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shino/carbon trap/ wax resist

updated mon 20 sep 04

 

Hank Murrow on thu 16 sep 04


On Sep 16, 2004, at 1:56 PM, Madrona Artist wrote:

> Any idea why the glaze bisqued pieces carbon trapped
> better than the glazed unbisqued pieces?

Perhaps the bisque drove the salts out in a stronger way than with out
the bisque?

Maybe Connie will address this.

Cheers, Hank
murrow.biz/hank

Madrona Artist on thu 16 sep 04


Hi All,
I am digging up the endless questions and few answers
for shino carbon trap again. I have seen several posts
on this but didn't read anything similar to my
findings in a recent firing. So here it is.
I was testing a malcom davis carbon trap Shino in a
friend's kiln (10 minute drive from my place). I had 2
sets of test tiles. One first set I glazed and brushed
with Wax resist. The second set I glazed, brushed with
wax resist and then bisqued it to Cone04. The reason I
made the second set was to make the glaze more stable
and to see if there was any difference in prebisquing
the glaze. If this worked then I shouldn't be worried
about raw glazes rubbing off in transportation.
Both the sets were glazed in reduction. The reduction
was started around cone08 (I have read that Malcom
Davis requires a reduction much earlier like cone 012
or 010). Anyways, the results have thrown me off
completely.
Pieces from the first set showed little or no carbon
trap. The ones with little carbon trap did show a
bright orange where I applied wax resist.
The second set (bisqued), showed excellent carbon
trap. Nice black spots, mettallic gray areas and nice
and orange on the inside. Suprisingly the spot where I
had applied wax resist before the prebisque turned a
nice bright orange. I thought bisquing the glazes test
tile would burn off the wax resist and wouldn't have
any effect. But that is clearly not true.
Any ideas why I am seeing this? Anyone else
experimented this way?

Thanks
Charan

=====
Madrona Artists Guild
3612 Center Street
Tacoma, WA 98409

http://www.madronaartistsguild.com
madronaartistsguild@yahoo.com




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Hank Murrow on thu 16 sep 04


On Sep 16, 2004, at 8:44 AM, Madrona Artist wrote:
> Suprisingly the spot where I
> had applied wax resist before the prebisque turned a
> nice bright orange. I thought bisquing the glazes test
> tile would burn off the wax resist and wouldn't have
> any effect. But that is clearly not true.
> Any ideas why I am seeing this?

Dear Charan;

The reason the waxed area turned red has nothing to do with burning the
wax away. The reason the glaze did not carbon trap there is because
when you waxed that portion, you prevented the soluble soda ash from
depositing there during drying. Thus, the soda ash deposits where there
was no wax carbon trapped, while the waxed areas did not receive this
soluble material and so stayed red. These glazes need to be handled
carefully also, because rough handling will brush away the soluble soda
on the surface. That is one of the reasons for some of the variability
shown on some shinos. Anytime that solubles are present in a
glaze(unwashed wood ash, soda ash, etc.), there is a new set of
concerns.

Cheers, Hank in Eugene

murrow.biz/hank

Pam on thu 16 sep 04


I am not the shino guru that many other folks on this list are, but I think
I know why you got orange where you waxed, even though you burnt off the wax
before the glaze firing. The wax resist does it's magic on soda ash shinos
before the firing. As the glaze dries on the pot, soda ash migrates to the
outer layer of glaze. Where there is wax, no soda ash can escape to the
outside layer, so it diverts to the edges of your wax, or just stays mixed
in the glaze. That is why you get the orange, and with Malcolm's, you
sometimes get lots of black outlining the orange, the soda ash being more
concentrated there.
hope that helps!
pam
back from mixing shino at the guild

Madrona Artist on thu 16 sep 04


Any idea why the glaze bisqued pieces carbon trapped
better than the glazed unbisqued pieces?

