Porcelain - Electric Mid&Hi Fired Ceramics2024-03-29T11:29:17Zhttps://cone6pots.ning.com/forum/topics/porcelain-1?commentId=2103784%3AComment%3A124989&feed=yes&xn_auth=noThank you guys for your help,…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1250002015-09-05T20:48:09.528ZRobert spicerhttps://cone6pots.ning.com/profile/Robertspicer
<p>Thank you guys for your help, I have much to learn and your wisdom is greatly appreciated.</p>
<p><br></br> <br></br> <cite>Norm Stuart said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/porcelain-1#2103784Comment124997"><div><div class="xg_user_generated"><p>Joseph - It's true that the the COE of commercial clays tend to increase as the maturity cone declines. This is an artifact of cost control as sodium and potassium are the least costly way to reduce the cone…</p>
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<p>Thank you guys for your help, I have much to learn and your wisdom is greatly appreciated.</p>
<p><br/> <br/> <cite>Norm Stuart said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/porcelain-1#2103784Comment124997"><div><div class="xg_user_generated"><p>Joseph - It's true that the the COE of commercial clays tend to increase as the maturity cone declines. This is an artifact of cost control as sodium and potassium are the least costly way to reduce the cone maturity.</p>
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<p>Using lithium as a flux, you can make extremely low COE Cone 6 "flameware clay" - far lower than the COE of any Cone 10 clay. Flameware is a clay body which can be heated over the burner on a stove because the difference in expansion between the hot parts of the ware and the cold part is not enough to fracture to pot. Flameware requires an engobe as most glaze can't withstand thermal shock.</p>
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<p>Boron, a flux in Cone 6 and Cone 06 glaze, does not increase COE and also helps glaze and clay bodies with a COE mismatch fit properly. Ceramic research papers show that boron allows the glaze to have one structure where it meets the clay body and a different structure further from the clay body. This could be a reason Cone 6 and Cone 06 glazes fit Cone 10 clays with very low COEs. </p>
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<p>But this doesn't explain Cone 10 glazes without boron and seeming excessive COE mismatches working out well, <strong>which leaves me wondering when does a COE mismatch create problems?</strong> It's seemingly more than just the numbers alone. Perhaps glaze strength is the missing factor.<strong><br/></strong></p>
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<p>One example is Pete Pinnell's Cone 10 Weathered Bronze Green with a <strong>COE of 8.7</strong> which seems a bad match for a Cone 10 clay with a <strong>COE of 3.46</strong> like Laguna 373 Dark Brown yet the glaze fits well.</p>
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<p>One of Pete's students discovered this glaze is wide-firing enough to also work at Cone 6, though I find it's more reliable at Cone 6 after adding 20% Ferro Frit 3269 (shown below). So it's become a popular Cone 6 glaze as well.</p>
<p><a target="_self" href="http://storage.ning.com/topology/rest/1.0/file/get/3127175811?profile=original"><img class="align-left" src="http://storage.ning.com/topology/rest/1.0/file/get/3127175811?profile=original" width="432"/></a></p>
<p><a target="_self" href="http://storage.ning.com/topology/rest/1.0/file/get/3127175963?profile=original"><img width="721" class="align-left" src="http://storage.ning.com/topology/rest/1.0/file/get/3127175963?profile=RESIZE_1024x1024" width="721"/></a></p>
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<p></p> Joseph - It's true that the t…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1249972015-09-05T05:39:58.100ZNorm Stuarthttps://cone6pots.ning.com/profile/NormStuart
<p>Joseph - It's true that the the COE of commercial clays tend to increase as the maturity cone declines. This is an artifact of cost control as sodium and potassium are the least costly way to reduce the cone maturity.</p>
<p></p>
<p>Using lithium as a flux, you can make extremely low COE Cone 6 "flameware clay" - far lower than the COE of any Cone 10 clay. Flameware is a clay body which can be heated over the burner on a stove because the difference in expansion between the hot parts of the…</p>
<p>Joseph - It's true that the the COE of commercial clays tend to increase as the maturity cone declines. This is an artifact of cost control as sodium and potassium are the least costly way to reduce the cone maturity.</p>
