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About RuthB

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    Charleston, SC
  • Interests
    Clay, Glazes, Kilns, Firing, Marketing, Teaching
  1. Glaze Disaster

    Sounds like the soluble boron soaking into the bisque, melting very early, before the rest of the glaze ingredients have a chance and preventing adhesion of the glaze. See the above repost from Karl Platt..... Ruth
  2. Vintage Materials

    Pull the other one, guys! Nice try!
  3. Glaze Disaster

    Here's the post from Karl Platt on crawling and Gestley Borate Date: Mon, 4 Nov 1996 11:18:13 EST Reply-To: kplatt@glass.com Sender: Ceramic Arts Discussion List <CLAYART@LSV.UKY.EDU> From: "Karl P. Platt" <kplatt@glass.com> Organization: Glass.com Subject: My Crawling Glaze Has Ghastly Borate To: Multiple recipients of list CLAYART <CLAYART@LSV.UKY.EDU> ----------------------------Original message---------------------------- This glaze, posted here yesterday, was noted to crawl: Recipe: Percent Batch Nepheline Syenite 47.30 2365 Gerstley borate 27.00 1350 flint (325m) 20.30 1015 EPK 5.40 270 Totals: 100.00 % 5000 gm Also add: cobalt oxide 1.00 50 red iron oxide 2.00 100 rutile 4.00 200 cmc (mix dry powders well)0.15 8 The composition above bears little relation to : 61.61 % SiO2 14.23 % Al2O3 8.49 % B2O3 2.37 % K2O 6.55 % Na2O 6.72 % CaO 0.05 % MgO I get something that looks like this: Wt% Mol% KNa2O 7.37% 7.85% CaO 7.62% 8.99% CoO 1.04% 0.92% Al2O3 14.50% 9.40% B2O3 14.19% 13.40% Fe2O3 2.08% 0.86% SiO2 53.20% 58.59% I get numbers that look a lot different. For several of the raw materials actual analysis were used and for others, the table in Parmelee's book, which has never really failed me, are applied. Rutile, as it is a highly fugitive material was not included in the calculation. This is all to say that there are some descrepancies somewhere that need to be reconciled. The analysis furnished in the original post does not account for the coloring materials. This is not a good thing to do as these can and do profoundly affect the character of the glaze -- especially here where we're looking at 1% CoO and 2% Fe. Anyway, none of this has much to do with the cause of the crawling and that is the use of Ghastly Borate. Ditch the Ghastly Borate and your problems will vanish. Why? Well, once again, Ghastly Borate has lots of water soluble borate. When the glaze is applied to the ceramic, the borates are carried into the pores of the clay and ultimately form a film between the body and unfired glaze. This film, being rich in pure-ish borate, melts a lot lower than the glaze sitting on it. It thus melts well before the glaze and prevents adhesion of the glaze once it does melt -- it's a surface tension thing I don't want to go into now. The effect can be likened to water on a waxed car. There are also reasons why this effect is concentrated on rims, etc., which has to do with how the article dries after it is glazed -- and perhaps with how it was dried in the first place, but the core problem lies in the Ghastly Borate. The reason anyone bothered to invent frit was to solve problems like this a long time ago. Why on earth does anyone still use Ghastly Borate? Study a bit on frit and one will see that a foremost reason for employing frit is to render borates insoluble. >>if fired higher turns greener<< This is related to the presence of TiO2 KPP -- Who'll use Ghastly Borate only if civilization ends
  4. My main concerns with material storage are space constraints, ease of access and moving things around. I just got a different IKEA container that seems to work well. Two fit on a furniture dolly from Harbor Freight, topped with a piece of plywood. In the pic there are three other wheeled containers that I found on Amazon. They're ok, but I think the IKEA ones have a smaller foot print and fit in closer together. The dolly goes under the table on its short side; I can get 2 in the space of one of the others. I don't transfer bags to the container, either, because of time and dust concerns. Instead, a large garbage bag goes in the bin first, then the bag of material, which I cut open after it is the bin. I used to use the stackable containers and found that they do sag and it's difficult to get full bags in. Everything has to be unstacked to load a new bag. Smaller amounts are in stackable containers on another wheeled shelving unit. The bin labels are placed in those plastic sleeves for packing lists. I don't fully attached the sleeve; one end is left open so I can change the label if needed. Same labeling system on my glaze buckets. I also put a card in the bins. Too many labels have fallen off, gotten wet, rubbed off, etc. over the years. I made the wheeled glaze table that the bins are under. There is a 6" deep shelf level with the table to hold frequently used items. Keeps them off the general work surface and I can move the table easily for cleaning and glazing. It only took 20+ years to figure out. But then I'm a fast learner.... Ruth
  5. Vintage Materials

