High Bridge Pottery

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 

 

I just had to find the full document: https://aura.alfred.edu/server/api/core/bitstreams/182c2504-e6ac-42f7-bb12-34492c950d5f/content
 

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.

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.

100% agree

I appreciate this question. As well as the notion that simple frit and clay glazes are best . 
In the 2016 paper, Matt refers back to the 2012 presentation, discussing results of 0.5 R20:0.5 RO samples in relation to boron. He concludes that paragraph with:
“Thus the quality of glazes is not dependent on any specific temperature for durability. Chemistry is the only relevant factor.”
Obviously, temperature does matter, if a glaze hasn’t melted it’s not complete. But once it has fully melted, why would a glaze that’s durable at cone 04 (say, 0.3 R2O:0.7 RO, 0.5 boron) be less durable if fired to cone 6? It might run all over, but that’s a different problem. 

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.

@PeterH @Clay17 @neilestrick @Dick White @Bill Kielb Just "finished" the site (or at least the major features). I'm sure there are some bugs to be ironed out, but so far it's working for me and for the files you all sent me (many thanks).
If any of you guys end up playing around with it and find any issues, let me know. Planning on trying to get the word out in the next few weeks and want to catch as many bugs as I can. 
www.fire-graph.com
 

Thanks Min, I think the issue was Epsom solution not saturated enough. I have made a new Epsom solution and results are promising. Thanks for all your help  much appreciated 

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

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 

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

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

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 

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?

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 

There's 1000kb limit per post but most csv files should be way under that.
 
I would prefer the x-axis in hours and another option for easier seeing of the firing is to dash the setpoint line so it covers less of the firing curve.

There had been discrepancies in Orton's online materials regarding small cone deformation temperatures*.
I used small cones for the kiln sitter (prior kiln), and I like them. They are a tiny bit cheaper.
Here's an excerpt from the message I received from Orton Engineer (circa March 2020):
Dear Sir,   Thank you for contacting Orton to draw our attention to some incorrect information on our website.  The small cones do in fact deform after the large cones.  We have updated the information on the website.    See also this thread (start at the bottom/end) Kiln Sitter cone for witness cone - Studio Operations and Making Work - Ceramic Arts Daily Community   *There still are! The 2016 cone charts are all "backward"   See the small cone page, SMALL CONES | Orton Ceramic
"Small Cones used on the kiln shelf deform at about 9°F after Large or Self-Supporting Cones of the same number." It's just because the small ones are smaller - the cones are same material; same reason a large candle will slump in hot weather before a small one.
 

The blurb on the right says  (incorrect information - see Hulk's next post)
 

The blurb on the right says  (incorrect information - see Hulk's next post)
 

They had the same problem at the old place I used to work. They were selling premade bisque forms and duncans PB but if the manufacturer fired the bisque hotter than usual customers would start complaining about glazes shivering/popping off.  I would try firing your bisque a cone hotter to see if that stops the crazing.

Barium carbonate will only precipitate out soluble salts not the iron etc. impurities.  I would try every clay you can buy and see which one works the best.

Barium carbonate will only precipitate out soluble salts not the iron etc. impurities.  I would try every clay you can buy and see which one works the best.

I thought they had stopped making it but potclays seem to have it in stock. https://www.potclays.co.uk/calcium-borate-frit I feel like it has doubled in price but I haven't bought any for a long time. 
If you want to look into making glazes start with limit formula https://digitalfire.com/article/limit+formulas+and+target+formulas
 

Yea, I would try a firing to only 100c first and figure out what's what. Something like 100c top temp, pot F1 set to 5, t.F1 set to 30 min and t.F3 set to 10 min and see what happens.