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glazenerd

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  1. Notes: all test samples shown are blended at 73% clay, 12% C&C ball clay, and 15% mahavir potash as a baseline: fired in oxidation. Red body is a generic term used to describe iron bearing clays that have a red hue. There are other iron bearing clays that can present as green, grey, and black; these are exceptions, not the rule for commercial bodies. The three iron sources found in natural clay are hematite, magnetite, and iron disulfide. Iron disulfide is the common iron source in the USA and Canada; however hematite and magnetite are included because they are sourced in other countries. Hematite and magnetite are also harvested by local potters in North America. Typical iron bearing clays average between 5.0 to 8.4% of iron by weight. The tile graph below shows unglazed red bodied clays, with a locally sourced magnetite ( dark gray) sample from NY. (TY Mary) All five fire to a traditional Tera Cotta at cone 04; although there is some variance in color depth. At cone 3, enough heat is present to cause some reduction resulting in color shifts. At cone 6; iron disulfide typically turns a deep brown; magnetite is nearly black; while hematite maintains a Terra Cotta color pending alumina levels, or a deep reddish brown. The note below identifies the labels for each clay; as well as their iron source. Additional Test Note: IM (IMCO Burgundy), and RA (Red Art) contains iron disulfide as the primary iron source. Newman Red (N) is a blended material that incorporates primarily hematite. H (hematite) is a locally sourced material that is not commercially available. Magnetite (M) is also locally sourced and not available commercially. Nerd
  2. From the album: Clay Tests

    © TJA2020

  3. From the album: Clay Tests

    © TJA2020

  4. From the album: Clay Tests

    © TJA2020

  5. From the album: Clay Tests

    © TJA2020

  6. From the album: Clay Tests

    © TJA2020

  7. From the album: Clay Tests

    © TJA2020

  8. From the album: Clay Tests

    © TJA2020

  9. Meghann: Mined clays can go through subtle changes as they dig the deposits; but unlikely to cause radical differences. Stoneware bodies have been changing over from potassium to sodium fluxes: which off gasses a bit more. The more likely culprit is kiln pack density. The denser and more tightly loaded (kiln pack) your kiln is: the greater the likelihood fuming will occur. A glaze with high levels of cobalt blue for instance will stain (fume) adjoining pieces. Have you changed how you load your kiln? Denser, closer together?
  10. Meghann: Min and Neil pointed out fuming from glaze and clay material- to which I agree. You clay body obtains its color (lt. brown) from iron disulfide. The iron disulfide and the fluxes in your glaze produces a gas as they melt- that gas is the source of "fuming" as Amin pointed out. You are not over firing by any evidence I can see. I do have two questions: you mentioned your white stoneware does this as well. Does this occur when you fire only white stoneware, or is it mixed in with this body? Second: you said this has not occurred before- is either the clay or glaze a new batch? Can I assume that you have fired this clay with this glaze with no prior issue? Is this the first time you have left some clay exposed when glazing? Do you have a kiln vent? Was it running? Nerd
  11. glazenerd

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    Left- zinc added to base clear glaze. Right- clear base. Fired to cone 3 in oxidation. Zinc reacted to hematite, magnetite, and iron disulfide bodies.
  12. From the album: Clay Tests

    © TJA 2020

  13. glazenerd

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    Johnny: yes, that is part of the equation. Several other parameters I am going to test as well. Glaze interaction with iron is on the table currently.
  14. glazenerd

    IMG_0237.JPG

    1. Hematite. 2. Pure clay( no additions) hematite. 3. Hematite with 3% TiO2 added. 4. Magnetite 5 Newman Red. 6. Red Art. All samples fired in oxidtion.
  15. From the album: Clay Tests

    © TJA 2020

  16. Hulk- good teaching moment. The blister formation in the first picture illustrates a large-raised- volcanic shaped rim. When blisters with "hoods" form: this is not only from red bodied clay- but also from additional sulfides. The additional sulfides are primarily from lignite coals particles: suspect this is a body made from Red Art or equal. The other indication is barren spots in the center of these blisters. Nep Sy produces small, finer bubbles with no hood. Potassium produces larger bubbles, but less numerous. Iron disulfide (red body clay) will produce blisters (large) , and when excess secondary sulfides are present- hood will form. Nep Sy gasses with less pressure than potassium; but iron disulfide (sulfides out-gasses under more pressure creating blisters- not bubbles. T
  17. Krueger Pottery Supply in St. Louis is shipping 25lbs for $15 for freight and 50 lbs for $19. Flat rate UPS shipping boxes 3-4 day delivery. Been buying from them for over a decade- good customer service. Link below shows inventory available for shipping. https://kruegerpottery.com/collections/flat-rate-clay Tom
  18. Lithium carbonate is 40% lithium and spodumene is only 7-8% lithium. No way to adjust for that large differential.
  19. Turned out well. Think you are ready to market. Good color development.
  20. Turned out well. Good color blend, crystal development is good. I see you are playing with growth rings. Good job.
  21. There are two methods: dry screening and wet slurry. If you collecting from a creek bed then you will get a range of material ranging from organis to large pebbles. The clay from a creek bed is typically very fined grained due to being sedimentary. Using a window screen to dry process is perfectly fine: then switch to 60 or 80 mesh to capture clay. Any particles larger than that would be rough on your hands anyway. You could dry screen through a window screen: then wet slurry what passes through the screen. Mix with plenty of water: mix with a drill/paddle or stir vigoursly by hand. Allow it to stand for 1-2 hours, then ladle off the water into a pillow case. Leave the sediment on the bottom, you are only capturing the suspended fine particles. All that said: collecting clay from a creek bed is not ideal because of all the Organics and large particles. Walk the creek and look for areas where sediments have collected in low spots or where there is little flowing waters. Sediments collect in these areas and your clay yield will be higher for the same amount of effort. Tom
  22. This article covers the stimulus package (USA) for individuals. It is formatted as FAQ, with corresponding answers. https://www.nytimes.com/article/coronavirus-stimulus-package-questions-answers.html
  23. Hi Mary: Thought you might be interested in seeing a hematite (iron) bearing clay. On the left is Red Art for reference, and on the right is hematite clay from OK. ( TY DA) it fires deep red at cone 6 J
  24. Hulk: Ball clay do more than just add plasticity. Clay basics: ball clay is a 2:1 particle which holds moisture on its inner platelets which extends drying time. Porcelain (kaolin) is a 1:1 particle ( no inner platelet) which holds moisture only on its surface which results in much shorter drying time. The higher the plasticity level of ball clay= the longer the drying time.
  25. Liam: jobs do not bring honor to the man: the man brings honor to the job.
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