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Min last won the day on September 19

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  1. Absorption

    Agreed with Neil, I would also try for a full cone 6. For large standard cones it’s tip touching the shelf for a full cone 6. With self supporting cones it’s tip level will the top of the wedge shaped base. (If you go tip touching shelf with the self supporting cones it’s only a few degrees more so that is okay too.) Some clays have more wiggle room than others. In my experience the closer to 0% porosity the less you can overfire without running into the occasional bloat or slump. I don’t have enough experience with US clays to know how much you can overfire the Standard Clays. I looked up the Standard 563, it’s listed as 1% @ ^6. But don’t forget that fudge factor of + or - 1%, gotta do your own tests to see if it’s okay for pots holding water. Sounds like an uneven kiln is not a problem, good. I didn’t know what you had so was trying to cover all the bases with my earlier comment. Couple thoughts re what is vitrified and if it will leak. Guess it depends on how you define vitrified and mature. I go with if the fired clay is impermeable to water then it is vitrified. (ie it doesn’t leak at all). Mature is not necessarily vitrified. Example would be practically all earthenware clays. They mature roughly somewhere between 04-2 but the porosity (how much water they soak up) is never going to be near zero, generally in the 10%+ range. Yup, they are mature, nope they are not vitreous. So to answer your question, your ^6 clay likely isn’t vitrified if it isn’t fired to maturity. Your wide range 6 - 10 clay is not fired to maturity at ^6 therefore no way will it be vitrified nor mature.
  2. Absorption

    Standard lists 213 at 1 point 7% absorption at ^6, 365 at 0 point 6 at ^6. There is usually a fudge factor of plus or minus 1% Do your own absorption tests to determine absorption figures for your kiln and how you fire. Also, how evenly does your kiln fire? Not uncommon to have a full cone difference between the bottom and/or top of the kiln and the middle section in manual controlled kilns or kilns with just 1 thermocouple. If this is the case with your kiln then the vases need to go in the hottest section of the kiln. I would also fire some unglazed little pots with flat bottoms, put cones beside them in the kiln. Fill with water, put them on newspaper for a couple days and check the paper for wrinkling/dampness. If it wrinkles the pots are weeping. For vases I would be looking for under 1% absorption for the cone you are firing to.
  3. The BUSINESS of Pottery

    The Wealthy Potter meets The Wealthy Barber. Totally agree, it's a lifestyle and a mindset.
  4. Kiln Install on Deck

    One thing that hasn’t been brought up is the ambient temp of the space you will be using your kiln. You mentioned snow but not how cold the climate is where you live. When the temp goes below freezing the controller can malfunction. It’s fine for the controller to get very cold but before you program in a firing or start the kiln you would need to warm up the controller to above freezing. A space heater a few feet from the controller for an hour or so works. Don’t apologize for this thread causing any issues, you have a valid question. Welcome to the forums
  5. http://shop.brackers.com/MAGMA-Miracle-Anti-Gravity-Multipurpose-Additive-P3316.aspx
  6. I enjoy trying to answer the questions posed in PQotW and I’m both impressed and covetous of the sheer volume of books Pres has. (no pun intended) Started me thinking about my own meagre collection and which one I find the most useful or enjoyable. So, my question would be, if you could only have one ceramics book what would it be and why? (plus, I’m curious what Pres would choose)
  7. Mixing glazes again.

    You work outside right Rex? No way I would dry mix ingredients indoors, there would be particles hanging in the air for days afterwards. The air might look dust free but it’s the tiny particles you can’t see that are the big problem. I know you aren’t advocating this but you never know if someone reads a post and goes ahead and does it in different circumstances.
  8. 1 - magnesia 2 - mattness 3 - kaki 4 - shino Wondering if one of the questions is one of the oops don’t answer to quickly type ones. Would microcrystalline glazes count as a matt glaze or a crystal glaze? Anyhow my best guesses, good questions again, gets me thinking.
  9. I've used lots of different brands, blues, reds, greens and neons in purple, aqua and orange and have never had a problem with it not burning out completely. I've also used Crayola liquid paint for kids (blue) and it works like a flocculant plus colouring and also burned out cleanly.
  10. Hump and Slump Molds

    Can also use bisqued clay for slump and humps. Or unfired dryish clay in a pinch.
  11. I still think you have 2 things going on. 1 is the bubbles and 2 is the crawling. Bubbles are not a big deal if you rub them over when the glaze is dry. You can spritz alcohol or hairspray into the glaze slurry before dipping if there are a lot of them in the bucket. The bare spots where the glaze has pulled back looks like crawling to me. My guess for why you are having it is putting on the glaze too thickly. Either the glaze is mixed with too little water or the plates are building up too thick a layer by being in the bucket too long. This is why I suggested measuring the specific gravity of the glaze. Like Denice said clear glazes can often go on quite thinly. I always try test tiles with 1, 2 and 3 thickness of glaze. How did you determine how much water to add to the dipping glaze and / or adjust it?
  12. Since your other glazes are not crawling my guess would be too thick a layer of glaze like Tyler said. I would measure the specific gravity of the glazes that don’t crawl and compare those figures with the sg of this clear. Does Amaco give a sg for this glaze? Are they in the bucket for too long? Are these the only pieces you dip and are they thin slipcase pieces? When you do the next tests I would scratch thru the dried glaze to see the thickness of it on one piece, then fire the other piece(s) and keep the unfired piece for reference of glaze thickness. Re bubbles, are there bubbles in the glaze slurry after you mix it up? If that’s the case then I think stirring rather than the mixer might be better. If there is a bubbly froth on top of the glaze a few spritzes of hairspray or alcohol into the slurry will pop them. If there isn't froth or bubbles on the surface of the glaze slurry then it sounds like you just need to give them a good rub with your finger as they would be from minuscule air pockets escaping through the drying glaze. Did you smooth out the popped bubbles with your finger prior to firing? I’m assuming the bubbled areas are not the areas with crawling like in your picture? Is your bisque fire hotter than your glaze fire?
  13. Glaze Gel Fix

    Might be an idea to measure the specific gravity of the glaze then add the water. A very rough ball park figure for specific gravity is 1 point 5. It only takes a few minutes to do and if you are new to mixing glazes it’s probably a good idea. Doing a sg weight will get you to approximately how much water is needed for this glaze. Don't really think you need to defloc a glaze with just this small amount of GB but get the specific gravity into the 1 point 4 to 1 point 5 range then see if it still feels too gelled and go from there. Definitely sieve the glaze. Different ways to measure sg, one method using a scale and measuring cup here.
  14. Thank you Joseph! Could these instructions be posted or pinned to the "Forum FAQ & Help Topics" so if this thread gets buried in the future it will be easier to find?
  15. Nope, I really wouldn't lift it by the rim. I don't use batt pins so am able to just give the foam topped batt the platter is on a nudge to get it centered. Do you use batt pins? If you do then I would put a thick ring or pancake of clay on your wheel, deep enough to cover the pins then place your batt on that. You would be able to nudge it into center then.