Paul Vernier on wed 11 feb 04
I just sent this summary to someone and thought I might post it to the list
for this discussion.
I have had several discussions with fellow Torchbearer owners and I have
come to the conclusion that the following three things have the most impact
on getting even firings from this beast.
1) A dual thermocouple pyrometer. You must be able to see the temperature
variances any time after about 1400 f degrees. There are many on the market.
I use the Fluke and place a thermocouple in the top peep hole and the
bottom.
2) The damper determines the distribution of heat as well as the flow of
primary and secondary air. Make VERY SMALL adjustments and watch their
effect with the temperature readings. But, don't react to the initial
reading. The changes can take a few minutes sometimes to have an effect.
Closing the damper (slightly) pushes the heat down, opening pulls it up.
Using the damper you should be able to get within 10 to 80 degrees top to
bottom, even in moderate reduction. Don't attempt to accomplish evening out
the temperature to early, red heat or later.
If you fire with propane use increased gas pressure for reduction.
Increasing gas pressure gives the best reduction while still getting
temperature increases. I have had more luck with gas pressure over damper
adjustments. This is not the best kiln for even reduction. An aspect of
updrafts. But, it can be somewhat mastered.
3) To take care of that last 10 to 80 degrees. Soak when your target cone is
just beginning to bend. Cut back on the gas and soak for an hour. Will
require a slight adjustment of the damper. This is a good practice for any
kiln.
This has worked for me many times.
OK, 4) I do use the baffle shelf and will continue to. The distance of 4
inches off the bottom is also required. The stacking of the kiln is not real
critical, within reason. I have done some pretty creative stacks and still
had an even firing. I am not sure how much redirecting of the burners
contributes to even temperature as two of the three in my kiln go straight
up the side. I believe the baffle shelf has more impact. I use a 17" octagon
shelf placed 1 1/2 inch from the lid. Olympic no longer recommends a baffle
shelf. But, I will continue to use it as it makes a lot of sense to me given
the small distance between the outside of the kiln and the vent, less that
12 inches. A quick exit for the heat with little reason to venture into the
stacked ware. I think it would work without the baffle. But, I would have to
think it would be a longer firing cycle to your target cone.
In addition. I made a fiber cap for the kiln to increase insulation and slow
cooling.
I am more than happy to help anyone if you wish to contact me off list. And
would enjoy hearing any other approaches that have proven successful.
Paul - Santa Cruz, CA
Paul Vernier
(408) 525-5763 Pager (408) 322-7452 or
pvernier@epage.cisco.com
Program Manager Architecture Baselines 375 East Tasman
https://mco.cisco.com/eng/eng-ops/ab/index.html San Jose, CA
95134-1706
Technical Operations Cisco Systems
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