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Showing results for tags 'ball clay'.
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Hi all, I'm based up in Finland and we have a lot of very clean local clay deposits. It's grey and fires to a dark red brown at the top end of it's range which I would guess is around 1100C looking at the glow. (the test we did was in a self built wood downdraft kiln without any cones or thermocouple. It started to boil and melt) There was a brick works on the site where I got the clay up until the '50's, so I know the clay is usable in some form or another. There is a LOT of clay around here, I guess as a result of glaciation? I dug a heap of clay about 15 years ago and it's been wrapped up outside getting deep frozen every year (-40C) I dried and washed a bucketful a few years ago which has been stored indoors since then. After hand wedging the clay it has a good smooth consistency but it feels quite strange. It almost like a gel?? It cracks and breaks as soon as you try to stretch it, but when you make a large ball of it, it starts to sag. If you manipulate it very slowly, say by squeezing, it deforms readily without cracking? It is not sticky at all, although in the bucket it looks like it should be as there is a fair bit of surface water on the clay. I don't have much experience with raw clay but I guess this needs an addition of a plastifier like Bentonite or Ball Clay or something? So a couple of questions... Should the clay be dried and powdered first? Or can I just work out the water content and wedge the appropriate amount of plastifier into it? ....and what percentage of plastifier would be a good place to start? Thanks in advance Rod
Hi there, I'm new on this forum and quite new to ceramics and glazes in general so please excuse my lack of knowledge... I've been making ash glazes using this Katherine Pleydell-Bouverie nuka glaze recipe; Mixed woodash 33.0 Feldspar 33.0 Kaolin 16.5 Ball Clay 16.5 On a recent trip to China I aquired some rice straw ash and I was really excited to turn this into a glaze. From what I read rice straw ash should be very high in silica too like other (mixed) wood ashes so I used the same recipe. The results came out rather different then expected or other wood ash based glazes I made using the same recipe. It looks like the glaze didn't melt or run at all. Please see photos for your reference. It seems like there is a lack of silica and fluxed present in the glaze. I want to do some line testing by adding silica in 10% increments and another one adding flux like gersley borate but perhaps somebody here sees something I'm missing or has other ideas. The other thing that could be possible is that I misunderstood in China and I've acquired rice HULL ash instead of rice straw ash. I'm firing in an electric kiln on 1240 degrees and have gotton desirible effects with mixed wood ash glazes based on the same recipe and firing. Thank you for any suggestions or advice.
Hi all, I want to try a formula for a ^5 gold glaze (it says 1230-1260 C, I suppose that's still ^5 ?) called "Gold Pigment" out of an old Ceramic Review issue, and I'm not sure what are the US equivalents to the UK materials the formula calls for. The entire formula is: Manganese dioxide 43 Copper oxide 5 Cobalt oxide 5 Red clay 57 Ball clay 4 Quartz 5 So what red clay? Redart? Which of all the different ball clays we have in the US?? If I use Silica 325 is it the same as the quartz this formula has? Is flint also the same as quartz? Also, another formula, a ^4-7 bronze, calls for china clay. Is it the same as kaolin? And to continue giving away that I know NOTHING of glaze formulation: how come this formula when added up is over 100? Thank you in advance for any wisdom you can send this way.