Something Exploded in the Kiln - Was It Clay fatigue? - Electric Mid&Hi Fired Ceramics2024-03-30T08:08:24Zhttps://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87871&feed=yes&xn_auth=noThanks. Neil Estrick said:
T…tag:cone6pots.ning.com,2013-08-26:2103784:Comment:880702013-08-26T14:59:43.827ZMeredith Walkerhttps://cone6pots.ning.com/profile/MeredithWalker
<p>Thanks.<br></br> <br></br> <cite>Neil Estrick said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87980&xg_source=msg_com_forum#2103784Comment87980"><div><div class="xg_user_generated"><p>That Dogwood article is interesting. I think just opposite is actually true in regards to salt migration during fast drying. The <em><strong>slower</strong></em> it dries, the more likely you are to get salt migrating to the surface. We see this…</p>
</div>
</div>
</blockquote>
<p>Thanks.<br/> <br/> <cite>Neil Estrick said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87980&xg_source=msg_com_forum#2103784Comment87980"><div><div class="xg_user_generated"><p>That Dogwood article is interesting. I think just opposite is actually true in regards to salt migration during fast drying. The <em><strong>slower</strong></em> it dries, the more likely you are to get salt migrating to the surface. We see this in carbon trap Shino glazes that have soda ash in them. If you want the slat to migrate to the surface for optimal carbon trapping, you have to dry them slowly, or at least at normal room temperature rates. Drying them in the kiln will not allow the salt to come to the surface.</p>
<p></p>
<p>If something blew up in the kiln, it was wet. Pieces that are fired too many times simply crack. They don't explode.</p>
</div>
</div>
</blockquote> That Dogwood article is inter…tag:cone6pots.ning.com,2013-08-26:2103784:Comment:879802013-08-26T13:37:59.604ZNeil Estrickhttps://cone6pots.ning.com/profile/NeilEstrick
<p>That Dogwood article is interesting. I think just opposite is actually true in regards to salt migration during fast drying. The <em><strong>slower</strong></em> it dries, the more likely you are to get salt migrating to the surface. We see this in carbon trap Shino glazes that have soda ash in them. If you want the slat to migrate to the surface for optimal carbon trapping, you have to dry them slowly, or at least at normal room temperature rates. Drying them in the kiln will not allow the…</p>
<p>That Dogwood article is interesting. I think just opposite is actually true in regards to salt migration during fast drying. The <em><strong>slower</strong></em> it dries, the more likely you are to get salt migrating to the surface. We see this in carbon trap Shino glazes that have soda ash in them. If you want the slat to migrate to the surface for optimal carbon trapping, you have to dry them slowly, or at least at normal room temperature rates. Drying them in the kiln will not allow the salt to come to the surface.</p>
<p></p>
<p>If something blew up in the kiln, it was wet. Pieces that are fired too many times simply crack. They don't explode.</p> Jeff Poulter said:
Also one…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:878712013-08-25T22:01:10.055ZMeredith Walkerhttps://cone6pots.ning.com/profile/MeredithWalker
<p><br></br> <br></br> <cite>Jeff Poulter said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87869&xg_source=msg_com_forum#2103784Comment87869"><div><div class="xg_user_generated"><p>Also one thing I do quite often is to set greenware on top of the kiln before I start firing it. It's a good way to dry it out w/o having to do a pre-heat. By the time the firing is done, the greenware is completely dry.…</p>
</div>
</div>
</blockquote>
<p><br/> <br/> <cite>Jeff Poulter said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87869&xg_source=msg_com_forum#2103784Comment87869"><div><div class="xg_user_generated"><p>Also one thing I do quite often is to set greenware on top of the kiln before I start firing it. It's a good way to dry it out w/o having to do a pre-heat. By the time the firing is done, the greenware is completely dry. jhp</p>
<p></p>
<p>Thanks!</p>
</div>
</div>
</blockquote> Jeff Poulter said:
Had any…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:879732013-08-25T22:00:40.740ZMeredith Walkerhttps://cone6pots.ning.com/profile/MeredithWalker
<p><br></br> <br></br> <cite>Jeff Poulter said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87869&xg_source=msg_com_forum#2103784Comment87866"><div><div class="xg_user_generated"><p>Had any of the shelves been exposed to water? Shelves that have soaked up enough water & then fired before being dried out have been known to explode. Usually though it takes part of the kiln with it! jhp</p>
<p></p>
<p>Whoops! No, no water…</p>
</div>
</div>
</blockquote>
