Joyce Lee, Jim Lee on thu 12 jun 97
So many Clayarters responded to my request for information about salt
firing in my small Geil fiber kiln (I'm not going to, thank you very
much, but may build or buy a brick salt kiln because I looove the look
of salt fired pots.), that I'm going to push my luck a bit and ask what
you salters use to get more color onto your pots when salting. The
orange peel look is what I think is so beguiling. I've sprayed a
watered-down white slip and like that look on toasty stoneware. I've
also decorated with a band of celadon when I've lined the pot with same.
Liked that. My disaster was splashing blue slip about and it turned
black and didn't blend as I'd hoped it might on some pots, while doing
exactly what I wanted on others (medium blue blurry splashes). I also
liked a matt white inside a largish (for me) bowl, and was pleased with
a Rotten Stone glazed rim on a tea (pepsi?) bowl. But that's it. My
question: How does one get the bits of blue, green etc within the orange
peel itself? I'd appreciate any information. I have a multitude of
books now (thanks to Clayarters' recommendations) and tapes but not much
on decorating "salties." (That doesn't sound right for rather robust
salted pots, does it? I just feel tender toward them, I guess. To me,
they are "salties.")
Thank you for any help you can offer. I always hate that I sound like
such an ignoramous when talking about pottery but, there you are, I just
am.
Joyce
In the Mojave getting ready to bake some Neiman-Marcus chocolate cookies
courtesy of somebody on the Internet. Arrived in my e-mail. I'm
impressed.
Paul M Wilmoth on thu 19 jun 97
Dear Joyce,
You will find that you get more regular results from colorants in
slips for salt firing(copper, cobalt, rutile, chrome etc.) Using glazes
for color is less predictible and more contingent upon atmosphere and the
amount of salt that is used (more salt - more dilution of color). I have
also had a copper glaze on a pot that fumed the whole kiln with the
result of pink to red orange peeling on white slip and porcelain.
I use both slip and glazes so that I have some predictibility but
not too much.
Good Luck -- Paul Wilmoth
FRANK GAYDOS on sun 19 jul 98
Dear Clayarters,
According to West and Lawrence in 'Ceramic Science for the Potter",
P210,
"The salt reacts with the water vapor present in the kiln atmosphere to
form sodium hydroxide and hydrochloric acid fumes which are given off in
the surrounding atmosphere."
Looking at the above statement, you can improve the quality of the
salting process by adding water to the salt before introducing it into
the firebox. In lieu of water some potters mix wood shavings or oil or
powdered coal with the salt for the same reason. Also, can mix other
ingredients for other effects but thats a different story for another
day.
Frank, in hot and humid Philly, heading to the pool.
--
Frank Gaydos
510 Gerritt St.
Philadelphia,Pa.19147-5821 USA
fgaydos@erols.com
Gavin Stairs on tue 28 jul 98
Hi Frank,
Again, this is not the whole story. Cetainly the reaction cited takes
place. That means that the kiln atmosphere has two highly reactive species
running about as gasses. But what happens when you place NaOH and HCl
together? Right: you get NaCl and H2O. These two, the salt water often
spoken of, are the natural end product of the kiln reactions, with one
exception: That Na which actually makes glaze, ie., becomes dissolved in
the glass on the pots and kiln walls, is not available to react with the
Cl- to produce salt again, so just about exactly that much HCl is produced.
Now go away and calculate how much HCl that represents. Not much. Now go
away and calculate how much CO2 (and therefore H2CO3, another acid) is
produced by burning fuel to heat the kiln. Quite a lot. And for every
molecule of CO2 produced, about 2-3 molecules of H2O are also produced.
There's lots of water in a kiln fire.
Gavin
At 02:19 PM 7/19/98 -0700, you wrote:
>Date: Sun, 19 Jul 1998 11:54:08 -0400
>From: FRANK GAYDOS
>Reply-To: fgaydos@erols.com
>MIME-Version: 1.0
>To: clayart list serve
>Subject: Salt Firing
>Status: U
>
>Dear Clayarters,
>
>According to West and Lawrence in 'Ceramic Science for the Potter",
>P210,
>"The salt reacts with the water vapor present in the kiln atmosphere to
>form sodium hydroxide and hydrochloric acid fumes which are given off in
>the surrounding atmosphere."
