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Carrick

Porcelain

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Hello fellow potters , 

could I have some advice regarding firing and glazing porcelain please .

I plan to bisque to 04 then fire to cone 6 . This is max my kiln will do .

my  question is what glaze can I use on the  porcelain bisque ware ? 

Can I use earthenware or stoneware glaze ?

This is the first time I’ve used porcelain and would love to make some bowls and jewellery.

hopefully someone can help me .

 

 

 

 

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Use a glaze which fires to the temperature range you plan on firing to! Ive often heard folks describe a "stoneware firing" as a synonym for a cone 10 firing. I dont think the former accurately describes the process enough; stoneware clays can be made to be fired from low fire to high fire; stoneware more describes a mixture of clays and a certain set of characteristics, just as porcelain, or earthenwares, it does NOT specify temperature range. Historically it may have been a little more synonymous to say that stoneware/porcelain firings meant cone 10, but nowadays I dont think that should be used.

If the glaze is designed to fire at cone 5/6, and your porcelain is as well, then you should have no problems. Commercial glazes should have a temp range listed on the containter somewhere.  If you are finding recipes from another source(print, online, magazines...), they almost always will list a temp range, and if they dont, with some experience you can usually tell what temp the glaze is designed to fire at, based on the feldspars/fluxes, the amounts of them, and the other materials in the formula.

Porcelains are whiter clay bodies, and will produce more vibrant colors out of the same glaze as compared to being fired on earthen/stoneware.

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It should also be noted, that the max temperature of a kiln, is generally not the temperature you want to fire it to.  The kiln will reach that temp, no doubt, but you will burn through elements quickly that way.  If you want to fire to cone 6, you'd want a kiln rated to cone 8. 

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31 minutes ago, Benzine said:

It should also be noted, that the max temperature of a kiln, is generally not the temperature you want to fire it to.  The kiln will reach that temp, no doubt, but you will burn through elements quickly that way.  If you want to fire to cone 6, you'd want a kiln rated to cone 8. 

Or even ^10. I had a ^6 kiln which was a very old and used kiln...I ultimately wound up selling it to a man who wanted something that fired to ^04. When I sold it, I told him it wouldn't fire higher than ^1. He was happy with that. I replaced the old kiln with a lot newer, but used ^10 kiln which will never see temps past ^6...

Welcome to the Forum, Carrick!

JohnnyK

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If your kiln maxes out at cone 6, it will only get to cone 6 if your elements are in perfect condition. Once they start to wear, they won't have the power to reach cone 6, and you'll have to replace them. That means you'll be replacing elements 2-3 times as often as if you had a kiln that could go to cone 10.  The general rule is that you want to be firing at least 2 cones lower than the max of the kiln if you want optimum element life. Even then, element life will be a bit lower than one that's rated for 4 cones higher than what you fire to.

As long as your clay and glaze are rated to mature at the same cone, you're good.

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carrick, what is your background in working with ceramic materials?   it sounds as though you may be working alone with no instructor.   you would probably benefit from visiting your local library and reading some of the very good textbooks that are available.

 

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I use porcelain quite often.  For pots and for buttons, ornaments, jewelry.  It behaves well.  As was pointed out, simply make certain your glaze temp matches the maturity of the clay. 

Good luck!

Roberta

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1 hour ago, Carrick said:

Thank you  all for great advice .

hi old Lady , I actually pot with a group but no one uses porcelain clay .

 I will let you know how I go . Thanks again 

Most of of my work is porcelain, just a preference. Throws slightly different, smooth, no grog, maybe slightly less elastic, more shrinkage.  But the thing I wanted to mention? Glaze fit! Porcelain is generally a lower expansion fired body than others so test your glazes first if possible to make sure they do not craze on your porcelain in addition to everything else that has been mentioned.

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I fire porcelain to cone 5 with commercial cone 5 glazes-jewelry, tea light holders-other "smalls".  I get great results with commercial glazes such as from Amoco, Coyote, Spectrum, Laguna--same with porcelain clay, sticking with the known suppliers and reading all the details. You can call supplies and ask for recommendations re: glaze fit, once you know which clay body you will be using-they can save you some grief up front. There are a number of cone 5 porcelains available from the major suppliers. It's not that much lower than your kiln max, but maybe it'll help until you can get a better kiln.  

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5 hours ago, Bill Kielb said:

Most of of my work is porcelain, just a preference. Throws slightly different, smooth, no grog, maybe slightly less elastic, more shrinkage.  But the thing I wanted to mention? Glaze fit! Porcelain is generally a lower expansion fired body than others so test your glazes first if possible to make sure they do not craze on your porcelain in addition to everything else that has been mentioned.

Warps easier, more finicky about even thickness, harder to go bigger, collapses at a different point.  These are my additions to your list of differences between stoneware and porcelain from someone who has been testing the waters recently.  Less of a difference between say, b-mix and porcelain than there is between my grogged iron stoneware and porcelain, but it's still pretty obvious.

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@liambesaw

I actually prefer it to others now but realize there is a difference. I have little desire to throw  other claybodies and prefer the touch feel and shapability. I think it is an acquired taste and notice some folks get hooked on it and others dislike it.

 I have thrown or tried to throw many others though including stoneware, high iron claybodies, flameware and my claim to fame a successful micaceous clay bowl. Micaceous  clay is not really something anyone should try throwing and the exfoliation is significant. Other than that, trying to throwing a stiff mixture of zirconium  silicate  and clay as I recall was probably the biggest disaster I can think of. Sort of like rubberized Jello that never dries out.

Still stuck on Porcelain, so I think I am hooked.

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7 hours ago, LeeU said:

I fire porcelain to cone 5 with commercial cone 5 glazes-jewelry, tea light holders-other "smalls".  I get great results with commercial glazes such as from Amoco, Coyote, Spectrum, Laguna--same with porcelain clay, sticking with the known suppliers and reading all the details. You can call supplies and ask for recommendations re: glaze fit, once you know which clay body you will be using-they can save you some grief up front. There are a number of cone 5 porcelains available from the major suppliers. It's not that much lower than your kiln max, but maybe it'll help until you can get a better kiln.  

Thanks so much , your advice is greatly appreciated.. got a bisque fire test going as we speak  04 . I’ll let you know what happens .

looking at purchasing another kiln .

cheers Susie 

 

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