside of a smoke fired =
and after drying was able to put water in it for fresh flowers with no
seepage or leaks.. I have a very large pit fired pitcher in the Lark =
Pitchers Book where I finished the surface with WeldBond and it looks as
bright as it did the day I pulled it out of the ashes.

I would also apply this material to raku to inhibit the reoxidation of =
copper and see if it works for that as well. I don't Raku, so can't test =

Hope this helps.

Bonnie Staffel
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