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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. Yes, wood ash could be used. Trees pull calcium and potassium from the soil, and often other alkaline. Cannot advise you on how much to use because the amount of alkaline is directly related to the soil it grows in. Good place to start would be 2-3% because of the weight differential between ash and minerals (Nep Sy)
  2. Your processing technique is good: enjoy the journey.
  3. You are dealing with a property called "cementing." This property is created by higher iron and alumina content which creates strong positive charges that "cement" particles together. It can be further compounded by the acidity of the clay. Without going down the clay chemistry rabbit hole: perhaps simple math. Negative charge = plasticity. Positive charge = cementing. In addition: alkalinity = deflocculation= plasticity. Acidity = flocculation= cementing. Cementing can be better understood as tight compaction/adhesion of adjoining clay particles. The solution requires more than just adding p
  4. Are you planning on adding tusks? Symmetry looks right to me. You plan to mold this for a bronze cast?
  5. 50% determination, 35% creativity, 10% planning, and 5% luck.
  6. Coleman porcelain is made from Grolleg kaolin. Search for porcelain bodies made with this very clean burning/ high white kaolin clay. There are cone 6 versions available. Tom
  7. LC88- will address this later, lost track of time. Edit add: the first photo is iron bearing clay; identified by its red color. The white clay is more likely white ball clay, rather than kaolin. Kaolin typically is non-plastic and would resist forming as you show. I have seen some deposits in Georgia, but tends to present "yellowish" due to high titanium levels. Clay harvested from creek beds, forested, or heavy vegetation areas most likely derive its plasticity from organics. Vegetation converts to humus: 2 types are commonly sold in garden centers as potting soil. The other two types:
  8. You assumption is correct: the glaze needs to be fluid in order for the mica to form crystals. I use pure muscovite mica: 37% alumina and 13% potassium. (325 mesh) Enough colorant to suggest color, but not so much as to over power the mica. Tom
  9. Sorry for the delayed response; family member passed recently and I have been tied up with settling her estate. Microcrystalline glaze form a specific ionic bond called HCP (hexagonal closed pack) crystals. This glaze is mica saturated: and you are seeing the large plate like structure; which is a common property. During the 16-17th century that would quarry large thin sheets of mica for use as window glass. Tom
  10. Many stoneware recipes have switched to Nep Sy as the primary body flux (Cone5/6). Nep Sy in the USA can have up to 14% soluble salts that migrate to form hard nodules in clay. You are getting the larger bits, many more smaller. No practical way to remix to consistent distribution. Tom
  11. Low fire bodies (06-04) incorporate talc primarily as both a flux (magnesium) and to control thermal expansion. Low fire bodies without talc can have COE values above 12, and bodies with talc can have COE around 9-10. Boron is also used in low fire bodies as a flux: both magnesium (talc) and boron are lower temp melts. Cone 6 bodies use KnaO (sodium/potassium) as the primary body fluxes that begin to melt around 2050F. In addition, cone 6 stoneware bodies have COE between 5-6 typically. While you can certainly mix the two and fire low: any functional use properties will be lost. Secondly,, you
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