C.Banks
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Posts posted by C.Banks
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On 4/16/2024 at 10:32 AM, Callie Beller Diesel said:
... we want to make sure that the clay is fired to a point where it would have less than 1% absorbion...
I'm curious how accuarte or outdated my understanding is here.
I always thought under 1% was reserved for porcelain or porcelaneous clay and can overfire quickly.
Under 2% was a good benchmark for stoneware that allows a more broad firing range. I'm even less familiar with eathenware but from what little I know they are dpendent on good glaze fit for surfaces in contact with food.
I only took up my own clay a few years ago so I'm happy to find new answers. I've seen this 1% number before and figured it was time to ask.
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16 hours ago, Min said:
I had a look through Hamer's Pottery Dictionary of Materials and Techniques and under the Crazing topic. Snippet from there reads "Where a glaze is overfired and then crazes it is because the overfiring affected the body more than the glaze." also "The crystalline silica in the body becomes fused silica and in this form it has a much lower rate of contraction. The glaze still has the same rate of contraction and therefore in proportion it contracts more when overfired than when correctly fired."
Hamer doesn't quantify how much overfired. I haven't seen it with a single cone higher firing, maybe more prevalent with very tight firing range claybodies?
aha
and from the dictionary too. I forget books are a thing apparently.
It didn't occur to me to consider overfiring.
This makes sense to me in terms of how much feldspar is present in glaze copmpared to clay. The way I understand it if there isn't sufficent feldspar present, in clay, some critobalite gets left out and doesn't fit on cooling - like musical chairs.
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On 1/31/2024 at 6:13 AM, davidh4976 said:
Is it correct to say that if a glaze/clay combination does not craze at cone 5, then it should not craze at a higher cone firing?
This is an interesting question.
I've always understood glaze fit in terms of the big changes in silica. Maybe somone can help me underastand too. Once that last big in quartz happens at 573c there is no ther significant change in size until cooling through 250 - the last change in quartz that can put the 'squeeze' on.
In my limted understanding, firing one cone hotter does not involve any significant change in the size of silica.
I look forward to understanding this better though. I get tripped up easily but do enjoy trying to fit the pieces together in my brain.
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On 1/13/2024 at 12:59 PM, Min said:
When I enter the MC6G High Calcium Matte 2 into the EU calculator I'm not seeing excess to the eutectics of CaO even though this is coming in at 0.90 in the UMF. I'm going to assume this glaze uses a different matting mechanism, perhaps the excess alumina and silica causing the matting or a micro rippled surface. If that's the case we need another recipe to test the theory with or reduce the silica and alumina perhaps.
I have a project that leads me to believe Al2O3 amounts over around 0.3 restrict the development of micro crystals. I know this is off topic and specific to do with magnesia mattes too so may not be too useful here. These mattes do respond to calcium though - or as much as I'm certain I remember a line blend proving + calcium = + matte in magnesia mattes.
I'm unsure this helps understand the Eucal results at all. This conversation only reminded me of a glaze project I'm somewhat familiar with.
*to add here - additions of calcium seem to reduce the claculated Al2O3
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6 hours ago, PeterH said:
I got the page, and it says that the demo is at
https://s3.amazonaws.com/nist-srd/ped_demo_5.1_setup_final.zipIf you have any further problems PM me with your email address and I'll try to email it to you.
that worked thanks
they sure don't offer much and without labels too
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1 hour ago, BobMagnuson said:
I was able to download, extract and use ACerS-NIST PED Demo from:
https://www.nist.gov/srd/nist-standard-reference-database-31
It's a fairly large file, so it does take a while to download.
i couldn't find that page - thank you
I had the editor on my ssd but it took up too much room. Now it doesn't want to open/install. I get the blank page file:///D:/PEDEditor.jar with nothing further.
It's not too important. I just wanted to see if I could make any sense of it. I might have enjoyed a career in material science or ceramic engineering 40 years ago.
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3 hours ago, Hulk said:
Thank you C. Banks!
...I'm looking at the article on sustainability now, also interested in the Coppage, Faber, Schade, Yimnirun, Davey, and Randall articles, oh, and the "Why Science Communication Matters" one as well.