>
>Looking at the above statement, you can improve the quality of the
>salting process by adding water to the salt before introducing it into
>the firebox. In lieu of water some potters mix wood shavings or oil or
>powdered coal with the salt for the same reason. Also, can mix other
>ingredients for other effects but thats a different story for another
>day.
>
>Frank, in hot and humid Philly, heading to the pool.
>
>--
>Frank Gaydos
>510 Gerritt St.
>Philadelphia,Pa.19147-5821 USA
>fgaydos@erols.com
>
>
Rick Sherman on tue 28 jul 98
I returned from a trip and discovered a long discussion on salt firing
among my clayart messages. There was reference to the research reported
in Cermic Review but I noted no reference to the panel presentation at
the Las Vegas NCECA chaired by Janet Mansfield. Gil Stengel presented
Salt Firing and the Ceramic Myth, Ruthanne Tudball offered Sodium Vapor
Firing-A Measure of Pleasure a Measure of Guilt, and Will Shynkaruk
provided a significant report on his research in firing with salt and
soda, drawing comparisons as to how much HCl exited the kiln as
compared to sodium peroxide in the soda firing. It was a
well-controlled experiment which some of you might wish to replicate in
order to resolve some questions. The report is to long to print here
but those interested can obtain a copy of the 1997 NCECA Journal by
contacting Regena Bown, P.O. Box 158, Bandon, OR 97411 1-800-996-2322.
If some of you want me to duplicate pages for you, just send me your
address and I will try to do so.
Rick Sherman
San Jose, CA USofA
sherman@ricochet.net
--------------------------from Gavin----------------------------------
Again, this is not the whole story. Cetainly the reaction cited takes
place. That means that the kiln atmosphere has two highly reactive
species running about as gasses. But what happens when you place NaOH
and HCl together? Right: you get NaCl and H2O. These two, the salt
water often spoken of, are the natural end product of the kiln
reactions, with one exception: That Na which actually makes glaze,
ie., becomes dissolved in the glass on the pots and kiln walls, is not
available to react with the Cl- to produce salt again, so just about
exactly that much HCl is produced. Now go away and calculate how much
HCl that represents. Not much. Now go away and calculate how much CO2
(and therefore H2CO3, another acid) is produced by burning fuel to heat
the kiln. Quite a lot. And for every molecule of CO2 produced, about
2-3 molecules of H2O are also produced. There's lots of water in a kiln
fire.
Gavin
Tom Buck on wed 29 jul 98
----------------------------Original message----------------------------
Gavin Stairs:
May I suggest that you have over-simplified a rather complex
situation. A kiln at 1300 C burning fuel at a furious rate is hardly a
static model from which to draw conclusions. I sincerely doubt the
chemical reactions you cited actually do occur, as such.
Salt, NaCl, quickly becomes vapour in such an environment, and
that means single unassociated molecules, perhaps partly ionized, and
there is no way H2CO3 could exist in such an environment.
We know that Sodium gets incorporated into the alumino-silicate of
the claybody (ie, the pot), and it would do so as Sodium oxide, Na2O,
fluxing the Al2O3/SiO2 and thereby forming a glaze on the pot's surface.
But does Sodium arrive on the surface as NaCL molecules or as Na+ ions, or
as Na2O molecules? If as NaCl as you suggest, and it does seem logical
since NaCL molecules would be the dominant form of Sodium in the kiln,
then when Na enters the glass on the pot's surface, what happens to the
Cl- ion?
Another factor that must be considered is the "dwell" time of the
volatiles in the kiln. The burning fuel and the volatilizing NaCl have
perhaps a second or two before exiting the kiln up the flue. What kind of
reactions can occur in such a brief period? One substance that must be
present in a kiln in reducing conditions is H2, and its presence could be
enhanced by catalytic behaviour; clay is a known pyrometric catalyst (eg,
in petroleum refining). I do think that the way a kiln is operated will
have a direct bearing on how much HCl goes up the flu.
If I can locate the Ceramic Review pieces, I will try to summarize
them here. Til later.
