Retxy
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Posts posted by Retxy
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Yes, several times. The underglaze was prefired at bisque (applied while piece was green)
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Can anyone recommend a recipe for a super flux that can help pull a glaze off of a currently obscured underglazed surface so I can see it again?
Thanks!!!
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Ret is retxy on a computer. For some reason I can't log in to the Ret account on my laptop.
Thank you SO much for this kind help you have given me. I appreciate the input and am relieved that the loss of a few coils shouldn't mess me up too badly. These mama jammas ain't cheap!!!!!
Thanks!
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Answered in an older topic. Thanks! Does anyone know where I can find the kiln sitter informational post posted by Neil? Thanks!
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I thought a quick Google/forum search would answer how one should tackle element replacement on a kiln who's manufacturer is out of business but alas.... Here I am bother you all. How does one go about getting the right element for a discontinued kiln?
Thanks everyone for your kind help.
D
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On 6/20/2022 at 11:50 AM, Min said:
Just had a brief look at what HyperGlaze can do, I really like the function of it that shows if a glaze is likely to melt at the temperature given. Have you found that to be fairly accurate?
"The Glaze Limits card offers some of the most unique features of HyperGlaze - the ability to look at glazes in a more visual format. Here the glaze is represented by the light blue bars of the graph, while the limit formula for this type of glaze is represented by the colored bars behind. The light blue bars (your glaze) can be easily dragged up and down using the mouse to adjust each oxide. Keeping the tops of the light bluebars within the limits (colored bars) ensures that the glaze will likely melt at the temperature given. The flux oxides (RO section) automatically readjust to maintain unity when any oxide is changed. Silica and Alumina can be linked to stay in in a specific ratio when adjusting. Custom limits are available and can be added by the user. The firing cone for the glaze can be automatically changed to adjust the fomula of the glaze to melt at higher or lower temperatures. And now the percentage analysis is visible all the time, too."
I have found those little toolbars indispensable actually. They give me soemthing to shoot for at the very least, along with the hard and fast rules that I learned in MC6. I really like this fucntion. I haven't figured out if there is a custom levels area yet, which would be useful if there is a set of parameters that one likes to reuse often, but if its there I will find it.
On 6/20/2022 at 1:15 PM, neilestrick said:For the most part, yes. I think the limit for MgO is a little low- I have several good glazes that are beyond that limit- but it's a pretty handy function for plugging in a problematic glaze and seeing very quickly where things might be out of whack. I've used Hyperglaze for almost 30 years, and it has served me well. It does seem to calculate COE differently than Digitalfire, but since I only use Hyperglaze I've got a good baseline for comparing glazes.
have you found that when going by the COE given by hyperglaze that the glazes you produce with it generally do well on your clays? I would think that would be testament enough. I don't know if you get your ware professionally tested, or if COE calculation can even be ordered with tests for durability (pretty sure those are two different processes) but it would be so cool if you have data.
THANKS SO MUCH EVERYONE. This community is a lifesaver
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7 hours ago, Min said:
I wonder why Hyperglaze makes it more difficult than it needs to be in regards to order of materials added? Seems like it would rely on people having knowledge of materials before using the calc. If an oxide is needed to be overloaded, like for a magnesium matte for example, do you just ignore the overload? Seems like the program was written when Limit Charts were more widely used.
I agree and I hardly know what I am doing. I tried to use the USE column to force what I wanted but it didn't work for me. I have been using glazy for the calculations then entering the recipe into hyperglaze to get an estimated COE for the glaze, which I haven't found a way to do in glazy. Also, hyperglaze does not do r20:ro, so even when I am using hyperglaze calculator to figure things out for me, I still have to enter it into glazy to get these, because I tried to manually calculate but was too... ahem dumb... to figure out how. Also tried to calculate coe manually and was getting huge numbers. so hyperglaze has helped with that!
I am going to try what @neilestricksuggested, and see if this will make a difference for me. I kept wondering why the program would stop calculating when there were still two ingredients left in the list of the recipe after using sort, but now I see this was just because I had met the limits. At least i think!
Thanks again so much for all being willing to share their knowledge. so very appreciated
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8 hours ago, neilestrick said:
Are you working in the Glaze Calculator section?
When you put in an ingredient that fulfills the requirements for certain oxides, but overloads other oxides, it shows as a negative number because it's showing how much you still need to fulfill. Needing a negative amount means you have too much of it.
As for the calculate button, that's just how the program works. It's doing the work for you. If you want a certain material to only supply a portion of what it could use, then you can put a precent in the 'Use' column as a decimal.
Materials need to be put into the calculator in order from most complex to least complex, and starting with your source of Boron, or it will be forced to overload oxides. If you put silica in first, it will fulfill all the silica, and then if you put in feldspar next it will over-fill the silica as it fulfills the other oxides that feldspar has. Here is the order in which you need to put things in:
1. Source of Boron, either a Frit or Gerstely Borate or equivalent
2. Feldspar or other Frits
3. Any material that contains 2 oxides, such as Wollastonite or Dolomite
4. Materials that only contain 1 oxide, such as Whiting, Magnesium Carb, Zinc Oxide, etc.
5. Clay
6. Silica
If you do things in this order, you'll have very little overloading of any single oxide, at least not enough to matter.
