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nairda

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nairda last won the day on March 11 2013

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About nairda

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    Southwestern Virginia
  1. Wanting to make an Amaco underglaze have just a little bit of shiny-ness, but not cover it with a clear glaze. Have made some cups with a lot of exterior surface texture. Will be using a liner glaze on the interior as well as over the rim and down about 3/4" inch on the exterior. Planned to paint the underglaze in the textured area and then wipe off, leaving material in the recesses. Firing to Cone 6. Wondering if adding a small amount of either Gerstley Borate or Nepheline Syenite to the underglaze would do the trick? Or a Frit? Thanks for any suggestions.
  2. Thanks so much for the quick responses! While I was fairly certain to not fire the pieces 'as is', the input from outside sources is very helpful for a community studio.
  3. While folks occasionally use newspaper as an internal support for hand built pieces at our community studio, a group has made a number of pieces, each about the size of a sub sandwich, built around densely wadded up newspaper held together with duct tape. The pieces have some holes in them, but there's not an easy way to remove the paper/tape forms before they're bisqued. How much paper is too much to safely burn out in a bisque without being harmful to the kiln, vent fan and other pieces in the bisque? It's a 10 cu L & L kiln with an EnviroVent. Thanks.
  4. Oval Pattern Creator

    If you have access to Microsoft Word...look on the drawing toolbar. An oval is one of the Auto Shapes. You can stretch it all directions and make it as large as your paper. You can also set the line thickness so that when you print it, it's easy to cut out. If you think you'll use the shape a lot, attach it to poster board (or cereal box cardboard) with rubber cement prior to cutting out the shape. Then cut on the line. They last a long time.
  5. I’ll be teaching a 2-hr clay class for high school students. The goal is to incorporate art into a science/math/engineering focus. An expectation is that they'll make a simple hand-built clay piece during the 2 hrs as well. 10 kids per session. I’ve put together a number of concepts to cover. One is that with raw, non-commercial glazes, what you see in the bucket is not what you get on the finished piece. I’ll give them the recipes for 4 glazes and simply name the recipes Blue, Burgundy, Green & Brown. They’ll also have cups of the raw glazes for a visual reference. The goal is to see if they can determine which recipe will produce which final color based on the colorant minerals in the recipes. Which got me to thinking...why is cobalt oxide black in color and cobalt carbonate pink? I checked DigitalFire and found the following, but still had a question. From DigitalFire - “The carbonate is produced from a liquid reaction between cobalt II acetate and sodium carbonate to produce red violet crystals that are recovered by filtration. The material is insoluble in cold water but will decompose in hot water.†So, am I correct in understanding that Cobalt Carbonate is not a material that is mined (or ever occurs naturally), but instead one that is always man-made using Cobalt Oxide? I understand that chemically, each has a different number of oxygen molecules and that the oxide form is much, much stronger in color than the carbonate (true for oxides vs. carbonates in general). Thanks. Who knows, there may be a future ceramic engineer or scientist who loves ceramic art in this group of kids!
  6. I'd recommend adhering your tiles with commercial 'thinset' to concrete stepping stones purchased from a building supply store. I've used 15" x 3" round concrete stepping stones and then made mosaic tiles to be added to the top. My handmade tile pieces are about 3/8" thick. Easy to dry and fire; and when coupled with the concrete base, they're very strong. Not sure how well it would work if you were trying to adhere one large tile. Using a mosaic approach allows you to adhere the smaller tiles, making sure there are no voids. Then grout around the mosaic. Using the mosaic approach might reduce the potential for one very large ceramic tile to crack. My stepping stones have been outside for 2 winters in -5F degree temps with no problems. Perhaps make 2 of them, install and see how they do over the course of a year. Adjust your technique if needed and then do the rest. Good luck! Nairda
  7. When I'm weighing out one glaze, I usually weigh out 2 others at the same time. I check to see what glazes I'm getting low on. I use 2-gallon, heavy duty zip-lock bags (Walmart) and label them with the glaze name, # of grams and the date weighed. I take my time, double-checking each material/weight as I go, so as to not dump the wrong thing in the wrong bag. Usually 3000 grams is the most I mix up at a time and that amount in dry weight fits the bag well. It's easy to roll the bag around and mix the dry ingredients without creating any dust. Then, when I'm getting low on a glaze, it's ready and waiting to be mixed. I've done this for years and it works great for me.
  8. Calcining Alberta Slip Clay

    Thanks. I went ahead and put about a tablespoon of it in a very small bisqued bowl in my kiln last night to test the outcome.
  9. Can Alberta Slip Clay be successfully calcined at Cone 06 or does it need a much lower temperature? The only information I've been able to find indicates bisquing to Cone 014. Since I don't fire anything else that low was wondering about bisqueing at Cone 06. Concerned that it may begin to melt at that point. Thanks.
  10. Slab Roller Recommendations

    The Bailey tabletop model is extremely heavy (70+ lbs in one piece) so it's not easy to move out of the way if you have a small work space. The similar size North Star tabletop model is a little more expensive, but extremely portable (50 lbs) and it comes apart in 3 sections that easily fit on a small rolling dolly under a table when not in use. And the North Star allows for slabs of infinitely variable thickness unlike a shim-board style roller.
  11. High Water Clays

    I've made a few oil lamps over the years and found that some bodies/glazes will 'weep' lamp oil through the base even though the body has been fired to its highest maturation temperature with a well-fitting glaze. Axner Pottery supply sells 'Lamp Liner'. It's a liquid for coating the inside of a clay oil lamp that seals it extremely well. Maybe 'water-tight' is different than 'oil-tight'. Perhaps lamp oil has 'skinnier' molecules than water?
  12. Turpentine Pot, Herty Pot?

    It was not hard to find Herty cups and a subsequent clay version (like a small loaf pan, but curved to fit the side of the tree) when walking in longleaf pine stands in the Florida panhandle in the 1950s. Wish I still had the ones I picked up back then! From Wikipedia - "The initial Herty system utilized two v-shaped galvanized iron gutters to collect the resin. The simplicity of the method allowed it to be taught to the existing workforce in the turpentine industry. Herty's method yielded more resin that was also higher in quality; however, the most important success of this new method was that it lengthened the useful lifetime of the pine trees from only a few years to decades. This extended use not only saved the trees but the naval store industry as well. Herty's less destructive collection method also allowed the trees to eventually be milled as lumber.[10] Herty subsequently moved from an iron gutter to a ceramic one, and his involvement with the Chattanooga Pottery Company in the production of the ceramic gutters eventually led to the creation of the Herty Turpentine Cup Company in 1909."
  13. If your kiln is vented through the bottom, you'll want to place your bottom shelf at least 1/2" off the floor; am guessing 1" might be better. I use I " supports beneath the bottom shelf because it allow for the vent to do its job and puts the shelf just a bit below the first row of elements. As others have said, easier to scrape or replace a shelf than a kiln floor.
  14. I Can't See/find My Cone!

    I always dipped the cone tip in some red iron slip. Less than a 1/4". While some say it will provide flux to the cone, I've put 'dipped cones' and non-dipped ones side-by-side in the kiln to see what effect it had; and they bent exactly the same. Placed the cone pack as close as possible to the peep. L & L kiln has good sized peeps so it was never too hard to see the cone at Cone 5-6 temps.
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