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High Bridge Pottery

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  1. Didn't realise Hulk had found the right diagram ages ago . I don't think it's a good idea to use a 40amp breaker if they suggest 10. The 250v fuse or something is connected to the coil that switches the relay and you should leave it there.
  2. I have the diagram for a different kiln but it looks pretty similar, mine is just a bit smaller. The website seems to be compressing it so I will find another upload. https://freeimage.host/i/JVcrpSa
  3. I would just email/ring pottery crafts for the circuit diagram so you knows what goes where. A lot of uk kilns seem set up for a simple swap from single to three phase. You will need a much bigger breaker and wire going to the kiln for single phase but the internals should stay the same. Most of the three phase just use each leg as it's own 240v supply.
  4. There's a skip full of IFB for free. Now to work out how many I can fit in my car/garden.

    1. Chilly

      Chilly

      I had a load you could have had.  Essex tho'.  

    2. High Bridge Pottery

      High Bridge Pottery

      Thank you for the offer but it is a bit of a drive from here :D They are rebuilding a hydrogen kiln at work that has about 6 brick thick walls so there's plenty for me to sort through and find the good ones.

  5. No reason you can't put the water into the old glaze bucket to start with. I agree with sieving once unless you have a specific reason for doing that.
  6. I finally got around to doing a few glaze tests and brushed some on these mugs. Can't feel any texture through the glaze so pretty happy with the results as I didn't do any cleanup on the mold print. Need gum for brushing, seem to have lost mine. Need to go back and work on my clay, maybe. The clay is great except it still takes 1.5-2 hours to cast the larger mug and it likes to hang onto bubbles. Fires like a dream, bisque in 4 hours (20 min to 100c, hold for 20 min then 3h to 800c and hold for 20 min) and glaze in 5.5. I could go faster on the glaze but after 800 my kiln stops climbing at 250 c/h. At 1000 to 1100 it can only manage 80 c/h but that's ok for hitting 1100 cone03.
  7. The digital fire link seems a pretty good example of the difference a smaller mesh can make. The smaller the better in my opinion for melting silica. I remember back to my bubble experiments and removing quartz/silica additions and trying to source from feldspars/clays always had a better melt. Glazenerd did send me some super fine silica that is still on my list to test about 7 years later
  8. They seem to agree with my theory that it's about crystalline silica and being high expansion in crystal form and low expansion when fused/melted/dissolved. As a wise member once said "it depends" Maybe your glaze is full of unmelted silica because you got 200 instead of 325 mesh and firing hotter lowers the expansion of your glaze, maybe your glaze is all amorphous and going hotter lowers the expansion of the clay crazing the glaze or a mixture of lots of chemistry melty and crystaly combined happens and it all evens out in the end and firing hotter makes no difference.
  9. I would theorise that firing hotter probably lowers the expansion of the clay, possibly by dissolving more crystalline silica and could make a glaze more likely to craze. I'm not sure it's a good idea to relate the permanent shrinkage firing clay with coefficient of thermal expansion.
  10. I didn't think being damp would change anything that much but good to know it does
  11. Does the power go straight from the plug to these wires or is it coming from that silver box? Can you post a photo of inside the box? The wires zip-tied up look more suspicious than power going through the bricks to earth. I am pretty sure all UK homes go through an RCD and there's quite a few of these old Cromartie kilns about but I have never heard of brick conductivity being an issue.
  12. If you know the specific gravity you can work out how much dry glaze you have in the quart or gallon. First you divide the SG of the dry material by itself minus 1. A good estimate is 2.6 so 2.6/1.6 = 1.625 Now you multiply that by the SG of your glaze minus 1. Say your glaze is 1.6 then we would do 1.625 * 0.6 = 0.975 Finally we take 0.975 and divide it by your glazes SG. 0.975 / 1.6 = 0.609375 or 60.9375% dry matter. Then all you need to do is weigh a quart of glaze and multiply it by 0.609375 and you have the total dry weight of the glaze slip and can work out what x% will be in grams.
