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Tyler Miller

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  1. Zinc in glazes

    I wouldn't worry about zinc solubility. As far as I know, the only strong acid commonly used in glazes is muriatic acid as a flocculant. I've never met anyone who's actuallt still does this. Glazes are generally mildly basic (or strongly if you like unwashed wood ash). Nothing really to worry about.
  2. I'm thinking you may have some glaze application/consistency issues. This would explain the crazing, crawling, and rough surfaces. This can be a challenging thing to get right if you're working solo as a beginner. Mark C. has a post somewhere where he talks about the use of a hydrometer--read through it and follow its use. It will help you evaluate failures and successes in a precise, quantifiable way. The application of each glaze is different and it will take a bit to get right. It's doable solo--I did it, but you're going to have some failures on the way (I have a pretty epic fail wall). Testing is key. Tiles, then a few simple shapes, then pieces that matter.
  3. A rough glaze surface can be caused by a few things. One being that your glaze is under fired. Were the appropriate cones down at kiln opening? Assuming it's fired properly, it can be that your glaze is applied too thin. And this might be a good time to ask--how thick/thin are your glazes being applied? The crawling and crazing could actually be a symptom of applying a glaze too thick. Even a well-fitting glaze will craze if it's applied like icing to a cake.
  4. Stoneware Limit Study

    John, Enough, eh? The horse is dead.
  5. I try to find something that's good about every day in the studio and use that to motivate the next. Sometimes it's a stretch to find something, but usually it's not too hard. The ups, downs, and mundane middles wouldn't let me get anything done otherwise. Yesterday was mug day, and it was fun just to tune out and make a pile of mugs. Last week as a treat to myself, I made a krater, those were good days. Trimming is always good. Firing is ALWAYS good, even when its not. I never get tired of the jet engine roar and watching cones fall. And sometimes screwing up a pot can be good, if you've got a sense of humour.
  6. Stoneware Limit Study

    Tom, believe it or not, I am trying to help you. I have some chem experience and some ceramic experience and I know how to research because I've been to grad school.. In Brownell's 1957 article (the one I have immediate access to) he's clearly saying he's using more than levels for descumming though. He literally says the product is not chemically beneficial but mechanically, which means lots. Leaving that aside, however, I wouldn't advise anyone to use barium carb to prevent scumming in a studio pottery environment, either, because there are dangers inherent in using and storing that product. I don't think it's wise to use ammonium chloride in bodies, for similar reasons. 1) because of the ammonia /HCl production 2) because it can react vigorously with salts commonly present in clays with decomposing organic matter. Which will probably not cause a problem, except likely damaging some pots. As for the corrosive aspect, pure HCl is a lot worse than sulphur dioxide. Salt firing is more destructive than soda firing because of the chlorides. And someone on here was using fluoride as a flux and that was very deatructive indeed. And yes, ammonium chloride is used on an industrial scale as a food flavouring agent, among other things, but that doesn't make it safe while heated or in the presence of salts that can be in a clay body (especially earthenware). I won't mention what they are because the combos are used to make high explosives like the ones used in the Oklahoma city bombing. Adding NH4Cl likely won't blow up your kiln, but it may kill a load of pots. Tom, not long ago you were messing with cadmium salts in your crystalline glazes and quite frankly that put a horrid pit in my stomach. This worries me too. You're a good guy and I want to see you and your equipment in good working order. I know I'm a pain in your rear but I really do mean well. If I'm honest, I worry that learning about stuff like cation exchange capacity (a measure of soil fertility) and Brownell's works on efflorescence are keeping you from being the best ceramist you can be. I want you to succeed, I want you to be an expert. Really, I promise!
  7. Stoneware Limit Study

    He also said the benefit was mechanical not chemical, opening the clay up. Using shredded paper or sawdust would be just as beneficial, without the risk to equipment and lungs. I would take what Brownell's doing with a grain of salt, since he's working in a context far removed from the studio potter. He doesn't provide a handbook, or even recommendations but illustrations of the mechanics of problems. I'm also not convinced the issues he's addressing are particularly relevant to the studio potter.
  8. Stoneware Limit Study

    Please no one do this. It produces ammonia and gaseous hydrochloric acid. There's also an explosion risk, since NH4Cl reacts pretty energetically with some common soluble salts. Just, please, no. I haven't been following this thread lately, but the usual electric kiln provides oxidizing atmosphere enough.
  9. Reducing thermal conductivity

    Just saw this thread now. Why not a double walled mug? They're becoming popular on etsy. Some are gorgeous with pierced work and carving on the outer wall. Like these: They may not be 100% functional in the reduction of thermal conductivity, but they look good?
  10. Red Clay

    Um, it doesn't. Iron will swap out for magnesium in olivine minerals, but another reaction occurs when what you're talking about happens. I'd happily be corrected, but I don't think iron can substitute for sodium or potassium ever. Maybe leave soil chem stuff out altogether? i know you're excited to share what you're learning (and it is exciting stuff) but it's tough stuff to make relevant in a clear and non-confusing way.
  11. Red Clay

    Tom, Dale Neese's cone 5 ox rust red stoneware body, and Linda Arbuckle's Orange cone 7-9 stoneware bodies get their red colour from redart, among other bodies. I thought I'd mention it as food for thought. Also, not100% sure that isomorphous substitution is the best way to explain the presence of iron in a secondary clay. It does occur, but the occurrence better explains the buff colour of fireclays and some ball clays than extensively weathered and impure secondary clays. Cool to see you learning about this stuff. Apologies to all for the minor hijack.
  12. Red Clay

    Success tends to be rather un-educational. Negative results are where progress happens.
  13. Red Clay

    Any bagged red clay will work although Redart is usually what's meant/used--it's also the most widely available. It isn't true that when in clay bodies it must be between 04-2 to stay red. The red to brown transition is a function of flux content and degree of vitrification. There are red stoneware bodies.
  14. Specific Gravity from Dry Ingredients?

    Joel, if you have a target specific gravity and desired volume, you should be able to figure out the weight of the glaze you want to make for your desired volume. With this you can figure out how much dry material (of a known specific gravity) you need, and then adding water to your target volume should be easy. Edit: It's also a useful formula if you should ever find yourself in a place where you're in a postion to steal the recipe of a traditionally formulated Japanese glaze
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