Kelly in AK

I’m wondering if anyone has ideas for fixing thixotropic clay. My local clay has this property and I’ve been able to improve it by adding 1% Veegum and 20% Lincoln 60. Epsom salts helps, but it doesn’t last. I’ve also used just Veegum at 1-1/2 to 2%. None of those additions make it go away completely. I’m hesitant to increase the Veegum in spite of the miraculous improvement it makes. The clay takes much longer to dry and I have to take a lot more care to prevent cracks. So I’m asking to see if anyone has thoughts or ideas on this, in case I’m missing some remedy I haven’t considered.

I agree, underglazes are a lot more “what you see is what you get.” Unless you find a reliable source for a tin (or zircopax) wash recipe you’re likely in for some trial and error, especially if there’s glaze on top. Underglazes can get eaten up by glaze when they’re really thin too, so that’s something to account for when you’re applying it.

I’ve always thought selling clay was a difficult business to be in, so I’m thankful for those who do it. Novices (sometimes even experts) have a hard time differentiating between operator error and a faulty product. Clay producers have thin margins and raw materials that change over time. I wouldn’t want to be the middleman. Over the decades in Anchorage there have been few clay distributors. We have two who have been in it for the long haul, and a few who came and went. Most people who buy in quantity order from “outside.” It’s tricky to make returns though when your retailer is 1500 miles away and you order by the ton. Those relationships have to be solid. It’s also a small market, so local sellers don’t really get away with shenanigans because news travels fast. All that said, the markup on clay is high here. It’s heavy and Seattle is a long way away. I do what I can to support my local supplier, and I tolerate the extra cost to a point. I greatly value being able to go down the street and pick up a bottle of underglaze or bag of zircopax. Kind of like how you’ll pay a little more for something at a convenience store. For small amounts of clay though it’s become a lot cheaper to get it delivered flat rate priority mail. 50 pounds, it fits, and if it fits it ships. Not only that, it’s dropped at your door. Hard to beat. Mostly I dig and mix my own. Only myself to blame. Some places I would certainly draw the line are foreign material in the clay, clay too dry to use upon receipt, and clay that doesn’t mature at the stated temperature.

I’ve never tried this, but seems like it would work- Put some in a metal can, like a coffee can, and stick it on a fire. Maybe in a barbecue grill.

When it comes to large pots I’ve always been smitten by the Cocuchas, from Cocucho in Michoacan. The second link has some process photos. It’s a man making those pieces, but I’m under the impression it’s traditionally women who make them. https://mansioniturbe.blogspot.com/2017/10/cocuchas-distinctively-michoacan.html https://www.mexconnect.com/articles/3633-david-santos-alonso-ceramic-art-in-the-mexico-town-of-cocucho/

In a situation like this most people put a pinhole through the closed off part. That’s all you need, just a pinhole. Put it in a place that won’t be glazed. You can count on it cracking if you leave it sealed off.

A ton of short clay, that’s a lot. I definitely understand the shipping situation though. I’ve used Epsom salt with my local clay which is short and thixotropic. It made a noticeable difference, but not as much as I needed. Veegum is what I settled on. 1-1/2% allows me to throw it reasonably thin, which was impossible before. It has to be thoroughly mixed with (hot) water beforehand, I do that a day ahead. I haven’t tried bentonite, but it’s a time honored plasticizer for clay bodies. Of course, you could also make a ton of tiles. When life gives you lemons…

Min & Bill, thank you for this thread! It’s a rare moment when I can be part of a discussion about ideas that roll around in my head with people who think about the same things. As I learned about clay I thought it was beautiful how these two places (cone 06-04 and cone 10) were natural landing points for firing clay. The bisque range was where most any clay got strong enough to use for everyday purposes. It’s a range beyond an average campfire that’s reachable with a rudimentary kiln. Lead glazes allowed more useful ware by making it sanitary. The next natural landing point was cone 10. It’s an order of magnitude greater to make a fire burn that hot. Feldspars, abundant in the earth, melt there. The refractory clays (originating from feldspars!) mature there. Pots that were vitreous and much stronger could be produced in this range. My conjecture is that it’s all about easily getting to a vitreous strong ceramic. Vitrescence is our modern standard for useful sanitary pottery. Cone 6 is a temperature common materials can be combined into a body that makes vitreous ware. You can certainly tune a body with frit to make mature ceramic at lower temperatures, but frits are far from common materials. There are clays that mature at temperatures lower than cone 6, but they’re all over the place. One will mature at cone 4, another at cone 02. Lower melting feldspars and neph sy, however, which are mined at great scale, melt near cone 6. All of the other factors, such as electric kilns, the desire to conserve energy, boron in a readily available non soluble form, and the economy of having infrastructure (shelves and what not) last longer, created a perfect environment for this new landing spot, cone 6. I’m delighted to see how it’s developed over the last two decades. We’ve come a long way from “imitation cone 10.”

Hi Katie, I love a good mystery. Given the description and photograph I’m afraid I can’t say much though. There’s a lot of things it “could” be. More photos would be helpful, pictures of the edges, the back, and perhaps with something for scale. Also measurements: length, width, and weight. Finally, tap it gently with a pencil. What does it sound like? Those details may help people sleuth out what you’ve got.