Tom Buck
) tel:
905-389-2339 & snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
Gavin Stairs on thu 30 jul 98
Tom Buck requested that I send this off-list reply to the whole list, so
here it is:
******************************************************************************
Hello Tom,
Thanks for your comments. I have intercalated some remarks in
clarification and extension below. But in brief, yes, I did simplify.
Oversimplify may be debatable.
At 1300C, salt is barely vaporized. The dominant species is certainly
NaCl. However, the hydration reaction certainly does occur. My major
argument in this phase of the discussion is that the return reaction is
favored, and the end state must be almost completely NaCl, except for that
small fraction of the Na which has been absorbed by the glaze coat.
When I first came to this problem, I wondered what fraction of the vapor
would be plasma. The answer seems to be very little. I forget the numbers
at the moment, but the ionization energy of NaCl is on the order of 1eV,
which means that the full ionization temperature must be about an order of
magnitude greater than the melting temperature, or kiln temperatures. Some
significant ionization might occur in a neutral gas flame, but that would
be short lived. It would be signaled by a strong yellow sodium emission
from the flame. I know of no reports of a strong sodium light coming from
a salt kiln.
At 11:22 PM 7/28/98 -0400, you wrote:
>Gavin Stairs:
> May I suggest that you have over-simplified a rather complex
>situation. A kiln at 1300 C burning fuel at a furious rate is hardly a
>static model from which to draw conclusions. I sincerely doubt the
>chemical reactions you cited actually do occur, as such.
I did not mean to imply that this environment was static. Rather that the
reactions are in some dynamic balance, tipped to the side of NaCl rather
than HCl.
> Salt, NaCl, quickly becomes vapour in such an environment, and
>that means single unassociated molecules, perhaps partly ionized, and
>there is no way H2CO3 could exist in such an environment.
Again, I was referring to the end state, and not to the kiln atmosphere, in
respect of the emissions of NaCl, HCl and H2CO3.
> We know that Sodium gets incorporated into the alumino-silicate of
>the claybody (ie, the pot), and it would do so as Sodium oxide, Na2O,
>fluxing the Al2O3/SiO2 and thereby forming a glaze on the pot's surface.
>But does Sodium arrive on the surface as NaCL molecules or as Na+ ions, or
>as Na2O molecules? If as NaCl as you suggest, and it does seem logical
>since NaCL molecules would be the dominant form of Sodium in the kiln,
>then when Na enters the glass on the pot's surface, what happens to the
>Cl- ion?
This is a question that I would very much like to investigate. I know from
discussion with Gil Stengel that in subsequent firings of a salt kiln
"salt" is reemitted from the kiln walls. What is the form? He says that
it forms the distinctive salt plume of white vapor, so I speculate that at
least some of the Cl- remains in the glaze, where it may contribute to
mobilizing other cations as well as the sodium.
> Another factor that must be considered is the "dwell" time of the
>volatiles in the kiln. The burning fuel and the volatilizing NaCl have
>perhaps a second or two before exiting the kiln up the flue. What kind of
>reactions can occur in such a brief period? One substance that must be
>present in a kiln in reducing conditions is H2, and its presence could be
>enhanced by catalytic behaviour; clay is a known pyrometric catalyst (eg,
>in petroleum refining). I do think that the way a kiln is operated will
>have a direct bearing on how much HCl goes up the flu.
The first necessity for a reaction is that the reagents come into contact.
In a kiln under full fire, a great deal of the vapor must not come into
such contact, and must therefore go straight up the flue. This is one
reason that most of the salt in a salt kiln is not reacted. Also, all of
the chemical reactions in the kiln are reversable, and it is therefore
advantageous to have an excess of reagent on the undesired side. That is,
an excess of salt. This changes the reaction dynamics to the favorable
side.
I suspect that the initial glazing reaction may be from simple adhesion of
NaCl to the solid body or glaze mixture, and subsequent exchange/diffusion
leading to local melting. In this initial phase, the Cl- ion might
exchange with O-- from H2O from the atmosphere, and then leave as HCl, or
it might participate in the glaze in an unconventioal way (i.e.,
non-oxide). Cl- being a stronger oxidizer than O--, I suspect that it
might form a bond to the most electropositive species around, and remain.
In most cases, that would mean that NaCl would remain in the glaze, and
participate as a polar molecule.
