penumbra
Imperial Masterpiece
It really is seldom the clays fault but clays can vary a lot on how they want to be treated. Each has its own learning curve.
Colorado’s Ceramics
- Thread starter Colorado
- Start date
sorce
Nonsense Rascal
Yes it is a high manganese clay….which at the time I didn’t realize was going to cause problems!
Is the “gassing” causing warping, do you think? Or just problems with the glaze? I don’t think I’m going to use that clay any more but I have quite a few pieces I’ve made with it that I might as well fire…
I’m going single fire on the unglazed!
Single for everything!
The gassing won't cause warping, but Standard recommends Cone 4 for the Mangy clay now, lower heat may minimize warping. But....whole load ..blah blah....
You may be able to use a soak at just under peak temp to let the bubbles heal back over.
Read digital fire.com all the answers are there!
Sorce
sorce
Nonsense Rascal
Too. Of firing length.
Even if you bisque forever .....
The glazes still want to go through their process slow as well. ...
I think a quick bisque and a long glaze fire is better. 16 plus hours.
Too ....
Invest in the upgraded elements upon replacement
Sorce
Even if you bisque forever .....
The glazes still want to go through their process slow as well. ...
I think a quick bisque and a long glaze fire is better. 16 plus hours.
Too ....
Invest in the upgraded elements upon replacement
Sorce
Colorado
Masterpiece
Thanks Sorce! I am going to try the single firing with glaze. Bisque is a pain in the ass! Especially with such a small kiln - can only do a couple pots at a time. Single fire would be much more efficient.
I am firing on the “slow” mode. So it takes about 12.5 hours to reach peak temp, and then about 12 hours to cool down. So definitely over 16 hours at high temps.
Kanorin
Omono
I'm digging your smooth transitions between body and feet - especially in that non equal-sided hex. To do that, are you adding feet. Or are you making a larger than needed base and then subtracting clay that is "not the feet." Do you know what I mean?
Colorado
Masterpiece
Thanks! I am adding the feet after I make the body of the pot. Then I run a rib over the seam until it is seamless. Hope this helps!
Wood
Chumono
What does the slow mode accomplish for you? My impression was that outside of an early candling hold, rate of temperature increase was more or less irrelevant. I'm mostly just gleaning stuff from listening to the For Flux Sake podcast, so I could be getting it wrong
Colorado
Masterpiece
No idea! I’m just doing it based on recommendations from the internet/other potters that slower is better. It’s just like barbecue, right?
I’ll have to check out the podcast!
Wood
Chumono
No idea! I’m just doing it based on recommendations from the internet/other potters that slower is better. It’s just like barbecue, right?
I’ll have to check out the podcast!
I think episode 25 is the one you want, but they're all a blur at this point: https://www.brickyardnetwork.org/forfluxsake/ep25 My takeaway impression was that the rate of increasing temperature was irrelevant until the last 100 deg (because that's relevant to the definition of a cone), but after reaching peak temperature, temperature holds or slow cooling matter to glaze chemistry/effects like crystallization. Candling to ensure that the clay body is dry is a different issue too
Easily could be wrong -- my firing knowledge is all theoretical because i'm just a community potter who's not on the kiln team
double edit: according to the notes, this episode apparently has tips on single-firing your work https://www.brickyardnetwork.org/forfluxsake/ep21
sorce
Nonsense Rascal
This is not the episode, but in one, he speaks about the different temperatures at which different things melt, etc....
The key is the crossover of these melting ranges.
The slower you go, the longer the crossover, allowing everything to interact how it's supposed to. Things that need flux get fluxed.
There isn't a period where a crossover isn't happening, so though holds may solve specific issues, EVERYTHING works better when the entire process is slow.
Sorce
On electric kilns the heat obviously comes from the elements on the outer edge. Heat can be transferred via convection and also radiation. At very high temperatures in an electric kiln the primary heat transfer is radiation from the elements and radiation from pot to pot. So the pot needs line of site to the elements. There is also convection but this is less in an electric kiln, it helps if you have a vent. What this means is the bottom and middle of your pot may fire a half cone or a full cone lower than the outer edges closer to the elements. The dynamic differential can cause warping especially on 20"+ pots. If you soak a long time this improves. if you fire slowly this also improves.
If you are firing smallish things its not a big deal and you can fire medium or fast.
In a (down draft) gas kiln the chamber is like a pressure vessel and there is a lot of convection. It fires much more evenly. So I bisque in gas now, stopped using my electric kiln entirely, and I crack big pots in bisque a lot less.
If you are firing smallish things its not a big deal and you can fire medium or fast.
In a (down draft) gas kiln the chamber is like a pressure vessel and there is a lot of convection. It fires much more evenly. So I bisque in gas now, stopped using my electric kiln entirely, and I crack big pots in bisque a lot less.
Colorado
Masterpiece
Thanks so much for weighing in, Nao! Really appreciate your input. Had no idea about the temp differential between edges/center, but makes sense.
I have a vent on order, should be here soon, so maybe that will help a little bit! Although seems that using a different clay body has basically resolved my warping problems.
I couldn’t help but notice you said you crack pots “less” not “never” ….it is reassuring to know that even the best get cracks sometimes
I will say below ~16" my failure rate is near zero, but the failures increase exponentially above ~20". I just visited Gyozan a couple weeks ago. I am happy to report he has many cracked pots, right down the middle as @mwar15 was sufferingThanks so much for weighing in, Nao! Really appreciate your input. Had no idea about the temp differential between edges/center, but makes sense.
I have a vent on order, should be here soon, so maybe that will help a little bit! Although seems that using a different clay body has basically resolved my warping problems.
I couldn’t help but notice you said you crack pots “less” not “never” ….it is reassuring to know that even the best get cracks sometimes
Colorado
Masterpiece
Gyozan….what an honor! I have watched all the YouTube material I can find featuring Gyozan but to visit in person must have been a dream.
My kiln is only 18” opening, so it will be a few years until I can upgrade to a larger kiln to have to worry about cracking 20” pots
My kiln is only 18” opening, so it will be a few years until I can upgrade to a larger kiln to have to worry about cracking 20” pots
Colorado
Masterpiece
Couple of unglazed hexes - no firing cracks!
Larger one is about 15” x 5”
Smaller one is about 10” x 2”
Larger one is about 15” x 5”
Smaller one is about 10” x 2”
Colorado
Masterpiece
15” glazed oval
The glaze came out kind of a mottled blue/green/grey with dark specks. Definitely unconventional but I like it!
The glaze came out kind of a mottled blue/green/grey with dark specks. Definitely unconventional but I like it!
HorseloverFat
Squarepants with Conkers
Colorado
Masterpiece
LOVE IT!
Thanks for the feedback! I wasn’t sure how people would feel about this one. Personally, it brings me joy to look at it!
Colorado
Masterpiece
Still can’t figure out the cream glaze. Tried it on a different clay body and I didn’t get a bunch of bubbles this time, but it still doesn’t look good. I think maybe it was too thin on the application? I did 4 coats of glaze but I guess it just needs more. Maybe next time I’ll also try firing it to cone 6 instead of cone 5.
HorseloverFat
Squarepants with Conkers
1st off.. you are right, that is a little thin, but not remarkable so.
2ndly... it Looks a tad like it never "matured"...
Appears to need to be "held" a bit higher, like at Cone 6 if THIS was cone 5
So I think YOUR thinking, dually, is on the right tracks.
