Bill Kielb
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Posts posted by Bill Kielb
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I am thinking the confusion arises from the lack of explanation of cones. While their chemistry is established they indicate by bending so not really fully melted. A cone 4 cone ground up and fired to cone 8-10 turns out to be a fully melted glaze. At present there is not a straightforward exact predictor of when a composition will fully melt. Stull did his work at cone 10 I believe (likely closer to cone 11 today). His map was for a very specific flux ratio and his glazes. Katz showed a reasonable correlation at cone 6 and lower further incorporated boron as a means to lowering the melting temperature. Sue McCleod presented a cone six version of this at a2018 NCECA (Google Sue McCleod and Stull. Stulls map does not predict the temperature something melts at. Higher melting temperatures would progress from left to right and upward in relative ranges. Limits are these tested ranges, but are approximate guidance Testing is generally the only way to know with reasonable certainty when something will fully melt.
Advanced knowledge of durability is a Katz thing where certain flux ratios may be an indication of durability.
I think the simple answer is cones fully melt 4-5 cones higher than their rating. I don’t think the author clearly represented this in the cited link.
I would also suggest that much of pottery is understanding the variability and by experience important trends. It is somewhat very exact and scientific but verified through testing.
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Looks like a small well powered kiln. Depending on reduction schedule and firing speed restrictions of the wares you will fire likely 8 - 10 hours. If your wares are not particularly thick and you can go 400 - 600 degrees per hour with let’s say a 45 minute early reduction maybe gets you a bit faster down to 6 hours. This kiln looks like it can go to cone 10. One thing about small updraft kilns folks are prone to stalling them in very heavy reduction. The supervision of damper and gas is often something to get used to and too heavy a reduction will drop your speed a bunch. In my experience most folks tend to stall these kilns on their way to cone 10 so cone 6 reduction should be easier to hit.
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1 minute ago, elenab said:
I have to process it now, then I come back.
It’s pretty easy to do by hand and if you are proficient with excel, there are some spreadsheets that relate it well. Regardless, knowing the concept then comparing glazes under UMF evens the playing field so to speak so one does not have to learn it to use it productively. The comparisons have more meaning and trends are more easily recognized under UMF.
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6 hours ago, Elmoclayman said:
Do I need to do a "Strike" at the end?
Sounds like you figured out gas / damper and reduction indicators for you so your heating rates are acceptable. I have never had to strike or go into heavy reduction at the end but if you get the result you are looking for, then it is a technique successful for you. There are many schedules and techniques, I have never had to strike nor clean up the kiln at the end. My goal is always to get the uniform reduction I am seeking without a smokey mess and waste of fuel. Some test tile pics and midfire / later fire flames below. I use an O2 probe and built monitoring equipment, so a bit unfair, but a way to learn / teach basic reduction.
What works best for you and your glazes you will figure out - have fun firing!
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3 hours ago, elenab said:
If the numbers of stabilizers and glass formers are not in any relation with fluxes, does it mean that any recipe with fluxes mol. e. equaling 1 would be good?
Nope, temperature and apportionment change. Under UMF fluxes add up to one by definition- always. So Glaze calculating software sums the fluxes to equal one and everything else is apportioned accordingly. The fluxes traditionally have been Lio2, K20, MgO, CaO, SrO, BaO, ZnO. Alkaline metals and Alkaline earths respectively.
You end up with a consistent way to compare glass former's, stabilizers, and even ratios that become meaningful with testing. Setting fluxes equal to one (unity) is a requirement to place things in UMF form
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If your electric shuts off at the fuse box that indicates a short or over current condition. You will need to have someone troubleshoot and find the shorted connection. If your firings have been taking longer that would indicate your elements are wearing out. When elements wear out their resistance value increases and your kiln actually draws less current which means less power to fire. You may have both problems but the short circuit that is tripping your breaker is the one to find first and fix. From there have your electrician measure the resistance of your elements and if they have risen from new by about 10%, they are ready for replacement. A thermocouple would not cause this to short and trip the main breaker.
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2 hours ago, MissyLee5 said:
Thanks for the replies everyone. Glad to hear it's not much of an overfire.