<p><br/> <br/> <cite>Jeff Poulter said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87869&xg_source=msg_com_forum#2103784Comment87866"><div><div class="xg_user_generated"><p>Had any of the shelves been exposed to water? Shelves that have soaked up enough water & then fired before being dried out have been known to explode. Usually though it takes part of the kiln with it! jhp</p>
<p></p>
<p>Whoops! No, no water exposure & the shelves & kiln are fine (I vacuumed the kiln.)</p>
</div>
</div>
</blockquote> Also one thing I do quite oft…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:878692013-08-25T21:25:04.286ZJeff Poulterhttps://cone6pots.ning.com/profile/JeffPoulter
<p>Also one thing I do quite often is to set greenware on top of the kiln before I start firing it. It's a good way to dry it out w/o having to do a pre-heat. By the time the firing is done, the greenware is completely dry. jhp</p>
<p>Also one thing I do quite often is to set greenware on top of the kiln before I start firing it. It's a good way to dry it out w/o having to do a pre-heat. By the time the firing is done, the greenware is completely dry. jhp</p> Had any of the shelves been e…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:878662013-08-25T21:21:50.214ZJeff Poulterhttps://cone6pots.ning.com/profile/JeffPoulter
<p>Had any of the shelves been exposed to water? Shelves that have soaked up enough water & then fired before being dried out have been known to explode. Usually though it takes part of the kiln with it! jhp</p>
<p>Had any of the shelves been exposed to water? Shelves that have soaked up enough water & then fired before being dried out have been known to explode. Usually though it takes part of the kiln with it! jhp</p> Bisqued clay is just like a s…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:879722013-08-25T19:41:43.886ZNorm Stuarthttps://cone6pots.ning.com/profile/NormStuart
<p>Bisqued clay is just like a sponge. If it was not, glaze would slide-off when you apply it.</p>
<p></p>
<p>When you apply a glaze it is usually about half water by weight. <strong>This means your bisque is wet.</strong></p>
<p></p>
<p>Clays, Bentonite in particular, can swell forming a crust on the surface which prevents the glaze and wet bisque body from drying out fully. It will feel bone-dry to your hand, but the bisqued ware is still filled with water from the glaze.</p>
<p></p>
<p>This…</p>
<p>Bisqued clay is just like a sponge. If it was not, glaze would slide-off when you apply it.</p>
<p></p>
<p>When you apply a glaze it is usually about half water by weight. <strong>This means your bisque is wet.</strong></p>
<p></p>
<p>Clays, Bentonite in particular, can swell forming a crust on the surface which prevents the glaze and wet bisque body from drying out fully. It will feel bone-dry to your hand, but the bisqued ware is still filled with water from the glaze.</p>
<p></p>
<p>This why garbage landfills are lined with several inches of clay or bentonite. Any toxic liquid leaking from the garbage swells the clay/bentonite preventing the liquid from continuing down to the water table.</p>
<p></p>
<p><strong>If your kiln is not designed to do a pre-heat, leave your glazed pieces in the sun or put them in your kitchen oven on warm.</strong></p>
<p></p>
<p>A piece which has been previously glaze-fired can be just as vulnerable as bisque if the clay didn't completely densify. Washing the piece and applying glaze can allow water into the bisque through areas which are not glazed.</p>
<p></p>
<p>Fired glaze is even less permeable than clay. So water that gets into the glaze-fired bisque is going to require an even longer pre-heat to evaporate fully.</p>
<p></p>
<p></p>
<p>This is an illustration of a man sprinkling glaze (clay and bentonite) into his lake to prevent water from leaking out of his pond.</p>
<p><img class="decoded" alt="http://www.sturgismaterials.com/wp-content/uploads/2012/12/sprinkle.jpg" src="http://www.sturgismaterials.com/wp-content/uploads/2012/12/sprinkle.jpg"/></p>
<p><strong>If glaze</strong> (clay and bentonite) <strong>can keep his lake wet, just imagine how effective it is at keeping your bisque wet!</strong></p>
<p><strong><img class="alignright size-full wp-image-625" title="Mixed Blanket Method" src="http://www.sturgismaterials.com/wp-content/uploads/2012/12/mixed.jpg" alt="" height="158" width="240"/></strong></p>
<p></p>
<p><img class="alignright size-full wp-image-626" title="The Pure Blanket Method" src="http://www.sturgismaterials.com/wp-content/uploads/2012/12/blanket.jpg" alt="" height="158" width="240"/></p>
<p></p>
<p><a href="http://www.sturgismaterials.com/products-view/sodium-bentonite/" target="_blank">http://www.sturgismaterials.com/products-view/sodium-bentonite/</a></p>
<p></p> Hi, Norm -
