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Tyler Miller

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Everything posted by Tyler Miller

  1. I seem to have stepped into something unintentional. I said two things in my initial comment. 1) There is a legal aspect of this that should be discussed with the proper experts 2) There is a ceramic aspect, which, given the conditions of the OP, is terracotta. I also said flameware bodies are superior in certain applications. The reasoning for my comment was the cost of research and development of a flameware body for personal use is disproportionate to its benefit. I would argue that the proper development of a flameware body for market is cost prohibitive for reasons related to the legal aspects (in Canada, I wouldn't try it). I then came to the defence of terracotta as a non-toxic material. The cited website's claims and studies are absurd, but so is the worry of toxicity of fired terracotta. My reason for saying this is that it's not a known issue. Firstly, if there were lead or cadmium in a meaningful form in a commercial terracotta body we'd know about it, especially the Californians. MSDS would contain it. So it's not a mainstream issue. Secondly, if you were to dig for the clay, you're doing a lot of testing,if bringing that to market, and the clay content is going to come to light anyway. Thirdly, there's no history of terracotta causing poisoning (FDA calls this generally recognized as safe). I'll fully concede the drawbacks. It is porous, until properly sealed. But so is cast iron, which will rust and leach and cause all kinds of issues if not properly cared for. It will break, and probably when fully of liquid and hot. I would never sell a terracotta body on any scale, and that's where a proper flameware body comes in. I'm of the opinion that studio potters shouldn't mess with flameware commercially because it's too much work and too much trouble to come back at you when things go bad. I apologize. I've misrepresented myself. I think we're in more agreement than initially thought, the devil is just in the details.
  2. Bill, I took the time to find the context of the article you posted there. I'm not sure it's saying what you're thinking it does? Full article you excerpted is here: https://maxwellsci.com/print/rjees/v3-541-545.pdf Health Canada's maximum acceptable concentration for arsenic in drinking water is "10 ppm" this can be expressed as 10 μg/g (see link here https://www.healthlinkbc.ca/healthlinkbc-files/arsenic-drinking-water). 10 micrograms per gram is the maximum concentration allowed to be contained in drinking water. The article expresses that the average As content of the earth's crust is 2 mg/kg of soil (2 ppm), with a range of 1-50 mg/kg possible (pages 541-542 of the article). In the context of this article's discussion on clay soils containing arsenic and mercury. 4/11 samples were within acceptable limits for drinking water, 3/11 are more or less at the MAC, and those that weren't are within 8.47 μg/g (ppm) of being so. And that's unfired soil samples and a limit set for drinking water--likely a very conservative limit for soil for clay. There is no mention of a firing schedule, temperatures reached, etc. This article, to mind, establishes that arsenic poisoning from clay from the developing world isn't an issue if the clay isn't contaminated. The devil's in the details, in this case, knowing that 10 ppm of As is an acceptable standard of drinking water and that μg/g of something is equal to its ppm. I would not put too much weight in the authors' knowledge of ceramics however, because they advise "the earthenware products should be well fired to reduce Hg levels to the lowest minimum since Hg has a tendency to evaporate at high temperatures." Arsenic also does this, as previously mentioned, and the mercury level is remarkably low (I'm sure your broad experience will agree). This might suggest that the implications of this data may not be entirely clear to the authors. If, as you say, As is at these levels pretty much everywhere. We're golden. No issues. Arsenic is within acceptable levels in some cases to drink the soil. Not saying anyone should drink soil, but what Health Canada says and the Ghanan scientific community have to say is interesting. I would like to see the many cases of heavy metal poisoning from eating clay. Soil ingestion is usually cited as a potential cause of lead poisoning, but it's also not something I've heard of happening in real life (maybe it was a thing when gas and paint were still leaded?). I feel like poisoning via soil poisoning is more likely to come from bacteria or parasites than the discussed metals and arsenic. Cadmium in rice: I don't know a lot about this, but the sense I get is that it's a concern in the sense that Cd is indeed an issue with rice, there have been historic incidents of contaminated grain, but actually characterizing the risk has been difficult. It seems like more of an economic issue (rejecting grain that exceeds maximum allowable levels). Articles that gave me this sense: Canadian discussion of Cd in rice. In over 55% of samples Cd was undetectable. https://www.inspection.gc.ca/food-safety-for-industry/chemical-residues-microbiology/chemical-residues/cadmium/eng/1369229974936/1369230037986 2008 Hong Kong discussion on this issue https://www.cfs.gov.hk/english/multimedia/multimedia_pub/multimedia_pub_fsf_26_01.html 2017 Article discussing cadmium uptake. https://www.sciencedirect.com/science/article/pii/S0269749116321376 Interestingly, Arsenic might be more of an issue with rice than Cd: https://www.fda.gov/files/food/published/Arsenic-in-Rice-and-Rice-Products-Risk-Assessment-Report-PDF.pdf As for terracotta being practical, useful, special or ideal, as a student of world cuisine I'd strongly disagree. Things heat and caramelize differently in earthenware. A well-seasoned tajine or cazuela is magical, a seasoning unto itself. Clay pot rice (I think called smashed flying rice) from Vietnam is one of the best things ever. Beans taste better when cooked in unglazed clay and La Grande Confrérie du Cassoulet have strong opinions on what kind of vessel their prized dish is baked in (glazed earthenware . This is a point of taste, no one ever need cook on terracotta and life is complete without