They sort of all follow that once gravity takes over they bend quickly within just a few degrees. From three o’clock on things happen pretty quickly
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Some folks use underglaze on greenware, some folks underglaze on bisque. Some folks underglaze one coat on bisque, bisque fire again and add more underglaze to their design without fear of disturbing their first coat. So on greenware, I guess it’s fired only once if it’s fired from green to glaze as a single fire. If it’s applied over bisque then it still only goes through a single firing - the glaze firing. If an extra bisque firing is done for multiple coats, then the first coat of underglaze is fired more than once counting the glaze firing.
So the extra firing allows one to decorate over an already underglaze decorated design.
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I would say a strong six or barely over six, almost darned near perfect. Maybe a degree or two or an extra minute or two. I would be pretty happy if my kiln fired that way all the time for that matter. You can do a small cone offset to get it to your liking, but I would do that based on a reasonably filled kiln, probably not a mostly empty one. Just wondering if the cone was damaged at the base before firing?
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Did the kiln turn off because it reached your firing cone? If it reached cone then even propped open slightly your firing ought to be near normal. What is your firing schedule, what is your target cone, what cone are your clay and glaze, what turned the kiln off?
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5 hours ago, LindsayM said:
Does anyone have any helpful advice? Very many thanks
This looks like one of those miracle clays but is really a cone 9/10 clay to get full verification. So it ought not bloat at cone 6/7. Can you post a picture or pictures of the defects you are seeing?
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20 hours ago, moh said:
I'm trying to do the opposite and spray the glaze + have it dry like normal glaze.
Likely need thin the glaze to spray. Dry the glaze as needed with half pull of the spray gun trigger - air only - should make spraying more doable. It’s good practice to learn the thickness with some test tape when spraying with glaze, since it’s thin to work in the sprayer it will go on very even, but thinner than dipping. Usually requires several even coats dryed in between by “air only“ from the sprayer. Don’t forget proper mask and ventilation!
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20 minutes ago, Elmoclayman said:
Honestly I need someone to walk me through a Cone 10 Reduction glaze firing from start to finish.
Thanks in advance!
Yes, updraft, downdraft powered and atmospheric it’s a dance with gas pressure and damper. Damper adjustments are often tiny. I have seen 1/16 inch have the effect of decent reduction or smothered not able to gain temperature. Firing with someone who is good at it would help a whole bunch. It’s always been better when I was personally there as opposed to digitally there on teams or FaceTime etc… Truly best if someone can show you IMO.
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6 hours ago, forest_chant said:
I so far didn't smell or feel anything. Yet I wonder, should I be worried about the fumes? Should I ask them to move the chimney further away? Is there any recommendations about this?
In the US minimum clear space is usually 10’ (3.048m) minimum. This will be dependent on local codes for your location. My thought: if they can relatively easily extend it farther regardless of the code, they may just want to do it voluntarily.
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Maybe post a picture or two, folks may recognize it by look. Come to think of it, maybe even pictures of the drive, wiring, controls.
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5 hours ago, HenryBurlingame said:
Does anyone here use porcelain with the advancers?
Yep, our porcelain plucks. But kiln wash is super easy, super smooth or a little alumina works just fine for us. Cone 10 furniture plucks as well but dipping the ends of furniture in kiln wash is super effective and lasts many, many firings. The weight of each load is 30-60 % lighter than ordinary shelves so to us they are worth it in reduced energy alone.
- HenryBurlingame and Hulk
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11 hours ago, Bear Creek Studio llc said:
. We fixed the breaker which was old
Ya probably already know this but worth mentioning I think. Breakers fail because they are old but also because they overheat. Here in the US the breakers you buy should not exceed 80% of the rating stamped on the breaker. For kilns which are considered continuous loads by code, per code they require a breaker at least 125% of the kiln full load and not more than 150%.
For a kiln that draws 40 amps, minimum breaker size is 50 amps (40X 1.25), maximum breaker size is 60 amps (40X1.5). I mention because electricians often get this wrong. The rule is there to prevent the breaker from overheating and failing prematurely. Often this is not common knowledge so I think worth passing along since you just experienced a worn out breaker on this kiln.
