clennell on mon 1 nov 04
A couple of weeks ago a clayarter posed the question of blue terra sig for
woodfire. No one to my knowledge answered. this idea twigged my interest so
I asked my collegue at Sheridan Dale Periera. He is on of the best low fire
guys i know.
Here is what Dale suggested
Make your terra sig as usual
Dry to powder form. this way you can weigh it and add your percentages of
oxides. he then said the oxides are still heavier and will sink to the
bottom so it is best to ball mill the sig/and oxides for two hours so that
the oxide particle size is similiar to the sig. he still maintains you will
have to keep the mixture stirred as it is bound to sink to the bottom.
The japanese mouse grey would be a very nice sig on porcelain in wood.
Hope the person with the question hung in long enough for this answer and
thanks for possibly adding something new to my pallette.
Cheers,
Tony
Tony and Sheila Clennell
Sour Cherry Pottery
4545 King Street
Beamsville, Ontario
CANADA L0R 1B1
http://www.sourcherrypottery.com
Sam Hoffman on tue 2 nov 04
I have had good success using a Navy Blue terra sig that can be made
either with Ball Clay or Redart. I weigh out the clay, then the oxides
separately. I make the terra sig before adding the oxides, even though
they are a little bit coarse. (Like Lee mentioned, the coarse
particles smooth out enough in the woodfiring) Even though I lose some
clay in the separation process of making the sig, I use the following
oxide percentages, based on the ORIGINAL amount of clay used. (yes, I
realize this will vary from batch to batch, but a little serendipity is
a good thing, especially with woodfiring)
100% - OM4 or Redart
1% Cobalt Carb
1% Manganese Diox
1% Copper Carb.
This yields a nice dark blue, almost black, on protected surfaces.
Where it is hit by ash or flame, it can go bright cobalt blue, or get
totally washed out into white or grey. It is a good candidate for salt
firing, as well. Terra sig is a good candidate for wood firing,
because the small particles are particularly susceptible to flashing.
Although blue can often contrast with the warm oranges and reds of
woodfiring, the terra sig retains the nice variations inherent in wood
firing. Here is an example (albeit not a great one) of a vase with the
Navy Blue Terra Sigilatta on the neck:
http://www.samhoffman.com/ArchivePortfolioPages/ArchivePagesWoodVase/
PortfolioPage01WV12.html
Tony, perhaps you remember some of the slides I showed at Kanayama;
much better examples of what this sig can do. Hope this is helpful!
-Sam
S.L. Hoffman Pottery
www.samhoffman.com
On Nov 1, 2004, at 6:04 PM, clennell wrote:
> A couple of weeks ago a clayarter posed the question of blue terra sig
> for
> woodfire. No one to my knowledge answered. this idea twigged my
> interest so
> I asked my collegue at Sheridan Dale Periera. He is on of the best low
> fire
> guys i know.
> Here is what Dale suggested
> Make your terra sig as usual
> Dry to powder form. this way you can weigh it and add your percentages
> of
> oxides. he then said the oxides are still heavier and will sink to the
> bottom so it is best to ball mill the sig/and oxides for two hours so
> that
> the oxide particle size is similiar to the sig. he still maintains you
> will
> have to keep the mixture stirred as it is bound to sink to the bottom.
> The japanese mouse grey would be a very nice sig on porcelain in wood.
> Hope the person with the question hung in long enough for this answer
> and
> thanks for possibly adding something new to my pallette.
> Cheers,
> Tony
>
> Tony and Sheila Clennell
> Sour Cherry Pottery
> 4545 King Street
> Beamsville, Ontario
> CANADA L0R 1B1
> http://www.sourcherrypottery.com
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
clennell on wed 3 nov 04
Sour Cherry Pottery
> I have had good success using a Navy Blue terra sig that can be made
> either with Ball Clay or Redart. I weigh out the clay, then the oxides
> separately. I make the terra sig before adding the oxides, even though
> they are a little bit coarse. (Like Lee mentioned, the coarse
> particles smooth out enough in the woodfiring) Even though I lose some
> clay in the separation process of making the sig, I use the following
> oxide percentages, based on the ORIGINAL amount of clay used. (yes, I
> realize this will vary from batch to batch, but a little serendipity is
> a good thing, especially with woodfiring)
>
> 100% - OM4 or Redart
> 1% Cobalt Carb
> 1% Manganese Diox
> 1% Copper Carb.
Thanks Sam. Nice to visit your website and see your smiling mug. I love red
art sig on porcelain in wood and was thinking i would aim for a mouse grey
much like described i think by Lee and a recipe given in JB's book for Gosu
slip.
With all this talk of Barnard clay. I have a 50# bag of it and I understand
it contains up to 3% manganese. Have you tried Barnard as a sig?
Cheers,
Tony
Tony and Sheila Clennell
Sour Cherry Pottery
4545 King Street
Beamsville, Ontario
CANADA L0R 1B1
http://www.sourcherrypottery.com
Sam Hoffman on thu 4 nov 04
Barnard clay does not make a very good sigilatta. It ends up being
really powdery after application, and does not seem to burnish like a
true terra sig. However, it can be used to great effect if mixed as a
flashing wash, with 80% Barnard 20% Soda Ash. It can turn yellow,
green, or beige, depending on how much ash and flame hits the surface.
The manganese in the clay can often yield iridescent surfaces. As far
as Barnard being unavailable, we have had no shortages on the west
coast...
A new favorite of mine is a similar flashing wash mixed with
Ravenscrag Slip Clay, which is available from Plainsman in Montana.
(same folks who distribute Alberta Slip) It can yield wonderful fiery
surfaces that remind me of Tiger's Eye. Let me know if these slips
look good in the Train Kiln...still intrigued with the design...
Peace,
Sam
PS-As far as mouse grey goes, I think a better approach is an iron slip
with a little bit of cobalt (0.25%) under a white shino glaze. Easier
said than done...
S.L. Hoffman Pottery
www.samhoffman.com
On Nov 3, 2004, at 1:27 PM, clennell wrote:
> Sour Cherry Pottery
>
>> I have had good success using a Navy Blue terra sig that can be made
>> either with Ball Clay or Redart. I weigh out the clay, then the
>> oxides
>> separately. I make the terra sig before adding the oxides, even
>> though
>> they are a little bit coarse. (Like Lee mentioned, the coarse
>> particles smooth out enough in the woodfiring) Even though I lose
>> some
>> clay in the separation process of making the sig, I use the following
>> oxide percentages, based on the ORIGINAL amount of clay used. (yes, I
>> realize this will vary from batch to batch, but a little serendipity
>> is
>> a good thing, especially with woodfiring)
>>
>> 100% - OM4 or Redart
>> 1% Cobalt Carb
>> 1% Manganese Diox
>> 1% Copper Carb.
>
>
> Thanks Sam. Nice to visit your website and see your smiling mug. I
> love red
> art sig on porcelain in wood and was thinking i would aim for a mouse
> grey
> much like described i think by Lee and a recipe given in JB's book for
> Gosu
> slip.
> With all this talk of Barnard clay. I have a 50# bag of it and I
> understand
> it contains up to 3% manganese. Have you tried Barnard as a sig?
> Cheers,
> Tony
> Tony and Sheila Clennell
> Sour Cherry Pottery
> 4545 King Street
> Beamsville, Ontario
> CANADA L0R 1B1
> http://www.sourcherrypottery.com
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
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