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Bisque Temp Problems


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I ran my kiln yesterday with a 06 bisque load and it ran for the normal amount of time (7-8 hours) and today I saw that the cone did not melt but the kiln turned off (timer wasn't on)..... My main question is- is it safe to just go ahead and glaze and do my glaze fire to a cone 5? Since the kiln ran for that long, I assume it got close to my 06 firing...? Or is it best to just re-bisque it? Still figuring this all out. :/  Any input would be great.

Thanks!

Victoria

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You should always check your kiln through out the firing.  I have a kiln setter and a pyrometer, but I still check the progress of the firing by the color of the glow.  If I have a firing that is running into the night either my husband or myself will stay up until it kicks off.    Denice

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Thanks everyone for the input.  So, I don't have a pyrometer... I did check the kiln every half hour- the pieces got to a glowing orange/red. The kiln shut off because the kiln sitter trigger had fallen so I just assumed the cone melted as normal. I checked using a gauge to make sure the kiln sitter was correct and it was... 

I think I will just re bisque to be safe and i'll get a pyrometer to double check.  

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Sounds like the cone may have gotten damp, causing it to break down a bit. Red orange is not hot enough, as you should be in the red orange orange range of color for a ^06 bisque. This is a handy chart to use to monitor your kiln when climbing, nearing or descending from temp.

best,

Pres

 

KilnFiringChart.jpg.c3901508d6495bf3e892bd6b9bf9834b.jpg

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Orton says don't go bad ......if stored under the conditions....so it depends.

still a bit grey...thhe witness cone didn't change, was crumby.v odd

still not sure what caused kiln to turn off if this was a witness cone or the cone in sitter?

short power outage??

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So now there are two potters who have had cones crumble / powder. Crumbling cones is not normal, if you can press on it and it turns to powder something isn’t right. Give Orton a call or email, send a picture and see what they have to say. (assuming they are Orton cones and not homemade ones)

edit: I still don't get how the sitter tripped if there was a cone / bar in it which didn't bend and didn't turn to powder until you pressed on it. 

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Yeah, I'm very confused by this whole situation.  The cone was in the sitter- something must have tripped it, not sure. The cones were Orton... and I bought them only like 3-4 months ago. The only thing that maybe could have affected them was that they did get below freezing but all my other cones are in the same place and haven't had this issue before. 

Pres- thanks for that chart, very helpful.

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I fire all of my firings with help from the chart . Cone packs let me know when to turn off my completely manual kiln. I run the cone pack parallel to the peep hole, and have the cones fall to either side so that I can see them fall in the little peep opening. Heat color lets me judge when to turn up, and when to turn down for cooling.

 

best,

Pres

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The only thing that I can put the finger on in the sitter case is. . . mechanical. If the sitter has a bent rod, or if it is not set perfectly level in the vertical, I know that things do not work right. I have had kilns overfire, and underfire because of the mechanical issues with the set up of the sitter itself. In my case the sitter sat over two sections of a sectional kiln; if the top section was off even a 1/4" of an inch it would cause problems with the accuracy of the firing. Take a look at you own sitters and imagine the sitter either leaning outward, or leaning inward rather than 90 degree vertical.

 

best,

Pres

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5 hours ago, Mark C. said:

My guess is its the sitter tube(which is the rod mechanism and tube)May be time to replace the tube.I have done this in my all mechanical Skutt .Its a cheap fix.

You will need to adjust it with the small gauge at that time but its included If I recall in the tube parts .

You can buy them from your kiln manufacture or from a place like this

http://www.kilnparts.com/dawson-kiln-sitter-parts.html

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