But this part of the discussion is entirely speculative on my part. I'm
hoping to do some Raman spectroscopy on some glaze samples one day to see
what's actually there.
It is difficult to convey to the Clayart population the sense of a hot
molecule, and the way in which changes in chemical composition may come
about. This latest phase of the discussion seemed to be concerned mostly
with the end state emissions, so I tipped my remarks in that direction.
It is possible to state fairly categorically what is possible to be emitted
just from the initial constituents and arguments like those above: there is
an upper bound to the possible emission of HCl and Cl2, and it falls well
short of the concerns of many well meaning people.
In a 40cu.ft. kiln, the glaze coat might contain ~1kg of NaCl/Na2O. This
comes from ~10kg of salt. About 10% of the salt is reacted.
The statement that the emissions are less than 1% is relatively meaningless
unless qualified. 1% of what? Over what period? Tons of gasses move
through a kiln during a firing. The amount of Cl available is ~1kg. That
puts an upper limit at <0.1% overall. The measurements you referred to are
spot measurements during a short period, <5% of the firing schedule. So
the overall concentration in emissions must be <5ppm, with a peak value of
<1% for a short period of time.
I believe that the actual values are well below this. I don't believe that
any significant Cl2 is produced, and I believe that the amount of HCl is at
or below that required to produce all the glazing effect by the reaction
2(NaCl) + H2O -> Na2O + 2(HCl).
I hope this clarifies my remarks somewhat.
Gavin
Gavin Stairs
Toronto, Canada
Stuart Ridgway on thu 27 aug 98
Some thoughts on salt firing reactions:
The salt load introduces sodium and chlorine into the kiln. The
sodium combines with the ware to form a glaze. What happens to the
chlorine? We all know that if we mix HCl and NaOH at room temperature we
get salt (NaCl) and water (H2O) and a substantial amount of heat is
released. We also know, (probably leChatelier's principle) that if we
increase the temperature the reaction will go slightly in the reverse
direction. Then let us remove one of the reverse direction products, say
the HCl, since it is a gas, and can be swept out by the burnt fuel gas
headed for the stack. The sodium is left behind, and also removed from the
reaction zone by combining with the clay and silica to form the glaze.
The water comes from the combustion, and is attached to surfaces of
the clay and silica particles. So these surfaces are the reaction zone.
The vapor pressure of sodium chloride at 1300 degrees C is about 2/7 of an
atmosphere, so there will be lots of sodium chloride available to the
reaction. Ferric chloride is quite volatile, so some of the chlorine could
depard with iron. Ferric chloride and water is quite corrosive, and could
share the blame for corroding kiln parts with HCl.
Stuart Ridgway
>----------------------------Original message----------------------------
>Gavin Stairs:
> May I suggest that you have over-simplified a rather complex
>situation. A kiln at 1300 C burning fuel at a furious rate is hardly a
>static model from which to draw conclusions. I sincerely doubt the
>chemical reactions you cited actually do occur, as such.
> Salt, NaCl, quickly becomes vapour in such an environment, and
>that means single unassociated molecules, perhaps partly ionized, and
>there is no way H2CO3 could exist in such an environment.
> We know that Sodium gets incorporated into the alumino-silicate of
>the claybody (ie, the pot), and it would do so as Sodium oxide, Na2O,
>fluxing the Al2O3/SiO2 and thereby forming a glaze on the pot's surface.
>But does Sodium arrive on the surface as NaCL molecules or as Na+ ions, or
>as Na2O molecules? If as NaCl as you suggest, and it does seem logical
>since NaCL molecules would be the dominant form of Sodium in the kiln,
>then when Na enters the glass on the pot's surface, what happens to the
>Cl- ion?
> Another factor that must be considered is the "dwell" time of the
>volatiles in the kiln. The burning fuel and the volatilizing NaCl have
>perhaps a second or two before exiting the kiln up the flue. What kind of
>reactions can occur in such a brief period? One substance that must be
>present in a kiln in reducing conditions is H2, and its presence could be
>enhanced by catalytic behaviour; clay is a known pyrometric catalyst (eg,
>in petroleum refining). I do think that the way a kiln is operated will
>have a direct bearing on how much HCl goes up the flu.