  13. I would be surprised if you made it to the other side of the curve but hard to know how much some sodium silicate is.
  14. I'm not convinced there's much evidence that 0.3:0.7 is the most durable ratio. I mean even in that ratio there's so many different fluxes included that there's too many variables for it to be a useful rule.
  15. Everybody starts off way over their head with glaze chemistry. I have been chatting about glazes on here for 10 years and I still feel things flying over my head. I find frit and clay glazes much easier to work with and control. You do have to add flocc/deflocc and possibly a binder to dial in the working properties but it is better than having raw materials bring variable qualities to the glaze slip. The fired result may be better or worse using frit but on getting the glaze onto pottery I like a simple glaze.
  16. Gillespie is even worse than gerstley for gelling glaze. I say keep adding more sodium silicate for the academic exercise and find a way to use a frit instead of Gillespie Borate going forward. There's nothing that is an exact swap so you would have to do a bit of testing and rejigging of ratios.
  17. I'm still not convinced there's much in the flux ratio or wide agreement that 0.3:0.7 is ideal. Stull doesn't really give a reason for choosing 0.3:0.7 in his paper and just seems to sit in the middle of Orton's limits. Even looking at borosilicate laboratory glass recipes which are pretty durable they have no RO fluxes at all in the glass. I would think if you smashed up glassware into a frit you could get a pretty durable glaze that's 1 RO:0 R2O and 10x the boron limit.
  18. Looks pretty old, I would try contacting kilns and furnaces https://www.kilns.co.uk
  19. Simple frit and clay glazes are the best. It's an interesting question, what happens if you fire a durable cone 04 glaze to cone 6? Does it lose any durability and become high in boron? I don't think I am looking at the same graphs, cone 10 glaze flux ratio look good from 0.6:0.4 to 0.2:0.8 R2O: RO and he even says the cone 6 no boron graph might be an error in his testing so that could be a pretty flat loss off gloss across the board. I would say his research is unconvincing about flux ratios but pretty good on boron increasing gloss durability.
  20. It's saying the temperature is too low to read. I would try swapping around the wires if you wired the thermocouple plug, or maybe it's a loose connection.
  21. So even in your smaller trials the glaze is the same thickness and settles out quickly? Can't see much in the recipe to make it thick. Been a long time since I used zinc but I think that can thicken glaze but probably not at 3%, 15% china clay shouldn't thicken it that much either and be pretty good at suspending the rest.
  22. I was doing a bit of reading and stumbled across a new Stull chart. He seems to be doing the same experiment but at cone9 instead of cone11. It is interesting that the OG Stull chart is cone11 but everybody uses it at any cone. This time he is glazing tiles and making the glaze into cones to see the deformation temperature. The solid line AB is his same “best gloss line”. The dashed line CD passes through the lowest deformation temperature in relation to Silica and the dotted line EF the same for Alumina. He then goes on to plot it on top of the original Stull chart but misses out his new gloss line so I have done my best to add it back in blue. It’s interesting how different the best gloss lines are. I tried adding on Silica:Alumina ratios but I haven’t had any good ideas yet. The wiggly silica line and shape of the deformation eutectic look like they tell me something but I haven’t figured anything out. If you want to read the paper - Deformation temperatures of some porcelain glazes – R.T Stull and W. L Howat. Transactions of the American Ceramic Society Volume 16. Page 454. Copyright 1914 by Edward Orton Jr Edward Orton Jr - https://archive.org/details/transactio16amer/page/454/mode/1up
  23. I was talking to a guy at work who did some glaze leach testing with lead glazes and grapefruit juice. They were getting really high lead readings but it turned out to be the grapefruits being grown near a road and nothing to do with the lead glaze. As safe as we can make a glaze a lot of the food/drink we put in is contaminated
  24. My glaze firings have always been quicker than bisque. It would be weird if you are firing on exactly the same settings but I am guessing you turn up the glaze firing faster?
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