Kelly Dudley/Kathy Roberts on tue 15 jun 99
Dear Clayart Brain Trust,
My friend David McDonald, who is not on Clayart, is having a serious
bloating problem. He asked me to ask the group for any help, as he is
at wit's end trying to figure this one out.
For the past 18 years David has used Laguna's (California) Amador cone
10 clay. He fires with natural gas like so: Very oxidizing up to cone
06, then a 30 minute body reduction (just enough damper closure to put
back pressure at the bottom peephole), followed by mild reduction up to
cone 10, then turns off the kiln. His work is slab built, from 1/4" to
3/8" thick, and he has never experienced bloating when firing Amador as
described above (same clay, same firing schedule for the past 10 years).
Bloating started to show up 3-4 months ago, but in only a few pieces. It
gradually got worse. For the last load, he was very careful and used an
oxyprobe to make sure he wasn't over-reducing. He monitored the load
carefully and turned off the kiln right at cone 10. Guess what? Even
more pieces bloated this time.
Additional information: David uses the clay right out of the bag, he
does not wedge it. He has been bisquing to 1700 degrees F., the same
way for the past 10 years also, no changes. He orders his clay from
Laguna, but has them mix it special for him, although the only "special"
thing he asks for is extra water, as he likes a soft clay. He got a new
clay shipment from Laguna about 3 months ago. HE has talked to a couple
of his friends who also use Amador and neither is currently having any
bloating problems, although one of them said that he has had occasional
bloating problems in the past, but only on slab built pieces.
David is really in need of some help. He hasn't freaked out yet, but he
is thinking about it. He is behind on his wholesale orders with no
remedy in sight. Can anyone help?
LATE BREAKING NEWS:
P.S. Before I could submit the above message to Clayart, I received the
following from David:
"So this morning I got John Brooks (Laguna Clay Co. owner) on the phone
for awhile, and was pleased with his honesty when I asked him if there
were any other complaints of bloating with Amador. The answer was yes,
a few. Any changes in the Amador mix in the past years? Yes.About a
year ago their supply of silica sand (used as grog in the clay) was no
longer available in California, so they were forced out of necessity to
switch to a FELDSPAR sand! And yes, when they tested this material in
their lab, it did give them some results that they were less than
pleased with. It is more of a flux, of course, which lowers the
maturation point of the clay body, as compared to silica sand. So
instead of being labeled a cone 10 clay body which used to be somewhat
tolerant of temps above cone 10, now it's a cone 10 clay body which
appears to JUST handle cone 10. And if there is any carbon or gases left
in the body from body reduction still there when the clay starts to
vitrify, guess what? It gets trapped there, and may bloat the clay out
as the gases continue to expand and try to escape. Brooks talked to one
of his lab techs (also named John) and had him call me back. This John
was also very willing to try and help me out. He said they were
experimenting with the Amador mix and he is sending me a box of it to
work with and compare. With the experimental mix they are cutting down
on the amount of powdered feldspar that they had put in the mix in the
past (which was there in order to have a vitreous body). Didn't think
to ask him why they didn't do that when they first switched to a
feldspathic sand. So, since receiving , making drying, bisquing,
glazing, firing this test clay could take awhile to see any results, I
asked John if he could give me a few ideas on what I might do with the
stock of bisqueware, and the 1400 pounds of clay I still have sitting
here. What he told me gave me some hope and made sense although it's
not what I would have guessed. Instead of reducing the clay body at
1860 degrees F, or cone 06, as is traditional, he said to try reducing
at 1950 degrees for the same 30 minutes. The reasoning is that the clay
is less open by then and the carbon from the body reduction won't likely
penetrate so far into the walls of the pots. therefore there isn't as
much carbon deep inside the walls to have to then get back out. He said
that the surface should still reduce just fine for the needed visual
results. He said that that's what works in their test kiln anyway, and
when they body reduce at 1860 degrees F. like I do, they get carbon core
and bloating too! So I'm feeling some hope to glaze and load up a
firing tomorrow and fire it off the next day. I'll see the results on
Friday. Sure would be nice if it works that easily. Also, the Amador
body apparently isn't alone in complaints of this problem. Their "LB"
blend has also given them problems. And looking at the clay descriptions
in their catalog, I see that many of their clay bodies are mixed with
sand. So...I'd be glad for more input, and will certainly share my
experience of what ends up working. David"
Kelly Dudley, in hot and dry Arizona
teco@getnet.com
June Perry on wed 16 jun 99
I can't believe that they didn't find another source of silica sand. I live
in Oregon just, across the border from California and I just bought a bag of
silica sand about a week ago to batch some claybody tests for my soda firing.
