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  1. FYI to anyone using a skutt kiln: they have gotten bartlett to design an electronic controller for them that does "cone fire" as a segment of a ramp/hold program, so you should get consistent results with every glaze firing, even if you do this slow ramp/hold to help the body mature and prevent micro bubbles. Very cool, and takes out a bunch of the guesswork. -jon
  2. we plan on using to reclaim wet and dry clay, and mix new clay from dry in batches. the venco that we run currently is a PITA, given how easily the screens clog up, and how the vacuum port can quickly be blocked with clay. The one advantage to the venco with it's screen is that it finds sponges, plastic, etc, that get into the reclaim. but otherwise that type of pugger seems painfully slow to use, and having to fill the hopper and press it in one lump at a time is annoying. we will be keeping the venco and our smaller soldner mixer, so will have all the options.
  3. Mostly stoneware. If we were to make any porcelain, it would likely be pugged out quickly and not left there to cause the aluminum to pit. We need to replace the big soldner sooner than later, and mostly do reclaim of wet slop and dry greenware at the moment. My biggest concern is the throughput, i.e. how fast can one reasonably mix up 100-140 lbs of clay in the VPM-60 from fresh dry ingredients and from recycled clay.
  4. We are looking at buying a new mixer for the studio where I work, and I was wondering about the relative merits of a bailey pugger with the longer barrel vs the peter pugger with the shorter auger and barrel. We currently have two soldner mixers, and one of them is going with the professor who owns it, since he has retired. The soldners work pretty good, but we still have to pug or wedge the clay after. The mixing puggers look like a nice option to cut down on the work required to make and/or reclaim old clay. Does anyone have preferences/arguments for or against a particular model? We are looking mostly at the peter pugger VPM-60 and the PM-100 at this time. I'm guessing the de-airing model is most convenient, but also need the ability to make a lot of clay fast, in order to keep students busy. The one thing I'm not sure about regarding the various mixer puggers is how small a batch they can do. the soldner mixers seem happiest when mix near or at their maximum capacity. I'd have to get too big of a mixer pugger and find our that it's impossible to mix a 50lb batch with any sort of efficiency, though it's probably better to be able to make more clay faster to keep up with our needs. still, it would be nice to be able to mix up small(er) test batches, or for more advanced students to make smaller amounts of special clay bodies to suit their needs. Thanks in advance for any input, jon
  5. I just looked at data sheets for sil-co-sil 52, their 325 mesh product, and the sil-co-sil 75, what I see sold as their 200 mesh product by various ceramic suppliers. Depending on which plant it comes from there are differences in what you get, but all in all, most of the particles are 325M or smaller. What I'm seeing in these data sheets is that only 8.8% difference in the amount passing through a 325M screen. there is very little 200M particles in this stuff, 2.2% is the highest amount in these data sheets. Does that small amount of larger particle sized material have that serious of an effect on the melt of a clay body, and the amount of cristobalite formed? http://www.ussilica.com/sites/ussilica.com/uploads/files/product-data-sheets/industry/glass/SILCOSIL75-Columbia.pdf http://www.ussilica.com/sites/ussilica.com/uploads/files/product-data-sheets/industry/building-products/SILCOSIL75-Pacific.pdf http://www.ussilica.com/sites/ussilica.com/uploads/files/product-data-sheets/industry/building-products/SILCOSIL75-MillCreek.pdf http://www.ussilica.com/sites/ussilica.com/uploads/files/product-data-sheets/industry/glass/SILCOSIL75-Berkeley.pdf http://www.ussilica.com/sites/ussilica.com/uploads/files/product-data-sheets/industry/building-products/SILCOSIL52-Columbia.pdf
  6. I'm going over things that need ordering and one of my suppliers has multiple types of grog available. We have mostly used the mulcoa/ce minerals m47-35 over the years, but have also had a batch of stuff shipped out once from christy minerals. The mulcoa stuff is listed as "white mullite grog", and costs about 42-44¢/lb. the christy minerals stuff is listed as MO fireclay grog, and goes for 24-26¢/lb. Am I going to see much difference in my stoneware body between the two? Does anyone have insights into using these two and which they prefer? From the data sheets, it looks like the mulcoa grog is a slightly more controlled/refined product, which is reflected in the price... for an iron bearing stoneware, maybe this isn't a big deal? Saving 50% on materials costs is awesome, though. http://imerys-refractoryminerals.com/wp-content/uploads/2014/09/Mulcoa-range.pdf http://www.christyco.com/pdf/cmc/calcined-flint-clay.pdf
  7. I don't bother crushing IFB up very small, depending on what I'm using the castable for. you can even leave large chunks over 1" in there with no problems that I've noticed. I made a castable mix using fire clay, sand, broken/mildly pulverized IFB, sawdust, and about 10% portland cement for insulating above the arch of our soda kiln. If I could have gotten it, my understanding is that calcium alumina cement holds up to heat better than portland cement. I used a bit of sodium silicate in the mix to make if flow a bit better without adding quite so much water. It insulates, and has held up well enough, despite not being properly fired all the way through. perhaps one could do better, but this did the job for us. I can dig up the exact recipe used if there is interest.
