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High Bridge Pottery

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  1. Like
    High Bridge Pottery reacted to Piedmont Pottery in Wollastonite lumps revisited   
    Wollastonite has a much lower LOI than whiting (1.6% vs 43.9%) and has a lower thermal expansion coefficient (9.0 vs 14.8) (data from DigitalFire).  Wollastonite also provides silica in addition to calcium.   My glazes are high silica/low expansion by design, and wollastonite gets me there.  And finally, Wollastonite cost me $0.59/pound the last time I bought it, whereas whiting cost me $1.17/pound.  I'm sure I could rework my recipes to substitute whiting, but there is a certain amount of inertia involved in doing that, as I'm generally happy with the way my glazes are behaving on my clay.
  2. Like
    High Bridge Pottery got a reaction from PeterH in Use frit not listed in a glazy.org recipe   
    If you click on the create option in the menu then choose new material you can add it that way if you have the frit analysis.

  3. Like
    High Bridge Pottery got a reaction from Hulk in Use frit not listed in a glazy.org recipe   
    If you click on the create option in the menu then choose new material you can add it that way if you have the frit analysis.

  4. Like
    High Bridge Pottery reacted to Bam2015 in QotW: What special tool that you work with would your really hate to lose?   
    My fingers! Seriously, they are my favorite pottery tools. 
    Betty 
  5. Like
    High Bridge Pottery got a reaction from Hulk in Bought new messed up kiln want it to get to life   
    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.
  6. Like
    High Bridge Pottery reacted to Hulk in Bought new messed up kiln want it to get to life   
    Check to see if this Operating Manual matches your unit?
    There's wiring diagrams at the end.
    Note the thermocouple spec, page thirteen.
    See also the current/power specs...
    Topworker P59750 P59760 P59770 P59590 manual A.pdf (wsimg.com)
  7. Like
    High Bridge Pottery got a reaction from Kelly in AK in An experiment in Fritware Zero3   
    Trying some frits as glazes, fired to 1100c (2012f)


  8. Like
    High Bridge Pottery got a reaction from Hulk in An experiment in Fritware Zero3   
    Trying some frits as glazes, fired to 1100c (2012f)


  9. Like
    High Bridge Pottery got a reaction from Pres in Mixing Pre-Made Dry Glazes   
    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.
  10. Like
    High Bridge Pottery got a reaction from Rae Reich in Mixing Pre-Made Dry Glazes   
    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.
  11. Like
    High Bridge Pottery got a reaction from Hulk in Mixing Pre-Made Dry Glazes   
    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.
  12. Like
    High Bridge Pottery got a reaction from Hulk in 3D Printing For Plaster Molds   
    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.

  13. Like
    High Bridge Pottery got a reaction from Babs in Mixing Pre-Made Dry Glazes   
    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.
  14. Like
    High Bridge Pottery reacted to Hyn Patty in 3D Printing For Plaster Molds   
    One of the reasons you are having difficulty with mold release is due to your print lines.  They add a texture that will cause the plaster to grip your 3D printed surface.  So any roughness needs to be filled in, sanded out, or smoothed over.  It doesn't mean that you can't have the texture but at least coat it with varnish or something to help smooth it out and fill in micro undercuts.  All those little places you have plaster sticking inside of the print lines are forming tiny undercuts.  The main problem with 3D printing, IMO, is that there is a TON of cleanup.    I 3D print resins of my horse sculptures and no matter how clean my prints, how much I fuss over no print lines, temperature and other issues still cause so many nit picky things that I can literally spend hours cleaning up a single print afterwards before it's usable for mold making.  
    By the way, you can also 3D print originals or mold masters in rubber!  This is super nice for pouring plaster molds and works a lot better than using the hard plastic.  But again, you need super perfect printing because you won't be able to clean up rough areas in rubber as easily as you can with plastic resin.  So as the technology is still evolving and not nearly good enough unless you really, really know what you are doing and that's a steep learning curve.  I've been 3D printing two years now and there's still a ton I'm trying to fine tune.  So mostly I still use the old fashioned methods of pouring rubber and building mold boxes.
    Pardon me - I see belatedly that others also pointed this out so I'll just agree with them!    (edited to add this comment)
  15. Like
    High Bridge Pottery reacted to neilestrick in Interesting Cooling Cycle Info   
    I usually fire my kilns at night so I don't really see what's happening with actual temps in the kiln, but today I started it up in the morning and was in the studio in the evening and got to see exactly what was happening during the cooling cycle. I do a slightly-slow cooling cycle to even out the results in my 3 kilns because they all cool at drastically different rates due to their sizes. I do a drop from the peak down to 2000F, then cool at 175F/hr down to 1500F. This gives me identical results from all 3 of my kilns. This firing I'm talking about here is in my 10 cubic foot L&L EQ2827-3, which has 3 zones, and was packed very tight in the middle. I was surprised at just how much slower the middle cools compared to the top and bottom. This photo shows how it's going part way through the initial drop from peak temp to 2000F:

