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About glazenerd

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    Clay Research

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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.

    Email: optix52@aol.com

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  1. glazenerd

    Hudson River Clay

    Both of these are 50% Hudson, 20% potash, 5% lithium, 20% silica. Added titanium to one of them. Did the job of melting, but the potassium created some pin hole issues. Will need a hold at peak. I took them out of the kiln at 350F, and plunked them into cold water- survived well enough.
  2. glazenerd

    Hudson River Clay

    Mary: calcium bentonite is also abundant along the Hudson. Magnetite (iron) will present itself dark grey to black in sedimentary deposits. Plenty of mica and calcite around the Hudson as well. When I was candling some of the material, got that musty aroma of humus as well, albeit very low %. At this point, my prime suspects in your Hudson River clay. arsenic is a normal by- product of natural oxidation/reduction of iron, especially magnetite. https://pubs.acs.org/doi/abs/10.1021/es702625e Tom
  3. glazenerd

    Hudson River Clay

    Think I found the cause of 8.31% iron content: https://thediggings.com/mines/usgs10296653 mostly magnetite mines along the Hudson.
  4. glazenerd

    Hudson River Clay

    Gred: oyster shells would provide calcium, not sure what else? The iron and magnesium levels are the highest I have seen in natural clays: not sure what the contributing factors are, but working on it. I originally thought the iron was hematite due to the color, but from reading; magnetite is more common in NY. Later this year I will demineralization a sample and have a look. I am fairly confident it is a combination of calcium bentonite and smecite montrollites. The old Albany slip was classed as non-plastic; this sample is highly plastic- approaching macaloid in nature. Interesting indeed! Tom edit: I will look into the iron levels in oysters
  5. glazenerd

    Hudson River Clay

    Mary: was reading several pieces on mineral resources found in NY: one referenced Cherry Hills. Might have read it wrong; might be an old mine? I could not find it either. Tom
  6. glazenerd

    Hudson River Clay

    Mary: been doing some research, trying to figure out your clay. calcium bentonite is found in your area. Calcite is mined and abundant all over NY state. More interesting, smecite is fairly common in the Arirondack Mts. Even more interesting is how it is formed: humus is drawn into existing illite deposits on the forest floor and is converted over (much) time to a smecite variety. Even more interesting, native NY smecite has a green/ gray cast: which I saw in your samples. The specific native NY smecite is 0.5 um particle size: in pottery speak 2500 mesh plus. Question: how far away is Cherry Hills? And it's proximity to the Hudson? Tom
  7. glazenerd

    What Is Ceramics, Is It Art?

    Perhaps the Moody Blues should have titled their 1969 album " In Search of the Lost Clay." DESTINATION: being defined in this topic as the pinnacle of success in forming, glazing, firing, or technique. that said: some people enjoy the journey (me) to that destination as much as arriving there. Others want to reach the destination as soon as possible. T
  8. glazenerd

    Cone 6 Red Stoneware Recipe

    Tin: mostly because potters try to doctor up lizella to get it to seal up at cone 6. Lizella has some percentage of chlorite minerals ( green cast.). The iron is lower than the more common clays such as red art and Newman. Greenstripe tends to bloat easier than most. you are trying to customize a fired color: which can be done. You need to do samples at 30%, then 40%, and 50%. Once in you get into your color zone, the 5% increments. 35% etc. tom
  9. glazenerd

    Hudson River Clay

    Cone 6. 60% Hudson, 20% spodumene, 20% mahavir potash, 3% NS suspender, 3% lithium. Carb. so far so good: going to thermal shock when I get time. Just slightly immature, but close. I see red streaks sprinkled throughout. Going to try 50%, which should go red! then 70%. The recipe brings silica just over limits, but the alumina is way heavy ( intentionally).
  10. glazenerd

    Hudson River Clay

    Both potassium and sodium are naturally occurring salts. In both cases, they can contain 14-20% soluble salts; which indeed migrate. Still makes me wonder if a water treatment plant is dumping upstream? Very unusual. Maybe you should call it "Calgon Hudson Clay" Tom Will have a test fire out later today: will post later.
  11. glazenerd

    Hudson River Clay

    Mary: Want to see your clay up close? You can see the alkali film bleeding across the sedimentation lines in the first pic. In the second pic which is towards the surface: looks like the high iron content is oxidizing. You definitely have a large amount of mica: can see the crystals in other views. Which explains the high potassium and higher alumina levels. I did an "unofficial" sieve test yesterday: I sieved about 1/4 pound through a 100 mesh screen. Then I took one level teaspoon and sieved through a 200 mesh screen: about 70% passed. Unofficial, but gives me some indication of what you are dealing with. I can also see a green cast in some views: usually associated with chlorite minerals. Early in the game at this point: but I am going with some smectite variety, which has heavy mica deposits, hematite, and ??? (will have to test more). What I was wrong about: little to no humus. Been awhile since I have seen natural clay bleed fluxes. Suspect this is your iron (8.31%) oxidizing as it is exposed to air. Tom
  12. glazenerd

    USB Images

    Taken with 20x to 800S usb microscope
  13. glazenerd

    Cone 6 Red Stoneware Recipe

    Frit by the way; operates on a simple premise: at cone 04 up to 33%, and as the cone climbs! the additions decline. Cone 6 for instance 10-15%. Cone 10- 0%.
  14. glazenerd

    Cone 6 Red Stoneware Recipe

    Tin: then I would start at 30% Newman Red, 25% OM4, 25% silica and 20% mahavir feldspar, Cone 6. stay away from laterite and lizella. Both have chemistry that will cause some issues. tom note: this is a starting point. Increase Newman by 10% until you get a color you like. Adjust OM4, silica, and spar downward .
  15. glazenerd

    Cone 6 Red Stoneware Recipe

    Tin: Newman Red and Redart are the two primary clays used in red bodied stoneware: there are others. Newman (now a blended clay) is more tolerant of heat than Red Art is: it will retain color at higher cones. That said, all high iron clays turn increasingly darker as the cone fire climbs. You could formulate a body at cone 3-4, that would retain a color closer to what you are after. Formulated correctly, the absorption could be held to 3-4%. Potassium would be a better flux choice; sodium creates a fair amount of pin hole issues in stoneware. You would have to hit 2100F in order to achieve any kind of vitrification: appreciable amounts of glass does not begin to form until 2050F. I would also explore alternate flux choices; and you could cheat by using frits. Fritware creates psuedo vitrification because frit begins to melt around 1450-1475. The frit creates the glass content in the body, which in turns reduces absorption. Depends how far down the rabbit hole you care to go: I live down here, so no big deal for me. Tom

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