<p></p>
<p>Using lithium as a flux, you can make extremely low COE Cone 6 "flameware clay" - far lower than the COE of any Cone 10 clay. Flameware is a clay body which can be heated over the burner on a stove because the difference in expansion between the hot parts of the ware and the cold part is not enough to fracture to pot. Flameware requires an engobe as most glaze can't withstand thermal shock.</p>
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<p>Boron, a flux in Cone 6 and Cone 06 glaze, does not increase COE and also helps glaze and clay bodies with a COE mismatch fit properly. Ceramic research papers show that boron allows the glaze to have one structure where it meets the clay body and a different structure further from the clay body. This could be a reason Cone 6 and Cone 06 glazes fit Cone 10 clays with very low COEs. </p>
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<p>But this doesn't explain Cone 10 glazes without boron and seeming excessive COE mismatches working out well, <strong>which leaves me wondering when does a COE mismatch create problems?</strong> It's seemingly more than just the numbers alone. Perhaps glaze strength is the missing factor.<strong><br/></strong></p>
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<p>One example is Pete Pinnell's Cone 10 Weathered Bronze Green with a <strong>COE of 8.7</strong> which seems a bad match for a Cone 10 clay with a <strong>COE of 3.46</strong> like Laguna 373 Dark Brown yet the glaze fits well.</p>
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<p>One of Pete's students discovered this glaze is wide-firing enough to also work at Cone 6, though I find it's more reliable at Cone 6 after adding 20% Ferro Frit 3269 (shown below). So it's become a popular Cone 6 glaze as well.</p>
<p><a target="_self" href="http://storage.ning.com/topology/rest/1.0/file/get/3127175811?profile=original"><img class="align-left" src="http://storage.ning.com/topology/rest/1.0/file/get/3127175811?profile=original" width="432"/></a></p>
<p><a target="_self" href="http://storage.ning.com/topology/rest/1.0/file/get/3127175963?profile=original"><img width="721" class="align-left" src="http://storage.ning.com/topology/rest/1.0/file/get/3127175963?profile=RESIZE_1024x1024" width="721"/></a></p> Although the COE of Cone 10 c…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1247182015-09-05T01:53:37.864ZJoseph Firebornhttps://cone6pots.ning.com/profile/JosephRosenblatt
<blockquote><p>Although the COE of Cone 10 clays fall in the same range as Cone 6 clays, we experienced a unique problem firing Cone 10 white clays to Cone 6. The clay remains so porous at Cone 6 that many glazes run through the body of the clay like a sponge, leaving a pool of glaze at the base and pin-holing on the rest of the ware. Not terrific.</p>
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<p>Learn something every day. Thanks Norm. I didn't understand this accurately. </p>
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<p>I think your best result…</p>
<blockquote><p>Although the COE of Cone 10 clays fall in the same range as Cone 6 clays, we experienced a unique problem firing Cone 10 white clays to Cone 6. The clay remains so porous at Cone 6 that many glazes run through the body of the clay like a sponge, leaving a pool of glaze at the base and pin-holing on the rest of the ware. Not terrific.</p>
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<p>Learn something every day. Thanks Norm. I didn't understand this accurately. </p>
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<p>I think your best result is going to be to find a nice white body stoneware, find a ^5-7 porcelain, or fire to ^5.5-6. Which of those you choose is up to you. I would pick which ever is the best for you. If your like the p5, learn to fire cooler but still very close to cone 6. There isn't huge functional absorbtion rate difference in p5 between ^4 and ^6. At ^4 its 3.3, and at ^6 its <1.</p>
<p>So if your firing at like ^5 your going to be somewhere in between, which is plenty good for a functional pot. There are a lot of stonewares that are marked as cone 6 but have absorption rates of around 2.5-2.75. </p>
<p>If your firing p5 to cone 5-5.5 I think you will be absolutely fine. Ideally you want the least absorption possible, which is why I was using p5. I wanted that <1 absorption rate so that I could use my pots in the microwave.</p>
<p>If you start getting above 5% absorption rates I wouldn't label them as microwave safe because they are gonna get hot quick over the lifetime of their use.</p>
