mel jacobson on thu 23 aug 07
a chimney is not just a system to make the kiln fire better.
it is a system of safety and venting, along with perfect firing.
it all depends.
no rule of thumb.
if you have to clear an eight foot ceiling, then you need more
than a chimney to the arch.
we cannot assume that all kilns are outside. many kilns
are in garages, storage buildings or free standing studios.
(not to mention the hundreds of schools and art centers.)
in minnesota an outdoor kiln is ok, but not the desired place.
we want shelter. -35F and windy...with 10 inches of snow.
don't want to be outside, loading that kiln.
so. the stack is based on building height, the peek of the roof.
it is desirable to be just a bit taller with the stack than the
peek of the roof. air currents, wind direction all play a role in
perfect chimney placement and height.
here is a perfect example.
kerry brooks has a 100 cu ft downdraft kiln/compressed air blowers. it sits in
an industrial building with a 14 foot ceiling. her stack must clear
that by 6 feet. so...her stack is about 20 feet tall. (these specs are from
my memory, but close.)
there is a flat brick wall that is four stories tall about twenty
feet from the kiln stack. if the wind starts to blow from the east...the
kiln will not fire. no draft at all. none. she shuts the kiln off
and waits for the
wind to shift. as soon as the east wind stops, the kiln fires like a dream.
if she is at cone 8 and the wind changes direction to the east....it
will not fire to cone
10. she just holds the kiln at cone 8 ...turns things down...and waits for
the wind to change. if it does not...she shuts it off.
that is why there is not `one size or style`...each kiln has a unique set
of possibilities.
the most important truisms are:
tight chimney..no leaks.
safe transition through the ceiling.
lots of air circulation around the stack and ceiling.
no blockage or insulation around the stack above the roof line.
(in other words, don't box in the stack.)
don't ever put a cap on a kiln chimney. nice for a wood stove, but never
a kiln. far too much energy and heat.
and, make sure the air flow across the roof allows for every day firing.
like captain kirk is told....`you canna not change the laws of physics`
even if you whine.
and yes, old books and texts have a lot of really bad information
about kilns and stacks. much of it from 1930.
do the math with the specs from the leach book. my god, you would
have a 50 foot chimney, 30 inches across.
i know others can add to this...some great folks out there with
good information.
like fred speaking of welding...he sure has it right...a great tool in the
hands of someone without knowledge is really dangerous. and, a little
bit of knowledge can really be trouble.
it is like my great line about chain saws...my new stihl weights 220
pounds....because, if you want to borrow it...it comes attached to me.
mel
from: mel/minnetonka.mn.usa
website: http://www.visi.com/~melpots/
Clayart page link: http://www.visi.com/~melpots/clayart.html
Edouard Bastarache Inc. on thu 23 aug 07
Mel & all,
Go check my chimney design, completely
out of this world, and it works fine for me :
http://www.flickr.com/photos/potier/page10/
You will see :
1- An interior chimney,
2-A five foot transfert chimney,
3- And an exterior one that is higher
than the gable by 3 feet.
The building is 28 feet high.
Gis la revido,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
http://www.ceramique.com/librairie/
http://www.flickr.com/photos/30058682@N00/
http://myblogsmesblogs.blogspot.com/
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