Bill Buckner on sun 3 aug 03
Thanks, Mel. I have seriously considered what you are proposing. I am
also of the mind slips make the best bodies. This is partly because aging
effects can occur more efficiently in the liquid state. But, I believe
another very important contributing factor is that the particles attain a
wetness saturation that cannot happen when dry clay is mixed directly to
the working state.
Working particles to slip, then back to the "clay" stage is definitely the
best treatment for producing good working bodies.
Here are some tests and observations I have made on this problematic clay body:
+ Early on, I mixed batches very soft - about as soft as one could
comfortably throw. At first, I thought the high water content of the very
soft clay was the cracking culprit. So, I mixed it stiffer, but with no
change in the cracking effect.
+ When I was in school, I used to mix clay in a Walker by letting the pug
mill dry mix the clay (I added shovels full of the individual components to
the hopper, let it blend a few seconds then added water to bring it to
consistency and threw in any scrap I had to reclaim. Over a two year
period of doing this, I never had a single crack.
+ I have been chatting with Linda Arbuckle at the University of
Florida. Linda has suggested the Nepheline Syenite I am using as the flux
may be the culprit (I inadvertently listed G200 as my flux in the recipe I
posted here - the body flux I am planning to change to and test). Glenn
Dair, at Callanwolde Fine Arts Center also indicated he thought neph. sye.
could cause weird effects when used as a body flux. Linda indicated neph.
sye. has deflocculating properties which could cause the cracking
problem. This seems consistent with the oddball cracking patterns I have
been seeing on this work. Initially, I chose neph. sye. because the body
contained 40% kaolin and 20 % ball clay. I figured the neph. sye. would
provide a more flux power (it is a stronger flux than potash feldspar or
soda feldspar) while keeping the non-plastic material to a minimum (10%, in
this case). Additionally, neph. sye. favors flashing in vapor kilns, an
effect I wanted to incorporate in my clay fired in my cross-draft soda
kiln. Unfortunately (as luck would have it!), no cracking appeared in the
initial (relatively small batch) tests I made of these bodies. So, I
missed the problem until I put it into production.
+ Unfortunately too, I do not have access to youthful, exuberant studio
assistants I can set to slaving away over a slip pit and a hot pug mill
mixing my clay bodies as I throw to my heart's content [on my treadle wheel
- that other topic!], or sit in the back yard sipping iced tea, shooing
mosquitos and listening to this summer's bumper crop of cicadas. The
system I am using came out of a need to custom blend a clay body to the
specifications I seek in my firing mode. Since my space and my facilities
are limited, I dreamed up this plan that would allow me to keep the dry
blend and slip on hand to mix as needed from whole bag quantities. My
throwing bucket slop and my trimming scrap get slaked and go back into the
slip bucket). The slip barrel allows that portion of the clay, at least,
to super-saturate and "age" (with the help of a bit of vinegar and/or
unfinished wine from the kitchen).
So, at this point, the plan is to purchase some commercial clay to get me
by until I can work out this cracking problem. I plan to work it out
instead of giving up on it. The solution, I am convinced, is a simple one
(like switching fluxes). I just need to zero in on the culprit.
I thank ALL of you who have contributed bits of information from your
experience or expertise. This is ClayArt working at its best, IMHO. I am
not always "on" ClayArt as I cannot keep up with the 50-90 or so daily
postings. However, I promise I will post the solution when I identify it.
BTW, the soda firing proceeded wonderfully, yesterday. I think I have
finally tuned the bag wall well as I had cones falling simultaneously all
the way up, it proceeded faster, AND I used less gas than in any previous
firing. But, the cracking clay was in this firing. We'll see how it fared
tomorrow night when the door comes down.
Cheers,
y'all,
-Bill
Atlanta
At 07:13 AM 8/2/2003 -0500, you wrote:
>i have found that the more water used in the mixing
>of clay the better...this goes back to reading i did in
>1955. `mixing slurry and then let it dry makes the most
>plastic, well mixed clay.`
>
>very few potters use blungers any more....some of those
>potters would mix for 24 hours in a slurry condition.
>
>the new high speed powerful pug mills seem to mix well,
>but, no water in the mix, and over dry mixing can cause
>problems, big problems in my opinion...bill's experience
>shows this.
>
>i always soak my scrap in buckets of water mixed with
>vinegar and ammonia. i let them sit for days. age.
>i dump them in my pug mill (old walker) and add a bit
>of continental clay stoneware clay dry and some sand
>and grog and lake superior found iron sand.
>
>for years at hopkins high school i found that soaking scrap
>was the way to go, it hid all the mess and old pots, but
>kept us with 50 gallon tubs of slurry. that was mixed
>in the soldner, or walker to make new clay. we re/cycled
>every drop of clay. kid power. always had a great deal of
>continental clay dry on hand. we would fill in with boxed
>clay.
>
>commercial pug mills seems to mix so much better than
>the average home or shop pug mill..deaire, etc.
>
>so, i am sure bill is on track with using more water, let time
>take its course. then run the clay through the pug mill
>at least 3-4 times.
>
>all i can say is that is how i do it, make a great deal
>of my own clay, and have virtually no cracking as you
>describe.
>mel
>from the farm/HAY CREEK
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
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>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
>
billBUCKNER
www.sodaglaze.com
Life is too important to be taken seriously.
-Oscar Wilde
Ron Roy on tue 5 aug 03
I have always heard that the kind of "aging" that improves workability does
not happen in the slip form - that the clay must be in the "plastic" state.
RR
> This is partly because aging
>effects can occur more efficiently in the liquid state.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Vince Pitelka on fri 8 aug 03
> I have always heard that the kind of "aging" that improves workability
does
> not happen in the slip form - that the clay must be in the "plastic"
state.
Ron -
This makes me wonder how much of the advantage is due to "wetting" rather
than aging. I do know that when we mix recycle clay slurry with enough dry
materials to stiffen to plastic consistency, we get a far more plastic clay
than one mixed entirely from dry materials.
Also, I get a lot of organic activity in slips stored for long periods of
time, and I don't understand why this would be different from the organic
activity that occurs in plastic clays. Either way, the byproduct is slimy
and acidic, lubricating and flocculating the clay.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
Ron Roy on sun 10 aug 03
I think there is an initial advantage to wetting but aging evens the curve
out - just needs to be mixed a little wetter. I have always used dry mixed
as opposed to wet mixed so I really don't have the comparison.
I suspect the aging in plastic clay goes faster than in the slip -
especially if "old" clay is added - because you are adding some "culture."
RR.
>Ron -
>This makes me wonder how much of the advantage is due to "wetting" rather
>than aging. I do know that when we mix recycle clay slurry with enough dry
>materials to stiffen to plastic consistency, we get a far more plastic clay
>than one mixed entirely from dry materials.
>
>Also, I get a lot of organic activity in slips stored for long periods of
>time, and I don't understand why this would be different from the organic
>activity that occurs in plastic clays. Either way, the byproduct is slimy
>and acidic, lubricating and flocculating the clay.
>Best wishes -
>- Vince
>
>Vince Pitelka
>Appalachian Center for Craft
>Tennessee Technological University
>1560 Craft Center Drive, Smithville TN 37166
>Home - vpitelka@dtccom.net
>615/597-5376
>Office - wpitelka@tntech.edu
>615/597-6801 x111, FAX 615/597-6803
>http://iweb.tntech.edu/wpitelka/
>
>______________________________________________________________________________
>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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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