I'm enjoying a few other contributors too.
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19 hours ago, GEP said:
It also needs to be pleasing to touch and hold
pleasing to touch and hold sells a lot of pots
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https://ceramics.org/publications-resources/ceramic-tech-chat/
The American Ceramic Society always seemed a bit exclusive for commoners like me but it turns out they do share.
An interesting note - I overheard an industry type person talking to a recognised academic about recycled glass and how there is a need*/opportunity to find a use for it. It's not the first time I've heard of people trying to peddle ideas for recycled glass. This: https://ceramictechchat.ceramics.org/974767/12251109-the-everlasting-relevance-of-brick-john-sanders briefly brings up the possibility of making brick with up to 60% recycled glass.
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Has anyone got the trial version of ACerS-NIST PHASE diagrams to run? All I got was what seemed like a forever loading bar on the title screen.
Has anyone tried 5.1?
I'm unsure how useful they are to me but maybe if I stare at the diagrams long enough some hidden 3d image will appear.
https://ceramics.org/publications-resources/phase-equilibrium-diagrams/
*it look slike the trial version is completely gone
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13 hours ago, Min said:
Well that's a nice little bit of light bedtime reading isn't it?
Glad I'm not the only one thinking precipitates effect calculated flux ratios. Interesting seeing the phase diagram overlaid with Stull but found it hard to decipher.
The folks who can interpret comlpicated ideas and express themselves in approachable language sure help the rest of us follow along.
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On 1/9/2024 at 10:59 AM, Min said:
during the cooling phase of the glaze
I was looking for the trial version of the NIST? phase diagram software and this: https://phasediagram.weebly.com/eutectics.html reminded me of some language here.
I don't pretend to understand it all although I do grasp the larger 'chunks' and descriptions of parts getting squeezed out and reforming encouarged me to wonder how many of the principles might apply to the glazes we find most appealing.
There was a discussion of overlays for the stull chart that gets stuck because the diagrams are copyrighted iirc.
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13 hours ago, Min said:
I went through the Techno File topics from Ceramics Monthly and the only one that struck me might possibly be it is the "Ingredients' Roles" article written by Steve Loucks in the Nov 2021 issue. It's behind a paywall but you can access 3 free articles a month. Basically Loucks looks at glaze components and lists them in a specific sequence of spars, fluxes, clays and glass formers then looking at the fired glaze in relation to what the ingredients do and what influence they have on the glaze. Alterations are then made to the base glaze to see how the different components change the base. There is a brief comment on UMF but not much. Possibly what you were referring to?
It was definitely older than 2021. I worry now maybe it was from the Potters Quarterly from the UK. I'll find it but it'll be a few months before I get back there.
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3 hours ago, Min said:
I'll try and do a search online for it in CM through ICAN, do you remember the author or anything else about it? I'll read the article you linked when I have time in the next few days.
Thing about flux ratios that doesn't make sense to me is using them to look at microcrystalline glazes. If a microcrystalline glaze is formed via the mechanism of the excess MgO, CaO, SrO, BaO, Al2O3, TiO2, ZnO, or MnO (or combination of these) that do not stay within the eutectic during the cooling phase of the glaze matrix then how does one measure for this? Same reason that COE figures don't work on semi or matte glazes.
I don't remember much about it other than gave me reasons to avoid decyphering the UMF.
I aquire magazines and some years I read less than others so this goes back at least three years and probably closer to five.
Something I didn't appreciate until only somewhat recently is just how many eutectics exist. It's possible small systems are forming within larger eutectics? This will expose how little I know but I'm ok not knowing things.
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3 hours ago, Bill Kielb said:
It would be interesting to see just how many departed significantly. Lots of old glaze recipes fall into a reasonable range around 0.3:0.7. I would love to see real comparison data on this, anecdotal often has the potential for perception bias.
I've been tempted to put in the work and see how the ratio holds up. It would make for good content.
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1 hour ago, Min said:
@C.Banks, is this a snippet of the UMF article? I can't access the full article, if it is maybe somebody can find it? It's from William Carty , Matt Katz and John Gill.
