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glazenerd

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  1. Like
    glazenerd got a reaction from Gusf in Cone 5 Sculpture Clay Body   
    Welcome Bois:
    Wish I could answer your questions in a short paragraph: but it will take a few paragraphs to walk you through these recipes. To start: a cone 10 stoneware recipe requires a minimum 10% feldspar addition to achieve any level of vitrification. The Soldate60 recipe calls for 50% Lincoln which is a 60 mesh fireclay: with an addition of 25% 60 mesh sand: which means 75% of this recipe is 60 mesh materials. The OM4 ball clay is the plasticizer and also serves as small particle distribution to help fill the voids that 75% 60 mesh create. The 2.5% Custer (potassium flux) at best serves to fuse the materials together: vitrification will never be achieved at this level regardless. This is a sculptural body- period. You could start experimenting at: 50% Lincoln, 25% OM4, 15% Imco 400 or Gold Art, and 10% Custer. The absorption rate will be dramatically less; but vitrification will not occur. The definition of vitrification being: 3% absorption in stoneware, and 2% or less in porcelain.
    The Stephenson Terra Cotta recipe was done on a glaze calculator. Unlike glaze: clay recipe additions of 0.25, 0.50, 0.75% have no real effect on  the outcome. Secondly: Red Art and Gold Art both have higher levels of sulfur (sulfides) than other red clay types such as Imco Burgundy or Newman Red. Red Art produces a good terra cotta color: but firing schedules need to be adjusted to insure you burn out these inorganic sulfides.  Talc is 20% magnesium: which is a low temp melter (1550F range), but it also helps reduce thermal expansion. However, in this case there is not enough of it to produce any tangible results. Low fire bodies are porous: if you can get in the 8-9% absorption range- be happy. This recipe will be low on plasticity: no ball clay additions. 45% Red Art, 15% Gold Art, 15% OM4, 10% Lincoln, 15% talc= 100%, then add 5-10 grog.
    VC Tile (cone 6) Cone 6 stoneware typically runs 15% feldspar additions, and cone 6 porcelain around 30% feldspar. The frit and feldspar in  this recipe is 42% of recipe: which means anything besides flat tile would be prone to pyroplastic deformation. The 5% alumina hydrate has been added to offset the effects of high levels of flux. This recipe only has a total of 38% of clay: combined with the other materials puts it in a hybrid category. Kaolin being the primary clay: leaning towards the porcelain arena. Personally, I would be concerned about this recipe fusing to shelfs due to the flux content. A standard cone 6 porcelain recipe is: 50% kaolin, 20% silica, and 30% feldspar; with 2% Bentone MA plasticizer. A common variant is: 35% kaolin, 15% OM$ ball clay, 20% silica, and 30% feldspar. The wollanstonite, alumina, and molochite were all added to offset the effects of 42% flux content. Frit does not to be added to cone 6 bodies: plenty of heat to get the job done. The frit addition comes  from translucent porcelain formulas: not necessary here. 
    Tom 
  2. Like
    glazenerd got a reaction from Hulk in Ron Roy Glaze E-Course   
    Ron Roy emailed me a few days ago: he will be doing two glaze E courses. (August & October) Additional information on this link including topics.
    https://www.teachinart.com/
  3. Like
    glazenerd got a reaction from cdub in Ceramics in a sauna?   
    Having been alerted to possible risks: you seem to be comfortable with proceeding.  Terra Cotta seems best suited: but suspect you will have to engineer it for this specific use. In the world of ceramics: 200F is not that extreme. The more relative points would be absorption and expansion.  12-14% absorption is readily obtainable if talc and magnesium are avoided in the formulation: both would lower absorption. Spodumene would be the body flux of choice because it would lower the expansion properties considerably. Equally important: peak firing should not exceed cone 04 (1945F) to ensure higher absorption: firing above this would defeat your purpose.
    Tom
  4. Like
    glazenerd got a reaction from Bill Kielb in Making crucibles for metal clay-Mount Magnet   
    I use 80% alumina hydrate, 20% talc, and 3% V-gum T. I fire it to cone 10. throwing?- No. Hand formed 3/4" walls. Very low expansion- very high heat tolerance. The talc adds enough magnesium to fuse the materials. A semi-quasi knock off of a cordierite body. You can research "corderite body"- it is what you need for your purposes. 
