Sylvia See on mon 23 aug 99
I'd like to thank all who emailed me on the list as well as privately about
my concern about the flue size on the kiln I was building.
It is now 5:21am. and I fired my kiln from 8:30am yesterday morning to now.
I got up to cone 4 or higher. Will find out when I get to open the darn
thing. I fired it for 20 hours with the 2 100lb propane bottles I had and 2
tiger torches. Great experience. Thank heavens I didn't spend a ton of money
on a gas kiln but made my own. It took alot of fiddling around until I got
it, but I learned a ton including, there is no way this ol lady will fire
with propane or gas. My kiln as of tonight will make a great kiln for
primitive and that's it. I can well do without 19 hours of firing, the worry
of how hot the ground got, sitting and hosing down the area after firing and
the unbelievable expense of firing those few pots. So much for my theory it
would be alot cheaper than my electric because it was 3 times the cubic
feet. I started with the flue really small and bricked it up from the
outside. As it started to go into reduction, I opened it up until I had a
really good burn. Had a bit of freezing with one bottle for a while, but I
think I had a pretty good learning process on the burners, and flue size
that works.
Thought I would let any others new at this know what happened to me and
why I was concerned because I couldn't get it to temp before running out of
propane. The firing the other day, after 8 hours my newly filled propane
bottles were empty. I fired with the torches higher, for 20 hours yesterday
and still have propane left in both tanks. This means only one thing. The
service station I filled the tanks at the other day only half filled them. I
went to a different service station yesterday and got them filled. They
overfilled them and we had some scary moments bleeding them and firing off
the excess for 5 hours the night before I fired my kiln. Then I still fired
for 20 hours, and have propane left. What scares the heck out of me is how
these service stations can sell propane when they don't know what the heck
they are doing. The girl who filled my last bottles, filled them so full
they froze at the connection, and she was totally unconcerned. Also it cost
me $38.00 a bottle for the ones half full, and $21.00 a bottle for the ones
overfilled. These service stations are a block from each other. I have been
rakuing for 10 years with 100 lb bottles and have a pretty good idea how
long I can fire them and how many times. I think I was pretty close with the
bottles today, after the bleeding and burning of the excess. I will be going
back to the UFA in the future, where they have a pretty good idea what they
are doing. This was scary stuff to me.
Anyway, why I would fire so long with such a touchy process, for so much
money, for the amount of pottery I am doing is beyond me. Thank goodness I
finally tried it. I will be getting new elements in my electric and using
this as a primitive kiln.
Great web site Jacka!!!
I'm off to bed and hope the steam around the kiln is nothing to worry
about. Leaving the gas to you younger, braver folks.
Oh yeah!!! I used those wall brackets for making shelf units, with the
metal brackets that stick into the slots on the wall brackets, to hold up
the fiber on the top of the kiln today. I had tried fiberboard first, and it
cracked right down the middle and folded into the kiln from the weight of
the fiberfax . That cost 89.00 a sheet for a 3x2' sheet. I ruined 3 sheets
and said many naughty words. 2nd attempt, used a sheet of metal that melted
at about 1400 to 1500 degrees F. Yesterday I used the wall brackets under
the fiberfax, with a sheet of galvanized sheet metal on top. It looks
exactly like it did when I started, but who knows when I open it up I could
have interesting metal runs on the pots. If they are intact, I will email
back to let you know by the cones, what temp they held up to.
Sylvia See Claresholm, Alberta Canada sylviac@telusplanet.net
Jung, Don on wed 25 aug 99
Sylvia,
You mentioned using 2 tiger torches... you may need to beef them up as their
btu rating may be too low. You can build your own or buy from various
sources. I suggest you go through the calculation of brick weight being
fired and the btu's needed to fire them to temp. The burner port should
also be of a appropriate size to get enough air and of course you're already
checking the flue size. Also, what kind of bricks are you firing up... hard
brick.. yikes! I hope you're making lighter insulated firebricks.
Nil's book, along with Olsen's book are excellent references. I like the
more up to date info in Nil's 'Art of Firing'.
If you want, I can send you the relevant formulas you need to go through to
calculate the orifice, btus, cu.ft of air, flue size, gas pressure. I've
gone through the exercise myself, built a little kiln 3'x3'x3' and it fires
wonderfully.
thx Don Jung
Vancouver BC
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