Jump to content


  • Content Count

  • Joined

  • Last visited

Everything posted by glazenerd

  1. Nancy: shrinkage is used by potters primarily to predict how they need to form custom pieces to match once shrinkage occurs. From the clay side: shrinkage from wet to bone dry will give some insight of clay composition: finer particles absorb more, so they shrink more, etc. fired shrinkage also gives insight: carbon content, molecular moisture, flux levels- all play into fired shrinkage. I use Glazemaster instead of Insight; it allows me more flexibility. Glazemaster also has a clay formulation module, which I find useful- most will not. It also allows me to write my own formula limits: which I have done for porcelain- will finish stoneware this year. I also have the benefit of imported recipes, with dilameter tested COE figures. I realized your desert clay was sandy, apparently it is real sandy. It would take an extra step, but the courser particles could be removed. Tom
  2. Surprisingly Ron already responded back: no recipes- sorry. I had in some of my notes about sulfur content in clay. Been too long? Tom
  3. @lilipil Welcome to the forums. Interesting request. Not an area of clay I have researched, but I do know a few things about it. There are a combination of oils; linseed, petroleum jelly, and bee or paraffin wax. I assume you know this clay has to be blended hot? The heat thins the oils and melts the wax, before any materials are added. From what I recall of a conversion back in 2016; the white variety is powdered limestone and the red body is made from Redart. Redart is available from most any pottery supply house. My friend is at NCECA at the moment, but I will email him to see if he has a recipe. Might be a bit before I hear from him. I would think there would be a recipe floating around in cyber space somewhere. Tom
  4. Finished four chapters, have drawn several charts and graphs. About 35% done! but have most outlines done. Took off Febuary and most of this month, have to go back shortly.

    1. LeeU


      Great project...good for you! That will be a fine and useful addition to the literature for ceramics. 

    2. oldlady


      you are well on your way to becoming the new go-to source for everything ceramic!:D

    3. glazenerd


      Somehow the address of my rabbit hole has leaked out.

