steviepeas Posted February 21, 2023 Report Share Posted February 21, 2023 Assistance please. I have seen potters in Japanese sites firing to 800c, what are the advantages or disadvantages please. Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 21, 2023 Report Share Posted February 21, 2023 I guess the bisque will be more fragile and porous so it depends on your perspective if that's an advantage or disadvantage. What advantage are you looking for? Lower firing costs? Quote Link to comment Share on other sites More sharing options...
steviepeas Posted February 21, 2023 Author Report Share Posted February 21, 2023 Thanks for your reply, I was just interested in the pros and cons, obviously it’s cheaper in energy to fire at 800 but I have seen several very successful Japanese potters fire to 800 instead of 1000 which seems to be the norm here. I would fire high, say at 1040 for glazing, I will have to experiment and see what effects transpire. Quote Link to comment Share on other sites More sharing options...
neilestrick Posted February 21, 2023 Report Share Posted February 21, 2023 The lower you bisque the greater the risk of not getting good burnout and having glaze issues. With a whit clay it's not going to be as big a risk, but with a darker clay it could be an issue. 800C is really, really low. Quote Link to comment Share on other sites More sharing options...
steviepeas Posted February 21, 2023 Author Report Share Posted February 21, 2023 Yes I thought there might be an issue with burnout, I’ve just looked again at a Japanese potter to make sure I’m not making it up and he was firing at 700c to bisque for some rice bowls with slipped surface ! Quote Link to comment Share on other sites More sharing options...
Min Posted February 21, 2023 Report Share Posted February 21, 2023 @steviepeas, could you post a link to his? Might be another factor we don’t know about. Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 21, 2023 Report Share Posted February 21, 2023 I'm not so convinced that 800c is really really low for carbon burnout. There doesn't seem to be a real consensus around temperature. Thickness, time, air flow and the amount of carbon present all play their part. You could bisque to 1000c with rubbish air flow and thick pieces quickly and get less burnout that a slow bisque with good air flow to 800c. Digital fire seems to say anywhere from 370c-950c others say that naturally occurring carbon in clay burns off at higher temperatures: up to 1200 F to 1400 F (650 to 760c) so I think temperature is just one variable. Rae Reich and Magnolia Mud Research 2 Quote Link to comment Share on other sites More sharing options...
steviepeas Posted February 21, 2023 Author Report Share Posted February 21, 2023 21 minutes ago, Min said: @steviepeas, could you post a link to his? Might be another factor we don’t know about. High Bridge Pottery 1 Quote Link to comment Share on other sites More sharing options...
Min Posted February 21, 2023 Report Share Posted February 21, 2023 Thanks for posting the link. My hunch is this comes down to expectations and the history of how glazing and firing methods evolve. We in western cultures seem to prefer "flawless" surfaces; pinhole and dimple free yet in other cultures pinholes and dimples add beauty to the pot. Reading some of the old clayart posts by Lee Love (who lives in Japan) mentions bisque firing to ^012 or cooler. Doing this is going to make a much more fragile pot, I would imagine glaze tongs could very well break some pots. Porcelain bodies have much less junk to burn off, you can get away with a cooler bisque for those bodies than say a high manganese body if your goal is to have a pinhole/dimple free pot. I believe it was Ron Roy who was one of the champions for raising bisque firings to ^04, many people have had success with this. I remember when I was learning about firing the norm was to bisque to ^08 - 06. Rae Reich, Babs, Magnolia Mud Research and 1 other 4 Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 21, 2023 Report Share Posted February 21, 2023 What kind of clay are you working with? You said "I would fire high, say at 1040 for glazing," which is cone 05/04 and pretty low for a glaze firing unless it's earthenware clay. Quote Link to comment Share on other sites More sharing options...
glazenerd Posted February 21, 2023 Report Share Posted February 21, 2023 5 hours ago, High Bridge Pottery said: I'm not so convinced that 800c is really really low for carbon burnout. There doesn't seem to be a real consensus around temperature. Thickness, time, air flow and the amount of carbon present all play their part. You could bisque to 1000c with rubbish air flow and thick pieces quickly and get less burnout that a slow bisque with good air flow to 800c. Digital fire seems to say anywhere from 370c-950c others say that naturally occurring carbon in clay burns off at higher temperatures: up to 1200 F to 1400 F (650 to 760c) so I think temperature is just one variable. Edward Orion, Jr. (yes, the cone guy) did the early studies on inorganic burnout back in 1906-1910 period. In reading his abstract: he cites inorganic burnout between 1250 to 1750F. T Rae Reich and High Bridge Pottery 2 Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 21, 2023 Report Share Posted February 21, 2023 I found it interesting after reading a few of the American Ceramics Society's work that they all seem to use celcius. What happened What's the title of that work? I would be interested to read it. Quote Link to comment Share on other sites More sharing options...
steviepeas Posted February 21, 2023 Author Report Share Posted February 21, 2023 4 hours ago, High Bridge Pottery said: What kind of clay are you working with? You said "I would fire high, say at 1040 for glazing," which is cone 05/04 and pretty low for a glaze firing unless it's earthenware clay. It’s a white body with firing properties from 1040 to 1240. I mainly fire at earthenware except for some hefty stoneware suitable for exterior planters Quote Link to comment Share on other sites More sharing options...
