David Beumee on mon 28 jan 08
When Pete Pinnell taught our Anderson Ranch glaze workshop group what was really going on in a reduction kiln back in 1989, it was news to me. At that time I was finally able to afford a gas kiln of my own, and I applied his practices, which he later reiterated in a series of Clay Times articles entitled "Secrets of Firing Copper Reds." As I have been able to find out and understand out over the years, his concepts apply to the firing of ALL reduction glazes. So, knowing that the method fired a kiln much more efficiently and produced terrific results, naturally I wanted to share the news when I began to be asked to be a workshop leader. It has always saddened me greatly that what Mel has observed is not only that outdated, incredibly inefficient firng methods are still being practiced, but that potters are unbelievably resistant to trying new firing methods. I saw it for years, every time I tried to talk to workshop participants. The red face in the audience, usually the pe!
rson re
sponsible for firing, and the hateful expression aimed at me of "who the f... do you think you are telling us how to fire?" So, I don't talk about any more. I don't want to be seen as trying to force anything on anybody.
David Beumee
www.davidbeumee.com
KATHI LESUEUR on mon 28 jan 08
On Jan 28, 2008, at 6:54 PM, Lee wrote:
>
> Pete did a workshop at Northern Clay Center around '95. He is a
> glaze wizard.
>
> He pointed out to us that it is nonsense to candle a gas kiln
> overnight. A waste of fuel. He fired quickly in the beginning,
> explaining that people usually go slow in the beginning, but hurry up
> in the end. He likes to hold the kiln at the upper temps for a while
> and that is where he spends the firing time.>>>
In the thirty years I've been firing my gas kiln I've never candled
it. I turn on two burners at the start and one hour later I'm at 800
degrees. Three hours later all burners are on. Four to four and a
half later I'm ready for body reduction. The whole thing is over in
twelve hours. Like Pete I hold the kiln at the upper temp for about
an hour. I fire a variation of the Abernathy kiln which has been
discussed here. It has no chimney. It has no bag wall. It uses
forced air. It is simple to fire. Even in both temperature and
reduction.
>
> He also brought an inexpensive CO2 probe that is used in
> industry with furnaces. Had to put water in it. Pumped a rubber
> ball. Said it worked well enough, so he didn't have to haul and
> expensive Oxi-probe around
>
What he used was a Bacarach CO2 analyzer. That fluid in it is not
water. It's a special fluid that expands at a precise rate when you
pump a sample from the kiln. I've used it for years. Far cheaper than
an Oxy-probe. One caveat. Don't buy the quartz sampling tube from
them. It will cost over $100. I buy several at a time from Superior
Glass located in Ypsilanti, MI. I think I paid about $40 for six of
them last time.
Kathi
Lee on tue 29 jan 08
On Jan 29, 2008 10:30 AM, KATHI LESUEUR wrote:
> What he used was a Bacarach CO2 analyzer. That fluid in it is not
> water. It's a special fluid that expands at a precise rate when you
> pump a sample from the kiln. I've used it for years. Far cheaper than
> an Oxy-probe. One caveat. Don't buy the quartz sampling tube from
> them. It will cost over $100. I buy several at a time from Superior
> Glass located in Ypsilanti, MI. I think I paid about $40 for six of
> them last time.
Thanks Kathi! For both the correction and the contact info. I
will look into buying one when I get back to Mpls.
Is this it? Looks much "prettier" than Pete's! ;^)
http://www.bacharach-inc.com/co2_analyzer_2010_15_20.htm
--
Lee in Mashiko, Tochigi Japan
http://mashikopots.blogspot.com/
"Tea is nought but this: first you heat the water, then you make the
tea. Then you drink it properly. That is all you need to know."
--Sen No Rikyu
"Let the beauty we love be what we do." - Rumi
Richard Aerni on tue 29 jan 08
I had one of these back in the late 70s and early 80s after reading a George
Wettlaufer article in Studio Potter. I must say, I never did get truly
consistent results from it (who can say if it was accurate?) and abandoned
it. I'd be curious, Kathi, if you could explain your usage and
interpretation of the results a bit more.
Thanks,
Richard Aerni
Rochester, NY
www.richardaerni.com
www.richardaernipottery.etsy.com
On Tue, 29 Jan 2008 12:57:09 +0900, Lee wrote:
>On Jan 29, 2008 10:30 AM, KATHI LESUEUR wrote:
>
>> What he used was a Bacarach CO2 analyzer. That fluid in it is not
>> water. It's a special fluid that expands at a precise rate when you
>> pump a sample from the kiln. I've used it for years. Far cheaper than
>> an Oxy-probe. One caveat. Don't buy the quartz sampling tube from
>> them. It will cost over $100. I buy several at a time from Superior
>> Glass located in Ypsilanti, MI. I think I paid about $40 for six of
>> them last time.
>
>Thanks Kathi! For both the correction and the contact info. I
>will look into buying one when I get back to Mpls.
>
>Is this it? Looks much "prettier" than Pete's! ;^)
>
>
KATHI LESUEUR on tue 29 jan 08
On Jan 28, 2008, at 10:57 PM, Lee wrote:
> On Jan 29, 2008 10:30 AM, KATHI LESUEUR
> wrote:
>
>> What he used was a Bacarach CO2 analyzer. That fluid in it is not
>> water. It's a special fluid that expands at a precise rate when you
>> pump a sample from the kiln. I've used it for years. Far cheaper than
>> an Oxy-probe. One caveat. Don't buy the quartz sampling tube from
>> them. It will cost over $100. I buy several at a time from Superior
>> Glass located in Ypsilanti, MI. I think I paid about $40 for six of
>> them last time.
