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glazenerd

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About glazenerd

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    St. Louis, Mo.
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    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. I was suggesting that 1500F was enough heat to cause a chemical reaction: which presented itself later when water was added.
  2. Lee- I get questions about crystalline on a regular basis in PM and email; and will answer publicly when asked or if from someone I have been working with. I still read what is posted on a regular basis. Been working on a couple of articles for CM about the finer points of firing crystalline glaze: as Brandon just proved in his first firing- not as tough as it looks if you know the "tricks." Tom
  3. Brandon: excellent results for first firing- I know many have not gotten this far in 30 firings. You are to be commended for researching and learning before diving off into the deep end of the glaze pool. I like to use crystalline posts as an educational opportunity for those who are following- there are many. You have the peak temp, growth ramps, and recipe down. A reactive recipe will grow crystals at the rate of 3/4 to 1" per hour of soak time. Great crystals on this one- exceptional in fact. Again note the cloudy (milk) on the upper third from excess titanium. I am very impressed with your first firing- very impressed. You can discuss exact recipe in PM if you have more questions. Tom
  4. Marcia: Speaking of crystalline glaze- I read a thesis paper on crystalline glaze written by a student at SIU-C in 1973. As a historical perspective: 1973 was 25 years before any formal books on crystalline glaze was published ( Macro Crystalline Glaze by Peter Isley) I have read it several times: the insights and theorem are well within the boundaries of modern crystalline chemistry. The author of this thesis paper was YOU. T
  5. Frits begin melting in the 1475F range. "Dictionary of Glass and Technique" by Charles Bray. Best resource book on glass, including making frit. Look at the course ground here- https://shop.bullseyeglass.com/accessory-glass/frit-powder.html
  6. Gen: Gold specks possible pyrite: but not mica- mica would be glassy or white. Pyrite is FeS (sulfur) and judging by your result with 50 local 50 B-mix: you have in excess of 8% iron content. The only issue that makes me doubt pyrite is the dried greenish color: hematite in the presence of calcium will present greenish. The simple test to determine that: iron disulfide (pyrite) will go brown at cone 6- hematite will keep a deep red tint. Alluvial soil is fine grained- sub micron and lower in alumina. If pyrite, doubt you can fire past cone 1-2 without pyroplastic issues. If hematite: then it should handle cone 6 because hematite and magnetite clay runs between 20-24% alumina- iron disulfide runs 15-17%. The test is simple: just put a button of you clay on a tile, scrap whatever and cook it to cone 6. Brown- iron disulfide- low fire. Deep red- hematite. Plasticity- your sample has high sand content which is "tempering" the clay- not the same as plasticity. Tempering comes from the brick industry- used to produce malleability, but not plasticity. (They do not want high shrink values). Plasticity- start with 20% OM4. EX. 200 grams OM4 per 1000 grams local clay. You are hand mixing I assume? If so, it will take 3-5 days before full plasticity will develop. Overdo the plasticizer then you will have the opposite problem of clay fatigue- slumping-folding. Burn a sample to cone 6- confirm what the iron source is: then address formula- cone value. Nerd
  7. Cone 6 stoneware 76% OM4, 14% feldspar, 10% silica. ( This is a plasticity fix only.)
  8. Coleman Porcelain. >Aatdvark Clay is highly rated for Cone 10. Laguna Frost porcelain- cone 6. Any "high white" porcelain will work. Translucency is not a requirement for crystals. Colorants should be 325 mesh. Alumina, titanium dioxide, red iron, copper carb, manganese, cobalt carb. ilumenite, and rutile are commonly used in crystal recipes. Small quantities: very little colorant goes a long way. Nerd
  9. Liam: acid etching usually involves full strength muratic acid with only mild dilution. Typically the PH hovers around 1.5- very corrosive to skin, eyes, and inhalation of fumes can damage lung tissue. Not only requires eye and skin protection, but also respirator for those specific fumes. If left to soak indoors: can rust any metals within a few feet within hours. Seriously bad idea to make that suggestion to a screen name with "hobby" in it. Yes, I play with some potent stuff: but I have the safety equipment, and the training (EPA) to do so. And I dispose of it within recommended guidelines.
  10. By the way- stay far away from acid baths: dangerous if you do not know what you are doing and do not have the proper safety equipment.
  11. In the crystalline world this is called: "Crap." If you do not get results in the initial firing: odds of recovery in a second fire is slim to none. However it is a good lesson of how colorants and oxides disperse in a firing. Notice the large run lines of the cobalt and the white streaks (tin) going down the sidewalls. This is also a good lesson on glaze application. Vertical pieces- 0.65-0.75 grams per square inch. Flat surfaces- 0.45-0.50 grams per square inch. When glaze application is excessive: it will pool and crystallize. A good record none the less: you now know what excessive glaze application looks like. To further explain technical terms: when you open the kiln expecting beautiful crystals and see this: the immediate reaction is "crap." Descriptive on both a chemistry and emotional level.
  12. Notice the streaks running down the side walls? In this case: that is the tin and zinc pooling to the bottom. Lose too much colorant- blotchy crystals. Lose too much zinc- no crystals. In dead center bottom there are too large blotches with raised rims. That is called "boiling" in the crystalline world. It is caused by excessive peak temp; but also common when excessive lithium carb is used in the recipe. Cobalt is reactive to excessive heat and/or excessive flux: boiling is a direct indication of those problems.
  13. Jess: going to turn your results into an educational dissection of results. You have inner and outer growth rings: just need a mild downward adjustment in ramp hold (growth) cycle temps. Do not worry about the crazing at this point. Dial in your peak melt temp, then your growth cycle temps : then adjust silica to control crazing later.RULE 1: only change one parameter at a time when testing crystalline: so you know exactly which change caused what reaction. Final assessment: you did exceptionally well for your first time out with this glaze- be proud.
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