Thanks for taking…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:880602013-08-25T17:51:39.271ZMeredith Walkerhttps://cone6pots.ning.com/profile/MeredithWalker
<p>Hi, Norm -</p>
<p></p>
<p>Thanks for taking the time to respond. The cookies aren't thick - perhaps 1/4" - and weren't wet (had been used a number of times.<br></br> <br></br> <em>Any ceramic which is repeatedly heated and cooled, in multiple ^6 firings, will inevitably develop cracks. I guess you could call that "clay fatigue" linguistically modeled after metal-fatigue, but it doesn't have any "explosive" potential. </em>----That makes sense to me.</p>
<p></p>
<p>This was a glaze - not a bisque…</p>
<p>Hi, Norm -</p>
<p></p>
<p>Thanks for taking the time to respond. The cookies aren't thick - perhaps 1/4" - and weren't wet (had been used a number of times.<br/> <br/> <em>Any ceramic which is repeatedly heated and cooled, in multiple ^6 firings, will inevitably develop cracks. I guess you could call that "clay fatigue" linguistically modeled after metal-fatigue, but it doesn't have any "explosive" potential. </em>----That makes sense to me.</p>
<p></p>
<p>This was a glaze - not a bisque - firing, so there wasn't any wet bisque in the kiln. And we do a medium speed glaze firing (and always a slow on bisque). The monitor who loaded the kiln said she remembered that one potter's piece had been re-glazed; we've learned since then that dipping & pouring (rather than brushing) a new glaze over a previous one could lead to such explosion. Do you have any experience with this?</p>
<p></p>
<p>Sorry to hear of the "genie bottle" incident!</p>
<p></p>
<p>Meredith</p>
<p><em> </em></p>
<div><div class="xg_user_generated"><p></p>
<br />
<p></p>
</div>
</div> Is a 4 hour pre-heat expensiv…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:881472013-08-25T06:00:12.299ZNorm Stuarthttps://cone6pots.ning.com/profile/NormStuart
<p>Is a 4 hour pre-heat expensive? <strong>No</strong>.</p>
<p>Working with a Cress kiln engineer, we calculated that a six hour pre-heat costs less than a penny in a Cress E-23 operating in a 65 F ambient temperature.</p>
<p></p>
<p></p>
<p>But using the SLOW firing speed, instead of MEDIUM, just about doubles our $5 ^6 glaze-firing cost.</p>
<p></p>
<p>The pre-programmed SLOW firing speed in the <strong>Cress customized</strong> Bartlett V6-7F-700 controller, customized for Cress, offers…</p>
<p>Is a 4 hour pre-heat expensive? <strong>No</strong>.</p>
<p>Working with a Cress kiln engineer, we calculated that a six hour pre-heat costs less than a penny in a Cress E-23 operating in a 65 F ambient temperature.</p>
<p></p>
<p></p>
<p>But using the SLOW firing speed, instead of MEDIUM, just about doubles our $5 ^6 glaze-firing cost.</p>
<p></p>
<p>The pre-programmed SLOW firing speed in the <strong>Cress customized</strong> Bartlett V6-7F-700 controller, customized for Cress, offers little practical advantage over MEDIUM-SLOW, as the ramp speeds through the critical 1,000F to 1,100F temperature range are both 100 degrees F per hour.</p>
<p></p>
<p>A standard <strong>Bartlett V6-7F-700</strong> offers only a choice of a SLOW-BISQUE (which is equivalent to a Cress MEDIUM-SLOW), or a FAST-BISQUE (which is equivalent to a Cress MEDIUM speed at 150 degrees per hour through the critical 1,000F to 1,100F temperature range).</p>
<p></p>
<p>The SLOW firing speed on the Cress customized version can be used as a <strong>very expensive</strong> glaze firing for extremely thick assembled bisqued pieces.</p>
<p></p> The CeramicArtsDaily.org foru…tag:cone6pots.ning.com,2013-08-25:2103784:Comment:878622013-08-25T05:07:41.466ZNorm Stuarthttps://cone6pots.ning.com/profile/NormStuart
<p>The CeramicArtsDaily.org forum seems pretty dead.</p>
<p>I've asked a question on that forum but haven't received any answers. Maybe it's just slow time of the year.</p>
<p><br></br> <cite>John Forstall said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87859&xg_source=activity#2103784Comment87859"><div><p>This is an interesting question.</p>
<p>Please also post it on this more active forum:…</p>
<p></p>
</div>
</blockquote>
<p>The CeramicArtsDaily.org forum seems pretty dead.</p>
<p>I've asked a question on that forum but haven't received any answers. Maybe it's just slow time of the year.</p>
<p><br/> <cite>John Forstall said:</cite></p>
<blockquote cite="http://cone6pots.ning.com/forum/topics/clay-fatigue?commentId=2103784%3AComment%3A87859&xg_source=activity#2103784Comment87859"><div><p>This is an interesting question.</p>
<p>Please also post it on this more active forum:</p>
<p><a rel="nofollow" href="http://ceramicartsdaily.org/community/forum/22-in-the-studio/" target="_blank">http://ceramicartsdaily.org/community/forum/22-in-the-studio/</a></p>
<p>Thanks,</p>
<p>John255</p>
</div>
</blockquote>