    As you can see, the middle and the top are nowhere close to each other. In a normal firing segment, a 73 degree difference would stop the firing with an error code. So why isn't it doing that here? It's because the cooling rate is set at 9999, or full speed. Any time you use 9999, whether it's climbing or dropping, the controller lets the kiln do its thing and doesn't care if the sections aren't even. Firing up or down at 9999 is the fastest, but you sacrifice evenness. As the temp continues to drop, we see this:

    Here you can see that the top section (TC1) has started firing again. The set point for this segment was 2000F, at which point it should start cooling at 175F/hr, yet the top section passed that by about 20 degrees before the relay kicked on and the controller stopped the drop. Why did it let it get so far below the set point? Because it's averaging the 3 zones. Once the average of the 3 zones hits the set point it will start to fire each section again as needed to match the set point.
    I get a lot of questions from customers about error codes and cooling cycles. The biggest problem is that the kiln can't always keep up with the programmed cooling rate. There are a number of firing schedules out there on the internet that people are trying that use a rate of 600F/hr or more for the fast drop portion of the cooling cycle, and many kilns simply cannot cool that fast, especially the middle section. When you have a specific rate programmed, the controller will send out an error code if the kiln can't keep up with that rate. So if you want a really fast drop you should use 9999F/hr, not a specific rate. For most people doing slow cooling with cone 6 work it won't matter if the sections are not totally even during the drop. If you do need more precision, like if you're firing crystalline work and it's important that you don't overshoot any target temps, then you'll want to put in a slower drop rate that the kiln can actually keep up with, and the controller will keep the sections even and not overshoot set points.
  16. Like
    High Bridge Pottery got a reaction from Callie Beller Diesel in What mesh (particle size) silica for your glazes?   
    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 
  17. Like
    High Bridge Pottery got a reaction from Hulk in What mesh (particle size) silica for your glazes?   
    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 
  18. Like
    High Bridge Pottery reacted to Bill Kielb in Crazing versus firing temperature   
    Crazing to me is a result of the differences in the rate of growth or shrinkage. Once fired clay and glaze  are the same size, so the clay has shrunk to what it will be and the rate of future expansion and contraction will be affected by its composition and its  physical (and thermal) properties such as density etc…. Firing the body to its rated cone will provide the best chance of a fully melted body with repeatable characteristics. So the COE will likely be different for a cone 6 body fired to cone 4 or even cone 5. Our glaze on the other hand if able, may tolerate the difference in speed of expansion / contraction  and not fail or craze as if pulled apart. As a glaze is fired higher will its COE change? Very likely yes. Will its physical characteristics change? Very likely yes. Glazes more resistant to wear as in surface hardness may fail more so in impact. 
    I think the difference here for me, none of this is about the starting size and all about rates and whether the glaze can keep the clay body in a slight bit of compression without the glaze failing. So firing both to their rated cone likely gives the best repeatable representation of the match for both. Firing lower and assuming the next cone higher will improve the COE match between the clay and glaze is likely not really reliable in my view. So in the end, fire to rated cone, firing to lower cones is very likely not a good indicator for how these materials react when fired to rated cone.
  19. Like
    High Bridge Pottery reacted to Bill Kielb in Crazing versus firing temperature   
    I think hard to generalize and no way to guarantee anything is craze free forever. I do think there is reasonable correlation though. Differences in the expansion rate of clay and glaze being the prime issue, followed by the long term reliance of the glaze to tolerate the slight inevitable difference. The fired COE is often a result of fully firing so a clay body or glaze not fired or fully melted may have a different COE than one that is. Just imagine a clay body or glaze under fired by two or thee cones, we would normally expect it to behave very differently than fully fired stuff because it is under fired. If both are under fired the same amount will their under developed  COE somehow be even between them?  While I think in the ranges you are working in, likely a decent indication, just firing hotter does not necessarily mean the glaze will have greater flexibility and could actually become harder and more prone to tensile failure.
    I think your logic is reasonable, but believe it’s always best to test the the clay and glaze combination fired to cone.
  20. Like
    High Bridge Pottery got a reaction from Piedmont Pottery in Stull Charts, Flux Ratios, Silica:Alumina Ratios - Open Discussion   
    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.
  21. Like
    High Bridge Pottery reacted to Chalkie76 in Kiln electrical fault - what am I missing?   
    Thanks to you knowledgeable folk my little kiln is now happily ramping up at sonic speed again.  It was indeed damp!!  I propped the lid (which was only possible as I bypassed the lid safety - @High Bridge Pottery (which is the silver box with the cable tied wires) and then I stuck my heat gun nozzle in the bung hole - it fitted perfectly!  Ran it a few times for 5 minutes and each time I lifted the lid tiny little steam clouds puffed out!!! 
     
