bruce/sue johnson on thu 22 oct 98
Dear Raku People: I have a problem with my crackle white glazes cracking at
the craze line all the way through. Not all the time but enough to cost me
some serious setbacks. My 2 glazes are 90 3134 10 EPK 10 Zirco. and the
standard 80 20 glaze. Most of the time I don't use any air or water on
them.Pieces range in size from 10 to 36 inches. big ones crack the most.It
does not seem to mater if the piece is thick or thin. Any help or ideas
would be great Thanks BJ xxxooo
Paul Bradford on fri 23 oct 98
Chances are its your clay body and no the glaze. Some clay bodys hold up much
better when it comes to temp. shock. Try Lagunas WSO cone 10, or a regular
Raku body.
Also check the pieces after bisque for crackes.
Good luck
Sheilah Bliss on fri 23 oct 98
In a message dated 10/22/98 8:40:56 AM, you wrote:
<<----------------------------Original message----------------------------
Dear Raku People: I have a problem with my crackle white glazes cracking at
the craze line all the way through. Not all the time but enough to cost me
some serious setbacks. My 2 glazes are 90 3134 10 EPK 10 Zirco. and the
standard 80 20 glaze. Most of the time I don't use any air or water on
them.Pieces range in size from 10 to 36 inches. big ones crack the most.It
does not seem to mater if the piece is thick or thin. Any help or ideas
would be great Thanks BJ xxxooo
>>
Hi BJ -
I do quite a bit of raku... use a glaze called Clear Crackle:
Gerstley Borate 80
Neph Syenite 5
Custer Feldspar 15
(This is a clear glaze so comes out white over a white clay body.)
But I suspect perhaps your clay-cracking problem may lie more in the clay than
the glaze. I use Seattle Pottery Supply's Alpine White clay body (actually a
^06-^6 fine white stoneware). I was having a bit higher mortality rate than
my sanity threshold could tolerate so in a moment of total madness, I wedged
in some Ione 412 grog (really fine, nothing like gravel...), also from Seattle
Pottery. Mortality rate of rakued pots has decreased noticably.
Another thing I noticed in my firings, if I try to fire really fast the odds
of my pots cracking up are greater. In the interest of obtaining that
orgasmically gorgeous (you know, like the hair shampoo?) rainbow hued rakued
piece, I've been known to fire slowly, gradually - gently nursing the firing
along. What I lose in time I save in fired pieces.
Hope this helps!
Sheilah Bliss
BlissPots@aol.com
Darrell Gargus on fri 23 oct 98
Hi! I found that when I took the raku kiln up too fast temperature,
that the piece experienced thermal shock. Sometimes the piece would
explode but most of the time there were just cracks. Do you warm your
pieces up first when it is cold outside? May not help out any, but it's
just a thought.
becky
bruce/sue johnson wrote:
>
> ----------------------------Original message----------------------------
> Dear Raku People: I have a problem with my crackle white glazes cracking at
> the craze line all the way through. Not all the time but enough to cost me
> some serious setbacks. My 2 glazes are 90 3134 10 EPK 10 Zirco. and the
> standard 80 20 glaze. Most of the time I don't use any air or water on
> them.Pieces range in size from 10 to 36 inches. big ones crack the most.It
> does not seem to mater if the piece is thick or thin. Any help or ideas
> would be great Thanks BJ xxxooo
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