Clay Gallimaufry: Red Glaze Experiments

Thursday, April 23, 2009

Red Glaze Experiments

The very first thing i want to do here is give a special word of THANKS to John Post. He's an awesome fellow. In my book, he stands 120 feet tall !!!

Gotta mention that for 3-4 years, i've been trying to achieve reds. Have mixed this chemical and that; followed this recipe and that. Testing one procedure after another.

Without success.

The fact, that neither of my kilns operate "right" hasn't helped my pursuit a'tall.

ok. All that said, let's get on with the story.

Found John's site: http://johnpost.us/ and perused his ceramic creations along with his detailed glaze information.

Decided to try out one of his glazes:

Petes's Tomato Red #13 (+ more bone ash) +++

10.8 % -- Frit 3134

23.1 % -- Nepheline syenite

10 % -- Bone ash

6.2 % -- Magnesium carb

7.7 % -- Whiting

21 % -- EPK

21.2 % -- Flint

John says to add:

2 % Bentonite

10 % Red iron oxide

However, i skipped the bentonite and only added the RIO.

Please see his detailed notes at the link above.

Ought-a explain here that it's in my nature to tinker with things. And i'd read that talc helps enable reds. And too, cause i haven't yet gotten either of my kilns to fire past ^5, i wanted to bring the glaze temp down a wee bit. So i reduced the 23.1% Neph. syenite to 22 %; reduced the EPK to 15 % and added: Wollastonite at 10 % and Talc at a generous 6 % plus Rutile at 1 %.

Now if you follow along his site you'll find that on one of his bowls, he puts a glaze called MYB over the top of the tomato red. I noticed that the flint, EPK, Neph, Whiting were all basically in similar amounts as the tomato red; the only additive which differed greatly was the zinc oxide.

And, being lazy that day, decided to use the tomato red base and add 12 % zinc oxide instead of the former additives.

Applied one thick coat of the PTR#13 with one thick coat of the MYB adoptation over the top quarter of the inside. John had said the MYB was runny and yes. even the adoptation was runny.

Now to stir this stew with absolute confusion: remember i mentioned that my kilns don't exactly work well ???

That being so, here's the scoop on firing: fired the gas kiln in oxidation, then at ^012 started body reduction. At ^05 -- returned to oxidation and continued firing. Even with extreme coaxing and trying every thing i knew, couldn't get the kiln to fire hotter than 2012 degrees F.

Had started firing by 5:30am and it was after midnight. Whether or not the pots had glazed, my eyes had glazed over with exhaustion !!! So. Put it back in reduction for approx. 20 minutes and shut it down.

The next day found that the glazes had not vitrified and there was absolutely no indications of a red color.

A couple of days later, had a new theory on how to get my electric kiln to fire to 2167 degrees F. In searching for a pot that i didn't mind losing if the theory failed, my eyes lit upon the pot described above. Put it in the electric kiln for a totally oxidized firing . . . .

And below, you can see the results:

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Now on this next photo, i changed the procedure of the glaze a wee bit. Had some dabs of a Rhodes #18 glaze. So applied this to the outside, and splashed the PTR#13 with zinc in a small area. Intriguingly, believe that if the whole had been glazed with the Rhodes and the PTR#13 would have achieved a most interesting red-surfaced pot exterior !