  8. I've noticed this a bit over the years too. Glad to know what the cause is, and I'll be looking over the recipes of the buckets I find with the crust on them. There is a place in Atlanta on east ponce called the dekalb farmer's market. They sell spices and a lot of other things in bulk for dirt cheap. I imagine they also get stuff like cream of tartar in bulk and would order cheap if one asked them to. There's probably some sort of restaurant supply/wholesaler in most big cities that would order a quantity of cream of tartar for you if you know the right people to ask and how to ask them. Sometimes bringing along a nice mug or cup as a gift gets folks in the mood to help.
  9. "The chemical analysis of a load received in Nov 2013 reports 10.1 K2O, 3.1 Na2O and 0.1 Fe2O3 (which very closely matches their reported numbers)." This made me think they had sent out sample(s) for testing at some point. I could be reading that wrong, though.
  10. Depending on where these deposits are located they aren't necessarily leaching into the local water supply or various streams and rivers. Often the nasty compounds are bound in ways that are less water soluble forms and as such are less harmful to various organisms in the environment, but after processing and refining by humans they become more concentrated, or are used in places where they have more potential to cause harm. There are plenty of places where natural deposits of chemicals cause problems, such as areas that naturally have excess fluoride in the water.
  11. The copper bowls people use for egg whites and other culinary purposes tend to be clean of oxides. Vomiting is one of the symptoms of consuming an acute dose of copper oxides - https://en.wikipedia.org/wiki/Copper_toxicity
  12. I'm pretty sure more copper leaches from the water pipes in my house than will leach out of most cups in ordinary use. There are certainly exceptions, and obvious situations where one should be aware, though. Dump enough copper in a glaze that does not get fired to maturity, and you end up with real potential problems, that one needs to inform end users about. product liability is a thing we need to pay attention to, in some locales and countries more than others. Europeans have pretty strict labeling requirements regarding items that are not compliant with basic food safety rules. Then there are the foolish actions of the youth... I once made soup for lunch in the studio, and didn't have a bowl. so I grabbed a copper bowl someone had made and used that. Vomiting ensued in short order from the oxides and such that were still on the surface of the bowl after washing and had dissolved into my soup. Lesson learned. One must take precautions with things, and should follow best practices for safe glaze formulation, but paranoia is not necessary to the level that many people take it. re: barium and other substances that are considered toxic waste, even a "small producer" of waste can have a relatively large effect on whomever or whatever is downstream from them. While discouraging people from going overboard, too many people poo-poo and have a complete disregard for the impact that they have and take no precautions whatsoever. Happy medium should be encouraged. I like to encourage students with whom I discuss waste generation and other safety issues to be thoughtful and reasoned on the subject, as in all things.
  13. Our concern at work was students washing mixing buckets/tools/sprayers/mistakes... And dealing with disposal of the spray booth filters. Not using this one ingredient means that our filters are not considered "toxic/ hazardous waste" by the environmental regulators and our in-house risk management and safety people. Some folks are careless, so we have to set things up in ways for the least common denomenator at times. I'm surprised/not surprised by how much stuff ends up in the sink traps in such short order. There are ways one could deal with it, but the logistics headaches weren't worth it to us. The liability differences between a single person running a tight ship, and an institution where people are encouraged to learn through their mistakes is very different.
  14. I'm wondering if the test method used by pacer and whatever is used by plainsman clays is different than the one mentioned above and whether that is responsible for the discrepancies with the test done for kaolinwasher? https://digitalfire.com/4sight/material/custer_feldspar_253.html I had reps from resco tell me to my face that goldart didn't have a sulfur problem, but testing revealed that it was at least 10x higher in sulfur content than the fireclay we used at the time. And mine eyes and nose didn't lie to me when I smelled it coming from the kiln and saw the damage it was doing to the kiln with every firing. Goldart gone, sulfur problems gone. I'm going to bring some of the custer feldspar we have to a lab and see what they say the potash content is, I guess. There are people who do soil testing and such at the university where I work who have helped me in the past. Thanks for having the tests run that you did, and sharing them with us!
  15. http://community.ceramicartsdaily.org/topic/16013-custer-has-changed-chemical-analysis-is-in-for-march-2017/?hl=custer Thanks Min for sharing the above link with me. test, test test! both the analysis, and how it actually behaves in one's working process.
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