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?