The one I'm thinking of is from an old ceramics monthly from the ? 90's?
The mention of calcium is interesting. Growing up we used forms of whiting (and feldspar) without any concern for R2O:RO. Our glazes did just fine but it turns our they were way outside 0.3:0.7.
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I followed the 10:1 rule from Olsen (firebox : flue size) on a similliar project and found I did not get enough pull with a 9 foot chimney of 81 inches in area. I came to the same conclusion that the exit flue is too small. I liked the idea of a fast fire kiln but in my case there were other issues with the depth of my firebox in relation to the heigth of the kiln.
I haven't got back to it but I'll rebuild with twice the flue size and look more closely to a ground hog deisgn with a low, wide chimney instead of the tall, narrow fast fire design.
Established kilns I've been a part of have run into heat saturation issues atfer too many hours of struggling with what amounted to overloading. I bring this up in repsonse to @Biglou13 as I'm sinscerely curious if your design has the mass to succeed as anything other than a fast fire. I don't mean this as a criticism I only mean to work out what expectations we should have from kilns with less mass.
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I wish I could remember @Min who proposed an alternative to the UMF. I have a few stacks of old magazines and perodicals I flip through. I have a suspicion the most relevant article is at the bottom of one of those stacks. Next time I'm in the shop I'll try to find it.
I know there are other references but they could simply be letters to the editor.
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On 1/7/2024 at 5:20 AM, Bam2015 said:
Maybe I have no business making my own glaze if the info in this thread is way over my head.
There is old criticsm of certain aspects of glaze chemstyr as being overly complicated and a bit elitist - the UMF system in particular.
Some of the most sucessful potters I've known grew up on a healthy diet of 'melt and see'. They wasted some time, energy and materials over time I imagine but we did just fine for our purposes.
There is obvious value in the UMF but please don't let the language muffle your curiosity.
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37 minutes ago, Biglou13 said:
I’ve used helmer as a flashing slip. I’m sure it would work. This body is pretty flashy already. I should try maybe get super flashy!
Now that I think on it i remember a version with significant chunks firing well but chewing through a few fish line cutting wires and creating difficulties while trimming .
We were paying significantly less for helmar kaolin back then I imagine.
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crushed up and screened soft brick can work nicefly in a flour sifter
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10 hours ago, Biglou13 said:
Modified 12 D (original)
EPK 36.8
Nephaline Syenite 24.5
OM4 Ball Clay 14.3
Silica 19.1
Bentonite 5.1
Redart 2.5
Total102.3
I'd be tempted to sub out some/all of the epk for Helmar.
Once fiing a foot thick cubes sounds adventurous. I'm a bit nervous at the best of times so for sure I'd be concerned about the time it takes water to escape.
again, I'm sometimes overly cautious so, for me, the additions of organic/inorganic grog helps to move water along more than anything else. I would not want to be responsible for 'surprises' below 100c.
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10 minutes ago, Gonepotty said:
Hi Mark, I have add 5 tablespoons to a 21L batch.
Hi Gonepotty,
I'll go back to lurking - better to remain silent and all that
Sourcing Hard Brick
in Equipment Use and Repair
Posted
The stories of jack pots of bricks from busted factories are turning into myth but we gotta keep trying. I'll admit to getting a bit jealous of the stuff I've missed out on but I try to mind my own business, for the most part.
The one thing I can try to add is the option to build with castable mixes although cheap alumimna is, again, a thing of the past. From what I can gather one of the most important part of success with castable refractory for salt and soda kilns is the wash. But this will only keep the degradation at bay for so long.
Ruthanne Tudball and Jack Troy published recipes for refractory mixes for salt and soda kilns. iirc they might be the same recipes though. Rhodes also mentioned something about brick degradation and density that would be worthwhile to consiedr if trying to modify or improve on a mix. I convinced myself it was possible to find a way forward without actually having any bricks.
I let the idea go after finding a precious seed hoard of super duty brick a few years ago but castable refractories would have scratched the itch for me. I'm still tempted to finalise a recipe and design but it's tough to just take something on for fun without a certain amount of spare time and disposable income. For now it's just a very interesting, very part time, research project.