Babs Posted February 22, 2023 Report Share Posted February 22, 2023 1040 to 1240, if only taken to c04 would not be vitrified so very high absorption for functional ware. Glaze for interesting. Not durable ware. The potters would know their clay and their customers. Some clay comes with a suggested bisque temp stamped on the bag. @High Bridge Pottery across the water, still work Fahrenheit, and miles etc , makes Maths more interesting and keeps some folk in the dark... Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 22, 2023 Report Share Posted February 22, 2023 I can't see many problems with doing a low bisque although the general instructions are to do a higher bisque and lower glaze firing. I assume that is to get absorption lower and a higher COE in the body to match with the glaze. Doing a low bisque could give you crazing issues with the glaze. It is certainly possible to make functional ware but you rely on the glaze completely covering all the clay to stop it absorbing water. Sometimes earthenware clay is better suited to being outside as it has good thermal shock characteristics with the body being more open. @Babs I wish we didn't use miles in the UK but that one has stuck around. It's funny, fuel is sold by the litre but everybody talks in miles per gallon Quote Link to comment Share on other sites More sharing options...
Babs Posted February 22, 2023 Report Share Posted February 22, 2023 OMG really, havent been back since 1971! Then there are the Scottish miles.. humans dont like simple ,eh. I remember there was an April's fool gag re making the calendar "metric" or whatever the equivalent would be. Folk freaking everywhere:-))))) Re original post. Try a low bisque , see if it works for you. Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
Min Posted February 22, 2023 Report Share Posted February 22, 2023 (edited) @High Bridge Pottery, re temps and what is happening in the bisque firing, do you have a copy of Hamer's The Dictionary of Materials and Techniques? If you do have a look at "Firing", it goes through all the stages and temps etc, really thorough read. The figures mentioned by Hamer mesh with what is in the pdf by Steve Davis below. (also the bit from GlazeNerd above re inorganic carbon burn out range) Includes organic carbons and sulphur etc also. https://www.aardvarkclay.com/pdf/technical/Bisquefiring.pdf @steviepeas, if you are making functional work that is to be used with liquids, it is best to use a clay with less than approx 1.5% absorption. With wide firing range clays, like so many are in the UK, it's best to fire them to maturity then check the absorption. If a clay is fired to less than the top maturity temperature / cone then it's apt to weep moisture if not. Edited February 22, 2023 by Min High Bridge Pottery 1 Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 22, 2023 Report Share Posted February 22, 2023 Had a read of the firing section but he seems to be agreeing that 800c is fine for carbon burnout. "This process requires at least the dull red heat of 700c (1292f) and reaches its climax around 800c (1472f). Most of the carbon has been burnt out by 900c (1652f) but some sulphur lingers until 1100c or 1150c (2012f or 2102f). "Some potters slow down the rate of firing or try to hold the temperature steady at 800c (1472f) for a couple of hours." I am not sure I agree about the sulphur being gone from 1150c onwards after seeing the glass batch with 1% sodium sulphate releasing SO2 gas from 1000c to 1550c but I would be interested to find the experiments that have been used for the ceramics data. These numbers must have come from somewhere. Quote Link to comment Share on other sites More sharing options...
glazenerd Posted February 23, 2023 Report Share Posted February 23, 2023 On 2/21/2023 at 4:48 PM, High Bridge Pottery said: I found it interesting after reading a few of the American Ceramics Society's work that they all seem to use celcius. What happened What's the title of that work? I would be interested to read it. Still looking for Orion work; lost a lot of info when my old laptop took a dirt nap. Brownell did similar studies as well. High Bridge Pottery 1 Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 23, 2023 Report Share Posted February 23, 2023 Thanks Tom, I will see if I can track it down too and try and find Brownell's paper. Looks like the Brownell is still in copyright until 2063 so it may be difficult to source. I think I may have found the experiment that is referenced in the 950c-1150c temperature or at least one of them. Seems which sulphur compound you have changes the temperature as a brick maker talks about iron sulphide releasing gas up to 900c. https://archive.org/details/transactionsofam13colu/page/689/mode/1up Quote Link to comment Share on other sites More sharing options...
Chilly Posted February 23, 2023 Report Share Posted February 23, 2023 3 hours ago, glazenerd said: looking for Orion work; Orion? or Orton ? Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 23, 2023 Report Share Posted February 23, 2023 He has issues with auto-correct Chilly 1 Quote Link to comment Share on other sites More sharing options...
glazenerd Posted February 24, 2023 Report Share Posted February 24, 2023 8 hours ago, Chilly said: Orion? or Orton ? Orton — auto-correct once again. Chilly 1 Quote Link to comment Share on other sites More sharing options...
glazenerd Posted February 24, 2023 Report Share Posted February 24, 2023 Most all the studies were related to the brick industry. We use the same red body (mostly) as that industry. Was looking at F.H. Norton Phd>earlier; same references. T Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 24, 2023 Report Share Posted February 24, 2023 21 hours ago, glazenerd said: Orton — auto-correct once again. I always turn off auto-correct, causes more issues than it solves. Sorry for going off on a tangent steviepeas, let us know if you try a 700-800c biscuit and how it turns out. Quote Link to comment Share on other sites More sharing options...
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