<p>I work with Red Rock which is also <1 at cone 6 for this very reason.</p>
<p>Good Luck.</p> As Joseph said, firing a Cone…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1247172015-09-05T01:46:38.517ZNorm Stuarthttps://cone6pots.ning.com/profile/NormStuart
<p>As Joseph said, firing a Cone 6 porcelain clay to Cone 5 leaves it not fully vitrified, so eliminates the warpage. </p>
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<p>Firing Cone 10 porcelain to Cone 5 isn't even slightly densified or vitrified. Better to simply use a white Cone 5 Stoneware. The concept of porcelain is it densifies so fully it essentially becomes glass, so firing to exactly the right cone is essential as molten glass is very plastic.</p>
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<p>Although the COE of Cone 10 clays fall in the same range as…</p>
<p>As Joseph said, firing a Cone 6 porcelain clay to Cone 5 leaves it not fully vitrified, so eliminates the warpage. </p>
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<p>Firing Cone 10 porcelain to Cone 5 isn't even slightly densified or vitrified. Better to simply use a white Cone 5 Stoneware. The concept of porcelain is it densifies so fully it essentially becomes glass, so firing to exactly the right cone is essential as molten glass is very plastic.</p>
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<p>Although the COE of Cone 10 clays fall in the same range as Cone 6 clays, we experienced a unique glaze problem firing Cone 10 white clays to Cone 6. The clay remains so porous at Cone 6 that many glazes run through the body of the clay like a sponge, leaving a pool of glaze at the base and pin-holing on the rest of the ware. Not at all terrific.</p>
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<p>As a result, we sometimes purchase high-iron Cone 10 clays like Amador which densify better at Cone 10, but the Cone 10 White clay I purchase is Laguna's Max's Paper Clay.</p>
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<p>Laguna's Orlando branch sells Sybil's Cone 6 paper clay, which I'd prefer to buy, but this would involve shipping cost from Florida. So I simply dip bisqued paper clay sculptures in a solution of potassium carbonate and lithium carbonate and leave them to dry before glazing to achieve a Cone 6 densification with a Cone 10 paper clay. This adds the extra flux the Cone 10 paper clay is missing to densify at Cone 6.</p>
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<p></p> What Norm said is how I feel…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1249962015-09-05T01:40:02.745ZJoseph Firebornhttps://cone6pots.ning.com/profile/JosephRosenblatt
<p>What Norm said is how I feel about it all. I have never fired an older kiln without a digital controller. I have only been doing this for 1.5 years, but I spend 5-6 hours a day doing this stuff, reading, advancing, updating everything. </p>
<p>When I was over firing I did what Norm did. I added a cone offset. Eventually I ended up using my own temps, then I built my own schedule, which I have tweaked and continue tweaking every firing. I also slow cool, not to form crystals, but to keep my…</p>
<p>What Norm said is how I feel about it all. I have never fired an older kiln without a digital controller. I have only been doing this for 1.5 years, but I spend 5-6 hours a day doing this stuff, reading, advancing, updating everything. </p>
<p>When I was over firing I did what Norm did. I added a cone offset. Eventually I ended up using my own temps, then I built my own schedule, which I have tweaked and continue tweaking every firing. I also slow cool, not to form crystals, but to keep my glazes looking the same no matter how full or empty the load is. My current schedule is 14.5 hours for a cone 6 glaze firing and slow cool.</p>
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<p>My glazes look fantastic though, and I can advance and improve them with each firing because I have removed the randomness of cooling depending on load volume.</p>
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<p>If you're serious about firing electric, get a digital controller. I mean it can be done without it, I know many people who don't have digital kilns, but you're going to have to worry about things like, not over firing, however when you have a digital controller and TC's you just fire, your worries are about glazes, form, improvement and testing. Not the kiln, which is how it should be when your doing electric.</p>