I'm assuming it was just easier for Laguna and cheaper to throw quality
control to the wind and go for the spar sand! Yuk!
If I were younger, I think I'd go into the claymaking business with Ron Roy
as my official advisor and lab tech. I'd tests all new batches of raw
materials, sieve the fireclays, etc. :-) Maybe we all need to talk Ron's clay
company to market their clays here on the West coast!
Regards,
June
Ray Carlton on wed 16 jun 99
you are lucky that your clay supplier has been honest with you...many would
say sorry no changes this end....I can't be sure but my feeling is fiddling
around with the reduction schedule will just ruin more pieces...I would
suggest the best fix would be to find out what temp to fire the clay too
without bloating...my guess would be around cone 6 as it seems to be a
popular place where many potters now live and the producers would have felt
cone 6 would suit most and released the clay at that..if the work is
unglazed you are already home and hosed..intial reduction around 8-900 deg
celcius......if it is glazed well you may have to consider other
options...the 1400 pound of clay left I would ship it back at their cost to
the factory as it is unsuitable for your purpose as by their admission it
is not what it is supposed to be or was... I realise that finding a new
body is a pain in the butt...but i see that apart from lowering your firing
temp it is your only option...on the other hand itr might a good time to go
to cone 6
I have been through this..... it went for months and didn't come right till
i changed the clay
good luck
At 08:23 15/06/99 EDT, you wrote:
>----------------------------Original message----------------------------
>Dear Clayart Brain Trust,
>
>My friend David McDonald, who is not on Clayart, is having a serious
>bloating problem. He asked me to ask the group for any help, as he is
>at wit's end trying to figure this one out.
>
>For the past 18 years David has used Laguna's (California) Amador cone
>10 clay. He fires with natural gas like so: Very oxidizing up to cone
>06, then a 30 minute body reduction (just enough damper closure to put
>back pressure at the bottom peephole), followed by mild reduction up to
>cone 10, then turns off the kiln. His work is slab built, from 1/4" to
>3/8" thick, and he has never experienced bloating when firing Amador as
>described above (same clay, same firing schedule for the past 10 years).
>
>Bloating started to show up 3-4 months ago, but in only a few pieces. It
>gradually got worse. For the last load, he was very careful and used an
>oxyprobe to make sure he wasn't over-reducing. He monitored the load
>carefully and turned off the kiln right at cone 10. Guess what? Even
>more pieces bloated this time.
>
>Additional information: David uses the clay right out of the bag, he
>does not wedge it. He has been bisquing to 1700 degrees F., the same
>way for the past 10 years also, no changes. He orders his clay from
>Laguna, but has them mix it special for him, although the only "special"
>thing he asks for is extra water, as he likes a soft clay. He got a new
>clay shipment from Laguna about 3 months ago. HE has talked to a couple
>of his friends who also use Amador and neither is currently having any
>bloating problems, although one of them said that he has had occasional
>bloating problems in the past, but only on slab built pieces.
>
>David is really in need of some help. He hasn't freaked out yet, but he
>is thinking about it. He is behind on his wholesale orders with no
>remedy in sight. Can anyone help?
