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Dick White

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Dick White last won the day on June 23

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About Dick White

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  1. My sentiments exactly. In the glaze calc class I teach, I have a fully annotated step-by-step spreadsheet table to show all the details of the derivation of the unity for a single simple recipe, which I give to the students and walk through once. They can study it on their own to work the math if they want to, but this shows exactly what is going on with the math already done (but annotated and visible) so one knows how it works. And then we go to the computer which does all the math (and more) so we can start making conclusions and hypotheses about a recipe. Doing the math by hand only proves pedantry.
  2. Well, maybe it is aluminum somethingelse. Perhaps rather than the precision implied by the word oxide we should use the undefined words tarnish or corrosion? Googling tarnish and aluminum tarnish leads to a lot of commentary about alkaline detergents causing darkening of aluminum cookware (sometimes the explanations involve atomic hydrogen too). Sounds like fluxes for clay to me. (Queue the trumpets for the entrance of Nerd to tell us about Na vs. K in clay bodies...). But exactly what is the black residue - oxide, sulfide, hydride (did I just make up a new chemical word) - ? But back the hantremmer's original question, I think we are all in agreement that it has no consequence to the clay/ceramic outcome. Or at least many of us have seen the black goo and suffered no consequence from it. Just part of the deal here. dw
  3. My considered opinion on the practical side without submitting my dirty sponges to an analytic house for spectroscopy: The wheelhead is probably not pure aluminum, rather is an alloy of some sort? Never tried rubbing my wheels (including those of the school and community centers, various brands and ages) with sandpaper to examine the abraded content, only that which happens naturally through use. Plastic wheelheads (ClayBoss) don't do it, nor an ancient steel one, only aluminum alloy wheelheads. If one leaves clay debris (esp. porcelain, where is Nerd when we need him to explain the chemistry behind it ) on the wheelhead, it will discolor. (Same thing as aluminum barrels on pugmills vs. porcelain.) Then you can "polish" it shiny again with a bit of white clay and water as a fine abrasive, but the abraded slurry will be black on the sponge or your hand. If the clay is brown/dark, it will still happen but you just won't see it as clearly as black on white. If you polish it long enough with intermittent clean sponge squeeze-outs, it will stop coming up black, suggesting whatever black oxidation has now been removed. The same will happen if you don't use the wheel for a long time, the surface of the aluminum will oxidize very slightly, perhaps imperceptibly when looking at the dry wheelhead, but the black slurry will come up as soon as you hit it with the white clay/water/sponge. As for color, yes the ceramic grade alumina oxide or hydrate is a white powder. But aluminum oxide sandpaper/grind stones/etc. are not white. And black is just concentrated gray, perhaps made to appear blacker than gray by the water? And so I stand by my opinion that it is abraded oxidized detritus from the aluminum wheelhead, and of no significant consequence to the ceramic ware in process.
  4. The black stuff is a slight amount of aluminum oxide that abrades off the aluminum allow wheelhead when you rub it with clay on your hands or sponge. It happens with all clay, but is more visible with white clay or porcelain. Aluminum oxide is one of the standard oxides in clay and glaze, so there is no adverse reaction that will occur if it is left on your sponge or clay. Even though it is black in color, the color will disappear when fired. There is not enough aluminum oxide involved to materially change the chemistry of the clay or any glaze on top of it. If your sponge has a lot of clay on it, squeeze it out in the reclaim bucket, no problem. If you still get some residual black on your sponge during the final wipedown of your clean wheel, rinse in the sink drain.
  5. confused over earthenware and glazes

    With stoneware, the typical bisque vs. glaze temperatures are bisque low (often the same as earthenware) and glaze higher. With earthenware, it is often reversed. Bisque a little higher to solidfy the ceramic and glaze lower. Just use the appropriate cones for each stage.
  6. Firing An Accidentally Glazed Green Ware Pot?