This helps more than words can say. THANK YOU SO MUCH!!!
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3 minutes ago, Bill Kielb said:
Yes, I don’t see it displayed but have never used hyperglaze. UMF originates from Hermann Seger I believe who was seeking a way to relate chemistry, composition and performance. Wiki link here https://second.wiki/wiki/hermann_august_seger. Anyway since the 1800’s it’s proven a useful way to understand glaze chemistry. For your recipe and materials substitution I believe digital fire makes substituting easy. For me I often just look up the materials, pick the next closest available and hand adjust as a quick way. While Glazy is not built directly for this Derek Au does do a few substitutions on video. One such similar posted by Sue McCloud https://youtu.be/z7k_X_1i-s0 does a reasonable job of explaining the process Using Glazy.
I really think the digital fire software allows one to substitute more easily though, but I do not use it so do not have direct knowledge.
I don’t want to speculate about limit warnings. if you reviewed the limit table, there is an amazing amount of overlap in the allowable so from cone to cone, table to table and there is no real way to correlate the effect of multiple limit violations. Just me though, some folks find them useful.Drop your recipe in Glazy, it will display the UMF and extended UMF
Bill,
If no one has ever told you that you are amazing, please know that you are. I can't thank you enough for your help with all of this!!! I have been playing around withthe katz spreadsheet just now, and the numbers i'm getting are vastly different from what hyperglaze is saying. So much fun. I can't wait to watch the videos you posted. Thank you!!
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a little background, the original recipe had FFF feldspar, but I'm trying to sub mahavir and failing miserably.
original recipe: https://glazy.org/recipes/9792
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28 minutes ago, Bill Kielb said:
You can learn UMF and Katz did have a free spreadsheet on his website that will calculate all this for you or if you enter your glaze on Glazy.org (free) the UMF will be generated for you. Most glaze software apps report R2O:RO (Flux ratio) for you. The essence of the research says a flux ratio of 0.3:-0.7 is likely the most durable. In generał I prefer to try and limit my flux range 0.2:0.8 to 0.3:0.7 for glazes I consider as liners. Higher than 0.3:0.7 seems to fall off in durability quickly.
Anyway, I would recommend The Katz course on glazes from a material science approach, he does a fair job IMO. Here is a Glaze below (on Glazy) Marcia and I (under Madison pottery) created it to be a Matte, but notice the flux ratio intentionally is in that magic range for us - 0.23: 0.77. The glaze software displays the value. BTW, still have a test piece in the dishwasher for probably over two years.
Am i missing this in hyperglaze? i have attached a selsor chun recipe that I am working on but i keep getting a message that potassium and sodium are undersuppplied but the ratio of these two is in a good range. so frustrating. but i don't see the r20:r0 ratios. I can switch to glazy or the katz website, but I went with hyperglaze bc mc6 recommended it. Is it there im simply not seeing it?
Thanks!
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11 minutes ago, Bill Kielb said:
If you read through his paper his research says glazes within a reasonable flux range are likely to be durable, those outside an acceptable range are likely not, so a bit more reassuring. Test, observation very important as well as using oxides and colorants sensibly.
Bill the r20:r0 ratio is a new concept for me. I have hyperglaze and am struggling to learn it. I don't see this as an offered ratio is this just something I get to calculate by hand?
Thank you for your rapid replies and kind help!! I am so grateful
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Bill the r20:r0 ratio is a new concept for me. I have hyperglaze and am struggling to learn it. I don't see this as an offered ratio is this just something I get to calculate by hand?
Thank you for your rapid replies and kind help!! I am so grateful
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18 minutes ago, Bill Kielb said:
Definitely agree, but the Katz research (pictured below) makes a good point re: the danger of passing that test: interesting research, interesting read, interesting presentation at NCECA 2016 interesting observations on gloss as well.. Full paper here for more clarity
Thank you so much for this! I'm scare now, but better to know now instead of later.
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On 6/17/2022 at 11:52 AM, Min said:
In the US at this point in time yes. I believe new regs are coming to some countries in Europe.
You can look at drinking water limits and compare them to ceramic glaze leaching figures from a lab such as BSC Labs which uses glacial acetic acid to drinking water to test for leaching.
Lets not throw the baby out with the bath water.
Practicing good studio hygiene and using transition metals (colouring oxides) in reasonable amounts and the least possible amount to get the desired colour and making a durable base glaze fired to maturity will negate most concerns.
Anybody that uses bright reds, oranges, and even some of the yellow and green underglazes or glazes is using stains that more than likely contain cadmium (Cd) in the form of an inclusion stain. Far and away safer and less leachable source of Cd than than using cadmium oxide. Many bright aqua, green and yellow stains contain vanadium. Again, in a stain form far and away safer for both the potter during making the pots and the consumer because the stains are far less likely to to be bioavailable than using the raw oxides.
