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glazenerd

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About glazenerd

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    Clay Research

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    Male
  • 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

    Email: optix52@aol.com

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  1. Mary: in my testing, I noticed Hudson clay is extremely sensitive to application thickness. Also noticed color shifts when I increased potash content. Soon as I get time, going to slurry down a sample and spray it on. Tom
  2. Marbled being the key word--- first run some blend tests. 3-5-7% of stain: find your color. Chris Campbell is a good resource as mentioned. step 2 (requires some estimating). Slurry the white clay into a paste ( slightly thicker than honey) with the color blend you decide upon. the fun part- slab roll your clay down to tile thickness 3/8". Use a 1 or 2 or 3" paint brush ( brush size = color vein size.) paint a strip of yellow down the length, leave a blank stripe, then your other color, blank space, then yellow, blank, then color, etc. etc. fold over evenly, repeat process, fold again, repeat process, final fold. Send through a final time under slight compression to remove air. caution- fold over slowly so you do not trap air between folds. Second caution: the more you wedge- the more the color will blend. EX. Less wedge = more color definition and marbling. More wedging = color blending and loss of definition. T
  3. Kaolin can have up to 15% natural shrinkage! most of which comes from combined molecular moisture. Specifications for natural clay are not expressed by "shrinkage" as is the case with blended clay bodies.LOI (loss on ignition) is used to express the loss of weight in comparison to the total weight. EX: LOI is 13% so for ever 100 grams of material, 13 grams will be lost when heating up to bisq temperatures. Organic materials, lignite coal, and molecular moisture are examples of materials lost on ignition. The primary reason kaolin is calcined (EPK) is control excessive shrinking of material during firing; up to bisq temps. Materials can flake off or crack when there is excessive LOI. Calcining does not effect material characteristics, nor does it lower melting temps. T
  4. Rod: from table 1 in your link: Finnish clay is 50% silica, 18% alumina, 9% iron. In addition, 9% LOI and 3% carbon (discussed later. i saw nothing about lead or cryolite content, so that answers those concerns. Those addressed, your molten pool would be caused by low alumina, further compounded by the early reduction of iron (1750F/ 1000C) in a wood firing atmosphere. The 9% LOI would indicate sulfide/ sulfate content, coupled with 3% carbon. Carbon would be a direct indication of lignite coal particles. Sulfur/sulfide/sulfate content which is high in Finnish clay is directly involved in reducing the iron (9%), which is a powerful flux in reduction. Firing in a reduction atmosphere (wood) further compounds the early reduction of iron. you need to slow down the firing cycle to 60C an hour from 600 to 1000C. I have not done a wood fire, so one of our forum members who have that expertise will have to chime in on this issue. The second issue is the low alumina content. 18%. Mark C recommended the addition of refractory materials which usually consists of 10-20% kaolin; which has 37% alumina content typically. His recommendation is correct, however I recommended 20% ball clay with 27-28% alumina content because you have a plasticity issue. I was addressing the refractory and plasticity issue with one fix. The ball clay you linked will not work, because it is likewise has low alumina. However, you could blend a combination of 70% Finnish clay, 20% of the ball clay shown in your link, and 10% kaolin. If you have a glaze calculator; use the analysis for Finnish clay shown in table 1 of your link as the data in the calculator. Try various blends of Finnish clay, ball clay, and kaolin until you achieve 21-22% alumina content by weight or a SiAL ratio of 5:1. Remember you need the ball clay for plasticity, but also the alumina in kaolin to raise the PCE of the clay. Finnish clay has 9% iron, so diluting it with ball clay and kaolin will still give you a reasonably high iron content. One of our forum members who we nick named Proud Mary started a thread in Clay & Glaze Chemistry called " Hudson River Clay". She chronicles her journey of working with a local clay with an iron content of 8.4%. You will find many similarities to your journey. Tom
  5. 1st pic is bloating. 2nd is pinholes.
  6. Liam: i agree, Mark has an inspiring success story in the pottery biz. After 45 years in carpentry, I am aware of the time, energy, and sacrifices he made to build it. Pottery is unique; full time, part time, weekenders, full time hobby, to monthly dabble. My only intention starting out was to "play" with crystalline glaze, until I accidentally fell down this very deep rabbit hole. Rabbit holes are also unique, but also common in pottery. To answer the QotW: I do not want to make any pottery plans: because it is the only area of my life that is not. I find the unplanned happy accidents of discovery a relief from a lifetime of calculations. T
  7. I spent the last 45 years telling myself that, not sure I agree these days. like most here, my life was the typical series of following schedules to earn a living. Planning, plotting, and projecting the path ahead. I find myself curious about not going to bed in order to get up at regulated time. I am curious to know what it is like not to meet deadlines, keep appointments, and plan for months ahead. Not sure I even know what "living for the day" means. I have held many titles over the last 45 years, most of which have little meaning: I find "couch tater" appealing lately. T
  8. After working on and building a 1000 plus houses the last 45 years: carpentry and mechanical skills. Most know I only make and sell custom tile designs. That starts on my AutoCad system as a drawing; which I can print up to 24 x 36". From there it goes to the scroll saw, and individual pieces are cut out of 1/2" plywood. Next I cut 1.5" strips of metal 16ga.) on my brake. I either bend the folds on my brake, or heat it and bend to form circles, arcs, concave,convex- whatever. The metal is then stapled 1/4" x 1" to the edge of the plywood: and now I have a die. The only thing I hand cut is a medium rare steak: the clay gets stamped. T
  9. If no one else will, then I will post a line from the Tina Turner classic "Proud Mary keep on Rollin". And you should be proud. Figuring out a recipe is not easy. T
  10. Effect of Temperature on the Charge on Kaolinite Particles in Water Systems by D.D. Button and W.G. Lawrence (Alfred U) Journal of American Ceramic Society. @ 60F the charge on particles held in suspension drops by one third resulting in warping or irregular particle stacking. @140F the maximum zeta potential (particle charge) is obtained. application: store it and pour it. Tom
  11. Your clay is fine; just need to wedge it throughly. T
  12. Min: sorry it happened to you, never fun.
  13. Had a long discussion with the math professor from SIU-E about writing math equations for crystalline glaze: she thought it was doable. Interesting!

    1. Show previous comments  3 more
    2. Benzine

      Benzine

      You do eat it, but only a little over three pieces...

    3. glazenerd

      glazenerd

      Are these three pieces squared?

    4. Benzine

      Benzine

      Naturally...

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