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About glazenerd

  • Rank
    Clay Research

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  • Gender
  • 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

    Engobe Questions

    Bangs head on kiln lid. 85% clay content? - faints! Okay, my cardiac event has passed- onward!
  2. glazenerd

    Natural clay

    Mix exactly 100 grams of clay with 35 grams of water. Hand mix to a pliable ball. If it feels tacky, then you have a high plasticity clay that will handle cone 3-5 on its own. If it is dry and surface cracks form: you have a short clay that will need some help to mature and can handle higher temps. Next roll the entire lump into a thin strand, roughly 1/8th if possible. If it maintains its pliability: congrats you have a great cone 3-5 clay. If it begins to fall apart before the 1/8th bench mark: you will need to add at minimum 10% feldspar, 10% silica! and 10% ball clay. (oM4) works just fine. These additions will put you in the cone .6-8 range. potters add fine sand to clay all the time: it makes clay life interesting. The only exception would be: does the fine clay have a green/grey hue? If so, it has high levels of calcium hectorite. If so, then cone temp goes way down. Hectorite is common in CA. T
  3. Finished COE graphs, alumina to CEC comparison charts. Okay, so I lead a boring life! It is what we Nerds do.

    1. Show previous comments  1 more
    2. glazenerd


      LT: think you misread my post. The COE is one graph, and CEC/ alumina is a separate graph.

    3. Magnolia Mud Research

      Magnolia Mud Research

      Ooo Kaaay.    

      Still, such a correlation would be nice.  Measure CEC and get a COE as a bonus. 

    4. glazenerd


      Interesting thought, but sodium, potassium and calcium all exchange at different rates. I do think you could work a loose table off of spars. I have enough data tables, might run that over the winter. My next article is due out in August? I think. The one after that will make your lights go on. <teaser ad>

  4. glazenerd

    Spooze Question

    Tiny crack in porcelain; then later you state a larger crack in porcelain after bisq. 1. If on the bottom of the bowl: possible compression issue during throwing. 2. More likely blowing through the quartz inversion temp(563C) too fast during bisq fire. 3. Porcelain formulated without enough plasticizers, resulting in rapid dehydration. ( short clay) which door would you like? 1-2-3 repairing cracks should not be the norm, but rather the exception. T
  5. Hi Kaley, and welcome to the forum. several questions to help narrow down the list of "possibles" 1. Are you using a premix: if so name please? 2. Are you mixing your own recipe, if so what body flux are you using? 3. Pics of this film perhaps? 4. Whose stain are you using: and color #? 5. Have you mixed this slip before without stain? If so, did you notice a film? tom
  6. glazenerd

    The Act of Pugging

    Actually clay and glaze follow prescribed chemical reactions. The only variables are the humans mixing and firing it. Then you can add the errant nature of internet info, regurgitated wiki posts, and fiction verses fact. t
  7. LT chapter 6: nucleation and crystal growth i'm in! TY. Tom
  8. Gokul: i have been looking for this link for some time, and came across it today while reading some notes. http://lawr.ucdavis.edu/classes/ssc219/biogeo/exchca.htm#clay some definitions before you read 1:1 describes a clay particle: in particular kaolin. On a microscopic level kaolin looks like a saltine cracker: a single layer with alumina one one side and silicon on the other. This structure is the reason kaolin is mostly clean: no iron, magnesium, sulfides- etc. but it is also the reason kaolin is mostly non- plastic: it has no inner layers in which to hold water. For this same reason, it dries much more rapidly. 2:1 describes a clay particle with two outer layers of silicone; with one inner layer of alumina. On a microscopic level it looks like a sponge. Ball clay, bentonite, hectorite, and macaloid are all 2:1 clay particles. 2:1 particles do hold and absorb water: pending their structure and chemical composition: they can hold lots of water. Bentonite can hold up to 15 times it's weight in water. This absorption plays a role in plasticity, and also explains why stoneware takes longer to dry. be sure to click and view the table for a CEC and AEC. Important section for you to understand. cation exchange = cations are positive! and they are exchanged for negative anions. The more negative the charge, the greater the plasticity. anion exchange: anions are negative and are exchanged for cations resulting in a net positive particle charge. There are three points of interest to you: PH, anion exchange, and hydroxols/ oxides. Most all of your clay is acidic (PH), most all of it is classified as " kaolinitic" meaning even your ball clays have kaolin like properties, and lastly: sesquioxides. Most all of your clay has higher levels. Pay close attention to the AEC levels associated with kaolin. Strong AEC levels combined with acidity creates the problem known as cementing. Cementing means clay particles are tightly bonded, creating a cementing effect. The shearing of your fresh pug shown above attests to the AEC of your clay. Simple clay plasticity rule: CEC = deflocculation = plasticity. AEC = flocculation = colloidal cementation. both are PH dependent. terra sig works because sodium silicate averages 11 PH ( high alkalinity). Drop just a few drops of sodium silicate into a bowl of slip and watch the film spread across the surface. You are watching the effects of a negative ionic charge spreading. (CEC) vinegar works in throwing water because it repels the clay from your fingers. Vinegar ( acidic) works when joining pieces because treating the joints causes flocs ( particle accumulation) to occur. iE: sticky clay. Bentonites work because they run between 9-11 PH.( in part) Sharing some info while I have time. tom
  9. glazenerd

