Hank Ray on sun 23 aug 98
Hello All...
with all the people on clayart and all the kiln gods out there... surely there
are some great minds that know at least a little something about alpine
kilns.... i am firing a HF-24 updraft w/power burners... it has a problem:
firing hotter on bottom than on top (everyone who has fired the kiln previous
to me has had the same problem)......the book (if that is what you want to
call it) that came w/the kiln mentions that the top may burn hotter than the
bottom and says to raise the flame tip by (1) increasing the gas input to the
burners and (2) by turning down the speed on the cumbustion blower motor....
-OR- a combination of the two.....
......i've tried the book's suggestions and nothing seems to make a
difference..... the book is missing a few pages so it doesn't have a "typical
firing schedule".....also, it doesn't mention what to do with or how to use
the doors on the air intakes of the combustion blower motors.....additionally,
there has been talk in the past about removing the muffle walls and radiants
-OR- removing the the porcelain tip of the burner to make them fire better
......does anyone really do this kind of stuff or is this just talk???.......
please help.....i know there will be numerous people watching to see if anyone
responds to this because the last time i posted about an alpine kiln problem
many individuals e-mailed me privately to see if i had found out any
information....
may buddha bless all those who respond...
Hank in oklahoma..........
Earl Brunner on mon 24 aug 98
In a message dated 8/23/98 7:34:44 PM Pacific Daylight Time, Helllll@AOL.COM
writes:
<< i am firing a HF-24 updraft w/power burners... it has a problem:
firing hotter on bottom than on top (everyone who has fired the kiln previous
to me has had the same problem)... >>
In the 70's we had an Alpine 24cf and an Alpine 30cf inour studio at college,
both updraft forced air. Every single firing was a battle to get even
temperature and the bottom if I remember right frequently was the hottest. Up
draft and forced air kilns I believe from my experience to be inherently
difficult to get consistent and even results. The velocity on an Alpine is
from front to back, do you place cones in the back as well, and is the front
different from the back as well as the top and bottom? Deflecting or altering
the flame path sounds like a good idea and moving/removing some of the baffles
may be a good idea, I'd leave the porcelain tip on the burner though.
Earl Brunner
Grimmer on mon 24 aug 98
Hank,
I fired foced-air updrafts quite a few times a few years ago. Yes, they
like to fire hot on the bottom, but good results are attainable. From what
I recall, here's what you have to do: Reduce early and well. Start at 010 or
so. Don't cut the air too much, but do slow it down a bit with the
shutters. Turn up the gas a bit. Trial and error will tell. The damper is
your main control. close it down so you get a bit of flame licking out the
botom spy hole. You should have a yellow/green flame at the damper. If it is
lazy and sooty, cut the gas and add air until it's lively again, then close
the damper some more so you get a little flame out of the bottom peep. Yuo
may have to fiddle with this for a bit. Relax, don't worry, have a homebrew!
Now the bottom will start racing ahead. Bit by bit, ease the damper open
and turn up the gas so you maintain positive pressure at the top peep. Don't
worry about the lower ones. If the top gets hotter than the bottom, close
the damper some. It's a fine line to ride, but you will figure it out soon.
Some points to remember:
1. Keep a good log and write down every change you make.
2. Change only one thing at a time. That way, you know what works and what
doesn't.
3. Wait a half hour at least between changes. Watch to see what happens.
Don't go fiddling every five minutes, though I know how much you want to.
4. Don't panic. Stay with it and think about where the flame tip is.
E. Build a Minnesota Flat Top and be done with it. :^)
steve grimmer
marion illinois.
yeesh, where did this humidity and these bugs come from??
----------
>From: Hank Ray
>To: CLAYART@LSV.UKY.EDU
>Subject: Alpine Kiln!!!!!!! updraft(please)
>Date: Sun, Aug 23, 1998, 9:22 PM
>
>----------------------------Original message----------------------------
>Hello All...
>
>with all the people on clayart and all the kiln gods out there... surely
there
>are some great minds that know at least a little something about alpine
>kilns.... i am firing a HF-24 updraft w/power burners... it has a problem:
>firing hotter on bottom than on top (everyone who has fired the kiln
previous
>to me has had the same problem)......the book (if that is what you want to
>call it) that came w/the kiln mentions that the top may burn hotter than
the
>bottom and says to raise the flame tip by (1) increasing the gas input to
the
>burners and (2) by turning down the speed on the cumbustion blower
motor....
>-OR- a combination of the two.....
>.....i've tried the book's suggestions and nothing seems to make a
>difference..... the book is missing a few pages so it doesn't have a
"typical
>firing schedule".....also, it doesn't mention what to do with or how to use
>the doors on the air intakes of the combustion blower
motors.....additionally,
>there has been talk in the past about removing the muffle walls and
radiants
>-OR- removing the the porcelain tip of the burner to make them fire better
>.....does anyone really do this kind of stuff or is this just
talk???.......
>please help.....i know there will be numerous people watching to see if
anyone
>responds to this because the last time i posted about an alpine kiln
problem
>many individuals e-mailed me privately to see if i had found out any
>information....
>
>may buddha bless all those who respond...
>
>Hank in oklahoma..........
Mike Gordon on tue 25 aug 98
Hi Hank,
I wouldn't take the tips off the ends of the blowers-they protect the
metal pipe from falling apart. I would leave the muffels and radients in
as well. I would try leaving the speed of the blowers on full and use
the metal discs to change the amount of oxygen to gas mixture, also try
playing with the dampers on top. All of these things will have an effect
on the eveness of the firing. Mike
JFTRT on tue 25 aug 98
Hank in Oklahoma-
At Michigan State University we had a selection of
Alpines from 24 up to 90. All the muffle walls
were removed and we would usually make an
adjustment during the firing if needed-and
some kilns needed that and some didn't.
To correct the "hot bottom" usually the
damper would be opened, say 1/4" or so, and
then the blower/gas mix adjusted to pre-
serve the reduction. These tips were
handed down from many years of fiddling.
Todd Turek
Juneau, AK (say good-bye to summer)
Debby Grant on tue 25 aug 98
Dear Hank,
I fired an updraft Alpine for many years and found that the stacking
pattern was the most important element in getting an even firing.
I always left the most room between the first and second shelf, stacked
tighter in the middle and tallest pots at the top. We also stopped using
the Alpine shelves which were long and narrow and went to much
smaller shelves which we stacked side by side with a two to three
inch space up the center. You may also have to raise the bag walls
a bit. In the event that the bottom is way ahead of the top at about
cone 8, just lower the gas and air until the top catches up, then cramk
them up again. However, with proper stacking this probably won't
happen. I can tell you that at the end of that kiln's very long life we
were getting very even firings with good reduction for many many
years. Keep experimenting. Every kiln fires differently.
Debby Grant in NH
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