centa uhalde on thu 22 jan 98
Hi,
I'm a beginner interested in exploring mid-range firing of maiolica because
I am attracted to the chip resistant, and tougher quality and the warmer
color tones. I've heard the term, 'post maiolica' and would like to explore
this process. My questions:
1) What clay(s) are available in Northern Calif that are RED, smooth
terracotta good for throwing and handbuilding (these might be two different
clay bodies) with a minimum of or fine grog content. The only body that has
been recommended is Navaho Wheel by Laguna, and it seems to fire rather
dark brown than true terracotta red in the mid-range.
2)How vitrified should the clay body be for functional maiolica ware?
3)Recently, I bought a piece of 'post maiolica' that said it was fired to
2150. It did not go any further than that. I was wondering if that is the
clay or the glaze that was fired to 2150? (F). Is there some standard
formula for "good fit" between clay and glaze when firing mid-range
maiolica (or is it between bisque and glaze firing in general)? I heard
something like, bisque higher, glaze should be fired two cones lower than
bisque. If I translate this to midrange maiolica does that mean bisquing at
cone 5 and glazing at cone 3? Or am I confused and it's the other way
around?
4) I prefer a more matt surface to the glaze/overglaze treatment. Any
suggestions for acquiring matt maiolica surface?
5)Are there high fire maiolica glaze recipes for use on red fine-grog
stoneware that anyone might recommend? My guess is that there could be but
that color selection would be much more limited and muted, and that it is
hard to find a really red terracotta that fires red at mid-range much less
at cone 10. Am I right?
6) Any suggestions for a beginning systematic approach for testing along
these lines?
Thanks,
Centa
Valice Raffi on fri 23 jan 98
>----------------------------Original message----------------------------
Centa wrote:
>1) What clay(s) are available in Northern Calif that are RED, smooth
>terracotta good for throwing and handbuilding (these might be two different
>clay bodies) with a minimum of or fine grog content. The only body that
Hi Centa,
you might try IMCO (Industrial Mineral Co) in Sacramento. They make a
"sculpture 412 red" that you might like. The last batch I bought (I
usually use their 412 buff - which is very groggy) was smooth and buttery
but held up to hand-building.
IMCO (916) 383-2811 (they also have a web page, but I don't have the
address handy)
(usual disclaimers)
Valice in Sacramento, birds are chirpin' like crazy - gonna be a great day!
Jreke on sat 24 jan 98
Hi- can only answer one of your six questions. As to a good red terracotta
clay in Northern California, I get the ^6 terracotta available from Claymaker
in San Jose. Bob Millavich makes it and I've used it for throwing and
handbuilding and like it alot. It's got a little grog in it but not much so
it's fairly smooth. Fires a nice brick red, tends toward brownish at ^6.
Probably redder if you only fire to ^5. Bob's phone number is 408 295 3522 I
think... this is from memory as I don't have my studio info here at home.
There is also an outlet for Claymaker clays in Santa Cruz. I think the higher
firing glazes are going to give you a very different look than traditional
majolica, but oxidation will yield plenty of colors. Jane Rekedal
Tony Hansen on sun 25 jan 98
>Is there some standard
>formula for "good fit" between clay and glaze when firing mid-range
>maiolica (or is it between bisque and glaze firing in general)?
No. Each clay and glaze have their own expansion, you have to find two
that are compatible or adjust to make incompatible ones more
compatible. The thermal expansion of glazes is very easy to adjust.
> I heard
>something like, bisque higher, glaze should be fired two cones lower than
>bisque. If I translate this to midrange maiolica does that mean bisquing at
>cone 5 and glazing at cone 3?
If you bisque too high you'll have trouble getting your glaze to stick
using standard pottery glaze techniques.
The porous nature of bisque ware makes it easy to glaze. You can
bisque higher than glaze in the cone 06 area because anything below
cone 02 is porous enough to take typical pottery glazes.
>4) I prefer a more matt surface to the glaze/overglaze treatment. Any
>suggestions for acquiring matt maiolica surface?
One very nice feature of Majolica is the concept of using one base
glaze for everything. To get a good matte white just take a balanced
durable cone 5-6 matte base that fits your clay body and add Zircopax
till it looks right.
>5)Are there high fire maiolica glaze recipes for use on red fine-grog
>stoneware that anyone might recommend?
Yep. Start with a balanced hard transparent stoneware glaze that fits
your body and add 10-15% zircopax. Actually the Zircopax should reduce
thermal expansion so even if the base glaze crazes a little the white
could be OK.
Remember to do a boiling water:ice water test to stress the ware to
see if the glaze crazes or shivers.
--
-------
T o n y H a n s e n thansen@digitalfire.com
Get INSIGHT, Magic of Fire at http://digitalfire.com
Hrnce on wed 28 jan 98
Tony mentioned that it was very hard to glaze a high fired bisque.I certainly
would not argue about that but is it not a common practice in the ceramics
industry? What is the additive they use and is it available to the lowly
potter?
Imco makes two more red firing claybodies : quarry tile(simillar to navajo)
and 50/50 which fires more red than the other two.Also East Bay Clay
510-233-1800 makes a nice cone 6 red clay body.
Jiri in Berkeley
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