Lithium is found not only in lithium carbonate but also in spodumene, petalite, a few frits and lepidolite, it is not an issue as far as toxicity is concerned when used with appropriate studio hygiene and reasonable levels.
Barium is one of the oxides that most people who fire to cone 6 avoid in North America.
Looking at the bioavailability of materials is important. Is the material bioavailable in the metallic form, oxide form, salt form or fumes? A material may be toxic in one form and not another. Manganese dioxide / oxide is an example of this. Manganese dioxide / oxide is not soluble in water therefore cannot be absorbed through the skin or even an open cut, and even if ingested cannot dissolve into the blood stream. Manganese fumes from the kiln firing however are bioavailable and harmful. (Manganese salts, chloride, nitrate, or sulfate, are very harmful but as these aren't commonly used by studio potters not likely an issue for this thread.)
Having a base glaze with as much alumina and silica as the glaze can melt into the glassy matrix is really important to a glazes durability. If a glaze is low on either of these the greater the chances of it not being durable. Insofar as utilitarian ware a durable glaze needs to withstand both acid and alkaline attack, be non staining and resist cutlery marking. Doing a lemon/vinegar test will rule out glazes attacked by acids, keeping a sample of glaze in the dishwasher for many months will rule out ones prone to alkaline attack.
"Limit" Formulas aka "Target" Formulas can be helpful to look at but there are many many glazes that fall outside the "Limits". What could be the most help to you is to look at the silica and alumina levels for a durable glaze. Try to avoid glazes at or below the lower levels of alumina and silica in "Limit" Formulas. If you put a recipe in Glazy you can see the amounts of each oxide present in the glaze, take these figures and compare them to "Limit" charts. These Limit or Target charts have gone out of favour with some potters but I think they can be a useful tool to have in the toolbox along with others.
A lot of the highly visually textured glazes will be overloaded with one or more of either boron or one of the fluxes. Boron is necessary for all but Bristol type glazes to get a good melt at cone 6. Oversupplying boron can result in some really beautiful glazes but by oversupplying boron the resulting glaze will be soft and less durable. Getting to know what qualities each oxide adds to the glaze is really helpful.
Welcome to the forum
Thank you SO much for this insightful reply!! Is getting to know each oxide just a matter of reading through the digital fire profiles on each or is there a resource that you have found helpful? I did not know that about manganese and honestly would not know where to pick up little tidbits like that.
I am struggling just now to learn how to do substitutions and not understanding what I am working with, so any resource you have found helpful I would welcome. I have MC6 and have found it useful, but aside from giving limits, there was not enough room for discussion of each of the recommended materials.
Thanks so much!!
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for hyperglaze users, why do excesses of different oxides present with negative numbers and in red in the unity formula? I am not sure why an excess would produce a negative number, unless i am missing something with the scientific notation? I feel rather stupid. and also, why must I be forced to use the calculation function instead of manually adjusting the ingredients myself? Is there a way around this?
Thanks SO much! If there is a better place to post this, please let me know.
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Bill,
Thank you so much for your wonderful reply!!! You correctly deduced that I was referring to masteringncone 6. Thank you so much for that article as it clears up a lot of things for me.
I agree that there are certain things that I also will not stop in my glaze chemicals, but was wondering if there were published standards somewhere as far as the leaching of other chemicals and if this was regulated. For example I did not know that over 5 mg per liter of copper bleaching gave food a metallic and bitter taste until I read mc6!!! And though the authors give some ranges I had wanted to know if there was some regulation that someone knew of from the FDA or others but now that I see that even Mako is only really concerned about lead and cadmium and I have learned enough on what to avoid ( batiumd, vamnadium lithium etc), I feel more confident!!! Thanks so much!!!
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Hello people much smarter than me!
I recently read mc6 and my mind has been blown. So much I don't understand. However I am barreling forward regardless!
My question is: when a large company labels a glaze food safe are they only required to use the leaching values for lead and cadmium? I understand the rules for toxic vs nontoxic, but not if these companies are using limit formulas for other items besides cadmium and lead.
If there are other standards they are held to, where could one find these published limits? Mc6 states that one can make their own guidelines but I am not educated enough and a point of reference would help me greatly.
Thanks!!!
D
Durable (i mean food safe) low fire glazes
in Clay and Glaze Chemistry
Posted
Hi there smart folks!
I am hoping to see if anyone can recommend any books or resources (free is nice, but not required) that explain limit formulas for the development of durable/food safe low fire glazes. I now feel confident after having read mastering cone 6 glazes that I am at least in the ballpark of safety when formulating glazes for midfire temps ( with testing to follow of course). But I have zero clue as to how to go about formulating recipes for low fire, where the stakes seem higher given clay isn't vitreous. I really wish that I could keep working with stoneware, but the cost to fire is now prohibitive for my life circumstance, so trying to see what the world of low fire can do for me so I don't have to give up the only source of sanity now left to me.
Thanks!
Ret