it, but to me, it's definitely special, like cast iron or tinned copper ware. All the best guys. Edit: In the interest of balanced discussion, I've found this article on Fish consumption advisories I'd bookmarked (in particular, Ontario's, which I use) which includes much more stringent consumption guidelines (and a critique of their adequacy). I suspect the reason for these guidelines being more stringent is that the chemicals found in fish are much more bioavailable than in drinking water. An example of how this is significant is the potential for a dammed waterway to release inorganic mercury from the soil into bioavailable things like methyl mercury by means of bacteria action. Google Site C Dam in BC for a current case study of this effect. Article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5381969/ Relevant Table: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5381969/table/t1/?report=objectonly And a much loved resource (don't eat salmon from Erie or Ontario): https://www.ontario.ca/environment-and-energy/eating-ontario-fish
  3. The website is health washing. Re: lead cadmium and barium (and arsenic! mentioned on the website). As long as your clay isn't coming from an industrial waste dump, it's a non issue? Cadmium that doesn't come from ceramics really only comes from industrial waste (google "itai-itai disease"). I'm pretty sure arsenic salts as a general rule sublimate out before earthenware matures (google that, though). I'm also pretty sure that any chemically significant amount of lead in a clay body (significant enough to cause toxicity issues) would have undesirable effects as a body flux on the clay in question. But that's giving too much credit to the issue. Before you have a solution you have to have a problem. I have never once heard of someone being poisoned by means of a terracotta vessel. Risks of lead glazing, cadmium pigments, chrome pigments, copper, cobalt, silica, barium etc etc all of these are characterized well enough in the literature to establish some kind of risk assessment. But where are the clay poisoning cases? People eat clay (Geophagia - sometimes in areas of poverty and famine by pregnant women to obtain vital minerals in the absence of other sources), people rub it all over their bodies, use it to stop bleeding (google Coolclot). Like, I'm sure someone's made a pot with mine tailings and that didn't work out for the end user, but it's literally not an issue. Just maybe no anti-scumming barium?
  4. There are two issues at work here. One ceramic, one legal. The legal aspect, is jurisdictionally related and is best left to the OP to figure out in their jurisdiction. Legal advice from legal experts, ceramics advice from ceramists. Mmkay? Good. The second question is re: non toxic cookware body. Terracotta, as has been mentioned, has been considered the standard cookware the world over for millenia across all human cultures. Firing low (like cone 017), sealing with oil, and using a heat diffuser on the stovetop are all you need. There are other flameware bodies (which are better suited to certain applications), but if it’s for personal use, not commercial, or if it’s for a market that you’ve done your due diligence on, terracotta is the best option. Flameware clay bodies require a lot of R and D to make work, especially of glazed.
  5. Guys, it’s albany slip. Hudson river...silty low fire clay with soluble salts.....
  6. I think the truth is industry could make a superior product, but cost/benefit analysis led them away from that long ago.
  7. Nothing at all. I do feel the need to say that the former link of the two French engobe sites is very much earthenware only. Immediately apparent to a French speaker, but maybe not to a non-fluent, or non-speaking browser in the context of a discussion on cone 6 engobes. At cone 6 that much talc and frit might not play so nice. The text of the second link looks very familiar...
  8. I had a semi-ridiculous conversation back in January while working in a studio in town. The crux of my interlocutor’s point was “what’s the point of makig functional ware? Industry does it better, so why try?” She’s a tile artist, and this opinion came out to Tony Clennell on another occasion (according to her). His response was “well, clearly you don’t drink enough tea.” A response I liked. My answer, then unexpressed, is that I prefer a life of messy stories of provenance, and a thoughtful interaction with objects that maybe don’t quite fit, but have flair in their failings. It’s why I prefer OHL hockey to NHL. The showboating for the scouts, sometimes sloppy passes, and skill differences make for a better game. “There is no excellent beauty that hath not some strangeness in the proportion.” What’s your answer, why do you make functional ware?
  9. Chronic vs. acute poisoning. The battered sweet potatoes were an incident of acute poisoning. This is a studio hazard to be sure, but a less likely one than chronic. Over time barium can cause problems with organ function eventually causing failure. The big one being kidneys. This can be the real hazard.
  10. Monona Rossol’s book is probably a good starting point. It’s generally addressed to artists, not just ceramists, but it should help. Then talk to your GP, talk about your concerns and maybe come up with a strategy. Your doctor is your #1 go to for health info. They may not know everything off the bat, but they know how to get you plugged in to where you need to be. It helps if you know a little about the materials going in, so that you can help the doc orient themselves in the issue. Pairing this with msds sheets (despite their limitations), and independent research will flesh out your knowledge. It’s sortof incumbent on each potter to know about their materials and their risks. But I totally understand how this could be an overwhelming task for some—the research is opaque, sometimes contradictory, and drawing conclusions from numbers can be a little abstract. For those doing research, a general rule: systematic reviews of evidence > meta-analyses > controlled studies > case studies. The WHO puts out a large amount of literature on things like this and its easily accessible by web. I know this isn’t the answer you were hoping for, but I do hope it helps.
  11. Honestas probitasque per se desiderandae.