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5 hours ago, Kelly in AK said:
Some people glaze greenware, it works
FYI - Quite often once fire folks will do a single firing at bisque speeds. In effect a bisque first to burnout everything then continue on to glaze temp, usually for tested clay and glaze products that work well this way without excessive glaze defects. If their clay is known clean or tested with a glaze known to work without issue then not so much at the reduced speed but the tested speed. I would not ignore the time at temperature unless verified ok through prior testing.
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1353 is cone 017 ish. I assume you were trying to go to cone 04. I would suggest refine to 04, hopefully you are using cones. Bisque firing removes organics and chemically combined water so how much time and how much time at temperature is the important part. I would troubleshoot the kiln, fix it then re-bisque to desired cone.
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Good find! They appear to be out of stock though. But now we know the measurements!
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They are still in business so a call to Amaco might be revealing. They also seem to sell Amaco motors as well as brushes on their site. Maybe matchup to what you have. Your motor hopefully has a nameplate. Amaco website https://shop.amaco.com/equipment/parts/brent/wheel-motors/
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I use a regular banding wheel often when I spray, most often cover it prior with cardboard or often with a small plastic bag over just the head and then set a piece of cardboard. It’s never motorized though, I need to hand spin it for control while hand spraying. I use my medium height banding wheel often. Whatever your final cover is it needs to be absorbent with minimal puddling and stiff enough to resist the air from the sprayer. When I am lazy I’ll just take a low height banding wheel and neatly cover and tuck in newspaper. All result in hand control (which I need) and minimal cleanup at the end of the day.
With this setup I hand spray with regular HVLP spray gun (glaze), touch up gun (glaze) and even airbrush (underglaze)
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Yes, mostly ought to be fine. One color can influence another a bit I suppose on occasion but folks use liner glazes different than their exterior glaze all the time. Folks often dip their tiles … 3 second, 5 second dip …. 1 coat, 2 coats. So using test tiles and brush applying each side has its drawbacks.
With respect to glazing the outside and not the inside or Vice versa this can create an unbalanced stress in the clay as the glaze often squeezes the clay so to speak. This tiny bit of compression can increase the strength of the ware significantly. So one side glazed and the other not can cause unequal stress in the ware. End result - more fragile ware occasionally breaking suddenly when someone puts hot coffee in a cold mug for instance. Fully glazed well matched - glaze and clay- generally enhances the durability of the ware.
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3 hours ago, MLSrunner said:
have been searching my house endlessly ( 4 years now) looking for mold as I have high levels of both Ochratoxin A and Mycophenolic Acid. Our entire house has been torn up. My office is empty right now and we have torn out a wall to look inside....... and yet no sign of mold or water damage. I have been banging my head against the "literal" wall trying to figure this out and then it suddenly occurred to me that I have an issue in my office and in my bedroom. Both of those rooms have clay on the walls!!!! I have the HLA gene, the MTHFR gene and even the last gene that makes me one of the most sensitive to mold. It is a real thing.
These seem to be very specific compounds / derivations of mold. Have you considered real mold testing and counts and characterization of mold present in your environment along with indoor air quality measurements. It might quantify and explain this as well as your doctors and hygienist may be able to suggest air filtration as a staple for you regardless of the origination. Most mold originates in the outside environment and then just finds ideal conditions for growth. Testing could reveal your area and environment are conducive to its growth providing some path to minimizing your exposure. Medical grade hepa very likely traps 99% of the spores so this could possibly be something that would help clay or no clay. Mycotoxins may be too small to filter but filtering mold could reduce the potential of specific molds that produce mycotoxins.
Anyway, this seems that real certified testing could help point you in a clearer direction than just searching for an origin. Understanding the origin (likely outdoors) and ways to modify your indoor environment (humidity, temperature, filtration) maybe could provide a path to reduction. Understanding if your current outdoor environment is high in these spore counts may also provide another strategy towards minimizing infiltration. My opinion, real air born testing inside and outside your home by a certified hygienist and real lab analysis could provide quantifiable help with your situation.
I would measure first and foremost before demolition. Demolishing things can lead to spreading mold around. Most mold remediation is done carefully so as not to spread, then everything is cleaned, hepa vacuumed and new samples and swabs taken before clearing the area.
questions about UMF
in Clay and Glaze Chemistry
Posted · Edited by Bill Kielb
Stulls graph does not show melting point in cones