    Joseph, a question about your holds. It seems logical to me to have the 30 minutes at 550F as that's a bit above ignition for many organics and this would encourage/improve burnout - or maybe you have a different reason. But I'm coming up blank in my little head what might be happening for an hour at 1600F?
  7. Minspar

    As Min indicates, Kona F4, a soda spar that is now obsolete and unavailable, is reasonably close to Minspar200 and can be substituted with little or no change in the fired glaze. However, just for clarification, back in the day Kona also produced a potash spar labeled A3. Check your recipe and confirm that it was F4 or A3.
  8. Cautionary Tale

    Peek-a-boo, I see youuuu... Yup, we had a glaze disaster on the bottom shelf in one of the school kilns, where the lava flow went down between the half shelves and dripped onto the soft brick. It didn't eat a hole all the way through like yours, but a substantial melt hole. We brought the base of the kiln up into the studio and repaired it during class time as an object lesson to the students about why we are so picky about cone numbers (the zero is meaningful, really, trust me, 06 is not 6...), clay bodies, and glaze application.
  9. I read the PMI article about using the pipe fittings, and being a cheap SOB, decided I could do the same for free. Get a large plastic soft drink cup (7-11 Big Gulp or similar) or a plastic food container that has a mouth just big enough to comfortably slip your hand through, and which has a rolled over edge for a rim. Cut the rim off the cup about 1/2" down, being careful to not damage the rim. It may take several successive cuts, first with a knife to cut a larger piece off the cup, and then scissors cutting around and around until you have a plastic ring. Smooth up the bottom cut edge with some sandpaper. Now throw a tall cylinder, the top of which has an inside dimension that exactly fits the plastic cup rim ring. Slip the ring down into the cylinder and gently collar it tight onto the ring. Now you have a strong support to keep the rim of your cylinder perfectly circular while you belly it out into the moon jar form. Use your heat gun/torch/etc. or not as you wish. When the form is basically complete, gently lift the cup ring out of the cylinder, or if necessary, use a needle tool to cut just enough of the rim to remove the ring. Now finish the rim as desired.
  10. Nerd, that's exactly how I do it, keeping things within the limits I developed in the spreadsheet. One minor difference from your observations - I'm trying very hard to stay on the "cone 6" party bus while the real partying is going on in the "cone 10" bus. In my spreadsheet, I separate statistics of the 6 and 10 recipes, and the unity limits for Zn are lower for the sixers, running between .5 and .6, because of the Li typically added to the cone 6 recipes intrudes into the flux unity. And as an aside, you have mentioned your beloved but crashed laptop. Do you still physically have it? Was it a mechanical failure of the disk or something else made it unusable? Have you tried disassembling it to extract the bare drive and re-mount it in one of those cheap external hard disk cases? The machine is dead meat now, so nothing to lose by taking it apart, but you may find the raw disk can still be addressed and then retrieve the lost data. cheers dw
  11. Nerd said up above a few spots... ... As Oly pointed out: 62.00 +/- molar silica is proportionate to a 20% silica addition. My Nerd O' meter thinks if you used this recipe as a base for a thicker growing medium at optimal flow: and added 10% silica and incorporated the usual holds: you very well may end up with mega crystals.. Hmmm... crystalline experiment # 2489. Interesting line of thought there. I bought this book for other reasons, and it's a pretty good general reference book for those other reasons. But I passed by that chapter because 1) I was already deep in the crystalline rabbit hole, and 2) those 2 recipes just didn't square with what I understood at the time - 75% frit/25% Zn and no silica? and the other one with no Li? But now that you mention it... One of the things I have done in my perambulations about in the rabbit hole is collect recipes wherever I find them and then plunk them into GlazeMaster as a convenient recipe filebox. And it magically calculates the UMF, which I then tabbed into a monster spreadsheet (you know, recovering accountant and all that, sometimes I fall off the wagon and do silly things like make a spreadsheet...) which I then ran some statistical analyses on (and sometimes when I fall of the wagon, it runs me over...) to see if there was any pattern, e.g., the standard argument of glaze "limits" but only for this peculiar brand of idiocy. And yes, there does appear to be a pattern of limits. So... when I set this 75/25 glaze beside the usual limits, it fits in as if it is one of the family. The increased Na flux from the overload of 3110 probably offsets the need for Li, and the overload of 3110 brings with it almost enough silica to cover the need. And when that ricocheted off the back of my brain, I tried subbing 413 in the calculation - and that one isn't too far off either. And then just for S&G I threw in my other 2 standard crystalline frits - 644 and 493 - but no love there. Neither of those have enough Si on their own. As if I didn't have anything better to do than experiment some more...
  12. FWIW, this recipe was promulgated by Michael Bailey in his book "Glazes Cone 6," on page 52.The published recipe (just 75% 3110 & 25% ZnO) included 2% CuCO3 and 5% SnO. The accompanying text reads: "One interesting characteristic of [this glaze] is that, in combination with tin oxide and copper carbonate, it can even form crystals without the need for a special cooling cycle. This was discovered by accident when the kiln controller failed to run the cooling part of the program. This could be useful in, say, a teaching situation, where one might like to demonstrate a crystal growing glaze with having to change the normal type of firing (taking the kiln up to temperature and switching off)." The pictures on the same page show other tiles with several different oxide colorant combinations, each soaked for 4 hours at temps of 950C - 1100C. The book offers a second recipe of 50% 3110 / 25% ZnO / 25% SiO2. This is a more conventional gathering, but as Nerd points out, typically would have some LiCO3 for cone 6. This book is, by its own title, only cone 6 work, so I don't understand the absence of the Li in the recipe in the publication. But what do I know? I tried the first recipe once (with no downfiring) just for S&G on the inside of a bowl as I had no idea what would happen and I didn't want to go the usual extremes with catcher saucers and risers. Meh. It was a very pretty aqua turquoise green (as would be expected with a very high alkaline copper/tin glaze) but the crystals were underwhelming. Or maybe I just did it wrong. Wouldn't be the first time.
  13. Crystalline Glaze Chemstry