    Tom
  5. Like
    glazenerd got a reaction from Mount Magnet in Making crucibles for metal clay-Mount Magnet   
    I use 80% alumina hydrate, 20% talc, and 3% V-gum T. I fire it to cone 10. throwing?- No. Hand formed 3/4" walls. Very low expansion- very high heat tolerance. The talc adds enough magnesium to fuse the materials. A semi-quasi knock off of a cordierite body. You can research "corderite body"- it is what you need for your purposes. 
    Tom
  6. Like
    glazenerd reacted to Dick White in Flocculation and deflocculation -- how much is enough?   
    Back to the original question of how to measure flocculation/deflocculation, or viscosity. Always measure specific gravity first to ensure the correct ratio of water to solids for that particular glaze the way you use it (i.e., spray, dip, brush, which can be further affected by the cone you bisque to). Then get a Zahn cup (expensive) or a Ford cup (cheap knockoff) to measure viscosity. Painters need to adjust the viscosity of the paint they are spraying and use a Zahn cup. It is a small cup with a handle that extends above the rim of the cup and a hole of a specific size in the bottom. Dip the cup into the glaze to fill it to the rim, lift it out and time how long it takes for the cup to empty through the small hole. I set my dipping glazes to a specific gravity of around 1.45 and drain from a #4 Ford cup in about 6.5 seconds. That's the scientific method. Others may use the finger dip or count the swirls until it comes to rest after a vigorous stir. Whatever works for you.
  7. Like
    glazenerd reacted to Callie Beller Diesel in Small cracking on mug handle -- Do you think it will break off in the kiln?   
    It’s just your clay being a bit short. No, it won’t cause structural issues. Your attachments look pretty secure, and that’s usually where things go wrong in the green stage.
  8. Like
    glazenerd got a reaction from Pres in QotW: Have you ever been in touch with ceramics teachers in  your area, offering support, having a beer or a cup of coffee, to attend workshops, or just to show a feeling of comradery or support?   
    Never had an instructor: then again I never intended to go down the rabbit hole this far either. I noticed early on in another forum where I lurked mostly: there would be ten different answers to one question. I understood that application and style could vary from potter to potter: but never made sense on the chemistry end of the equation. So I made the decision early on to seek out information by those with PhD behind their names. Oddly enough, found variance there as well- who knew? If I had a mentor; that would be Ron Roy: who I had the pleasure to spend three days with at NCECA in KC (2016). We email back and forth to this day. I have been asked several times to do classes in St. Louis- to date I have always declined. My wife, siblings, and two friends even know that I am involved with clay. Has always been my private sanctuary: and never discuss it locally.
    Tom
  9. Like
    glazenerd got a reaction from Hulk in QotW: If a workshop were offered at a reasonable distance from you (after we are loose, of course), who would you want as the presenter?   
    Oddly enough: I would like to spend a day unseen in a corner, watching a newbie throw their first form, open their first kiln firing, or sell their first cup. The joy and excitement is contagious. Would have loved to spend a day with W.G. Lawrence (Phd@ Alfred) and pick his brain. Same for Orton Jr, Koppatchu, Horton, and a few others who laid the foundation on which modern pottery is built. 
  10. Like
    glazenerd got a reaction from Pres in QotW: If a workshop were offered at a reasonable distance from you (after we are loose, of course), who would you want as the presenter?   
    Oddly enough: I would like to spend a day unseen in a corner, watching a newbie throw their first form, open their first kiln firing, or sell their first cup. The joy and excitement is contagious. Would have loved to spend a day with W.G. Lawrence (Phd@ Alfred) and pick his brain. Same for Orton Jr, Koppatchu, Horton, and a few others who laid the foundation on which modern pottery is built. 
  11. Like
    glazenerd got a reaction from Sarcasticcrab in Ceramic body stain issues. Cant achieve desired colours with Chromium Tin Pink stains   
    Porcelain bodies will have 22-25% alumina, and stoneware lower. Alumina content will effect color development in red bodied clays: but typically only effects lighter pigment stains. . The % of stain required in a clay body will always be higher than glaze: because the molar % is different. Encapsulated stains do not work well in clay bodies because because the amounts of calcium or zinc required to release them is also much higher than glaze. Go through the Mason stain chart and find those specifically marked as "body" stains. The red body stain will produce a bright red at 12%, and lower % will produce pastels. I often mix different % of colors to get teals, etc.
