Tonya Tippit on sat 11 apr 98
Greetings fellow clay artist:
As Advanced Ceramic Students at MWSC we have been given the assignment of
researching remedies for a problem we are having with our salt kiln. We
would appreciate any suggestion any of you might have regarding our kiln
and salty dilemma.
Thanks in advance for your assistance.
History: For a number of years we fired a cross-draft hard fire brick
kiln (wood was previously used with gas burner back up during inclimate
weather) this outdoor kiln would reach cone 10 in approximately 10 - 12
hours . The last 2 + hours or so we would salt with granular dry salt at
10 minute intervals. Sometimes we had difficulty in reaching cone ten due
to wet condition of wood stored outdoors but always we were achieving good
salt glazed surfaces on our ware.
This past year we disassembled this kiln and moved it to a patio area of
our new ceramic facility. We used the same basic design with the only
exception being we now must use gas as our only fuel. WeUve fired this
kiln 4 times easily reaching cone ten in 12 hours or so. We have salted
just as before - our draw trials have good salt build up yet when the kiln
is unloaded we find minimal salt glaze build up on our pots. Both
porcelain and stoneware surfaces are coming out dry and rough. Even the
walls of this kiln are showing minimal salt build up. WeUre suspecting
that our chimney may be too tall creating extra draft thus pulling out the
salt vapor before it can affect the surface of our ware.
Our kiln is a 40 cubic ft. hard fire brick cross draft kiln. We fire on 4
gas burners and have no trouble reaching stoneware temperature. Our
chimney is 15' tall with a 13 x 9 cross section at the base tapering to a
9 x 9 cross section 5' from the bottom of the chimney. We're using dry
granular salt from a local farm supply store and have generally used about
15 to 20 lbs, by the ten's our draw trials have built up a good coating of
glaze. We introduce the salt into the kiln by way of a long piece of
angle iron loaded with salt on the end 10". This angle iron is then
tipped and spills the salt into some stoneware Rsalt boxesS that have been
placed at various places within the kiln (top of bag wall, etc.)
We may simply not be putting enough salt into our kiln, the lack of wood
ash in the atmosphere of the kiln may be altering our results or as stated
earlier our chimney may be creating too great a draft (we have tried
dampening down the stack while were salting with no discernible
difference seen in salt build up.)
If any of you have suggestions we would greatly appreciate your input.
Thanks again.
Tonya Tippit & Tony West
MWSC Ceramic Students
VandRKatz on sun 12 apr 98
I would suggest you call TURN - N - BURN Pottery in Seagrove, N.C. David has
been salt glazing for YEARS, has built lots of salt glaze kilns, is very nice
& supportive.
Vicki Katz
Katz Creek Pottery
Vince Pitelka on sun 12 apr 98
Tonya and Tony -
I am not an expert on salt firing, but have had lots of experience with a
limited number of different salt kilns. The following is based primarily on
our salt firings here at the Craft Center, where the the salt kiln is one of
our most heavily used kiln. I expect you will get good advice from others
on the list.
I am not familiar with your technique of salting into containers scattered
around the kiln. In my experience salt vaporizes most efficiently with lots
of heat and air movement, and is almost always dispensed directly into the
firebox, the hottest place in the kiln. We used to insert the rock salt
with a trough as you do. The trough was inserted through ports located
above the fireboxes, and gently inverted so that the salt dropped directly
into the firebox. Also, the salt is usually moistened with water before
salting. The resulting steam helps the salt vaporize and disperse more
efficiently, and the flame turbulence in the firebox helps carry the salt
throughout the kiln.
I don't think that that the height of your stack is a problem, but you very
well might want to close down the damper a little bit to make a less direct
flame-path through the kiln and keep the fumes in the kiln longer.
