G. Fer on tue 22 jun 04
I was wondering if you bisque your pieces for raku at a higher temp, let's
say for example at cone 2,does this make the pieces more resistant for raku?
thank you very much for your time and i will be awaiting your replies.
Gustavo
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Snail Scott on tue 22 jun 04
At 01:40 PM 6/22/2004 +0000, you wrote:
>I was wondering if you bisque your pieces for raku at a higher temp, let's
>say for example at cone 2,does this make the pieces more resistant for raku?
When you say "more resistant for raku", do you mean less
cracking due to thermal shock?
Actually, the more vitrified the clay, the more vulnerable
to thermal shock it becomes. It will be 'more resistant' to
breakage from rough handling, but if what you are seeking is
resistance to cracking due to the abrupt cooling of typical
raku processes, bisquing higher won't really help. How much
difference a higher bisque will make depends on the clay
body, but unless it's got a high content of thermal-shock-
reducing ingredients, I wouldn't recommend it.
-Snail Scott
Edwardsville, Illinois, USA, Earth
Bruce Girrell on tue 22 jun 04
> I was wondering if you bisque your pieces for raku at a higher temp, let's
> say for example at cone 2,does this make the pieces more
> resistant for raku?
My experience is that a higher bisque temperature makes the pieces more
likely to crack. It also makes them harder to glaze.
Bruce Girrell
in cool northern Michigan
waiting for the warmth of Summer
Laurie Kneppel on tue 22 jun 04
Hi Gustavo,
I have never tried this. I still bisque my raku pieces to cone 04,
which is still a somewhat higher temp than they get raku fired to,
which is "around" 1800-1850 degrees F. I think the thing that makes the
pieces more resistant for raku is the clay body itself. For me, less
grog means more chance of breaking.
On the other hand I have known people who fire their raku pieces three
times. First for bisque, second to cone 6 with a liner glaze on the
inside and the rim, and third is the raku firing to get that effect on
the outside only of the piece. You don't get the same crackle on pieces
fired this way, but the matte raku glazes still work pretty well and
the pots can hold water unless they crack from shock. I've seen this
technique work for vases quite nicely, but I have never tried it
myself.
Laurie
Sacramento, CA
http://rockyraku.com
Potters Council, member
Sacramento Potters Group, member
On Jun 22, 2004, at 6:40 AM, G. Fer wrote:
> I was wondering if you bisque your pieces for raku at a higher temp,
> let's
> say for example at cone 2,does this make the pieces more resistant for
> raku?
>
> thank you very much for your time and i will be awaiting your replies.
>
> Gustavo
Wesley Derrick - Derrick Pottery - Jackson, MS on tue 22 jun 04
G,
In my experience...the higher a piece is fired in bisque, the less
resistant to cracks it becomes....I use a clay body that is particularly
designed for RAKU and seems to hold up pretty well no matter what temp it
is bisqued to...but I have lost some (very few) that was fired to 2150F and
then put through the raku process. I've never lost one to cracking or
blowing up in the post-reduction water-dipping that was simply fired to
1850-1900.
They glaze alot easier at lower bisque temps as well....a plus in my book.
wesley
Eva Gallagher on tue 22 jun 04
I also am trying to get stronger pots from Raku. I tried some flameware =
clay - thinking that if I fired it to cone 6 (it is cone 8 recipe so =
would be almost vitrified at cone 6) and then glazed and Raku fired it =
the flameware clay would withstand the thermal shock of the raku. The 2 =
small flat pieces worked OK but they were hard to glaze of course as =
they were vitrified. However a bowl that I made with a wide flaring rim =
cracked.=20
Has anyone else tried vitrified flameware for Raku?
Eva Gallagher
Deep River Potters' Guild
Deep River, Ontario
----- Original Message -----
From: "G. Fer"
To:
Sent: Tuesday, June 22, 2004 9:40 AM
Subject: bisque fire for raku at cone 2
> I was wondering if you bisque your pieces for raku at a higher temp, =
let's
> say for example at cone 2,does this make the pieces more resistant for
raku?