    But seriously, I do share what I know (which isn't everything) but some things have too many intersecting dimensions to easily share.
  14. Crystalline Glaze Chemstry

    Some (though not me) abide by the two fundamental rules of a master: 1) Don't tell all your secrets.
  15. Crystalline Glaze Chemstry

    I have to admit, I have never tried any of the commercial crystalline stuff. It used to be just the Laguna dry mix Crystal Palace or something like that. Now you can buy it premixed in pints. Ackkk. Maybe for others, but none of that here. And let me guess on that shino - soda ash is hidden right there in plain view, dissolved in the water in your spray bottle... But seriously, you've merely been a guest in the foyer of the crystalline rabbit hole and you bumped into the closet door trying to hang up your coat, which was not your fault, but rather we have a very strange way of doing our doors and closets down here. So you left to pursue other things. That's ok too. And now you wandered by again and looked in the window. Sure, c'mon in. Once a year I teach an 8-week course in this at one of our local art centers. We can't do that over an internet discussion group, just too much and a lot of the glaze mixing and application is done by feel which we can't really discuss as quantitative measurements. Yes, there are measurements, but you work by feel, and that takes practice. For distance learning (the new buzzword at the college) in the early stages, I return to my recommendation of the Price and Price book. Some would deride that text as paint-by-numbers art compared to the Old Masters Ilsley, Creber, and Shimbo, but it really does lay out the details. Read it twice, and then study the key codes below each picture. Once you begin to make the associations of commonality between the several classes of recipe (e.g., cone 6 vs. 10, which are not precisely 6 or 10, but merely a means of dividing the club into those who fly way up in the stratosphere vs those who fly down in the troposphere...) and see some of the commonalities between firing schedules, then you can start exploring the variations. Then come back and we can talk some more about confusing things or nuances.
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