Also, you have a choice whether you want smooth or pebbled surfaces. Iif
you want really smooth surfaces, be sure not to salt within an hour or two
of the end of the firing. This gives the sodium more time to react with the
silica in the clay, and for the resulting glass to interact with other
materials in the clay. For smoother surfaces, we start salting when cone 9
begins to tip. Some people back off the gas pressure a bit at this point,
but I have found that salting usually stalls the kiln anyway, so I like to
keep the gas pressure up to give more turbulence, which helps circulate the
salt throughout the kiln. When we have salted until we are satisfied with
the draw tiles, we slowly bring cone 10 down over several hours. But when
we want textural surfaces, with more pebble or "orange peel" effect, we
start salting when cone 9 is down, and when we are satisfied with the draw
tests we bring cone 10 down over fifteen minutes to an hour. Be sure to
have enough draw tiles in the kiln so that you may continue to check the
progress after you finish salting, to determine the degree of smoothness.
If you are salting in the firebox in the normal fashion, your draw tests
should show a surface very similar to that on your pots.
As I said, we USED to insert the salt with a trough. Now most of my
students salt with burritos. We wrap the rock salt in a single sheet of
newspaper in one-pound charges, so the package resembles a burrito. The
burritos are wrapped with several wraps of string, masking tape, or duct
tape (torn down the middle to give a narrower strip), like a ribbon on
christmas package. Several hours before you are ready to salt, immerse the
burritos in a bucket of water. The masking tape or duct tape keeps the
burritos from disingegrating in the water. Fifteen minutes or so before you
are ready to salt take the burritos out of the water and let them drain a
bit. Be sure to use rock salt - not table salt. You can purchase rock salt
from grocery stores, farm stores, or from places that sell supplies for
water filters and softeners. The burritos are simply tossed into the port
above the firebox. The tape and paper immediately burn away, and the
moistened salt vaporizes very effectively.
Good luck, and let us know how it goes.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Marcia Selsor on sun 12 apr 98
Are you dampering down to keep the salt in the chamber while it vaporizes?
Marcia in Montana
Tonya Tippit wrote:
>
> ----------------------------Original message----------------------------
> Greetings fellow clay artist:
>
> As Advanced Ceramic Students at MWSC we have been given the assignment of
> researching remedies for a problem we are having with our salt kiln. We
> would appreciate any suggestion any of you might have regarding our kiln
> and salty dilemma.
>
> Thanks in advance for your assistance.
>
> History: For a number of years we fired a cross-draft hard fire brick
> kiln (wood was previously used with gas burner back up during inclimate
> weather) this outdoor kiln would reach cone 10 in approximately 10 - 12
> hours . The last 2 + hours or so we would salt with granular dry salt at
> 10 minute intervals. Sometimes we had difficulty in reaching cone ten due
> to wet condition of wood stored outdoors but always we were achieving good
> salt glazed surfaces on our ware.
>
> This past year we disassembled this kiln and moved it to a patio area of
> our new ceramic facility. We used the same basic design with the only
> exception being we now must use gas as our only fuel. WeUve fired this
> kiln 4 times easily reaching cone ten in 12 hours or so. We have salted
> just as before - our draw trials have good salt build up yet when the kiln
> is unloaded we find minimal salt glaze build up on our pots. Both
> porcelain and stoneware surfaces are coming out dry and rough. Even the
> walls of this kiln are showing minimal salt build up. WeUre suspecting
> that our chimney may be too tall creating extra draft thus pulling out the
> salt vapor before it can affect the surface of our ware.
>
> Our kiln is a 40 cubic ft. hard fire brick cross draft kiln. We fire on 4
> gas burners and have no trouble reaching stoneware temperature. Our
> chimney is 15' tall with a 13 x 9 cross section at the base tapering to a
> 9 x 9 cross section 5' from the bottom of the chimney. We're using dry
> granular salt from a local farm supply store and have generally used about
> 15 to 20 lbs, by the ten's our draw trials have built up a good coating of
> glaze. We introduce the salt into the kiln by way of a long piece of
> angle iron loaded with salt on the end 10". This angle iron is then
> tipped and spills the salt into some stoneware Rsalt boxesS that have been
> placed at various places within the kiln (top of bag wall, etc.)