<p></p> If you're willing to eventual…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1248092015-09-05T01:20:36.798ZNorm Stuarthttps://cone6pots.ning.com/profile/NormStuart
<p>If you're willing to eventually invest the money, you'll never regret replacing witness cones and a kiln-sitter with a digital controller.</p>
<p><a href="http://www.clay-king.com/kilns/kiln_parts/kiln_controllers.html" rel="nofollow" target="_blank">http://www.clay-king.com/kilns/kiln_parts/kiln_controllers.html</a></p>
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<p>Before we began down-firing with a six-hour slow-cool, I had reprogrammed the pre-programed ^5 Cone Fire program to fire to a ^5.5 using the "Cone Offset" option…</p>
<p>If you're willing to eventually invest the money, you'll never regret replacing witness cones and a kiln-sitter with a digital controller.</p>
<p><a rel="nofollow" href="http://www.clay-king.com/kilns/kiln_parts/kiln_controllers.html" target="_blank">http://www.clay-king.com/kilns/kiln_parts/kiln_controllers.html</a></p>
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<p>Before we began down-firing with a six-hour slow-cool, I had reprogrammed the pre-programed ^5 Cone Fire program to fire to a ^5.5 using the "Cone Offset" option to add 32 degrees F to the target temperature.</p>
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<p>The controller actually fires accurate cones with an accumulation of area under the curve, recording the temperature every few seconds. Digital controllers make firing a kiln no harder (or easier) than using a microwave oven.</p>
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<p>When we made the change I initially validated firings with several witness cones at ^016, ^06, ^04, ^5 and ^6 to discover any quirks, then again as the kiln aged. With perfect cones every time, you can focus on the other variables - of which there are many, and frankly you lose interest in repeatedly identical witness cones.</p>
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<p>Digital controllers also add easy down-firing (slow-cooling), and candling (pre-heating) for 0 to 6 hours or more and costs virtually nothing yet can eliminate a lot of problems.</p>
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<p>We have a Cress modified <strong>Bartlett V6-CF</strong> which sells for $430 and directly replaces a Kiln Sitter. We've been very happy with it over the past five years - and our kiln is outdoors with merely a stainless steel sheet screwed onto to the lid to protect the electronics.</p>
<p><img src="http://www.clay-king.com/images/electro_sitter.jpg" alt="Bartlett Electro Sitter" height="293" border="0" width="588"/></p>
<p>The Clay King website sells the Olympic versions of the Bartlett controllers, down at the bottom of the webpage.</p>
<p><a rel="nofollow" href="http://www.clay-king.com/kilns/olympic_kilns/electro_sitter.html" target="_blank">http://www.clay-king.com/kilns/olympic_kilns/electro_sitter.html</a></p>
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<p>When the $35 nickel-chrome Type-K thermocouple needed replacement after a few hundred firings, we replaced it with a $125 platinum Type-S thermocouple. The Type-K loses accuracy as it ages and has a much shorter life-span but, from my n=1 experience, not so much that you notice a difference in witness cones. The change-over required switching the Thermocouple Type in a hidden menu, about ten buttons to push in total.</p>
<p><a target="_self" href="http://storage.ning.com/topology/rest/1.0/file/get/1605081749?profile=original"><img width="721" class="align-left" src="http://storage.ning.com/topology/rest/1.0/file/get/1605081749?profile=RESIZE_1024x1024" width="721"/></a></p> Yes, you would have to find g…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1248082015-09-05T01:13:00.975ZJoseph Firebornhttps://cone6pots.ning.com/profile/JosephRosenblatt
<p>Yes, you would have to find glazes that fit cone 10 clay, but melt right at cone 6. This would be very difficult.</p>
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<p>Read: <a href="http://digitalfire.com/4sight/education/the_effect_of_glaze_fit_on_fired_ware_strength_202.html?logout=yes" target="_blank">http://digitalfire.com/4sight/education/the_effect_of_glaze_fit_on_fired_ware_strength_202.html?logout=yes</a></p>
<p>and: …</p>
<p>Yes, you would have to find glazes that fit cone 10 clay, but melt right at cone 6. This would be very difficult.</p>
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<p>Read: <a href="http://digitalfire.com/4sight/education/the_effect_of_glaze_fit_on_fired_ware_strength_202.html?logout=yes" target="_blank">http://digitalfire.com/4sight/education/the_effect_of_glaze_fit_on_fired_ware_strength_202.html?logout=yes</a></p>