    I am so relieved I don’t have to explore the RCD or current leakage issue just yet!  But fyi my cooker has its own dedicated fuse but it’s still protected by the RCD. 
    now I’m debating if I should hook up the lid switch or leave it out as I quite like the idea of propping the lid to reduce the speed the kiln heats up but I do t like the idea of accidentally touching the elements when the kilns power is on…….  i guess I would only make that mistake once…… 
    I will never leave the lid open or off for anything (other than loading and unloading) ever again!  
     
    thanks again everyone 

     
  22. Like
    High Bridge Pottery reacted to davidh4976 in Stull Charts, Flux Ratios, Silica:Alumina Ratios - Open Discussion   
    I just had to find the full document: https://aura.alfred.edu/server/api/core/bitstreams/182c2504-e6ac-42f7-bb12-34492c950d5f/content
     
  23. Like
    High Bridge Pottery got a reaction from StonedStudio in Stull Charts, Flux Ratios, Silica:Alumina Ratios - Open Discussion   
    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.
  24. Like
    High Bridge Pottery reacted to davidh4976 in I tried to explode a cup in the microwave   
    I tried to explode a cup in the microwave. The test was to see if a cup with water absorbed into the body would explode when microwaved. My cup got really hot, but did not explode.
    I started with two nearly identical cups made from a white stoneware with an estimated absorption of 3.7% as previously measured with test bars. Each cup has a foot ring and was glazed inside and out with a clear glaze. The foot ring and the bottom area inside the foot ring was not glazed.
    One cup was set aside and was not subjected to any water.  It weighed 433.9g.
    For the other cup, I kept it upside down on my desk and kept filling the area inside of the foot ring with water for a few weeks. My thought is this would simulate water absorption from being subject to multiple rounds in a dishwasher. Periodically, I would check its weight. After a couple of weeks, the water absorption stabilized and the weight of the cup went from 426.0 grams to 441.8 grams, a gain of 15.8g or about 3.7% (which matches my test bar estimate). This means it absorbed about a tablespoon of water. It did not gain any additional weight/water with more time beyond a couple of weeks.
    Then, I microwaved both cups (both empty) at the same time in a 1.4kw microwave with rotating platform for 15 minutes. I very quickly measured their temperature after each minute of microwaving. The cup with absorbed water reached a maximum temperature of 433F. The cup without absorbed water maxed at 250F. Neither exploded. The cup with absorbed water crazed, but no other damage.  The cup with no absorbed water did not craze and was not damaged. The graph shows the temperature in degrees Fahrenheit over time in minutes.
    After microwaving letting the cups cool, I remeasured their weight. The cup with water applied went down to 425.4g indicating that all of the water was boiled out. The cup without applied water was 425.3. After microwaving, both cups weighed a less than their original weights.
    So, I was not able to explode my cup. This does not mean that your cup won't explode. This was for one particular clay and may not be representative of other clay bodies.  If others have time, it would be interesting to repeat the test with other clay bodies.
    Notes: Microwaving empty pieces is not recommended because it might damage the microwave oven.  I use an old microwave that I don’t care if it breaks. I used an infrared Infrared Thermometer Temperature Gun to be able to very quickly measure the temps. If you decide to repeat this experiment, note that I got 30F difference between the top and the bottom of the cup and averaged the reading.


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