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Magnolia Mud Research

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About Magnolia Mud Research

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    ceramic chemistry

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  1. I (and several others in the college studio) have added red iron oxide (RIO) into a commercial clay by sprinkling red iron oxide on the clay in thin layers combined with the Stack and slam wire edging technique of Michael Wendt. see his youtube video: A little iron will make a BIG change in the surface appearance of the clay. As I remember I used a something like a big salt shaker to sprinkle the RIO on the clay. check the iron content of Red Art clay and use that as a maximum level to add to the commercial clay. LT
  2. I often trim bone dry clay by wiping the area to be trimmed with a wet sponge, and then scrap the surface with a trimming tool. The wet area is kept small and shallow to prevent cracking. Slow going, but after a some practice, a rhythm sets in and the wipe, scrape, wipe, scrape gets the job done. I have no experience with Air-dry clay bodies, but expect the technique would work. LT
  3. Seriously consider using less water to thicken the slip along with the increased starch.
  4. I have an Olympic doll kiln that runs off 120 VAC (standard garage circuit) that I use for "test of concept". I have fired to cone 10 cold to cold in less than 6 hours. The difference between cone 3 and cone 10 is less than one hour. There is more mass in the kiln and furniture than in the ware. Since I am firing to resolve issues of concept concerns rather than final effects, the differences between this electric fast fired kiln and my routine firing in a large gas kiln are not a problem. To fill the gaps between the lid and the lid support, I would use either a fiber blanket or the clay-sand-aluminia hydrate-sawdust wadding often used to seal the door of a wood kiln. LT
  5. Here are two authoritative sources for the meaning of “talc” and pyrophyllite. The more recent source is listed first. TALC Talc: A member of the 2:1 phyllosilicates (sheet silicates) with a composition Mg6[Si4O10]2(OH)4; sp. gr. 2.58-2.83; hardness 1 (it has the lowest hardness on the Mohs’s scale of hardness); monoclinic; rare crystals are tabular, often massive; white to green; cleavage perfect {001}; massive talc (soapstone or steatite) can be formed during the low-grade metamorphism of siliceous dolomites; and as a secondary mineral during hydrothermal alteration of ultrabasic igneous rock along shear planes. It is associated with serpentization with serpentine changing to talc and magnetite by addition of CO2. It is used extensively as a mineral filler. Reference: Allaby, Michael. A Dictionary of Geology and Earth Sciences, 4th ed., OUP. (2013). Talc: 1. An extremely soft, light green or gray monoclinic mineral Mg3Si4O10(OH)2. It has a characteristic soapy feel and a hardness of 1 on the Mohs scale, and it is easily cut with a knife. Talc is a common secondary mineral derived by hydration of magnesium silicates (such as olivine, enstatite, and tremolite) in basic igneous rocks, or by metamorphism of dolomite rocks, and it usually occurs in foliated, granular, or fibrous masses. See also: steatite. 2. In commercial usage, a talcose rock; a rock consisting of talc, tremolite, chlorite, anthophyllite, and related minerals. It is used as a filler, coating and dusting agent, in ceramics, rubber, plastics, and lubricants. Reference: Bates, R. L. and J. A. Jackson. Dictionary of Geological Terms, Third Ed. American Geological Institute. pg. 514. (1984). Pyrophyllite Pyrophyllite: Uncommon silicate mineral Al2[Si4O10](OH)2 belonging to the phyllosilicates (sheet silicates) and with properties to muscovite; sp. gr. 2.65-2.90; hardness 1-2; occurs as a secondary product from the hydrothermal alteration of feldspar, and as foliated masses (see FOLIATION) in metamorphic schists. It has been mined as a substitute for talc. Reference: Allaby, Michael. A Dictionary of Geology and Earth Sciences, 4th ed., OUP. (2013). Pyrophyllite: A white, gray, or brown mineral AlSi2O5(OH). It resembles talc and occurs in a foliated form or in compact masses in quartz veins, granites, and esp. metamorphic rocks. Reference: Bates, R. L. and J. A. Jackson. Dictionary of Geological Terms, Third Ed. American Geological Institute. pg. 413. (1984). My observations and comment: Both materials, talc and pyrophyllite are in the same structural network – sheet silicate – but chemically they are