    Tom

  12. Like
    glazenerd got a reaction from PeterH in Ceramic body stain issues. Cant achieve desired colours with Chromium Tin Pink stains   
    Porcelain bodies will have 22-25% alumina, and stoneware lower. Alumina content will effect color development in red bodied clays: but typically only effects lighter pigment stains. . The % of stain required in a clay body will always be higher than glaze: because the molar % is different. Encapsulated stains do not work well in clay bodies because because the amounts of calcium or zinc required to release them is also much higher than glaze. Go through the Mason stain chart and find those specifically marked as "body" stains. The red body stain will produce a bright red at 12%, and lower % will produce pastels. I often mix different % of colors to get teals, etc.
    Tom

  13. Like
    glazenerd got a reaction from Rae Reich in Making test tiles for first time - how to avoid overwhelming amount?   
    Agree with clay body suggestions. The same glaze will have variations on porcelain, white stoneware, buff, or red bodied clays. Potter preference and style plays more of a role in selection of clay and glaze: your "dream" glaze and forms work better on some clays than others. I have a test tile trick that I have yet to share: good as time as any. I peel the label off a regular empty soup can: punch a hole in the other end to prevent suction: and punch out an 100 test tiles in less than an hour. Limited use: but if you are simply exploring color development or testing glazes on a variety of clay bodies: it is quick test that takes little kiln space. Can always punch a hole at the top if you like to hang them for reference. 
    Tom
  14. Like
    glazenerd reacted to Min in Making test tiles for first time - how to avoid overwhelming amount?   
    When I want a lot of little bowl shapes I do the same thing as Tom then press them on my bent elbow for super quick rough and ready bowl shaped test tiles. cling film / saran wrap on the clay so it doesn't stick to the can.
  15. Like
    glazenerd got a reaction from Min in Making test tiles for first time - how to avoid overwhelming amount?   
    Agree with clay body suggestions. The same glaze will have variations on porcelain, white stoneware, buff, or red bodied clays. Potter preference and style plays more of a role in selection of clay and glaze: your "dream" glaze and forms work better on some clays than others. I have a test tile trick that I have yet to share: good as time as any. I peel the label off a regular empty soup can: punch a hole in the other end to prevent suction: and punch out an 100 test tiles in less than an hour. Limited use: but if you are simply exploring color development or testing glazes on a variety of clay bodies: it is quick test that takes little kiln space. Can always punch a hole at the top if you like to hang them for reference. 
    Tom
  16. Like
    glazenerd got a reaction from Hulk in Blisters/Pinholes in Glaze   
    Salt:
    Looking at your cone pack- you hit perhaps cone 5+ or so. Clay body fluxes are still off-gassing at this cone temp. In your first picture; upper right hand is a blister with a raised rim and exposed clay in the center. Anytime you get a raised rim: that means off gassing spars in the clay have created enough pressure to raise the glaze where it pushes through. Raised rims also occur when firing over red body clays; when inorganics have not been properly burned off- not applicable in this case. Potassium body fluxes create blisters, with less population and sodium body fluxes create pinholes: but more numerous. I would recommend a -20 degree thermocouple offset. Look in your kiln manual for TC or thermocouple offset and follow the steps to program that. If your current controller is reading 2000F, after you make the offset it will still read 2000F, but will actually be 20 degrees hotter. Judging by your cone pack: that should get you pretty close to a true cone 6 bend. 
    The red glaze has potassium body flux and the green has sodium body flux. It will help you judge what you are dealing with in the future.  Tom
  17. Like
    glazenerd got a reaction from Hulk in Blisters/Pinholes in Glaze   
  18. Like
    glazenerd reacted to Mark C. in Blisters/Pinholes in Glaze   
    Tom
    (a blister with a raised rim)
    I call them innies and outies
    the innies sometimes you can live with  as they fall back on themselves-the outies never as they are sharp
    Since I use about 400-500#s a year of rutile dry glaze I see my share of this stuff
  19. Like
    glazenerd got a reaction from Shelly-jvp in BSZ Engobe flaking off clay   
    A clay with 25% grog has a vastly different drying rate than a stoneware: or even porcelain. The porosity of a clay body is much higher: which means it will also wick moisture from anything put over it. An analogy would be a dry sponge wicking up water. ( extreme, but you get the picture)  A body with 25% grog is primarily designed for sculptural or large format use.  