>
> We may simply not be putting enough salt into our kiln, the lack of wood
> ash in the atmosphere of the kiln may be altering our results or as stated
> earlier our chimney may be creating too great a draft (we have tried
> dampening down the stack while were salting with no discernible
> difference seen in salt build up.)
>
> If any of you have suggestions we would greatly appreciate your input.
> Thanks again.
>
> Tonya Tippit & Tony West
> MWSC Ceramic Students
paul wilmoth on sun 12 apr 98
Tonya,
A couple of things to consider about your salt kiln. * You may need to
"pump" your damper when you are salting to change the flow in the kiln
which will give a more even salting. *The test rings are probably in a
position where they are "in the flow of the salt" and giving a false
reading. * In my wood salt kiln the test rings are fairly accurate to
what I get on the pots however in every gas salt kiln that I have fired
(many) the test rings always needed to be over salted to get a good
coating on the pots.* Lastly a hard brick salt kiln is like a wok - it
needs to be "seasoned" and this may mean more salt than what you are
putting in.* Some think that only a few pounds are needed, I say "put in
what ever it takes to get out good pots".
good luck - Paul
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Laura Conley on mon 20 apr 98
I unloaded my first salt kiln today, so I am not an expert by any means. I
was pleased with the results!
Our kiln is fairly new and we are still using 30lbs of salt per firing. The
draw trials did seem to have a much smoother surface than the pots. Salting
was done three times. After each salting the damper was closed down for 20
minutes.
Have you changed clay bodies? Are your glazes maturing nicely? Is everything
reducing well?
Laura Conley
Tonya Tippit wrote:
> ----------------------------Original message----------------------------
> Greetings fellow clay artist:
>
> As Advanced Ceramic Students at MWSC we have been given the assignment of
> researching remedies for a problem we are having with our salt kiln. We
> would appreciate any suggestion any of you might have regarding our kiln
> and salty dilemma.
>
> Thanks in advance for your assistance.
>
> History: For a number of years we fired a cross-draft hard fire brick
> kiln (wood was previously used with gas burner back up during inclimate
> weather) this outdoor kiln would reach cone 10 in approximately 10 - 12
> hours . The last 2 + hours or so we would salt with granular dry salt at
> 10 minute intervals. Sometimes we had difficulty in reaching cone ten due
> to wet condition of wood stored outdoors but always we were achieving good
> salt glazed surfaces on our ware.
>
> This past year we disassembled this kiln and moved it to a patio area of
> our new ceramic facility. We used the same basic design with the only
> exception being we now must use gas as our only fuel. WeUve fired this
> kiln 4 times easily reaching cone ten in 12 hours or so. We have salted
> just as before - our draw trials have good salt build up yet when the kiln
> is unloaded we find minimal salt glaze build up on our pots. Both
> porcelain and stoneware surfaces are coming out dry and rough. Even the
> walls of this kiln are showing minimal salt build up. WeUre suspecting
> that our chimney may be too tall creating extra draft thus pulling out the
> salt vapor before it can affect the surface of our ware.
>
> Our kiln is a 40 cubic ft. hard fire brick cross draft kiln. We fire on 4
> gas burners and have no trouble reaching stoneware temperature. Our
> chimney is 15' tall with a 13 x 9 cross section at the base tapering to a
> 9 x 9 cross section 5' from the bottom of the chimney. We're using dry
> granular salt from a local farm supply store and have generally used about
> 15 to 20 lbs, by the ten's our draw trials have built up a good coating of
> glaze. We introduce the salt into the kiln by way of a long piece of
> angle iron loaded with salt on the end 10". This angle iron is then
> tipped and spills the salt into some stoneware Rsalt boxesS that have been
> placed at various places within the kiln (top of bag wall, etc.)
>
> We may simply not be putting enough salt into our kiln, the lack of wood
> ash in the atmosphere of the kiln may be altering our results or as stated
> earlier our chimney may be creating too great a draft (we have tried
> dampening down the stack while were salting with no discernible
> difference seen in salt build up.)
>
> If any of you have suggestions we would greatly appreciate your input.
> Thanks again.
>
> Tonya Tippit & Tony West
> MWSC Ceramic Students
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