> If I can locate the Ceramic Review pieces, I will try to summarize
>them here. Til later.
>
>Tom Buck
>) tel:
>905-389-2339 & snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
>(westend Lake Ontario, province of Ontario, Canada).
>
Evan Dresel on sun 30 aug 98
I don't have all the answers, by a long shot but one thing you can count on
in chemistry is that things remain electrically neutral, overall.
That means that if you are reacting Na+ with the clay body you either have
to be adding some negative ions also or else losing some other positive
ions. Don't think I've ever got an static electric shock from touching a pot:-)
So would you be able to incorporate OH- into a glass? I suppose Fe+3 loss
could be a possibility, too. Seems like you would have to lose a bunch
though. I'm thinking it has something to do with breaking the
sheet-silicate structure of the clay into kind of random chains in a glass
and Na grabs onto some dangling bonds. Still got to do something to keep
neutral though. Or as the classic cartoon shows a lab-coated scientist
gesturing to a blackboard covered with equations and explaining to his
collegue, "...then a miracle occurs."
I wouldn't be surprised if mostly you are just putting in NaCl in one end
and shooting NaCl out the other in a really inefficient process. Yes there
must be something else happening but it may be swamped out by the massive
amount of salt lost.
-- Evan in W. Richland WA, USA where we get our precipitation the
old-fashioned way: we make it.
At 09:21 AM 8-27-98 EDT, you wrote:
>----------------------------Original message----------------------------
>Some thoughts on salt firing reactions:
>
> The salt load introduces sodium and chlorine into the kiln. The
>sodium combines with the ware to form a glaze. What happens to the
>chlorine? We all know that if we mix HCl and NaOH at room temperature we
>get salt (NaCl) and water (H2O) and a substantial amount of heat is
>released. We also know, (probably leChatelier's principle) that if we
>increase the temperature the reaction will go slightly in the reverse
>direction. Then let us remove one of the reverse direction products, say
>the HCl, since it is a gas, and can be swept out by the burnt fuel gas
>headed for the stack. The sodium is left behind, and also removed from the
>reaction zone by combining with the clay and silica to form the glaze.
>
> The water comes from the combustion, and is attached to surfaces of
>the clay and silica particles. So these surfaces are the reaction zone.
>The vapor pressure of sodium chloride at 1300 degrees C is about 2/7 of an
>atmosphere, so there will be lots of sodium chloride available to the
>reaction. Ferric chloride is quite volatile, so some of the chlorine could
>depard with iron. Ferric chloride and water is quite corrosive, and could
>share the blame for corroding kiln parts with HCl.
>
>Stuart Ridgway
>
>
Matthew Cope on wed 3 jan 01
I found this article:
Gil Stengel wrote in the Ceramic TECHNICAL issue #7 page 8
"....Ceramic Industry magazine, I have found evidence that salt firing was
widely abandoned by industry in the '50s in favour of much stronger and
better fitting applied glazes. The sewer tile industry in particular
apparently left salt-glazing behind due to the high coefficient of thermal
expansion of salt-glaze..."
Mitsuru Cope
Clay Creatures
www.mitsurucope.com
PS.My e-mail cannot send this message.
Gail Adkisson on thu 9 jun 05
Salt Firing Workshop July 16, 17 & 20, 2005
Come revel in the soda firing process. Participants will work as a team
and become familiar with all aspects of the process. Marianne Cordyack
reveals glaze recipes, loading techniques and her experience with previous
firings.
Each student may bring 12-15 pots which must be bisque fired prior to the
workshop. Discover how the addition of soda and salt to the kiln can
enhance the surface of your form. This will be an impressive experience
to add to your journey with clay!
For information, contact Gail @ 703-750-9480, visit website:
CreativeClayPottery.com,email: daisy_gail@msn.com
Hank Murrow on thu 2 feb 06
On Feb 2, 2006, at 9:27 AM, Christine wrote:
> I am new to salt firing and am looking for a better clay body that
> takes
> salt well. I really enjoy the look and texture of heavy salting, but I
> don't want to destroy my kiln. I would really appreciate any clay body
> recipes that i could use as a jumping off point. I also was wondering
> if
> anyone has any slip recipes that also work well in salt firing that
> they
> wouldn't mind sharing. I am particulary interested in flashing slips.
