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About lwa

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  1. Starting another thread rather than hijack JBaymore's thread on his event..... If anyone is looking for courses in the UK on glaze chemistry then CityLit in London seem to have one, among their vast array of pottery/ceramics courses. I've not been on any of their courses, so can't vouch for them, but may be helpful: http://www.citylit.ac.uk/courses/Art_and_design/Ceramics/Ceramics%3A_how_glazes_work Also this at Kigbeare: http://www.kigbeare.co.uk/node/72
  2. I'm no wiring expert, but I too have an old electric kiln with fairly rudimentary controller - although not as extreme as what you've set up... Easy way to avoid over-firing is to place the cones near the spy hole and pay attention near the end. Get some goggles from bath potters or CTM or where-ever to assist looking in to the kiln. Also after a few firings you'll get to know when it's nearing the end from the colour.
  3. I called them a while ago and they didnt't unfortunately...
  4. It's only £12 on apple iBook if you have any apple device... Also as acg said above if you keep an eye on amazon they do come up slightly cheaper from time to time - it was down around £60 in mid December...
  5. That's actually the book I took the quote "do not assume these glazes are safe to use" from! I like that book too (I think since taking up pottery i've spent about 5 times as much money on books as on clay!). But do take him at his word regarding safety. The 'perfectly balanced' Base Glaze 1 presented in chapter 3 is probably good for functional pots, but the deliberately unbalanced glazes in the following chapters are very likely not...
  6. Hi Oly, I'm in a similar boat to you - a beginner searching for a few basic glazes to work with. I just wanted to add my voice to those recommending Mastering Cone 6 Glazes, especially if you want to make functional/food use pots. I've found it very useful - It's the only book I've yet come across which really addresses specifically functional glazes. All the other glaze books I've looked at either say nothing at all, even while presenting lead based and barium based glazes, or just have the disclaimer "do not assume any of these glazes are safe". The only caveat is that it's all based around US materials, so you have to get your head around the glaze oxide formula to make good use of it...
  7. Hi Celia, Are you talking about Linda Bloomfield's book 'Colour in Glazes'? Since the question of food safety is being discussed I'll just mention that while it's a great book for getting colour ideas, there isn't much talk of food safety, and there are glazes in there which I'm fairly sure are a long way from food safe. I'm a beginner going down the route of mixing my own glazes to fire in a small electric kiln. I haven't had to set aside a huge amount amount of space (yet)- just using my small (standard UK size) garage. I'm doing it this way because as a hobbyist I'm free to pursue what seems more interesting to me, without worrying about the occasional mis-hap or kiln-load of ugly brown failures! Like you, I've not been able to find any kind of formal education on glazing. I did go to evening classes for a while, but we were kept at arms length from the kiln and all glazes were commercially bought - it was more aimed at people wanting something to make something to "show and tell" rather than wanting to learn. Anyway, I've found the following three books good to get started with this: - Mastering Cone 6 Gazes, Hesselberth and Roy. Lots on information on how to formulate stable and reliable glazes -- all based around the fires oxide composition of the glaze. Frustratingly only the e-book is available now, and you need an apple device of some kind. There is a black and white version printed still, but shipping to the UK was rather a lot. - The Craft and Art of Clay, Susan Peterson and Jan Peterson. This is not specifically about glazes, but it has an appendix with a relatively thorough explanation on how to calculate the oxide composition of glaze from the raw materials, and vice-versa. - Colour in Glazes, Linda Bloomfield. Good for info on colouring oxides, and also has typical material analysis for standard UK frits and raw materials - very useful for combining with the above two. Liam
  8. Thanks folks for the additional thoughts. clay lover, sorry - should have been more clear - it was 9 hours from kiln on to cone 6 down... Actually checking my notes more carefully it was 9 hrs 30 - then the cool down as described above - an additional 4 hrs 30. I wasn't exactly following H&R's schedule, partly because with my manual kiln it seemed easier to make a series of holds rather than smooth ramps on the way down. Based on your suggestion, I think on the way up I might set a top temperature of 2195*F (1200*C) then hold to get cone 6 down rather than letting the temp keep rising as I did last time. On the way down, H&R do say in the text that a fast drop from top temperature for the first 100-150*C is fine. Though, I've just noticed that on their suggested program, on ramp number 4, there is an inconsistency between the *C numbers (which I used) and the *F numbers. It says to slow the cooling from 1000*C or 1900*F, but 1900*F is 1040*C - maybe that 40*C window is important for calcium crystals? For oxides I added 1% Copper oxide, 2% red iron oxide to the high calcium semi-matte... angela, thanks - I might try to mix up some glossy base 2 before firing again on Friday Cheers all, Liam
  9. Thanks for the thoughts. If I understand correctly, you're saying the one that turned out matte but should be glossy I should try thicker, and the one that turned out glossy but should have been matte maybe try thinner For each glaze I did do a few test bowls with a variety of thicknesses and all had the same surface qualities.... Though maybe none with the glossy base 1 were thick enough. I'll run the kiln again on Friday and try some more systematic tests regarding thickness, Thanks, Liam
  10. Hello All, I'm new here, and something of a beginner to pottery. I recently bought a old small electric kiln --- basic thing controlled by two dials: power 0% to 100% and target temperature up to 1300*C, and a flick switch for 'hold' or 'power off' once above the target temperature --- and am trying to work out some basic glazes. I've just fired two glazes based on Glossy Base 1 and High Calcium Semi-Matt 2 from Hesselberth and Roy, and am baffled by the results. The glaze based on High Calcium Semi-matt has come out rather glossy, and the glaze based Glossy Base 1 is matt --- very very matt. Can anyone shed any light on what might be going on? I fired up to Cone 6 (cone bent over until the tip is touching the base) over 9 hours. The last 100*C took an hour and half, the cone was over at a little over 1200*C. (I can roughly check the temperature according to the pyrometer by turning the target temperature dial and seeing when the relay kicks on/off.) Fired down as follows: - Natural drop to 1000*C (1830*F) took around 35 minutes - Hold 1000*C (1830*F) for 30 minutes - Hold above 930*C (1700*F) for 30 minutes - Hold above 900*C (1650*F) for 1 hour - hold above 870*C (1600*F) for 1 hour - hold above 840*C (1545*F) for one hour - kiln off The only thought I have is that Glossy Base 1 has MgO 0.279 in the unity formula where as High Calcium Semi-matte has only an incidental amount (0.04) and maybe something in the firing cycle is causing the magnesium to give matt but not the calcium in the high calcium semi-matte. The overall rate of cooling is not so different to that recommended in H&R, but obviously they assume a continuous ramp down, but because of how my kiln works I've used a series of holds -- could that cause some effect? Any thoughts gratefully received! Liam

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