Thanks
Charan
--- Hank Murrow wrote:

> On Sep 16, 2004, at 8:44 AM, Madrona Artist wrote:
> > Suprisingly the spot where I
> > had applied wax resist before the prebisque turned
> a
> > nice bright orange. I thought bisquing the glazes
> test
> > tile would burn off the wax resist and wouldn't
> have
> > any effect. But that is clearly not true.
> > Any ideas why I am seeing this?
>
> Dear Charan;
>
> The reason the waxed area turned red has nothing to
> do with burning the
> wax away. The reason the glaze did not carbon trap
> there is because
> when you waxed that portion, you prevented the
> soluble soda ash from
> depositing there during drying. Thus, the soda ash
> deposits where there
> was no wax carbon trapped, while the waxed areas did
> not receive this
> soluble material and so stayed red. These glazes
> need to be handled
> carefully also, because rough handling will brush
> away the soluble soda
> on the surface. That is one of the reasons for some
> of the variability
> shown on some shinos. Anytime that solubles are
> present in a
> glaze(unwashed wood ash, soda ash, etc.), there is a
> new set of
> concerns.
>
> Cheers, Hank in Eugene
>
> murrow.biz/hank
>
>
______________________________________________________________________________
> 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.
>


=====
Madrona Artists Guild
3612 Center Street
Tacoma, WA 98409

http://www.madronaartistsguild.com
madronaartistsguild@yahoo.com

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Rod Wuetherick on fri 17 sep 04


Charan,

The reason why the bisque pieces trap better is that the
bisque can absorb the soluble soda. This of course will allow
more to migrate to the surface during drying and firing. You may
have noticed when loading your pieces that the bisque pieces had
some "fuzz" on them while the green pieces would have been most likely
bare.

There are so many factors that come in to play with shinos as you
know. The most important ones are obviously the amount of soda in the
recipe, draft (while drying), length of drying time and of course
reduction. I reduce my carbon trapped white glazes and shinos at
7.6 on the oxy-probe for heavy reduction and 6.9 - 7.1 for a lighter
quiet trapped glaze.

If you are firing a shino on a porcelain be forewarned the recipe will
probably need to be adjusted. Porcelain bodies have more flux in them
than stoneware bodies. This can change some shino glazes dramatically.

Shino's are magical and painful.
The pain is worth it though isn't it?

Cheers,
Rod

Any idea why the glaze bisqued pieces carbon trapped
better than the glazed unbisqued pieces?

Madrona Artist on sun 19 sep 04


Thank you everyone for your input on my questions. I
need to keep experimenting and figure out what works
and what doesn't.

Thanks
Charan
--- Rod Wuetherick wrote:

> Charan,
>
> The reason why the bisque pieces trap better is that
> the
> bisque can absorb the soluble soda. This of course
> will allow
> more to migrate to the surface during drying and
> firing. You may
> have noticed when loading your pieces that the
> bisque pieces had
> some "fuzz" on them while the green pieces would
> have been most likely
> bare.
>
> There are so many factors that come in to play with
> shinos as you
> know. The most important ones are obviously the
> amount of soda in the
> recipe, draft (while drying), length of drying time
> and of course
> reduction. I reduce my carbon trapped white glazes
> and shinos at
> 7.6 on the oxy-probe for heavy reduction and 6.9 -
> 7.1 for a lighter
> quiet trapped glaze.
>
> If you are firing a shino on a porcelain be
> forewarned the recipe will
> probably need to be adjusted. Porcelain bodies have
> more flux in them
> than stoneware bodies. This can change some shino
> glazes dramatically.
>
> Shino's are magical and painful.
> The pain is worth it though isn't it?
>
> Cheers,
> Rod
>
> Any idea why the glaze bisqued pieces carbon trapped
> better than the glazed unbisqued pieces?
>
>
______________________________________________________________________________
> 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.
>


=====
Madrona Artists Guild
3612 Center Street
Tacoma, WA 98409

http://www.madronaartistsguild.com
madronaartistsguild@yahoo.com



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