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About glazenerd

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    Now & Then

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  • Location
    St. Louis, Mo.
  • Interests
    Crystalline glaze chemistry. Porcelain, Stoneware, Fritware, 04 Colored Porcelain clay research & formulation.
    Ceramics Monthly Articles: Jan. 2018 Cation Exchange (plasticity), April 2018 SSA Clay Formulation, May 2018 Bloating and Coring.
    Feb. 2019 Ceramics Monthly- Clay Body Shopping Guide
    March 2019 Ceramics Monthly - Porcelain 201
    June 2019 Ceramics Monthly Clay Restoration
    Sept. 2019 Clay Memory
    Oct. 2019 Firing Programs

    Email: optix52@aol.com

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  1. The best commercial suspender widely available is BentoneMA. This product is highly refined hectorite. you need to disperse any suspender in dry ingredients before water is added. Bentonite is a rather poor suspender; but it is cheap and gets the job done. Cosmetic bentonite are highly refined in order to get USPS- food safe grading stamps. I use USPS food grade zinc in recipes intended for functional use. Tom
  2. D.D. Buttons (Alfred U) did extensive studies on the effects of temperature on particle distribution. At 68F, the negative particle charge on clay particles drops by 1/3rd. As the temperature continues to drop: so does the particle charge. Sodium Silicate and Darvan work (in part) by imparting a strong negative charge which suspends the particles in water. The water carries that charge: and as temperature drops; it effects suspension. When particles drop out of suspension in an irregular pattern: it weakens the form. Stain can also drop out in an irregular fashion. I do think Min's comments on
  3. Sbsoso- welcome to the forum. You did not State clay body type: but I will go with porcelain. When doing production: not a bad idea to keep 25lbs from the previous lot to compare to the new lot if problems arise. No problems before, and now problems means the first stop is to check with supplier if others have reported issues. Like potters, clay manufacturers shop for low prices: which sometimes creates issues. You have a plasticity issue which you can only resolve by adding water. Adding water does not increase plasticity; just moves the body closer to its liquid limits. Adding water wil
  4. About half the tradesmen around here retired, or moved south. Of the other half: 90% are 45+ years old. Everyone once in awhile I see 20-30's at the lumber yard. Local colleges and schools ceased trade classes over a decade ago. Most schools have dropped art classes. Local community college cut pottery classes way back. State college still has a strong pottery criteria; but heavily focuses on sculptural work. Prez: that would be an interesting question: do your local schools/colleges still teach pottery courses (historical, not Covid related) Changes in focus, technique etc. You get the
  5. Mark: built my last house in 2018: sold off ski steers, trucks, backhoe, trailers, etc in .2018/2019. Since then, I only do high end finish work. Custom cabinets, wainscot, crown work, custom only wood/Ceramic. Already put the word out; cutting back to 7-8 months next year. Time for the young people to step in.
  6. Mark: One of the drawbacks of any trade: downsizing when the time comes. Took off before Thanksgiving, and not going back until Jan1-12. Never took that much time off in 45 years. I like it!
  7. Well Mark- you have a 35CF car kiln=== just sayin... I would love nothing more than to stay where I am at. Yet, I know that I will not be able to take care of it as time marches on.
  8. Like Min; moving is in my near future- next year or so. Will have to decide which kilns to keep, which to sell; along with other equipment. I built a 26x44 work studio over a decade ago that is stuffed with equipment and supplies; most of which will not go with me into my golden years. Truthfully, I wrestle with just walking away all together. Would not miss the glaze so much as I would miss the clay-chemistry. Tom
  9. Bois: the recipe from Alfred is more in range to your goals. Given the grog additions; I would use Lincoln 60 mesh in lieu of Hawthorne 35 mesh. I use Hawthorne 35 in one stoneware body: you will find some very course particles- almost cuts the finger. You do highlight one issue: not everyone has ready access to clay. Tom
  10. Liam: looked in your original post but did not see: what cone was the clay rated to?
  11. Welcome Bois: Wish I could answer your questions in a short paragraph: but it will take a few paragraphs to walk you through these recipes. To start: a cone 10 stoneware recipe requires a minimum 10% feldspar addition to achieve any level of vitrification. The Soldate60 recipe calls for 50% Lincoln which is a 60 mesh fireclay: with an addition of 25% 60 mesh sand: which means 75% of this recipe is 60 mesh materials. The OM4 ball clay is the plasticizer and also serves as small particle distribution to help fill the voids that 75% 60 mesh create. The 2.5% Custer (potassium flux) at best se
  12. The 2190F peak comes from an U of I study done on feldspar reactions (KnaO) At this temp, potassium and sodium are spent; having achieved their mxiumum potential- past this temp it is all heat work. Ougland & Brindley (British Ceramic Society) measure the effects of heat work on a triaxel porcelain blend: 61% glass at cone 6 and 66% glass at cone 10- measured effects of heatwork. The 15-30 minute hold came from a study in Rio (Brazil) using a gradient kiln which found it takes heat an additional 30 minutes to penetrate an 1/2" clay wall. Edward Orton, Jr. Came up with 108F an hour climb wh
  13. Mark H. You are correct- course is a subjective term in pottery. There are several factors involved for determining suitable porcelain bodies. Translucent bodies like Coleman or Ice use Grolleg kaolin, or a blend of Grolleg and NZ kaolin. They also use premium plasticizers such as Bentone MA, and the flux levels are spiked to produce more glass. Kaolin can be fine mesh:-2 microns, or course 20-40 microns. Helmer kaolin for example is more suitable for large format bodies. Molochite as mentioned: likewise can be 325 mesh, of 50 mesh. The tradeoff being finer mesh to maintain functional pro
  14. Sounds like you have a good handle on what's around you. Natural color gives some indication: "green ash" usually indicates calcium. "Sticky and elastic" indicates a specific type of humus (organic) called muck. Common for natural clay deposits to derive some/all their plasticity from Organics. Yellows typically indicate iron; while purple tends to be iron, with some titanium. The key word is functional: which sets the safety bar much higher. "Trace" toxins such as lead, cadmium, selenium, arsenic, and mercury are common in many Ceramic materials. Understand that "trace" by definition means be
  15. Harvesting and processing wild clay is an emerging trend; more popular than most realize. Many are processing their own silica, fluxes, etc from wild sources. Natural basalt is gaining popularity for some amazing reds. The best looking celadon I have seen is processed from natural materials. Certainly not profitable or suitable for production: although some are heading that direction. Hunting wild clay is somewhere in the panning for gold category: hoping to find the perfect pit. Firing crystalline; absolute No for me- cannot give up modern kiln controllers. Tom
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