Having just participated in a wood/salt firing at Tom Rohr's Pleasant
Hill Pottery, I will hazard an answer. Years ago the best clay I ever
found for salt was Jordan clay, but it has not been available for some
time. Nowadays I try to use a body with Helmer and/or McNamee kaolins,
and ball clay and feldspar and fine sand. You do want to not have too
much Al2O3 in the body, because the salt doesn't like to form a glaze
with alumina. Similarly, don't have too much iron in the body either.
Fine grained light stoneware with trace impurities seems to work well.
Cheers, Hank
www.murrow.biz/hank
Christine on thu 2 feb 06
I am new to salt firing and am looking for a better clay body that takes
salt well. I really enjoy the look and texture of heavy salting, but I
don't want to destroy my kiln. I would really appreciate any clay body
recipes that i could use as a jumping off point. I also was wondering if
anyone has any slip recipes that also work well in salt firing that they
wouldn't mind sharing. I am particulary interested in flashing slips.
Thanks a Bunch!
Christine
June Perry on fri 3 feb 06
If you want to use less salt in your firings then what you will want to look
for is a clay body that has a ratio of about 4 -5 to 1 silica to alumina.
The higher silica will attract more of the salt onto the pots instead of
your bricks.
If you want a body that flashes well, then you would look for a ratio in the
2-3 ratio.
There are many clay body recipes around so once you decide what color you
want, run some of them through one of the glaze chemistry programs to find out
the ratios.
If you live on the west coast, they have some high silica fireclays like
Lincoln 60 that would work well as part of the formula. Foundry Hill Creme is
also higher in silica and would be a good addition to a body.
I've been designing some clay bodies recently (test bars are drying as I
write); and I'm looking for both types -- one that flashes a nice rust body
color on exposed parts and another that will take the soda well over non flashing
slips.
If your local suppliers have a generous selection of clays, as we had when I
lived on the west coast, you should have no trouble picking out those
fireclays and balls clays with the higher silica content. You can also add some
silica to the body; but make sure you have enough spar in there to balance it.
You can check out my web site (link below). I have several ball clay, kaolin
and fire clay test pieces that I fired in my soda/salt kiln and you can see
the fired color as well as how they salted or flashed.
To get a blown up look you can copy the pictures and paste them in a program
like Paint Shop Pro or similar and enlarge them for a better view.
Warm regards,
June Perry
_http://www.angelfire.com/art2/shambhalapottery_
(http://www.angelfire.com/art2/shambhalapottery)
June Perry on sat 1 mar 08
You may want to check out my soda/salt firing group on Yahoo. You have to
join (no fees). Joining is just to keep spammers out. You'll find the link in
my signature at the end of this post.
We have a photo file where soda/salt firers have posted pictures of their
kilns and some samples of their work and there's an extensive file of soda/salt
flashing slip and glaze recipes that is continually being added to.
As far as your questions:
Yes you can single fire. That is very common.
Soda/or salt is a choice based more on the look you want. I use
soda/augmented with salt and I use plain sea salt since I don't have a source for
dendritic salt which I used when I lived on the west coast.
Currently I'm using a moist paste mix of soda and salt that I put on small
pieces of wood. My kiln has an area built in for this purpose. Prior to my hip
problem, I was mainly just spraying the soda solution. I also have a piece
of angle iron that I can use to introduce salt or soda as an emergency choice
if my sprayer goes kaput.
Claybodies: I use Moon White, a white stoneware, and Phoenix, which is a bit
darker, but still light firing stoneware. Darker bodies can make your
flashing slips go from orange/bright orange to a more dull brown and too much iron
in the body give a dark sewer tile look to the clay. The darker bodies will
also muddy colored slips. Your choice will be based on what look you want to
achieve.
Glazes: Glazes with high calcium/magnesium/boron/and or barium work well in
soda/salt. Amber celadon, Oribe, Barium blues, some chuns, temmokus etc. do
fine. You can check the recipe folder in the soda/salt group if you decide to
join.
Both soda and salt will create toxic conditions in the air. You can probably
do a google search to get a more exacting run down of this. The soda
emissions won't be as obvious as salt which puts out a huge cloud of white smoke.
