Friday, April 2, 2010

Our new best friends

Well let's be honest here Chris and Adream were already pretty good friends. I worked with Chris for two years at Mark Hewitt's in North Carolina. We've stayed pretty close ever since, Chris even officiated our wedding. However after receiving this little beauty:

They've certainly secured themselves a position as our best friends. Of course it's just here on a temporary loan, still.... pretty good. Thanks guys!
For those of you who aren't potters reading this blog what you are looking at is a de-airing pug mill. To put it simply it eliminates the need to wedge clay (though I still do wedge for bigger pots). I'm guessing the pug mill will say me personally at least an hour a day. Not to mention Christy's wrists...
Might just be we'll have to purchase our selves a pug mill when Chris needs his back (no rush Chris), though they are pretty costly. Definitely something worth saving up for though.
As a little aside for those of you who don't know one inch out of a four inch pug mill is one pound of clay:

Yes, that's right folks not only does this machine save you hours by wedging your clay it also eliminates the need to weight you clay after wedging:
Five pound bowls anybody? Well enough of that, needless to say we're pretty excited.

In other news I picked myself up a fluting tool. I've never used one before so it might take a little while before I really get the hang of it. Still pretty fun:

In less exciting news we picked up materials to mix more clay with. We made the following changes. We removed 16% ball clay and added 16% 50mesh Hawthorne bond (the way our formula ended up one full bag of clay is approximately 8%, thus the 16%). This is the finest mesh they offer. Our thinking being the finer mesh fire clay is least likely to interfere with the flashing that we like so much. Also less likely to contain contaminants that could cause problems. Also after Ron's comment about the neph sy I looked into it a little more and ended up changing the neph sy to G200. According to Jack Troy's wood firing book neph sy does give the clay more sheen, but at the expense of the contrast that often comes from the flame moving through a cross draft kiln. I had noticed when using clay other than our own that the other clays tended to have more distinct dramatic flashing. Less sheen but more variation... we'll see. Either way neph sy certainly melts at a much lower temperature than other feldspars, so it maybe leading to a little bit of the slumping that occurred in our last firing.
Lastly our good friends Jeff and Steph asked about the cracking in our clay body. Which I probably should have posted pictures of earlier:

It usually only occurs in three or four pots a firing, always the pots in the front of the first chamber. It usually does not go all the way through the pot. We bring the temperature up quite slowly. I'm hoping it will be solved with the addition of fire clay. If this batch have the same cracks I'll probably try the larger mesh fire clay. Of course if anybody as other thoughts or idea, I'm all ears.
Well back to making pots. We're joining in a firing with our good friend Krista Loomans at Bethel Horizons where she and Aaron Weaver work. They've got a nice anagama kiln, with a catenary arch on the back. We start loading next week. Should be fun. We'll post pictures of the kiln during loading.
take care


Ron said...

Nice to have use of that pugmill for sure! I have a little Bluebird 440 and it's a life saver. It will be neat to see what changes come of the new clay formula. Do you have some of the old body left? Maybe do a couple side by side tests in the next firing. I guess I didn't realize you didn't salt at all. Good to know. I fooled around a lot with mixing bodies when I was salt glazing. Honestly I never found what I wanted, what I saw in my head. Maybe someday I'll get back to it. That's part of the adventure, the search. Best, Ron

deanandmartinpottery said...

Hey Joe and Christy,

I think you have the right idea about using different size materials in your clay body. You said you have included kaolin,ball clay,flint, grog and a bit of nef sy for the flashing and to tighten up the body. My thinking is maybe you could drop some of the kaolin and ball clay and add in some stoneware clay and some fireclay. The nef sy is a soda feldspar that has a lower fusing point. Maybe you could substitute Kona F4 or NC 4 feldspar for the nef sy if you think it is causing the body to slump. I think it will probably do much better though with the addition of some stoneware clay and fire clay but I still would keep the addition of nef sy under 10 to 12%. You probably could use some redart under 10% if your body was composed of 50% stoneware and fireclay to accentuate the flashing.The more varied your particle profile is then the better your clay will perform from the throwing and drying through to the firing.There is a fine line between a body being fluxed but not too fluxed or open but not too open. You need small particles to fill in between the large ones and they all need to be fully hydrated during the mixing and aging process.
Here is a couple of reliable flashing off white stoneware bodies.

12%--- Helmar
16%---Tenn #9
12%---Kona F4
6%---Alumina calcined/Hydrate (200 mesh)
Light grey in oxidaton to light grey brown in reduction. It shows soda and wood flashing very well.

Plastic wheel stoneware

25%---OM4 We wish you both the best.
25%---Goldart Happy testing hope this
15%---AP Green will help you guys.
8%---Kona F4
Light grey/brown
Flashes well in wood , salt and soda

brandon phillips said...

i think you guys will be body is 50% fireclay and it flashes ok if i don't reduce. neutral is best on the fireclay i think. good luck! i'm hoping someday to have a pugmill, i'm just over 1/3 through my life expectancy and my elbows already hurt.

deanandmartinpottery said...

Hey joe,

I forgot to tell you that any ball clay can be used in these two bodies. Both of these bodies contain gold art which is a good clay but it contains sulphur. If you stay out of reduction until 900 degrees C you shouldn't have any problems with the sulphur gas coming through your glazes. You may be able to sub C&C clay or FoundryHill Creme for the gold art. The foundry hill is high in silica so you might have to make an adjustment to keep the glazes from shivering. The shrinkage is also quite high but a positive is that it is smooth and non specking. The C&C is really clean and it is white firing. I hope this info will help you and christy. The pug mill is a wonderful thing to have you will really enjoy that. Good luck with your clay test.

Sue Pariseau Pottery said...

Nice fluted bowl. I picked up that fluting tool a while ago and still haven't gotten the hang of it, but only try it occasionally. Just need more practice I guess.

Good luck with the clay changes.

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createniks said...

Right on you lucky dog!
But now you wont have arm mussels the size of melons.

Your fluted bowl is lovely. If that's the first time you used that tool look out world.