    1. Min

      Min

      Thank goodness for google translator, guessed at most of it. Good tenant to live by.

    2. Tyler Miller

      Tyler Miller

      It’s a paraphrase of Cicero, against the Epicureans.

  12. χαλεπὰ τὰ καλά

    1. LeeU

      LeeU

      Say what?????????//

    2. Tyler Miller

      Tyler Miller

      It's from Plato -- difficult/hard are the good/noble things.

  13. It's not really glaze day if there's no glaze in my hair by the end.

  14. Glazenerd, of course it ignites. That's the point. Actually, I'm going to side with you on this. I've done it, it didn't produce the mess you had in your experience. But it's a a bad idea. The fumes are scary. And zinc oxide is cheaper than zinc. And the reaction needs fumes. Use the powdered zinc to cast with. Make some metal soldiers or something. As long as you can control your temps that's safe. Tom, you're right.
  15. Calcine in bisque firing in a BIG pot. It grows in volume exponentially and may do goofy things like form streamers. Store air tight or you'll have to recalcine; it's hygroscopic. Edit: this makes french process zinc oxide. Edit for diaclaimer (not so much for Wyndham, for whom this is likely obvious): good ventilation and oxidation is a must. Zinc fumes are a bad news. Ask me how I know
  16. Tom's hit on a variable most don't think about--thermal mass. Underwhelming crystals from a regular cooling cycle would benefit from a large, fully packed. extra insulated kiln. There's still a devit window at work, and crystal growth still a function of time within that window. How big is Michael Bailey's kiln?
  17. It's ceramics, not surgery. If you ever feel things are too complex to explain. Remember that you're talking about something that is in books, on other forums, on websites. Others, the "old masters," thought differently. Best, Tyler
  18. The premix is the same as any other batch, they just give the paint by numbers info. The "middle road" complete with disclaimers is on the tin. It was a good starting point and matches up with the book content. I think I understand why you've kept stories of your successes and failures mum. Cattle salesmen don't give away free milk. . I can respect that. It's premium content. That's more than fair. I really just stepped into this to keep the science accurate and steer things toward experience. Maybe I'll take your class one day. Re:Shino--I haven't used soda ash in any shino since my first year of ceramics. Not an American shino guy. This is a littlw more subtle.
  19. Dick, I've been down the rabbit hole. If you want to know my experiences, I'll be happy to share. I'm genuinely disappointed no one else is willing to share. Narrative can be a helpful thing. I tried crystalline glazes to early in my ceramics career. First time I fired, it was in hard reduction (didn't quite know what oxidation looked like). The book I got the info from provided a batch recipe and a "firing schedule.". Fire to cone 10, then down to cone 6. Which is useless information. I used this, without knowing about holds and the proper temps. There were other issues as well. I wasn't good at getting smooth surfaces, which doesn't help. Nor did I really know how to apply glaze. I have three successful crystalline pots to my name. One with my mother, one in storage, and one an ex broke. The success? From that laguna premix. Found a friend with a controller and finally got crystals. That's my experience. Colour was awful, so I never bothered again. I might try post fire reduction at some point, but but it's a low priority. I remember once, I got some advice about shino. I cautaued because I thought the guy was an expert. The "secret" advice he gave was just second hand knowledge. Made my face hot as he gave it to me. I felt lied to. He didn't know the method at all. No hands on experience. I still think he thinks he did me some favour that I'm ingrateful for. I had found his trick months before. The "big secret" actually