Is there a difference between peeking & flash venting? -

Is there a difference between peeking & flash venting?

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Is there a difference between peeking & flash venting?

Postby Stephie » Tue Sep 09, 2003 6:19 pm

I have read both to and to not flash vent, but everyone needs to have a look. Is it not harmful to the kiln if you just peek?

Dick Ditore
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Postby Dick Ditore » Tue Sep 09, 2003 9:11 pm

No, a quick peek is fine. The only danger is opening too much or too long as it cools and you risk thermal shocking the glass.


Avery Anderson
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Postby Avery Anderson » Tue Sep 09, 2003 9:17 pm


Looking in your kiln to monitor what the glass is doing, and flash venting are very different. You can certainly look in your kiln safely above 1000 degrees. You would do this to monitor when the glass has fully fused, when it has slumped, when enamels have matured, etc. Flash venting was something that was recommended years ago, to prevent devitrafication. My personal feeling is that flash venting is adding needless stress to the glass and so I never flash vent. The only time I can see that this would be necessary is if you were doing a drop out mold or you wanted to catch the glass slumping at a certain point.


Ron Coleman
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Postby Ron Coleman » Tue Sep 09, 2003 9:51 pm

Whether you open the kiln to peek or vent, do it slowly. Opening the kiln quickly will cause a drop of pressure inside and the kiln will inhale a big gulp of air. Any dust around the door opening gets drawn inside with the air and may land on your glass.

Also, closing the the lid with a little too much gusto can cause brick particles to fall right where it does the most damage.

Just open and close the kiln like you're getting a midnight snack from the fridge without anyone knowing and you shouldn't have a problem.

My worst distaster opening the kiln too fast caused a sheet of glass to actually shift on the shelf. :shock: This happened on ramp-up and the glass had a little air trapped under it. The sudden pressure drop in the kiln caused the air under the glass to expand and the glass lifted and floated on the shelf. This was at 1000 f and the only thing to do was anneal, cool down and try again the next evening. #-o


Tony Serviente
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Postby Tony Serviente » Wed Sep 10, 2003 9:17 am

Another aspect of either peeking or flashing is the corruption of meaningful data. If you are trying to be methodical about learning the glasses behavior, as well as your kilns, you'll be keeping some sort of records. The simplest being graph paper and a notebook, the other extreme being a software database with digital photos. If you are dutifully recording ramps, soaks, anneals, etc. and you do it with a known and stable kiln environment you can duplicate your results. Once you open the kiln lid, much of this can become meaningless, unless you open the kilns lid every time, at the same temperature, to the same height, for the same length of time. Keeping the kiln sealed through the cycle gives you a reference point to work from. I virtually never open my kilns, unless I'm doing some kind of one off or combing.

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Postby Bob » Wed Sep 10, 2003 9:48 am

Hi Stephie,

I always look in the kiln to see what is happening. My first peak is at 1000F to see if the piece has thermally shocked. If so I just shut the kiln down and work on my vocabulary of four letter words. If going to full fuse I peak again at 1475ish to see of the dreaded bubles are starting to form. I peak numerous times during every firing, always checking for visual observations that indicate if the piece is firing or slumping properly.

Like Ron, I open and close the lid very slowly, and I open the peep hole before opening. Some people say that opening the lid is hard on the softbrick in the lid. Perhaps, but luckily I have been doing it for years without an unusual amount of spalling soft brick.

If you are intending to do production work that will repeat schedules I believe that Tony's comments apply... but for prototypes and one-off pieces I am a firm believer in peaking.

I used to flash vent but have been convinced by people on the Board that it is not necessary.



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Postby Stephie » Wed Sep 10, 2003 10:40 am

Thanks everyone for your comments :D


Postby Janz » Wed Sep 10, 2003 11:11 pm

I was taught to flash vent from full fuse, down to 1000F, to "stop changes in the glass, and prevent devit." The few times I actually went down to 1000F I'd hear cracking, and snapping sounds. When the glass came out of the kiln it looked ok, but still....
I'm pretty new at this, but I don't think all that popping was a good thing.

Now I ease the lid open a few inches, bits at a time and vent to 1300F, then I prop the lid with a post. When temp. reaches annealing range I shut it and let the kiln do it's thing, usually overnight. I haven't had devit. problems, but that might be luck.

Lynne Chappell
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Postby Lynne Chappell » Sat Sep 13, 2003 12:45 am

The popping and cracking sounds are coming from your elements. Crash cooling is pretty hard on your kiln. I used to do this, mostly because I was in a hurry to get the kiln down to the annealing range so I could go to bed. Open up the lid as far as I could and hold as long as I could stand the heat. Did this several times. Eventually the poor kiln rebeled and started dropping bits of kiln brick and element pins into my glass. I've reformed and though I may open the lid at the top end to make sure everything is the way I want it, I don't leave it open any longer than necessary and let it cool naturally. The kiln is much happier and the glass didn't seem to care.

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