Thursday, January 8, 2009

Trading a gem

I got an email this morning from Joy Tanner accepting an offer for a trade. Her choice: this teabowl. Okay, we make non-Japanese teabowls... what else can one call them? They sure arent cups, or bowls... in any event... this glaze had given us fits just prior to Christmas. It was coming out wicked thin regardless of how long I let it stand in the bucket. Weird. So did some thinking and decided to add some flocculant in the form of calcium chloride. Some folks like epsom salts, but I found in grad school that the magnesia can really mess up some colors that are super sensitive to MgO. Which means CaCl2 is my deflocculator of choice. Plus on mornings like yesterday where we had over an inch of ice to walk on.... it is the BEST ice melter out there!!

Adding a teaspoon full of CaCl2 to a small (1/4cup) amount of glaze, and made it gel. Then I slowly added the gel to the batch and watched as it thickened before my eyes. I love this stuff!

Fired up the batch of Forest Green and got nothing but gems from that firing.

Fast forward a few weeks and I caught myself reading a posting from someone (probably John Hesselberth) on Clayart talking about how solubles from Neph Sy and some frits, mess with the state of flocculation in a glaze over time. Result, glazes can thin quite a bit MONTHS after mixing up. Wow. I knew it empirically but seeing someone else confirm this gave me a different look at this ongoing problem. I think I may need to keep track of how long this takes based on the glaze batch size. Wild fun stuff! Combine this with my new grasp of rheology thanks to John Tilton's blog... and I am in for a fun Spring as we play with new glazes!!!!

Thank you Joy! Now it feels like Christmas. Pottery in the mail! Is there anything better?


Judy Shreve said...

I have a couple of glazes that would benefit from this revelation! Do yo buy the calcium chloride at your pottery supply?

Your work is gorgeous -- I'm a clayart lurker so I'm familiar with your name - but hadn't seen your work. What temp do you fire? Is that porcelain?

Alex Solla said...

Howdy Judy-

Thanks for your kind words.

To answer your questions:

CaCl2 can be found at just about any hardware store or grocery store or gas station anywhere that gets snow. Usually sold under the Prestone or Firestone brand... but there are plenty of other brands. Just make sure the label says CALCIUM dont want Magnesium Chloride or Potassium Chloride... all work great as de-icer but just dont have the same effect on glazes. Easy to find, and to double check, it usually comes in the form of little tiny balls, about the size of styrofoam beads one would find in a beanbag chair.
Buying CaCl2 from a ceramic supplier would probably be 10-20x the price. I think I pay about $11/50# bag. We kill off about 3 bags a winter, with some leftover for the studio.

As far as our claybody... it is a porcelaineous white stoneware. Technically, any time a white claybody has more than half the body comprised of clays, it steps out of the realm of porcelain (and is usually a bit less vitrified too)...

Trade off for sure. I love our claybody though. Tuckers Smooth White. They make ours a LOT wetter than their normal mud. I love it!

Nice to know someone is seeing the few things I post to clayart. I seldom post there much anymore. I guess I figure that what I have to offer is already being offered 10x over by the time I read postings from the day.

So where can I see some images of your work?