karen terpstra on wed 20 aug 03
Hi Sam,
Your baby is similar to the first one we built here in La Crosse. We
have quirky weather here and have had to work through various weather
situations. Yes, wood kilns will stall in low pressure but we try to
work through them unless a tornado is just around the corner. Here's
what we have been doing lately:
1. Keep more than enough wood on hand to work through the stall.
Continually and patiently throwing wood in still keeps the kiln hot even
though you don't get a rise in temp on the pyrometer. It still gives
you "flashing" time and even some reduction. So, I think it is more
efficient to work through the stall than to stop and start over. Keep
in mind you probably have to cut back a little on the amount of wood to
keep from choking it up. Plan on enough people to help so you don't wear
yourself out.
2. We have a barometric pressure/thermometer nailed up near the wood
kiln so new wood fire people don't panic when the kiln stalls and
everything else seems to be in place.
3. We have learned to stack the kiln loosely and evenly. This is very
important when it's difficult to get that draught that you need. If you
stack the kiln too tight you and the kiln have to work that much harder
to reach temperature.
4. The most important and critical thing for us to do when we have a
stall due to the weather is to open up the dampers as much as possible.
We use passive dampers on our chimney which means we close them up, (put
the bricks back in) and let the chimney draught what it can. If you are
using mechanical damper(s), open it up all the way. learning to use the
dampers is crucial.
5. Play with the primary and secondary air ports. I used to think I
needed everything open but I finally learned that I was wasting too much
fuel that way. We started leaving the bricks in loosely and sometimes
open the ports partway. I couldn't see how your kiln is designed and
each one has it's own peculiarities so you really need to find out what
works best.
6. If you are getting back pressure, open up the chimney and close up
more of the primary air.
7. It looks from the picture that your chimney is long enough and the
flue opening is adequate, but you might try adding a foot or two to the
chimney. Its surprising what that can do. And make sure you don't
block the flue opening with too many pots.
These are just a few suggestions for you to try. We now welcome low
pressure throughout the firing. We get better flashing and makes for a
more relaxing time.
hope some of this may spark some ideas for you.
Karen Terpstra
La Crosse, WI
From: Maid O'Mud scuttell@ODY.CA
"...I fire to ^10, though a good low pressure system will stall the kiln
at = 08....it needs a good high pressure system to run at peak. There is
= probably a way to fire in a low system - but I haven't found it yet.
So = we just stop when it stays stalled too long and start the next
clear = day. We use a pyrometer and cones to judge heat. Eyes and nose
are our = best indicators ;-)
It takes 10-20 hours to fire to ^10 depending on weather. If we start =
super early in the day (really really hard on me) and we reach ^10 mid =
day, then we can hold as long as we like for best ash deposit.=20
I use a mix of hard and soft woods split pretty thinly. I watch the =
smoke to judge stoking. There is no "timing" by clock I can give you. =
We use about a face cord per firing. Most of the wood is free - =
collected from the local rafter factory; the rest scavenaged from the =
woodlots around here. Occasionally we purchase dry wood because when it
= gets down to $40 or less per face cord, it's cost effective to
purchase = rather than "drag"...."
Claudia MacPhee on mon 11 apr 05
Hello All,
This is something I am very interested in. Up here wood is free and
there is LOTS of it. Propane is ridiculous in price (electric heating is
cheaper). There is a hydro dam so electric is actually less than some places
down south (below the 60th parr.)However trucking bricks 1,500 miles adds
up.
I saw a photo in a book called 'Primitive Pottery' by Hal Riegger(sp) of
some little wood kilns his class had built in the Calif. desert for salting
and low-firing out of rocks. Wondered if the basaltic rocks we have an
abundance of would work....for hard brick sub.?
Probably lots more people interested in this idea.
Claudia MacPhee, in the S. Yukon where we woke up to snow! Yuck.
Anyone done Raku with a wood fueled kiln?
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