was floating around the internet for years. Ruined the depth of colour. The real method, just a simple thing. And no big secret. Found in a narrative by a prominent potter. No big secret either. If he ever wants to know how to really do it, all he has to do is ask. I've got a few other secrets as well he might like. I don't hold any ill will anymore, maybe one day I'll buy him a beer. That's why I've taken the position I have. Quality information is hard to come by, even from apparently reputable sources. And when you're without a compass, it's discouraging. Doubly discouragin in a closed and decptive environment. Real world experience and sharing real world stories is really helpful. If you ever want to share yours,successes and failures, that would be much appreciated. Talking things out in a dialogue makes things easier. Books are great, but stuff's always left out. And when you don't know what you don't know, you don't get very far. Cheers, Dick, you're a good egg.
  20. Dick, John Thanks for your replies. I should say I'm not personally going to try to fire crystalline glazes in a gas kiln. I'm just looking at this like a beginner and trying to tease out useful and orienting information a beginner would find useful. Since I found that initially lacking. Out of this, I've got the following: atmosphere control is important. Accurate controllers are essential, and results are unpredictable, with consistency as the desired end state. In addition, there are complex variables at work, not all of which you need to focus on immediately to be successful. How is this grounded in your studio practice? When firing crystalline glazes what do YOU strive for? How do you measure success or failure? You've said that you focus on application and glaze content, because that's most in your control. What is your method there? Are you talking about seeding and colourants or...? Do you post-fire reduce or strike fire? What is the benefit of the latter? It seems a less complex option for altering a result. I'd like to hear more about that. -Tyler
  21. I won't say the sarcasm is undeserved, because it probably is, but this is still a little unhelpful. Thank you for including times in your sarcastic decision tree. That was what i was going for. I got X result from doing W, Y, and Z with B recipe. Yes, experimentation is necessary, but a concrete example provides a kind of beacon. Fara Shimbo's book provides a number of firing schedules and examples of what can be achieved with the recipes she provides. Yes, the higher temp creates spikier crystals and lower temps create rounder crystals. But there are other factors to account for, that have been accounted for. Like bringing the glaze down slowly and steadily through the devit window creates variable effects in the crustals, whereas holding creates more regular effects. Time within the window matters, and while it can be whatever you want, obviously a 1 hr hold isn't going to look like a 5 hr hold. People can and do replicate effects, and guidelines toward gaining those effects gives confidence. Like how Diane Creber explains her process with goldstuff and how to get different colours in reduction. And if you look, people shoot for those benchmarks. The results are unpredictable, I realize, but things aren't as plain as you state either. I've held off giving any advice myself because I don't have massive experience with crystalline glazes--I haven't touched an electric kiln in probably 5 years and fire almost exclusively in reduction. Tom was in a position, I think, to speak about the finer points of passing through the devit window. But maybe I've worded it wrong. What I was hoping for was a result and the set of practices that got it there. I don't think just asking for a firing schedule fully expressed that. In which case, the sarcasm I've received is deserved, since the question seems foolish. Thanka for answering.
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