>
> Thanks Kathi! For both the correction and the contact info. I
> will look into buying one when I get back to Mpls.
>
> Is this it? Looks much "prettier" than Pete's! ;^)
>
>
> http://www.bacharach-inc.com/co2_analyzer_2010_15_20.htm
>
>
> --
>
No. That's the new high-tech model that is not useful for firing a
kiln. When you go to their site click on "products". Then click on
"combustion and environment". Then click on "Fyrite Gas Analyzers".
That's the model you want. There are two models. You want the
0-20%. There was a book called "Getting Into Pots" by George
Wettlaufer that explain the use of the CO2 analyzer. It's long out of
print but if you can find a copy it will help explain it's use. If
you can't find it, let me know and I'll give you directions.
Anyone producing glass instruments for scientific use should be
able to make the glass tubes for you. Get several. They break.
Kathi
KATHI LESUEUR on tue 29 jan 08
On Jan 29, 2008, at 8:02 AM, Richard Aerni wrote:
> I had one of these back in the late 70s and early 80s after reading
> a George
> Wettlaufer article in Studio Potter. I must say, I never did get
> truly
> consistent results from it (who can say if it was accurate?) and
> abandoned
> it. I'd be curious, Kathi, if you could explain your usage and
> interpretation of the results a bit more.
> Thanks,
> Richard Aerni
> Rochester, NY
>
> www.richardaerni.com
> www.richardaernipottery.etsy.com
>
> On Tue, 29 Jan 2008 12:57:09 +0900, Lee wrote:
>
>> On Jan 29, 2008 10:30 AM, KATHI LESUEUR
>> wrote:
>>
>>> What he used was a Bacarach CO2 analyzer.
I rarely use the CO2 analyzer now because I have years of records and
my kiln fires very consistently. But, when I started using a new
series of glazes I went back to the analyzer to find the best
reduction and oxidation cycles for those glazes.
The analyzer is just a tube with a fluid that expands. A sample of
kiln gases is taken from the kiln. To do this a sampling assembly
consisting of a bulb and tubes attached to the a15" long quartz tube
is inserted in a hole of the kiln wall. Think blood pressure bulb
and you'll get the idea. Consistency of readings depends on a number
of things. The fluid level in the reservoir needs to be the same
every time. Always turn the sampling tube over and back twice. Always
pump the bulb the same number of times. Count. twenty-two times will
give a different reading than twenty-four. Always take a sample from
the same location. Change only one thing per firing until you get the
results you want. Keep good records. Time, temperature, reading. I
even noted weather, outside temperature, and barometric pressure. If
you are new to the kiln you are firing it will take some time to zero
in on the right firing cycle for you. I found it as accurate, or
useful, as an oxy-probe that was loaned to me.
The analyzer works on relativity. If you take the numbers from
Wettlaufers book, they may not be right for you. His body reduction
and glaze reduction numbers did not fit with my experience. The
analyzer measures CO2 in both oxidation or reduction. So, it's
important to find neutral for your kiln. The instructions will give
you a number for neutral, but it may not be right for your kiln. To
find neutral you put the kiln in obvious excessive oxidation. Take a
reading. Say an eight. Then slowly reduce the oxidation and take
readings. The number should rise until you start into reduction
cycle. At that point it will begin to fall. The lower the number,
the more reduced the kiln is. Neutral for my kiln is 12. I body
reduce at 9 1/2. Then, take it up to 10 1/2 until cone eight starts
to bend. Then back down to 9 1/2. This is a rather light reduction.
But, it gives the color I want. I've found heavier, but shorter
reductions don't give the results I want.
I found this a useful tool. Especially when I tore down and rebuilt
the kiln. But, once I really learned my kiln it wasn't necessary. I
still use it once in a while if firing start going wacky. I realized
that my kiln was leaking more heat than it used to and rebuilt part
of it. Then it was fine.
Kathi
Lee on tue 29 jan 08
On Jan 29, 2008 3:56 AM, David Beumee wrote:
> When Pete Pinnell taught our Anderson Ranch glaze workshop group what was
> really going on in a reduction kiln back in 1989,
Pete did a workshop at Northern Clay Center around '95. He is a
glaze wizard.
He pointed out to us that it is nonsense to candle a gas kiln
overnight. A waste of fuel. He fired quickly in the beginning,
explaining that people usually go slow in the beginning, but hurry up
in the end. He likes to hold the kiln at the upper temps for a while
and that is where he spends the firing time.
He also brought an inexpensive CO2 probe that is used in
industry with furnaces. Had to put water in it. Pumped a rubber
ball. Said it worked well enough, so he didn't have to haul and
expensive Oxi-probe around
--
Lee in Mashiko, Tochigi Japan
http://mashikopots.blogspot.com/
"Tea is nought but this: first you heat the water, then you make the
tea. Then you drink it properly. That is all you need to know."
--Sen No Rikyu
"Let the beauty we love be what we do." - Rumi
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