  20. Like
    glazenerd reacted to Bill Kielb in Bentonite   
    Sounds like many things really really need to remain suspended!
  21. Like
    glazenerd reacted to JohnnyK in Bentonite   
    I've found that a belt can also be used to reduce the need for suspenders but the ones made with clay tend to fall apart...
  22. Like
    glazenerd got a reaction from liambesaw in Marks on colored clay   
    D.D. Buttons (Alfred U) did extensive studies on the effects of temperature on particle distribution. At 68F, the negative particle charge on clay particles drops by 1/3rd. As the temperature continues to drop: so does the particle charge. Sodium Silicate and Darvan work (in part) by imparting a strong negative charge which suspends the particles in water. The water carries that charge: and as temperature drops; it effects suspension. When particles drop out of suspension in an irregular pattern: it weakens the form. Stain can also drop out in an irregular fashion. I do think Min's comments on scumming is lso applicable: blotchy color pattern suggests that as well.
    Tom
    side note- nice bird bath Liam
     
  23. Like
    glazenerd got a reaction from Hulk in Pugged Clay Becomes Short   
    Sbsoso- welcome to the forum.
    You did not State clay body type: but I will go with porcelain. When doing production: not a bad idea to keep 25lbs from the previous lot to compare to the new lot if problems arise. No problems before, and now problems means the first stop is to check with supplier if others have reported issues. Like potters, clay manufacturers shop for low prices: which sometimes creates issues. You have a plasticity issue which you can only resolve by adding water. Adding water does not increase plasticity; just moves the body closer to its liquid limits. Adding water will also increase drying issues such as warping. Your plasticity issue is caused by one of two things: the % of plasticizer has been lowered, or the plasticizer (ball clay) has lower plasticity properties. The second is Nep Sy being used as a body flux. Nep Sy has 14% soluble salts that can migrate: which can cause rapid dehydration of water. Sodium is hydrophobic- fancy word for- not fond of water. Again adding water compounds the problem by allowing further migration of soluble salts. 
    As others stated: de-airing pugmill has zero influence. All a de-airing pluggers does is remove the air between clay particles which speeds up the transfer of negative particle charges. De-airing has zero influence of the actual chemistry of the material.
    Tom
     
  24. Like
    glazenerd reacted to LeeU in QotW: What do you think 2021 may bring to your potting life?   
    Our New Hampshire  Institute of Art (NHIA-reference John Baymore, and the anagama kiln standing unused (hoping to be moved-that is still a possibility) at the now-defunct Sharon Arts Center) has been swallowed up by New England College (NEC-top heavy on education & business) and is  called the Institute of Art and Design at NEC. Ceramics was listed as a minor for a short period after the takeover  but the page is now archived and there is no link to anything.  NEC abruptly (no notice) spat out Maureen Mills, the  extraordinary director of the ceramics program, after she built it up to something truly excellent. Checking the website today,  Ceramics Dept. is totally gone-and clay is not mentioned or pictured in the sections for Art or Fine Art. Those potters I know from the NH Potters Guild (a not very active guild) seem to be doing OK in NE galleries  and local shows, to the extent that they are happening at all.  There are minimal small classes at the tech school or community--the intro-style  offerings seem to attract young people who  want to be able to make some pots or small sculptures that are nice for fiends & family (based on the work I have seen; I mean no disparagement-this is a subjective observation).
  25. Like
    glazenerd reacted to Hulk in QotW: What do you think 2021 may bring to your potting life?   
    There's at least one young full timer here in the neighborhood - standalone dedicated shop/studio in their back yard; her friend, also young, is a serious part timer. Met several young folk at the local JC Ceramic lab (a few years ago) on the road to full time potter (wouldn't expect them to all make it there, however), and a few building their portfolio for graduate applications... 
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