different – one has aluminum and no magnesium and the other has magnesium and no aluminum. The elemental makeup of the two minerals clearly indicates that the minerals are not interchangeable in a recipe of either clay body, glaze, or slip. They may be interchangeable where the material mechanical properties are the key reason for use and the elemental makeup are not important – such as for a dusting powder, filler, or insulating concoction. In ceramics, the usefulness of a mineral depends on the elemental composition since the ingredients must react with each other to produce a particular homogenous melt or a particular solid composite where the bonding among the particles is chemical rather than frictional. LT sidebar: My experience has been that the studio pottery literature has often ignored the scientific definitions of many of terms and created their own jargon (but then, Ik ben een ingenieur!). The same goes for material brand names. I suspect that the term Desert Talc was a tradename (or local jargon) for a powdered rock from a certain desert mine that some potter used as his “unique” ingredient for making his pots seem different from all the others.
  6. Laguna B-Mix 5 and the Aardvark b-mix equivalent. of course the answer to your question depends totally on the definition of "truly white".
  7. I wonder if the apparent 'bleeding' is a technique used at the time the blue colorant was applied to the pieces - that was the way I achieved similar effect on canvas with water color and pastel crayons. after lots of practice a "light" stroke with the "right" brush would produce the allusion of bleeding. LT
  8. My assumption is you are making items that are decorative art rather than utensils for food or similar functionality. The following are approaches I have successfully created texture: 0. the texture most likely will NOT be easily obtained with glaze; therefore, accept the surfaces will be unglazed ; a wash with baking soda at the final firing might provide some shine to the surface after firing without significant change to the texture. 1. Add fine sand to the surface layer of the porcelain; various sand sources and grain size are available from almost everywhere; I get mine from the street, around the ponds and water holes, and occasionally from a sand pile. Mix the sand with a little thin porcelain slip, and smear on at the leather hard stage, or even at the bone dry stage. 2. use a cone 10+ porcelain and fire the ware to several cones below the maturity . the surface will be porous and can be textured with coarse emery paper to produce a an even rougher surface; pastel art sticks or colored chalks can be used to add color to the surface after the final firing; if you are firing with say a cone 5 porcelain, use a cone 10+ porcelain slip as a finish layer where the texture is needed so that the surface will remain porous. 3. apply a kaolin or fire clay slip (or dry) layer to the surfaces of the where texture is needed; application is done at the wet leather hard stage; 4. use a piece of coarse sand paper as a 'stamp' to impress texture to the surfaces at the leather hard stage. 5. Sandblast the surfaces either at the bisque or mature fired stage to raw (unglazed) areas. 6. use rough concrete surfaces as "stamps" to create texture at the leather hard stage. 7. combinations of the above. LT
  9. Amaco is what we use and the few I use have met my expectations. Try it is the best way to find out how a glaze (or underglaze, colorant, etc.) performs with your clay body and your firing conditions. Put on some pots and see what happens!
  10. Yes. it works . Try it and see what happens; depending on the firing temperature and the glaze underneath, the final surface can vary from matte to shiny gloss.
  11. my bisque target is cone 08. This is the standard at the college and has been 2007
  12. Try mixing small amounts of the clay body into the glaze recipe and see what happens. Use bone dry clay body and measure the amount added to the recipe.
  13. Peter, From what I have read the "solubility" issue is that the "strontium aluminate based pigments" must NOT be soluble in the melt. Aqueous solubility probably is also important, for if the pigment is dissolved in water, the doped crystals may not reform as doped crystals on drying and therefore will not available for storing the energy need to produce the "glow" (that would answer your earlier question "why they mixed it with alcohol rather than water"). Am I close or way off base in my understanding? LT
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