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justin1287

bypassing the bisque step?

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OffCenter    82

also, what would happen if one was to make clay from powder, and add glaze materials to it, and water, then just fire it?

 

 

You'd probably make a mess. But, it is worth doing. Just go slow and easy with incremental additions of dry glaze to the clay and, obviously, protect your kiln and shelves from the experiment. I've tried adding powered glass and dry glazes to porcelain slip several times and so far have not been happy with the results.

 

Jim

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Marcia Selsor    1,301

also, what would happen if one was to make clay from powder, and add glaze materials to it, and water, then just fire it?

 

I agree with Chris in that it would be similar to using Egyptian paste. And I agree with Jim, you could end up with a big mess. Egyptian paste has salts in it that migrate to the surface and glaze the surface when fired at a low temperature.

 

Marcia

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JLowes    28

Taking the topic "bypassing the bisque step", you could single fire the work. Make the pot, let it dry, glaze it, fire it slow like bisque, but let it continue to maturing temperature.

 

Google "Steven Hill pottery" in the images tab, that will bring up plenty of examples of single fired work. That is his method as he thinks the bisque stage loses the momentum of the creative process. I have done this a few times, but did not find it something I wanted to do all the time. A bit of research will give you ideas on how to do it.

 

John

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justin1287    1

Cool....thanks everyone. I think this will help me figure out some ideas......i cant really find the egyptian paste anywhere, but think that single firing may be the way to go for me. I'm thinking about switching to porcelain, and saw a comment on the web that said single firing works well on it. I throw a small product that takes me 30-60 seconds to make, so if i have a small failure rate, it wont be a big deal.

 

I'm thinking i may have to start making my own glaze for single firing though to get a proper fit.

 

one more thing.....is egyptian paste pugged into clay?

 

I watched a "how its made" episode on youtube about making toilets, and they skipped the bisque, so that is how i got the idea. Never touched clay til 8 months ago, so I'm learning everyday!

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justin1287    1

ps....i own an old skutt 818 kilnsitter kiln

 

low for 2 hours up to 500 degrees

2 for 2 hours up to 800 degrees

4 for 2 hours up to 1300 degrees

6.5 until done for a bisque, and high until done for a fire

 

i just follow the instructions on it....is this still the current schedule that people use for a 2.6 cubic foot kiln?

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OffCenter    82

Cool....thanks everyone. I think this will help me figure out some ideas......i cant really find the egyptian paste anywhere, but think that single firing may be the way to go for me. I'm thinking about switching to porcelain, and saw a comment on the web that said single firing works well on it. I throw a small product that takes me 30-60 seconds to make, so if i have a small failure rate, it wont be a big deal.

 

I'm thinking i may have to start making my own glaze for single firing though to get a proper fit.

 

one more thing.....is egyptian paste pugged into clay?

 

I watched a "how its made" episode on youtube about making toilets, and they skipped the bisque, so that is how i got the idea. Never touched clay til 8 months ago, so I'm learning everyday!

 

 

Egyptian paste isn't something you pug into clay. Just google it and you'll find out more than you want to know about it.

 

Jim

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OffCenter    82

ps....i own an old skutt 818 kilnsitter kiln

 

low for 2 hours up to 500 degrees

2 for 2 hours up to 800 degrees

4 for 2 hours up to 1300 degrees

6.5 until done for a bisque, and high until done for a fire

 

i just follow the instructions on it....is this still the current schedule that people use for a 2.6 cubic foot kiln?

 

 

Bisque and Firing schedules are up to you. Your kiln is small so it should be no big deal to test to get a faster bisque which will save you time and money. For example, when bisque firing the biggest danger is taking the kiln from room temp to boiling point for water (~212 depending on altitude) so to be safe say 250 degrees F. There's still chem water in the clay after 250 but it's not much of a problem with small pieces and can pretty much be ignored. So with only a few small, thin pieces in kiln:

low to 250 or so

high to finish

 

If any pieces blow up (that you are sure were bone dry when loaded) then slow it down a bit.

 

So much of pottery is testing, testing, testing; not following directions, following directions, following directions.

 

Jim

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Chris Campbell    1,087

If you are making a small item in that little time, then you probably wont have much trouble with single firing it. Troubles come with the different tensions on complex objects, varying thicknesses of the walls and the need to glaze inner and outer surfaces.

Before you get into a complicated solution, look up a recipe for a glaze suitable for single firing, then apply glaze on dry clay, fire and see what happens. Protect your shelves by placing the tests on a bisqued tile or stilts so you don't give yourself the gift of a day of shelf grinding if the glaze runs.

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Lucille Oka    16

If you want to try out the Egyptian Paste, Amaco did have some on clearance due to it is being discontinued. I don't know if they have any more left but you can ask or go to the clearance page on their website and take a look. The colors were wonderful and authentic to the real Egyptian products. It was sold as a powder that you mixed with water.

 

The trick with the paste is your ware has to rest, while drying, on a non absorbent surface as the glaze develops around the piece. As it dries you do not disturb the salts that comes to the surface.