<p>and: <a href="http://digitalfire.com/4sight/education/understanding_thermal_expansion_in_ceramic_glazes_198.html" target="_blank">http://digitalfire.com/4sight/education/understanding_thermal_expansion_in_ceramic_glazes_198.html</a></p>
<p>and: <a href="http://digitalfire.com/4sight/glossary/glossary_glaze_fit.html" target="_blank">http://digitalfire.com/4sight/glossary/glossary_glaze_fit.html</a></p>
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<p>Also, if your making anything functional, it won't be vitrified. If your going to move up to avoid warping, you would be best to go to something that has a cone 7 top end. Something like 5-7 range. </p>
<p>What type of kiln do you have? Do you have a digital controller? If so you should be able to fire to cone 6 pretty easy with a good series of test with pyrometric cones.</p>
<p></p> Would their be a downside to…tag:cone6pots.ning.com,2015-09-05:2103784:Comment:1249942015-09-05T01:09:57.817ZRobert spicerhttps://cone6pots.ning.com/profile/Robertspicer
Would their be a downside to using a cone 10 porcelain and firing it to cone 6
Would their be a downside to using a cone 10 porcelain and firing it to cone 6 It would help, but it would a…tag:cone6pots.ning.com,2015-09-04:2103784:Comment:1249892015-09-04T23:22:53.879ZJoseph Firebornhttps://cone6pots.ning.com/profile/JosephRosenblatt
<p>It would help, but it would also increase the absorption rate. The best thing would to be to find a nice place in the middle of Cone 5 and Cone 6. Something like 5.5 or as close to 6 as you can get without going over. It would take some testing.</p>
<p>Remember what Norm said, certain forms are always going to warp more in porcelain than in stoneware. It is just the nature of the beast. You can increase the strength of pots by adding structure to them. Like a rim, or a rolled rim, or say…</p>
<p>It would help, but it would also increase the absorption rate. The best thing would to be to find a nice place in the middle of Cone 5 and Cone 6. Something like 5.5 or as close to 6 as you can get without going over. It would take some testing.</p>
<p>Remember what Norm said, certain forms are always going to warp more in porcelain than in stoneware. It is just the nature of the beast. You can increase the strength of pots by adding structure to them. Like a rim, or a rolled rim, or say pinching 3 corners into the rim. etc etc, anything that adds structure to the pot will help to prevent warping.</p>
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<p></p> Joseph Rosenblatt said:P5 w…tag:cone6pots.ning.com,2015-09-04:2103784:Comment:1247122015-09-04T22:34:36.659ZRobert spicerhttps://cone6pots.ning.com/profile/Robertspicer
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<cite>Joseph Rosenblatt said:</cite><blockquote cite="http://cone6pots.ning.com/forum/topics/porcelain-1?commentId=2103784%3AComment%3A124884&xg_source=msg_com_forum#2103784Comment124802"><div><div class="xg_user_generated"><p>P5 warps very easy if fired over cone 6 even slightly. When I was using P5 if my self supporting cone tips were touching the shelf the P5 would warp. If they were perfectly bent to cone 6, meaning the tip is bent to the base, then they wouldn't be warped.…</p>
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<cite>Joseph Rosenblatt said:</cite><blockquote cite="http://cone6pots.ning.com/forum/topics/porcelain-1?commentId=2103784%3AComment%3A124884&xg_source=msg_com_forum#2103784Comment124802"><div><div class="xg_user_generated"><p>P5 warps very easy if fired over cone 6 even slightly. When I was using P5 if my self supporting cone tips were touching the shelf the P5 would warp. If they were perfectly bent to cone 6, meaning the tip is bent to the base, then they wouldn't be warped. A cone tip touching the shelf or almost touching it is only a few degrees higher than cone 6. </p>
<p>I eventually quit working with P5 because I disliked it because of this reason. The clay body throws fantastic and drys very well for a porcelain, but the warping was so annoying. I also had a lot of glaze fit issues as well on that clay. I much prefer Frost by Laguna, although it has its problems as well, but it is much more resilient to warping and glazes fit a lot better, or at least the ones I use do.</p>
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You are right, the P5 throws beautifully. I really enjoyed working with it on the wheel. Would firing to cone 5 be better for this clay body and produce less warping.