Ishihaze glaze recipe
Posted 11 December 2012 - 12:54 AM
Posted 11 December 2012 - 02:03 AM
I will sometimes add a 50/50 mix of dark (iron rich) silica sand and high iron grog to a white stoneware body yielding a nice white background with plenty or flecking. the raw clay has a sort of "cookies n' cream" candy bar look.
Or adding granular magnetite or ilmenite can give similar effects when added to your favourite clear or white glaze. Pitting and uneven/ hard to control flecking can also occur.
Firing in reduction will enhance the flecking/speckling from the clay body.
Posted 11 December 2012 - 02:11 AM
Posted 11 December 2012 - 02:20 AM
IDK anything about this!
But it sure sounds like a big old hunk of heavy iron grog, maybe even use kyanite like in Soldners Raku body.
Posted 11 December 2012 - 02:25 AM
Ishihaze. A "stone explosion." Before firing, many of the impurities of the clay are removed. But some potters like rougher clay, and leave in small stones that sometimes burst out on the surface during firing - called ishihaze. Often found on Bizen and other yakishime (high-fired unglazed stonewares). http://www.e-yakimon...techniques.html
Posted 11 December 2012 - 02:39 AM
A video called Japanese Pottery History said there is Potash and iron in the clay body, so maybe that's it.
I was about to ask can you add GROG to the glaze or the clay to create this effect and the answers below suggested this.
What is it like round2potter to throw with the grog clay? I just bought some fine grog today, but it doesn't look so fine to me and i'm wondering how to make it finer.
I wonder if I can make a billyjoesbutterwhite by adding some iron to the body? Or Mark, do you know where to find the recipe please? Or would iron shavings from a bbq scourer do the trick? How much exactly would I need to use?
And is it food safe with so much iron in the clay?
Edited by Essaily, 11 December 2012 - 03:09 AM.
Posted 11 December 2012 - 03:20 AM
Food safety depends on the glaze and the clay, and the firing schedule.
I LOVE TO THROW WITH GROGGY CLAY!!!
A lot of people i have worked with complain that the groggy clay i use tears up their hands.
As a result my hands are always baby smooth.
But it all depends on what you are doing with it, and just how big the grog is. I don't really use much anything bigger than sand size pieces; half of what I add to the white stoneware (which has fine grog) is sand.
Only once has grog drawn blood for me; and I was removing the excess clay at the skirt of a pot with my finger. The pressure onto the wheelhead caused a hunk to sink itself in the pad of my finger.
I do however use fine grog in my clay,
The added strength is amazing, and i am fairly certain it helps the clay to withstand thermal shock
Also, heavy grog will catch and drag on a trimming tool; its not a problem really, but some would say a fine grogged body is easier to trim.
Posted 11 December 2012 - 10:48 AM
For the "premier" examples of this effect, research the ceramics made in the town of Shigaraki in Shiga Prefecture. The best clay for this in Shigaraki is called Kinose. The deposits of the best clay are severely depleted... and if you can get it.... it is very expensive stuff.
One interesting technique (not from Shigaraki) is to put a layer of a high kaolin white slip in a thin coating over the clay body containing the rocks. Then the rocks sort of break through the slip layer as the clay shrinks in the firing. Over this is a layer of a milky transparenty glaze.
If you want a US commercially prepared clay that is somewhat like this kind of Shigaraki Nasty Clay thing, get "Grogzilla" from Clay Planet )Orton Cone 9-10 clay).
The images you posted look more like just the effect of hematite (iron) nodules in the clay body bleeding into the glaze layer rather than "ishihaze". But it might be the resolution of the pictures so I can't see it.
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art
Posted 11 December 2012 - 11:43 PM
Posted 13 December 2012 - 04:20 AM
2bonsaiinside.jpg 107.74KB 53 downloads
Anyway, Grogzilla is crazy groggy, some of the grog is almost 1/8th of an inch so its probably not great for wheelwork. Works fine handbuilding though!
Whistling Fish Pottery
Posted 19 December 2012 - 01:31 AM
Posted 20 December 2012 - 03:51 AM
A technique I've used for pitted surfaces with hand-building is to roll cornmeal or coffee grounds or some other organic material into the surface then burnish it in. It burns out in the firing, leaving a bunch of small pits that are pretty cool.
Whistling Fish Pottery
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