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Mistake Made During First Firing - Left Top Peep Hole Plug Out.

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#1 gkillmaster


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Posted 15 April 2014 - 09:13 PM

I did my first electric kiln firing today. I'm using a downdraft system (Envrionvent 2 with Skutt Cone 10 kiln). It specifically says to fire with all the peep hole plugs in but I mistakenly left out

the top peep hole plug. I'm worried this may not "prime" the kiln correctly or may have some other negative effect.


Please, those of you who know technically about firing, could you let me know if this is a problem? Everything seemed to go ok. Took about 8 hours to reach cone 04 on medium speed setting.


Many thanks!


Greg K.

#2 Pres


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Posted 15 April 2014 - 09:20 PM

I often fire with one of my plugs out, but then I am not using any downdraft system. I would say that as long as you reached your target the every thing will be oK. However, I may be wrong, as not using the same system. Maybe someone else will confirm or disavow my answer.

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#3 Diane Puckett

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Posted 15 April 2014 - 09:38 PM

I have had very experienced potters who use a vent say they always fire with the top plug out. I leave mine in, as I figure the kiln is far from airtight.
Diane Puckett
Dry Ridge Pottery

#4 gkillmaster


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Posted 15 April 2014 - 09:44 PM

thank you Diane and Pres!


Starting to feel a little better. By leaving the top peep hole plug, I bet I may have messed up the flow of air in the kiln but maybe it didn't damage the new elements and it was only a priming and test firing with just kiln washed shelves.  It did reach temperature.


The floor is super hot. About 200 degrees! (bamboo floor). Guess I should probably cover it with some fire resistant dry wall. I was told it was ok to fire on this floor with the 8" stand, but it worries me a bit.

#5 mregecko



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Posted 15 April 2014 - 11:46 PM

Who told you it was OK to fire on a bamboo floor? Every kiln spec / manufacturer's recommendation I've ever seen says only to fire on a fire-resistant substrate. Concrete, tile, or fire-resistant boards of some sort.

#6 Mark C.

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Posted 16 April 2014 - 01:53 AM

No worries on the left out spy plug
But big issue on bamboo floor
It's a real fire hazard and you need to put at least some tile board or better down as mregecko above says
There are lots of threads on this just do a search on this forum
Mark Cortright

#7 Marcia Selsor

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Posted 16 April 2014 - 07:11 AM

I agree. Plug isn't such a big deal but you are playing with fire without protection on that floor..literally. What are the walls made of? Ceiling? How high? Can you put some cinder blocks (holes sideways) under the kiln stand? Even regular brick spacers supporting a hardi-backer board would help it to keep the heat away from the floor. 



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#8 neilestrick


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Posted 16 April 2014 - 09:22 AM

Your vent probably didn't do much with the peep hole out. A hole that big will spoil the draft. But it won't do any damage to the kiln or pots.


Kilns should never be placed on a combustible floor. Over time the wood will dry out, lowering the flash point and eventually catching fire. Put two layers of cement tile backer board under the kiln, extending out beyond the kiln at least 6 inches.

Neil Estrick
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#9 PSC


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Posted 16 April 2014 - 11:35 AM

Kilns will wreck a floor. For some reason the center where i teach put linoleum on the floor in the kiln room long before i ever taught there, the linoleum is cracked and and loose under the kilns was like that also when i started teaching there.

Of course when i got there the room vent in the ceiling was on a thermostat and would only come on when it was hot in the room. It took two years to convince them to take the thermostat off as the vent was suppose to be venting fumes not heat and in the winter the the vent fan would never come on to vent the room.

So talking them into taking up the linoleum is impossible....its been near 8 years and the linoleum is still there.

#10 gkillmaster


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Posted 16 April 2014 - 12:21 PM

Wow! I can't thank you all enough. I'm used to posting on other (non ceramic) forums and having to wait a long time. Seems like a great community. I'm really grateful to have this information you all have provided. I'd rather not say who told me it was ok, but I will certainly let them know what I've found out!


Neil, what cement tile back board would you recommend. Marcia said hari-backer but will any brand do? I found these insulating firebrinks (to put under the kiln). They have are K20 (whatever that means). Will these work as well or is the unsulating better with the backer board?


Many thanks all!


Greg K.


p.s. Marcia, the walls are regular dry wall. Kiln is 18" from them. Ceiling is redwood. I am using the Skutt Envirovent 2 downdraft system with my kiln.

#11 gkillmaster


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Posted 16 April 2014 - 12:35 PM

oops forgot link to insulating 1" (picture shows 2.5") firebricks:



#12 InspireArtStudioandPottery



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Posted 18 April 2014 - 01:52 PM


It says on the link that the bricks are good for up to 2000 degrees.  Are you firing higher than that?

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