    How do I make black slip?

    Megan: The photo below is the black recipe I spoke of. The piece is upside down, so you can see the black color with and without glaze. Mason Stains have a chart; only a select few are marked as " body stains." U.S. pigments also has a select group marked as "body stains." The 3% red iron oxide and 5% black stain is based on dry weight. So in calculating that for slip: simply deduct 40% of the weight to reach dry recipe. EX: 10lbs of slip minus 4lbs. (40% water) = 6 lbs dry material. Slips are generally 40% water. +/- start with small batches until you get the color you are after: make notes of the additions used in each. T
  10. glazenerd

    How do I make black slip?

    Several of these colors start with small amounts of iron, including the yellow.
  11. glazenerd

    Pressure gauge reading

    No Babs, posted it to the black slip thread: it landed here.. Sorry OP oh Mods, need your help.. Move above post to black slip thread please.
  12. glazenerd

    How do I make black slip?

    There is a trick to it: start with 3-5% iron oxide to darken the slip down. Then you use much less stain- 4-5%. Iron is cheap, stain is not. Mason has two black stains: one with cobalt and one without. Forgot the numbers- sorry, but no cobalt. The cobalt will bleed a blue hue. t
  13. Pres: would you please start a new thread titled: " pictures of people taking selfies of their hands." I have to see Callie taking pictures with her nose.
  14. glazenerd

    Glaze Bilsters...

    Gokul: one thing about clay and glaze testing: you have to keep detailed notes. The recipe, application rate, firing schedule, etc. When you retest this issue: same clay, same glaze: but only change the hold time and application rate. The usual protocol is changing one thing at a time. If multiple things are changed at one time; then figuring out the source of the issue gets complicated. By changing the hold time only, you will know if the glaze boiled. Then change the application rate in a second test. If problems persist: then look at the recipe. t
  15. glazenerd

    Glaze Bilsters...

    Gokul: the color of the foot ring attests to the iron content of your than and ball clay. You sent me the spec sheets a month or so ago. You have unusual circumstances in India: it either takes months to get testing samples, order by multiple tons, or just wait. I think we discussed the clay Min suggested a couple of months ago as well: availability issue as I recall? to give you a point of reference: Western clay with 1.50-1.80% iron with 500-600 PPM sulfates/ sulfides run 9.50 LOI typically. the clay Min suggested is well below 1% iron, yet the LOI is nearly 13%. Even though it is a large particle, much cleaner ball clay: it still has much higher sulfate/ sulfide content. What makes clay formulation in India so tough. If the calcium bentonite would ever show up; that i had you order two months ago: could reformulate a whiter stoneware body. hematitie is FeO3, and has ferro- magnetic properties: even on a molecular level. Unlike iron pyrite, hematite binds sulfides to it, making it much harder to burn them off. Now how that effects glazes with these clays included, I am uncertain. Few years back I ran several glaze tests on clean porcelain : testing sulfides in the glaze. Below is a pic of 4% moly sulfide on porcelain at cone six: classic glaze defect blister. However, when iron/ sulfur in the clay body causes early vitrification: the escaping spars escape under pressure: causing a raised area around the blister: like a volcanic cone. And when off gassing spars are not under pressure, but simply have not been given time to escape: you get small pinholes and bubbles. follow the bubble pattern and it will tell you the causes. tom

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