>
> thank you very much for your time and i will be awaiting your replies.
>
> Gustavo
>
> _________________________________________________________________
>
Craig Dunn Clark on wed 23 jun 04
I don't believe that there is anything that can be done to solve the
inherent lack of strength issue associated with Raku. It is a drawback of
the process. Pieces that are raku fired are for decorative purposes and
folks that make, handle, sell and buy them are aware of the problem. It's
kinda like the fading issues Tom Buck first wrote about. The information is
now out there and it is the responsiblity of the individual potters, dealers
and buyers to be aware.
While bisque firing to a higher temp will help, there is the associate
problem of glaze application and more loss due to cracking. The process that
I'm refering to here is when the pot is taken from the kiln at roughly 1800
to 1900 degreess F and then put into a container for post firing reduction.
The thermal shock experienced by the clay is indeed traumatic and the
"tighter" the body the more prone it is to cataclysimic cracking. I'm
convinced that virtually all raku pots experience some type of unseen
cracking from the rigors of the process. This one more reason to use raku
for decorative purposes only.
As the clay body becomes more vitrified, the stucture becomes
increasingly dense. This does not help with the problems associated with
thermal shock. It does the opposite. So the best to hope for is the magical
point between the two. The highest point at which you can fire the clay body
that you are using that will both make the piece stronger, and the point
where it will still take the thermal shock and recieve the glaze of choice
without to many headaches. It is all a matter of give and take and what you
are after specifically.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Eva Gallagher"
To:
Sent: Tuesday, June 22, 2004 2:54 PM
Subject: bisque fire for raku at cone 2
I also am trying to get stronger pots from Raku. I tried some flameware
clay - thinking that if I fired it to cone 6 (it is cone 8 recipe so would
be almost vitrified at cone 6) and then glazed and Raku fired it the
flameware clay would withstand the thermal shock of the raku. The 2 small
flat pieces worked OK but they were hard to glaze of course as they were
vitrified. However a bowl that I made with a wide flaring rim cracked.
Has anyone else tried vitrified flameware for Raku?
Eva Gallagher
Deep River Potters' Guild
Deep River, Ontario
----- Original Message -----
From: "G. Fer"
To:
Sent: Tuesday, June 22, 2004 9:40 AM
Subject: bisque fire for raku at cone 2
> I was wondering if you bisque your pieces for raku at a higher temp, let's
> say for example at cone 2,does this make the pieces more resistant for
raku?
>
> thank you very much for your time and i will be awaiting your replies.
>
> Gustavo
>
> _________________________________________________________________
>
____________________________________________________________________________
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Lee Love on wed 23 jun 04
Snail Scott wrote:
>When you say "more resistant for raku", do you mean less
>cracking due to thermal shock?
>
>
I thought he was talking about being more durable after the work
is finished. I suspect it would be more durable, but you would have
to adjust your glaze, maybe with soda ash like David H. does because the
bisque will be less absorbent. Also, you might want something like an
ovenware body that would be thermally resistant.
It would be worth a test, I think.
--
Lee in Mashiko, Japan http://mashiko.org
http://journals.fotki.com/togeika/Mashiko/ Commentary On Pottery
Lee Love on thu 24 jun 04
Craig Dunn Clark wrote:
> I don't believe that there is anything that can be done to solve the
>inherent lack of strength issue associated with Raku.
>
If you want, can do like they do here in Japan and pull
highfire pots out of the kiln at temperature. They get some great blacks
this way. Put them in reduction materials if you like (the black here
is oxidized) , but if you want strength, even in normal "`Merican" raku,
don't put them in water.
I have raku latte bowls glazed with TAK Fat white (copper
splashes on the outside) and get heavy use that are 14 years old. TAK
is pretty durable. I put them in reduction materials but I did not
quench them in water. The water quench is what weakens the clay body.
--
Lee in Mashiko, Japan http://mashiko.org
http://journals.fotki.com/togeika/Mashiko/ Commentary On Pottery
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