mel jacobson on sun 28 nov 10
if you weight the shelves, furniture and the ware
going into the kiln, it should give you a fairly accurate
picture of the time it will take to fire your kiln.
you must heat everything to apex temp when firing.
if you have thirty sil/carb shelves in the firing, and all
the posts to hold them in place, and then a full set of
dishes, and companion pieces....it will take much longer
than firing twenty casseroles on ten shelves.
just makes sense.
many fire their kilns with `heat dams`. those are those
blocked off places from big bag walls to shelves far to
close together. and of course, if you have two 50 brick
bag walls in your kiln, those bricks have to be heated to
apex temp too. you are firing those bricks over and over
every time you fire...and often they have no purpose.
(many still argue that bag walls protect the ware...) from what,
heat?
bag walls in wood fired kilns with ash flying and sticks and wood dropped
in the kiln make sense...but a modern gas kiln? not to me. we have been
sold a bill of goods about walls in kilns from 1930 books, and folks
still believe them. (read any science book from 1930....and try to
find things that are still believed. hard to find.)
any fuel kiln needs to have a flow of heat going through the
ware to the flue. if you block that flow, you block the
rise in temp. a free flow of heat is the best. we use a full
thumb size between pots. i never over stack my kiln...i fill it,
but leave space for heat to flow. those extra pots you fire
will probably be poorly fired anyway...so, save them for the next firing
and make racers out of them.
the best ecology is a kiln full of perfectly fired pots with no waste.
nothing to be thrown away. all perfect racers. that is what potters
should be striving for, not overloaded kilns.
also, you serve your bottom line when you fire perfect pots. waste
pots cost you a great deal of money. if you want to save whales, do
it with perfect firings, not overloaded kilns.
i worry first about cost and bottom line, then the ecology takes care
of itself. it is about knowing what you know, and trusting it. think firs=
t
and follow good scientific thermo-dynamic principals. does anyone really t=
hink
that industry wants to waste fuel? my god, it would cost alcoa aluminum
company 6 million dollars a year to waste gas. a million dollar savings
a year is a big savings. they may have done that in 1950, but not 2010.
fuel use is charted to the penny. and, alcoa does not need `kiln gods`.
bisque firing can be overloaded....i put pots in pots, stack them tight
as can be. i fire very slow/electric...twenty hours. and, slow
firing electric
costs the same as fast. how many amps do you use over a time span?
you have to heat the kiln to cone 08, how you get there is not very
important, except you get great bisque firing slow, never fast. only
bad things can happen when firing a bisque kiln in four hours.
read nil's book, read our new book. they is chock'd full of new informatio=
n
and real stories of how and why from many potters. modern science, not
1926.
mel
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
new book: http://www.21stcenturykilns.com
alternate: melpots7575@gmail.com
Michael Wendt on sun 28 nov 10
To add to Mel's comments about firing economy,
this last summer I logged the fuel use of our 12 cubic foot
Olympic style gas updraft kiln ( the one in Mel's book)
and found it costs us $22.00 per load to fire it to cone 10
in about 6-7 hours (low end load values are $1200... high
end is about $2000 to fire for $22 worth of fuel).
That is not a guess but an actual average of loads fired
over the summer when we do not use any gas for heated the
studio
so we know all the bill is for the kiln.
Making the kiln a top hat design allowed me to increase
the size of the kiln while reducing both firing time
and fuel costs by using fewer kiln shelves and "up posting"
shorter wares to use the void space that exists between
and above pot intersections in loads.
see:
http://www.wendtpottery.com/clayart.htm
for a close-up of the setter and of the stacking method.
This stacking method really helped even out the loads
top to bottom by making the top and bottom layers extend
more into the hot middle zone of the kiln.
An overly hot top or bottom is a common difficulty cited by
users of gas fired updraft circular ring kilns.
If anyone is interested, I am willing to do an electric
conversion
to allow easier loading of the larger electric kilns that
are so hard
to reach the bottom on unless you are very tall and have
very long arms.
Regards,
Michael Wendt
Mel wrote:
i worry first about cost and bottom line, then the ecology
takes care
of itself. it is about knowing what you know, and trusting
it. think first
and follow good scientific thermo-dynamic principals. does
anyone really think
that industry wants to waste fuel? my god, it would cost
alcoa aluminum
company 6 million dollars a year to waste gas. a million
dollar savings
a year is a big savings. they may have done that in 1950,
but not 2010.
fuel use is charted to the penny. and, alcoa does not need
`kiln gods`.
bisque firing can be overloaded....i put pots in pots, stack
them tight
as can be. i fire very slow/electric...twenty hours. and,
slow
firing electric
costs the same as fast. how many amps do you use over a
time span?
you have to heat the kiln to cone 08, how you get there is
not very
important, except you get great bisque firing slow, never
fast. only
bad things can happen when firing a bisque kiln in four
hours.
read nil's book, read our new book. they is chock'd full of
new information
and real stories of how and why from many potters. modern
science, not
1926.
mel
from: minnetonka, mn
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