 

Egyptian paste is a hand building medium; throwing it is near to impossible. It is not very plastic and has a short modeling time before it begins to dry. Adding wet additions to the ware is almost impossible as well, but it is perfect for press molding small figurines just the way the Egyptians used it.

Be aware this product is not for food service. But you can make realistic Egyptian artifacts, jewelry, beads, cabochons, hangings, plaques, small bowls and Ushabtis. Be sure to kiln wash your shelves before firing.

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perkolator    54

also, what would happen if one was to make clay from powder, and add glaze materials to it, and water, then just fire it?

 

 

 

this can be done to a certain degree, but i'd strongly recommend you do a line blend to find the right combo and fire the test in a saggar or tray to contain the undesirables. our students do this every year as a test and some choose to explore it further.

 

if you're wanting to skip bisque and once-fire your work you can definitely do this. our studio fires 90% of our work this way. saves time and energy. doesn't work for everything, like thin stoneware pottery, but works GREAT for large-scale sculpture at earthenware to midrange temps.

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justin1287    1

Percolator, can you explain the types of glazes you use? I currently use coyote midfire glaze. Do i need to make my own glaze that a certain amount of clay in it? Can i just add 3% macaloid to my glaze? I'm having trouble finding all the info i need. A link would be much appreciated......thanks.

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perkolator    54

i can't really comment on the clay in the glaze, but most every glaze has some in it to make it stay put. you MAY have to tweak your glaze if you're once-firing, so do some tests. dunno about the macaloid in your glaze for anything other than keeping it in suspension in the bucket, perhaps someone who knows more glaze chem can give input here. if the issue is crazing or something, i'll usually tweak the silica content first. this is why sculpture is great - glaze flaw might be what you WANT since you don't need it to be food safe.

 

like i stated before, it doesn't work for everything. works great for us because we are a large-scale sculpture studio and not producing functional pottery like most people on this board. most of the time, we're firing at ^04 because we're in CA and don't have issues with outdoor sculptures being subjected to severe weather and because the 10wk quarter system goes by so quick and we need quick-ish turnaround. additionally, it's nerve racking enough to move a 100# sculpture to a kiln stack that's 70" tall - so doing it TWICE would give everyone gray hair! if we bisqued everything, we'd never get anything done in the time crunch! our technique works just fine at ^6 as well, but not for every glaze vs low-fire where we have hardly any issues. usually the issue is pinholing/bubbles from carbonaceous stuff trying to pass through a layer of glaze but it really depends on the glaze itself.

 

as for clay, we're using a house recipe that's a stoneware body with a good amount of grog in it - this is probably what helps the most in being able to once-fire large-scale sculpture. For glaze, we use dozens of different glazes (or whatever the students bring in/find online) and mix everything on a per-batch/piece basis and don't keep "studio glazes" around. glaze testing is pretty much the standard for determining whether or not it'll work. Personally, I test everything both bisk and once-fire as well as ox/red if I have time, and almost always on 4 surfaces (raw clay, white/red/black slip). I've used the Coyote glazes a few times when working at ^6 but usually mix my own glaze. Low-fire, usually it's Duncan/Amaco or similar commercial glaze. for functional pottery or something made from commercial clay i'll usually bisk it depending on how thin it is or what i'm doing. test test test!

 

i guess if i were to mention a few things about once-firing it would be: use porous/stoneware body, glaze when bone-dry and wait a day before moving your 100# sculpture or risk it falling apart on you, apply glaze slightly thicker than on a bisk piece to account for clay absorbing it slightly, dipping greenware is VERY hard so brush/spray it on, fire really slow (our stuff is thick and over 24" on average), test test test!

 

hope this helps, good luck!

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Avaviel    0

I've read that 8% bentonite added to the glaze can help with once-fired. I also remember something about glazes not running as much if once-fired.

 

Also, test test test! Do test tiles and test bowls and such. That way you can figure out what glazes work best, modified.

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TJR    359

I've read that 8% bentonite added to the glaze can help with once-fired. I also remember something about glazes not running as much if once-fired.

 

Also, test test test! Do test tiles and test bowls and such. That way you can figure out what glazes work best, modified.

 

 

Avaviel;

The reason once-fire glazes don't run, at all, is because they are basically slip glazes. They have up to 35% plastic clay in the form of ball clay. You can make a slip glaze by substituting ball clay for kaolin in the glaze. Some shiny glazes won't work, as they don't have enough clay content in them. The other great thing about slip glazes, is they don't settle out.

TJR.

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OffCenter    82

I've read that 8% bentonite added to the glaze can help with once-fired. I also remember something about glazes not running as much if once-fired.

 

Also, test test test! Do test tiles and test bowls and such. That way you can figure out what glazes work best, modified.

 

 

Avaviel;

The reason once-fire glazes don't run, at all, is because they are basically slip glazes. They have up to 35% plastic clay in the form of ball clay. You can make a slip glaze by substituting ball clay for kaolin in the glaze. Some shiny glazes won't work, as they don't have enough clay content in them. The other great thing about slip glazes, is they don't settle out.

TJR.

 

 

I disagree with that. While slip glazes do work well, so do other glazes. Probably the most famous potter who single-fires almost everything, Steven Hill, uses a palette of glazes that are not slip glazes.

 

Jim

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