carbon trap recipe substitution

updated thu 12 oct 06

Hank Murrow on fri 15 sep 06

On Sep 15, 2006, at 6:12 PM, Lee Love wrote:

> 70 Neph Sye 30 ball clay works for me without soda ash as a shino.
> But not carbon trap.

Say Lee;

Was Swanica's shino on her blog yours or mine? Did you get mine to
work? Would like to see a pic or two of those pots.

Cheers, Hank
www.murrow.biz/hank

Eric Newman on fri 15 sep 06

Has anyone done any experiments substituting soluble pearl ash for soda ash
in carbon trap/shino recipes? How about adding soluble colorants (e.g.,
cobalt or copper sulfate) to their shinos? I'm just starting my own
experiments, but would like appreciate any direction from others. And yes,
I will be careful in dealing with these soluble compounds! Thx, Eric

Lee Love on fri 15 sep 06

70 Neph Sye 30 ball clay works for me without soda ash as a shino.
But not carbon trap.

--

Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi

Lee Love on sat 16 sep 06

On 9/15/06, Hank Murrow wrote:
>
>
>
> Say Lee;
>
> Was Swanica's shino on her blog yours or mine? Did you get mine to
> work? Would like to see a pic or two of those pots.
>
>
It was mine. I will put some photos up this week.

--

Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi

Des & Jan Howard on sun 17 sep 06

Eric
As I remember, sodium as in soda ash, sodium
carbonate, sodium chloride (cooking/sea/table
salt) is needed for the red in shinos.
Potassium as in pearl ash/potassium carbonate
helps in glazes like Juns or blue celadons.
Des

Eric Newman wrote:

>Has anyone done any experiments substituting soluble pearl ash for soda ash
>in carbon trap/shino recipes? How about adding soluble colorants (e.g.,
>cobalt or copper sulfate) to their shinos? I'm just starting my own
>experiments, but would like appreciate any direction from others. And yes,
>I will be careful in dealing with these soluble compounds! Thx, Eric
>
>

--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au

Eric Newman on mon 9 oct 06

If anyone is wondering, in my tests, substituting Pearl Ash for Soda Ash
in my Carbon Trap recipe, the glaze came out much dryer, like an
underfired shino; the change in flux seemed to lead to much less melting.
Also, there appeared to be no carbon trapping. I have since read that
Soda has a special affinity for the carbon atom, so the trapping is not
just a function of the deposit of soda on the surface of the glaze as it
evaporates. Love that chemistry!

Vince Pitelka on mon 9 oct 06

> If anyone is wondering, in my tests, substituting Pearl Ash for Soda Ash
> in my Carbon Trap recipe, the glaze came out much dryer, like an
> underfired shino; the change in flux seemed to lead to much less melting.
> Also, there appeared to be no carbon trapping. I have since read that
> Soda has a special affinity for the carbon atom, so the trapping is not
> just a function of the deposit of soda on the surface of the glaze as it
> evaporates. Love that chemistry!

Eric -
Please sign your name at the bottom of your posts.

The sodium atom might have a greater affinity for carbon, but I don't think
that's the primary issue here. Sodium is a more powerful flux than
potassium, with a greater solvent action. I believe that soda ash is also
much more soluble in water than pearl ash, and carbon trapping absolutely
depends on the soluble soda ash soaking into the clabody, and then being
redeposited right on the surface of the glaze as the water evaporates. I
don't think that pearl ash will do that.

Last year we had Peter Rose come over from Knoxville to woodfire with us,
and he brought a bevy of shino recipes. One of the things he stressed
regarding shinos containing soda ash is the importance of letting the glazed
pots dry for several days before the firing, to make sure that all the soda
ash migrates back to the surface. You will note that the dry glaze on pots
glazed with shinos containing soda ash feels very crusty and firm - that's
the coating of soda ash on the surface of the glaze.

When you start reducing at a relatively low temperature (cone 014 or 012),
the soda ash has not yet sealed the surface, and the early reduction impacts
carbon into the surface. When the soda ash causes the surface to seal soon
after that, the carbon is trapped within the glaze beneath the fluxed soda
ash coating.

This is how I understand it from practical experience. I'd love to hear any
other explanations.
- Vince

Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/

Ivor and Olive Lewis on tue 10 oct 06

Dear Eric Newman,=20

<atom, so the trapping is not just a function of the deposit of soda on =
the surface of the glaze as it
evaporates.>>

I can find no mention of either Sodium or Potassium Carbide in my =
reference books though Calcium Carbide is well known.

What is certain is that molten carbonates of both Sodium and Potassium =
melt in the 850 deg C region.They can then aggressively dissolve free =
silica. When molten these compounds will dissolve mature Porcelain.

IF you are not getting trapped carbon then your firing schedule may need =
revision to get Carbon deposited before molten carbonates seal your =
sintering glaze.

Perhaps you might like to check your sources of information.

Best regards,

Ivor Lewis.
Redhill,
South Australia.