Tweaking a Clay Body: Part Two
So, as you may have gathered from all of my Cone Six Throwdown posts, I’m finally letting go of my down-to-the-molecular-level control of my work. The reasons for this are many. If you recall from Tweaking a Clay Body Part One, The main concern is that my clay body was just fine back when I had access to a pugmill. Pugmills compress, homogenize, and de-air the clay, making it immeasurably more workable. When I moved to the University of Louisville, I no longer had access to a pugmill. I started adding ingredients with the intention of making the clay more workable. Although I still struggle to make work with my un-pugged clay, I did have some success in making the clay at least somewhat more workable and plastic.
The results of the first tweak, adding ball clay at the expense of EPK, were not noticeable. I then tried mixing a batch where the bentonite, instead of being added as a powder, was blunged. Blunging is adding the powder to hot water and then mixing it at high speed in a bucket with a drill mixer until it is a smooth gel. Once this is done, it is added to the mixer with the reclaim and then all the dry ingredients are added. The idea behind this process is that the bentonite, which is a very powerful plasticizer, needs to be activated. The tiny particles will do their job much better if they are nicely encapsulated in a thin film of water. Time will do this, when clay is aged for 6 months or so, the water is given time to evenly disperse between all of the particles, resulting in a slightly more workable product. I found that I could notice the difference in this change, so from then on, I resolved to add this extra step to the clay mixing process.
Still, the clay was having severe problems, especially in the pulling of handles. I have been resorting to drying out reclaim stashes for handle pulling. This is done by blunging the reclaim, or throwing scraps and rehydrated trimming and pots that cracked in the drying. I added a lot of water and mixed in a bucket until it was smooth. Then I would run the slip through a talisman sieve onto a plaster slab. This is left to dry until it becomes a nice workable consistency. It is wedged and stored in specially labeled bags, this stuff is precious! If I had the time and the setup, I would mix my clay this way. Blunged and dried clay is unbelievably superior to clay that is not. I hope to someday own a filter press, an industrial piece of equipment that does this process in minutes rather than days.
One remarkable discovery in this quest was Veegum T. This is a highly expensive, but highly effective additive. A member of the same mineral family as Bentonite, this material is fluffy and a pinkish cream color in it’s dry form, sort of reminds me of coffee non-dairy creamer powder. I blunged 2 pounds for my 200 pound batch in a bucket of hot water. The results were astounding. Although it still fell short of what I was hoping my clay could be, it was much, much better. There finally seems to be a little bit of suction, or clay particle attraction. The throwing process brought out a lot of gel-like surface slip, and handles are possible from this clay without specially preparing it.
Although I finally decided to move to a commercially prepared clay body, I feel that my recipe would be something to go back to if I find myself with access to a pugmill next time I move studios.
I was wondering what you found when using the laguna WC-617…i ,in a rush, got the wrong body I do like how it throws…very easy…lol…but read that it is good for slabbing so i searched and found your note on testing it in the cone 6 throw down…anyway, i was wondering if you remember what you found when throwing this clay…i havent the funds to buy all new right now so i am worried! thank you!
I guess I don’t understand the question. You got it, then threw with it and liked how it throws, and you are asking me how I think it throws, right?
I like it. The last batch I got was way too soft, so I have to dry it out on plaster for 4-5 hours before I can use it. There are little metal flakes in it which is a pain, but probably(hopefully) that was just isolated to the one batch. It shrinks a lot, but it is beautifully vitreous, translucent, and bright white. The fineness of the particles even results in glossier glazes. Don’t fire it to cone 7 or it will warp. It is much happier at 5-6. The handles were cracking off until I got the clay figured out. Now it is problem free. does this help?
Jeff, I am a student at ball state university studying under Ted Neal… I just completed my senior show using completely studio made porcelain. It entirely consisted of thrown forms many with handles. I also had to devise my own clay recipe without the use of a pug mill.
My recipe for porcelain is
OM4 ball clay – 15%
EPK Kaolin – 10%
Grolleg Kaolin – 25%
Custer Feldspar – 25%
Bentonite – 3%
I mixed this recipe to a thick slurry in a 5 gallon bucket and then laid it out on plaster to get to working consistency. I do let it get a little dryer than normal for stability in throwing larger forms, but after drying it is very dense and quite plastic.
Let me know what you think.