Comment

Comment by Norm Stuart on November 20, 2013 at 6:19pm

Both pucks of Kyanite and Wollastonite mixture sieved together fired just like stoneware at Cone 6.  Without access to a machine to perform pressure tests I'll have to make new batches in a bar-shape to test their strength.

Both the 80/20 and the 70/30 seem just as hard and take glaze well.  Both look similar to Alexandre Bigot's finished pieces but perhaps more granular, so I'll add Talc to the next batch of pucks. I think the damp 70/30 with more Wollastonite seems slightly more compressible and able to hold its shape prior to firing.

It's an interesting exercise because every material I know which could add plasticity will off-gas during a kiln firing, causing thick form pressed pieces to crack or explode, yet the pieces have to hold their shape prior to firing.

Comment by George Lewter on November 19, 2013 at 12:44am

Yes, I know that the regular kaolin helps with the suspension of the glaze slop, and with making the powdered glaze harder and better adhering to the body before firing. I only plan to use the Glomax to partially replace regular kaolin where I find excessive shrinking, cracking, and crawling, before and during the glaze firing. Licorice is in a prime example. If I put it on thick enough for good coverage, it is likely to crack during drying, and then crawl during the firing.

Comment by Norm Stuart on November 19, 2013 at 12:05am

Glomax calcined Kaolin reduces shrinkage, but this product has lost all of it's ability to suspend glazes, so there's a limit in using it as a substitute.

Comment by George Lewter on November 18, 2013 at 7:00pm

I bought calcined kaolin recently to reduce drying shrinkage and crawling in my high clay glazes. No results to report yet. 

Comment by Norm Stuart on November 18, 2013 at 5:28pm

I sieved together two combinations of Kyanite and Wollastonite today. The first is 80/20 the second 70/30.

I found I needed to use a water spray to make it slightly damp to hold together after compressing each into a puck using a hammer in a ceramic vase mold.  I glazed each and stuck them in a Cone 6 firing. I also placed them on some alumina hydrate in case I guessed wrong and they become too molten.

I'm confident Bigot's stoneware powder is something very much like this. It's grey in color and will have a 0% LOI. The compressed body is loose enough that the water I sprayed in will easily evaporate.

We'll see what happens when they fire the kiln.

Comment by Norm Stuart on November 18, 2013 at 10:24am

The roof and ceiling was made to look like majolica in 1900, but the lack of flaking from water intrusions suggests that it too is actually stoneware made at the Zsolnay studios in Budapest.

Bigot explains in his patent how the thick pieces are made in a mold by painting the inside of the mold with moist glaze paste, then shoveling in dry stoneware base and using a hydraulic press to form the piece for the kiln.

Because of the extreme thickness, this "stoneware" needed to be material which does not off-gas in the kiln - so pre-fired grog with a meltable spongy binder like Wollastonite, or some other type of meta-kaolin mix without 12% water in its chemical structure like pre-fired kaolin and ball clays.

The source of the "stoneware powder" aka "Grès Flammé"  is the secret not revealed in Bigot's patent - but he had a separate part of his studio workshop making the "stoneware powder" where visiting artists were not allowed to venture. When he visited other studios as he did in Frankfurt and Budapest, he had the "stoneware powder" shipped in, explaining that it was an ordinary clay from the banks of the Seine - although there is no evidence he sourced his material there.

Comment by Denice E. Demuth on November 18, 2013 at 6:13am

Norm is the ceiling a majolica tile and did they let you get the formula for the clay?   Denice