    4. Show next comments  12 more
  5. BUT, unlike cars; when your clay breaks down there is no shop to take it to.
  6. I remember both: more so the storms in 73. Over 500 of us juniors and seniors were let out of school to sand bag when all that snow started melting. At 2am a Budweiser truck showed up with a rather large supply. The State Troopers just walked away; we had been going non stop at that point for 16 hours. About 7am we went home: and the surrounding towns were still dry.
  7. I started with crystalline glaze, and still firing crystalline glaze. I experiment with other glazes from time to time; but mostly to see their reaction to a specific clay body. Now I have been working on a series of "reactive" porcelains, to see how they react to reduction, wood, salt, and raku firings. Thanks to my fellow potters who have helped me in that research. Tom
  8. July 4, 1976? I was probably at MRF (Mississippi River Festival) at SIU-E campus. Do not remember what musicians, but probably Fogelberg, jackson Browne, or Little Feat. Been too long...pony tail, bell bottoms, bandana- no hat or beard.
  9. Last one: May 1976: the price of clay doubles, as the nation wide shortage continues after Mark C ramps up production for his July 4, show.
  10. How about this one? 1955, Mark C. Forms his first cup from partially dried Malt-O- Meal. Then later that day builds his first pro type model 40CF gas kiln from Legos.
  11. Yes bentonite would help: maximum of 3% or recipe. Disperse dry and blend before adding water. by the way: looking at your river clay ( brownish) very possible you have magnetite .(iron) in it. Magnetite has a brown/ gray cast.
  12. Yes it does. Flux levels play a big role in vitrification, but so does particle size. Potters are use to dealing with 200-325 mesh, etc. the general theory being 325 melts faster than 200 mesh, etc. when you deal with clay; you are dealing with microns. If you converted the microns found in clay to mesh: 20,000 to 30,000 mesh.
  13. Benz: not sure if you are asking about the chemistry of clay bodies, or the effects of PH in slip? The easiest way to understand either is to look at all those specific terms such as: electron volts, bond energy, cations, anions- as magnets. Every molecule has a positive and negative charge; just as every element ( silica, potassium, sodium, lithium, iron, zinc) has strong to weak magnet pull. In the case of crystalline glaze: zinc has the strongest magnetic field: which attracts the weaker magnet to it which is silica. The reason lithium is used as a flux: it is the weakest, and does not influence the attraction between zinc and silica. Porcelain bodies influence it because of the type and amount of fluxes used in them. Sodium (Nep Sy) in porcelain has a strong magnetic field that disrupts the formation of zinc and silica. Most all glazes are covalent bond or they are chemically bond (eutectic melt). Crystalline glaze is an ionic bond: which means they are formed by the magnetic attraction between elements. Any element with a strong magnetic (atomic) field can disrupt the bond. in slip chemistry; increasing the PH does in fact increase the surface charge ( magnets again) of the particles. I will use grains of rice as an illustration of clay particles. The sides of the grain would be positively charged, and the ends would be negatively charged. If you mixed clay and silica and poured it out: it would be pouring a cup of rice on the counter: no defined arrangement of the particles. If you mixed clay, silica, and flux ( sodium or potassium) and poured it out: some of the grains would be arranged in order, some would not. Once you add a flux, you are increasing the PH: when you increase the PH, you are increasing the magnetic field. Now when you add sodium silicate: the PH spikes, which in turn spikes the negative charge in the water film: and all the rice (clay) aligns as if you took the time to stack them neatly. The term is called particle stacking, the magnetic attraction is called bond energy. Just like any magnet: negative attracts positive. The water film is negative: so the positive edges of the clay ( rice) stacks in perfect positive order. For the same reason above: porcelain has memory. The sodium flux in this clay body creates a strong negative charge in the water film. When you throw, or slab roll porcelain: you distort that magnetic particle arrangement. So after you finish forming and it dries: the magnetic stacking tries to reform: which results in warping. for the record: most porcelain bodies are 8.25 up to 8.40PH. When you use them as slip and add sodium silicate: it spikes to just under 10 PH. So what is perceived and measured as thinning: is actually particles stacking in perfect ionic order. When particles are disordered, it measures thicker. So in reality: viscosity is measuring particle alignment caused by PH increasing the negative charge. Tom
  14. Ooopppssss. 1953: Marks' mother begins to slip sodium silicate into his formula to prepare him for a life in pottery. record corrected.. My bad
  15. The History of Slip.... Yes it has a history. 1708. Porcelain discovered in Germany. ( folk lore says) it was discovered accidentally when a farmer scrapped off whitish mud from the hooves of his horses. 1710 Meissen hard paste porcelain is used commercially in Germany. Link to Meissen vase circa 1730 below. https://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Meissen_hard_porcelain_vase_circa_1730.jpg/991px-Meissen_hard_porcelain_vase_circa_1730.jpg 1710 to 1740 hard paste porcelain is developed commercially in France and England. 1833. First recorded use of deflocculants used to thin paste. 3% potassium carbonate- Germany 1891 first commercial patent for deflocculant issued in Germany. 1903 first commercial application of deflocculated paste used in Germany. 1910 early laboratory experiments started to investigate the properties of deflocculation. 1941 A.F. Horton (M.I.T.) releases first cohesive study on the effects of PH on viscosity. A modified "viscometer" is used. 1948 A.F. Horton ( M.I.T.) releases his theory of "Strecthed Membrane" to illustrate the effects of sodium in deflocculation. 1950--- "viscosity becomes the measuring standard for slips. side note: up until 1900; potassium carbonate was used as a deflocculant.
  16. Congrats; you have a fine grained alluvial earthenware clay. Tom
  17. Your guess would be correct Liam. Nep Sy was used as the body flux. White vinegar lightly brushed will help some, but usually migrating salts bleach out color. After washing try applying red iron oxide, and wiping off: to stain those areas. Soluble salts in raw clay below.
  18. I have been reading some journals from D.D. Buttons and W.G. Lawrence on suspension, ionic charges, and other thing slip chemistry related. For those who have ever wondered about the particle sizes of Terra-Sig: 0.21 up to 0.67 microns or 25-30,000 mesh. To answer a second question: at 60F, the charges that hold particles in suspension drop by nearly a third at this temperature, and decreases further as temperature drops. The term is called particle stacking: which means the negative charges that hold particles in near perfect alignment diminishes: with larger particles dropping out of suspension. This ionic disorder results in warping of fired pieces, with increase in absorption. As the temperature increases above 60F: the ionic charges increase: resulting in a high density green ware and absorption below 2%. ( if formulated correctly.) Tom
  19. Calcium in the natural form- calcite, and potassium.. Both found in a cave in So. missourri that I have explored many times: so yes I am familiar with that scent. Actually the lack of a "moldy" smell tells me that clay bed has been around awhile.
  20. I made a comment in a different thread about large covalent sodium ions disrupting the water membrane. That relates back to the age old question of the difference between calcium and sodium bentonite. Why does sodium bentonite congeal, while calcium does not? calcium is a smaller ion, with less energy than sodium. Calcium does not disrupt water molecules as noted below: W= water. Ca= calcium sodium is a larger ion, with stronger ionic energy that looks like this. The sodium ion disrupts the water membrane, which in part plays a major role in creating the gelatinous nature created by sodium bentonite.
  21. Babs: the secret of maneuvering the rabbit hole is rejecting information that is not clay/ glaze specific. I do not care about the metes and bounds of PH, other than how it effects clay. alkalinity in clay= negative particle charge = plasticity. Alkalinity in slip= suspension, and as PH is spiked by the addition of sodium silicate or synthetic polymers (Darvan) = particle alignment increases because of higher negative charges. The specific gravity changes as the negative particle charge increases, because higher alkalinity creates stronger negative ionic charges. acidity = flocculation! because acidity lowers the negative charge in the clay water film, which in turn creates attraction between clay particles! resulting in flocs forming. I will post the effects of sodium and calcium in my slip chemistry thread. That seemed to be a curve ball.
  22. Babs: " it depends" is what started my obsession. I fire crystalline glaze; and the same recipe changed every time I fired it on a different porcelain. I came to the conclusion that yes it does depend: depends upon the chemistry of each clay body. I now have access to the Americam Ceramic Society Journals: the rabbit hole has new furniture:) example: did you know when you measure the specific gravity of slip; you are actually measuring the effects of PH? Tom
  23. SIU-Edwardsville is having a big "art" open house later this month. Most all the pieces are "art", including those made of clay. Received an invitation, thought perhaps I would go to see what the new generation is up to. T
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.