>
>
>LATE BREAKING NEWS:
>P.S. Before I could submit the above message to Clayart, I received the
>following from David:
>
>"So this morning I got John Brooks (Laguna Clay Co. owner) on the phone
>for awhile, and was pleased with his honesty when I asked him if there
>were any other complaints of bloating with Amador. The answer was yes,
>a few. Any changes in the Amador mix in the past years? Yes.About a
>year ago their supply of silica sand (used as grog in the clay) was no
>longer available in California, so they were forced out of necessity to
>switch to a FELDSPAR sand! And yes, when they tested this material in
>their lab, it did give them some results that they were less than
>pleased with. It is more of a flux, of course, which lowers the
>maturation point of the clay body, as compared to silica sand. So
>instead of being labeled a cone 10 clay body which used to be somewhat
>tolerant of temps above cone 10, now it's a cone 10 clay body which
>appears to JUST handle cone 10. And if there is any carbon or gases left
>in the body from body reduction still there when the clay starts to
>vitrify, guess what? It gets trapped there, and may bloat the clay out
>as the gases continue to expand and try to escape. Brooks talked to one
>of his lab techs (also named John) and had him call me back. This John
>was also very willing to try and help me out. He said they were
>experimenting with the Amador mix and he is sending me a box of it to
>work with and compare. With the experimental mix they are cutting down
>on the amount of powdered feldspar that they had put in the mix in the
>past (which was there in order to have a vitreous body). Didn't think
>to ask him why they didn't do that when they first switched to a
>feldspathic sand. So, since receiving , making drying, bisquing,
>glazing, firing this test clay could take awhile to see any results, I
>asked John if he could give me a few ideas on what I might do with the
>stock of bisqueware, and the 1400 pounds of clay I still have sitting
>here. What he told me gave me some hope and made sense although it's
>not what I would have guessed. Instead of reducing the clay body at
>1860 degrees F, or cone 06, as is traditional, he said to try reducing
>at 1950 degrees for the same 30 minutes. The reasoning is that the clay
>is less open by then and the carbon from the body reduction won't likely
>penetrate so far into the walls of the pots. therefore there isn't as
>much carbon deep inside the walls to have to then get back out. He said
>that the surface should still reduce just fine for the needed visual
>results. He said that that's what works in their test kiln anyway, and
>when they body reduce at 1860 degrees F. like I do, they get carbon core
>and bloating too! So I'm feeling some hope to glaze and load up a
>firing tomorrow and fire it off the next day. I'll see the results on
>Friday. Sure would be nice if it works that easily. Also, the Amador
>body apparently isn't alone in complaints of this problem. Their "LB"
>blend has also given them problems. And looking at the clay descriptions
>in their catalog, I see that many of their clay bodies are mixed with
>sand. So...I'd be glad for more input, and will certainly share my
>experience of what ends up working. David"
>
>Kelly Dudley, in hot and dry Arizona
>teco@getnet.com
>
cheers Ray Carlton
McMahons Creek Victoria Australia
Evan Dresel on wed 16 jun 99
Huh? They can't get silica sand?? Seems to me they should try a bit
harder. I find it very hard to believe that it is a rare substance.
You should be able to get it in almost any size in any quantity.
Sheesh!
-- Evan who is signing off clayart for the rest of the month so fire
away!
Kelly Dudley/Kathy Roberts wrote:
>
> ----------------------------Original message----------------------------
> Dear Clayart Brain Trust,
>
> My friend David McDonald, who is not on Clayart, is having a serious
> bloating problem.
> Any changes in the Amador mix in the past years? Yes.About a
> year ago their supply of silica sand (used as grog in the clay) was no
> longer available in California, so they were forced out of necessity to
> switch to a FELDSPAR sand!
Lesley Alexander on thu 17 jun 99
There's a company near Sacramento that sells a product similar to Amador
called Sandstone Buff; lovely to work with. Anybody remember how to contact
them?
Rick Brady on fri 18 jun 99
Your probably referring to Quyle Kilns in Murphys, Ca. Very nice clays, Sandsto
Quyle Kilns 209-728-3562
3353 E. Hwy 4
Murphys, CA 95247
-----Original Message-----
From: Lesley Alexander [mailto:celadon@silcom.com]
Sent: Thursday, June 17, 1999 2:29 PM
To: CLAYART@LSV.UKY.EDU
Subject: Re: Bloating Emergency (Long)
----------------------------Original message----------------------------
There's a company near Sacramento that sells a product similar to Amador
called Sandstone Buff; lovely to work with. Anybody remember how to contact
them?
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