Hank Murrow on sun 11 apr 04
Dear Jennifer;
Water dissociates at higher temperatures, causing the Hydrogen to
create reduction conditions, and Hydrogen is a powerful reactant. The
Batelle Institute published some very interesting papers dealing with
this subject in the 50s and 60s, mostly to educate the brick and tile
industry to the advantages of employing water vapor as a reduction
agent. Propane has little water, while natural gas has anywhere from 8
to 12%. I think the water vapor contributes greatly to the melt. In
addition, water vapor will help to even out temperatures in a chamber.
Cheers, Hank
www.murrow.biz/hank
On Apr 11, 2004, at 10:27 AM, Jennifer Boyer wrote:
> I was just going through some notes that I took at a Pete Pinell
> workship a few years ago. Good luck trying to write down all the
> information he throws at you!
>
> I showed him my cone 10 Temple White glaze on light stoneware and he
> admired the glaze surface. I sheepishly admitted that I don't put my
> propane kiln into reduction (long ago needed to maintain consistency in
> my surfaces and didn't want speckling) and wondered if everything would
> look the same in an electric kiln. He said no: that part of the benefit
> in firing with gas comes from the water content of the fuel. I guess
> that might apply to wood firing as well, and it rang a bell: I went to
> the NCECA speaker who had researched Asian "water kilns" that have a
> water reservior that's filled at the height of the firing cycle...
>
> Does anyone know more details about how the water idea actually works?
Jennifer Boyer on sun 11 apr 04
Hi,
I was just going through some notes that I took at a Pete Pinell
workship a few years ago. Good luck trying to write down all the
information he throws at you!
I showed him my cone 10 Temple White glaze on light stoneware and he
admired the glaze surface. I sheepishly admitted that I don't put my
propane kiln into reduction (long ago needed to maintain consistency in
my surfaces and didn't want speckling) and wondered if everything would
look the same in an electric kiln. He said no: that part of the benefit
in firing with gas comes from the water content of the fuel. I guess
that might apply to wood firing as well, and it rang a bell: I went to
the NCECA speaker who had researched Asian "water kilns" that have a
water reservior that's filled at the height of the firing cycle...
Does anyone know more details about how the water idea actually works?
Jennifer
************************
Jennifer Boyer
Thistle Hill Pottery
Montpelier, VT
http://thistlehillpottery.com
Fredrick Paget on sun 11 apr 04
>Hi,
>I was just going through some notes that I took at a Pete Pinell
workshop ......................................................
> .........part of the benefitin firing with gas comes from the water
>content of the fuel...........
>.............. Asian "water kilns" that have a
>water reservior that's filled at the height of the firing cycle...
>
>Does anyone know more details about how the water idea actually works?
>Jennifer Boyer
This is the well known (in chemical engineering circles) water cycle.
Water vapor (steam) at high temperature reacts with carbon to give
hydrogen gas and carbon monoxide, both powerful reducing agents in a
kiln. I suppose that there is carbon in the kiln atmosphere
especially if it is smoking. So the water vapor can react with it
and increase the reduction and cut down on the smoke.
They used to make gas for home use before natural gas became
available by blowing steam through a white hot bed or coke. Piped it
right into your home. A leak of that stuff was bad - all that carbon
monoxide. It was called producer gas or illuminating gas.
Fred
--
From Fred Paget, Marin County, California, USA
fredrick@well.com
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