Top Peep....to peep or not to peep

[vadie bond]

hello all,

I have been asked to get information on a "healthy debate" going on at our
local community potter studio(approx 22 members some more involved then others)

Since I know there is a wealth of info here...

the question is...

We have a Skutt KM 1027, with an inviro-vent. do you use the TOP PEEP or leave
it out??? what are the "pro's" & "con's" of each?

we have a teacher who fires her own kiln with the top peep out and no vent for
years, so she fires at the studio with the peep out then we have another half time potter who has been a member for 6 years
who says to fire with the peep in. and some of the members who have been there
for 6 yrs also but now getting interested in firing the kiln for their own loads
are asking the "question" and are getting different answers.

so i'm here to bring them more information so that they can decide what's best
for them


thank you

[Jeff Poulter]

If the Enviro-vent was installed properly with holes drilled in the lid, that should be sufficient air coming in through the holes & the peep-hole should be plugged.  The vent pulls out the gases & distributes the heat better.  I fire outside & fire my kilns with the top peep out for all bisque firings, but on some glaze firings I leave it in, depending on what the glazes are & what effect I am going for.  Also with the Fallonator system, you don't have any peeps open & the kiln has to be pretty tight.  jhp

[Donna Ferrara]

I was curious as to why we do what we do and went to the video tape (in this case the manuals)

I fire a skutt 1227 manually with an envirovent.

the skutt manual says that firing with the top peep left open will add years of life to your kiln sitter assembly.  It also says the top peep should be left open during the entire firing.  This will reduce deterioration of the kiln's metal parts. This is for an unvented kiln.

The enviorvent says that with proper installation firing will be more even, little or no fumes, safer because the lid's not open  and  the metal kiln components will last longer.

I have to change my elements around every 2-3 years, and in 10 years have just replaced the tube assembly once,  how often does anyone else replace these things?  I use the length of firing as a guide to my elements wearing out but also they start to slant together, and get compressed. 

[George Lewter]

Having the vent system changes the air in your kiln by drawing it down at the top and evacuating it at the bottom. This serves the purposes of getting water vapor and other gases out  of the kiln and out of the building. The vent operates by lowering the pressure inside the kiln so that any openings or cracks are drawing air in. If you leave the top peep hole open, you let in a large volume of air that may neutralize the negative pressure in kiln, turning the center top vent and any other small openings near the top into exhaust ports.  Sometime with the kiln above 500 degrees, try opening the peep hole, and then hold a lighted match at the hole in the kiln lid. If some of the flame and or smoke is not drawn into the hole, then you are exhausting at least some gases into the room. 

My guess is that a properly adjusted power vent is pretty much equal to open peeps as far as element life goes. Elements are much cheaper than lungs or other organs, so it's better to err on the side of health rather than element economy.

[Norm Stuart]

We fire 3 - 4 times a week and need to change a heating element, thermocouple, or one of the two power relays once a year. We change everything at the same time because our experience has been if you spend the effort to diagnose the faulty part and change that one thing, you'll need to change one of these other items within a week or so, and another weeks or two later.

The parts were changed far less frequently on our old kiln, but our new kiln kiln puts out 50% more heat, which required us to upgrade our 220 volt line outlet to 50 amp from 30. Our computerized Bartlett controller never over-fires and gives us tremendously more control. We switched when it looked like we needed to replace quite a few parts on the old kiln. Due to shorter firing times, the new kiln uses less energy.

Our newer Cress-E23 kiln is outdoors with a zinc-plated cap we made for the top to protect the electronics. If it were inside, of course we would have the ventilation system. I'd see if there is much difference is the output from the ventilator with the peep hole open or closed. My impression is these foam-core brick kilns are pretty porous all over.

As with our old outdoor kiln, which had a Dawson kiln-sitter, we leave the top peephole open, which loses no noticeable heat but the stainless casing metal the first inch above the peephole is discolored over time from escaping moisture and other fumes. One person did a "firing" in our old kiln with both peepholes open, and needless to say the firing took a very long time as the heat loss is substantial.

We use a blow-torch occasionally to put elements back into alignment. But other than that I just repair the occasional broken brick with 1.5 grams of Wollastonite mixed with 1 gram of 85% Phosphoric Acid. Once the bubbling stops add water to the consistency you need and you have a moldable pH neutral putty that sets at room temperature and fully heat cures by 600 F.  Most of these brick repairs are caused by carelessness, but over time the elements put pressure on some of the containment channels and they have to be cemented back into place with the same cement using more water to make a glue.

The relatives of a deceased potter recently offered us an old Cress kiln, I think from 1965 or 1970. It ran on 110 volt current with 1 foot thick fiber walls beyond the 3inch firebrick. Inside, the kiln was about the same size as ours, but square rather than octagonal. But on the outside it was about 6 foot by 5 foot, and four feet high - with a sixty pound counter-weight for the 9 inch thick lid. The weight of the kiln was enormous. I can't imagine how it was moved. It was amazing to see how technology has changed.