    I wood fired a lot in the 90's... hence the Avery. Yes, I am well aware of its value! My current kiln was built as a wood/gas kiln. It's been wood fired twice. First time the chimney was too short. Second time, the chimney was too tall. Third time, hopefully we'll hit the Goldlilocks spot. Some of the Avery will go in this firing. After that, the kiln will be fired with gas.... ^10. I also have electric, for ^6 or ^9 ox... A potter can never have too many kilns, eh? I'm not looking to use these in my existing glazes... I'm well versed in glaze calc and the software. I'm really looking for those "lost" glazes... the gorgeous spods, the "if only that old spar was still around" glaze, etc. Clinchfield will go to some Celadons, but I was wondering if there was something else special that anyone remembers. I'll keep y'all posted with results... Ruth
  6. I have several pounds of some "classic" materials that are no longer available, at least in these vintages. The supply dates from the 90's, 80's and earlier. There's at least 25 pounds of each. Cornwall Stone, Spodumene (Foote), Clinchfield Spar ( a high Pot Spar from 1960!) and Avery Kaolin. I've been hanging on to them, thinking about the best way to use them up. Then, I thought... why not ask some other long time potters! Any suggestions of classic recipes that used to work that didn't survive one of these material's changes? Complimentary tea bowl with your glaze as a thank you for your suggestion. Ruth Ballou
  7. Glaze Disaster

    Questions, questions, questions! I've known Ghastly Borate to sputter, even in low amounts in a glaze, but not calcium frits.... Even with one that I've used a lot that is 90% Frit, frequently loaded right into the kiln. Have I just been lucky? I would be surprised, because if it can go wrong, it has. Perhaps mistakenly, I considered that sputtering was one of the main issues of Ghastly Borate and reason enough to avoid it. Somewhere on the hard drive, I have a post from the 90's by Karl Platt all about the bad behavior of GB. I will try to find it. R
  8. You can add grog to wet clay. You can wedge it in or add it in a pug mill (much easier). You can make a few test tiles with different amounts of grog (somewhere in the range of 20% by weight) to see what works best with your existing clay body. Or find a clay to which grog has already been added.... Raku clay usually qualifies. Your supplier should be able to tell you how high the raku clay can be fired. Also, I have found that a pizza cutter works well for cutting the tiles. Drag is reduced and it is easier to keep the pizza wheel at a consistent angle while cutting. I usually let the clay sit for a few hours before cutting, though that depends somewhat on the humidity. The clay is usually too dry the next day. Grogged clay will also help with your larger pieces.
  9. I have the VPM 20. The only the I don't like about it is that it didn't come with a twin. It would be great to have one for stoneware and one for porcelain. The cleaning necessary for changing clays isn't that easy. It's not stainless. I primarily use it for porcelain and have not had any of the reported problems. Keeping my fingers crossed. The Peter Pugger used to be the only mixer/pugger on the market. Now Shimpo and Bailey make them.
  10. Making Your Own Glaze

    Good start for a glaze kitchen. Custer, however, is not consistent anymore. You're lucky if you have a stockpile. The alternative G 200 Feldspar is going, if not gone and will be replaced with a similar spar from Spain. For those just starting to mix their own glazes, it's good to learn about material availability and consistency. So while it makes sense to buy small amounts from a from a financial or space perspective, if your production isn't high, be aware that testing each new purchase may save you some trouble. Ruth
  11. The best thing you can do for tiles is to make your clay body bullet proof by adding grog for stoneware and molochite if you're using porcelain. Paper clay might work, too. Be careful to flip the slab while sandwiched between 2 pieces of wall board when you're rolling it out. Cut when leather hard. Let dry for a week or more in a stack before touching to reduce the memory problem. Wish my memory was as good as the clay's! Ruth
  12. Hi Ruth, I have this pugmill. I bought it about 3 yrs ago. I use it to put scraps from handbuilding, trimming and throwing scraps plus reconstituted clay. If I have clay that is too stiff, I add very soft clay and run it through a couple of times. I cut a long log from it to put directly across my slab roller to make a big wide slab (so easy). Sometimes there are bubbles and I pole a hole in them to de-air them. I make the clay nice and soft to wedge for throwing, for the big slabs I don't wedge. If you look at the picture of this pug mill, you'll see the handle is directly over the mill. I put mine together easily with the handle facing out of the side for better leverage. This does disable the auto shut off mechanism so the pug mill doesn't turn off when the hopper is open, but I work alone so it is not a worry for me. I may at some future date add the de-airer to it, but for now it serves my needs. Karen Thanks! Exactly the info I was looking for. And good to know that I can add the vacuum later. Ruth
  13. Does anyone have the Shimpo NRA-04 or any double auger machine? The Blurb says that this double auger blender/pugger produces "practically" air free clay without a vacuum. Thoughts? Thanks, Ruth
  14. Glaze Formulas Without A Picture

    Ian Currie's grid series has proven to be very helpful with unknown glaze recipes. I have my own library of the tests from Stoneware Glazes: A Systematic Approach. These were fired on my clay bodies, in my kiln. Now I run the glaze through Hyperglaze and look it up on the tiles. As John says, it's amazing how many glazes out there are really a variation of one of a few basics. The tiles also let me see what's in the neighborhood around the glaze, varying the clay and silica. I can see if the glaze will have a wide or narrow firing range, based on a glaze's appearance on surrounding #'s. Every other # has a brushstroke of metallic oxide or opacifier, so I get an idea of that variable, as well. As Ian said, this is glaze fishing with a net, not a pole.
  15. You just never know where a question to this forum is going to lead! John, I'm forwarding the link about footwear and tire impressions. Hopefully, these are ordinary leaves . Thanks to everyone for your suggestions.