I'd recommend the Tudball soda book, the Rosemary Cochrane book and the Jack
Troy book as good sources for soda and salt information.
Regards,
June
_http://www.shambhalapottery.com_ (http://www.shambhalapottery.com/)
_http://shambhalapottery.blogspot.com_
(http://shambhalapottery.blogspot.com/)
_http://groups.yahoo.com/group/sodasaltfiring_
(http://groups.yahoo.com/group/sodasaltfiring)
**************Ideas to please picky eaters. Watch video on AOL Living.
(http://living.aol.com/video/how-to-please-your-picky-eater/rachel-campos-duffy/
2050827?NCID=aolcmp00300000002598)
Sojourner Forspam on fri 25 nov 11
I have no idea where this topic left off - I've been offline due to healt=
=3D
h
stuff, and I'm not really up to wading through old messages looking for t=
=3D
he
old thread.
So I'm not trying to start an argument - or continue one if one was actua=
=3D
lly
going on. But I did manage to track down at least one of the articles up=
=3D
on
which I base my statements re the safety of salt firing.=3D20=3D20
Salt and the Atmosphere - Gil Stengel - Ceramics Technical - Vol 7 - 1998=
=3D
p 3-8
I have a pdf scanned copy of this article I could send to the list as an
attachment if anyone wants to read it, but I don't know the rules about
doing that. I'd rather not try to send it out individually because I don=
=3D
't
check e-mail regularly. On the other hand I don't want to clog anyone's
mailbox with a 1Mb attachment.=3D20=3D20
In this article, the author concludes that salt-firing (in small home and=
=3D
studio kilns) doesn't pose an environmental danger. However much of the
data was gathered from a single 50 cu foot kiln fired at Ohio University.=
=3D
=3D20
We don't know what may happen in larger or smaller kilns, or how firing
schedules may affect things (if at all). (He talks about 2 salt fired ki=
=3D
lns
that were used to generate data in England or Great Britain but I don't s=
=3D
ee
the actual data for those so we have no details about those kilns).=3D20
Therefore this study is indicative but not conclusive.=3D20=3D20
However, as long as we're talking about doing salt-firing in a properly
vented kiln, it's close enough for government purposes (or ours in this
case). At one point he talks about finding HCl in the kiln chimney but
concluding that this is OK because no appreciable amount was detected
outside the kiln; remember that an unvented kiln HAS no chimney.
A telling quote from the article:
"Salt or other fumes from any kilns should not be inhaled. Prudent and
proper use of a respirator can easily eliminate hazards to persons in the=
=3D
vicinity of a traditional salt firing - or any other fuel firing."
Definitely it should not be done in a garage in an unvented shell of an o=
=3D
ld
kiln!
I agree with the position that salt-firing is overall no worse than any k=
=3D
iln
firing and the additional fumes produced are easily handled in a properly=
=3D
vented kiln. HCl is produced in such a firing, but (properly vented) doe=
=3D
s
not pose any great additional hazard. Chlorine fumes probably are produc=
=3D
ed
under at least some circumstances but I can't lay my hands on the researc=
=3D
h
that showed that so I'll have to let that slide. It's frankly not that
important to me, because NO kiln, salt-firing or not, should be operated =
=3D
in
an enclosed space without proper venting. A salt-fire kiln can be safely=
=3D
operated without undue risk to the environment or people given that the
normal safety precautions are followed.
Anyway I have a PDF of the article if it's ok to send it through to the
list. If that's ok, if whoever is responsible for that could post a messa=
=3D
ge
with the header saying something like "It's OK to send an attachment to t=
=3D
he
list" I'll do it, but if you send it RE this thread I'm not going to see =
=3D
it.
I'm still pretty tired so I"m not going to be reading much on the forum =
=3D
for
quite awhile yet. Sorry!=3D20
Right now I'd rather get back to trying to figure out which bats to buy. =
=3D
My
new wheel arrived the day before Thanksgiving with no bats - I thought I =
=3D
was
getting 2 with it, oh well.
Vince Pitelka on fri 25 nov 11
Sojourner Forspam wrote:
"Chlorine fumes probably are produced under at least some circumstances but
I can't lay my hands on the research that showed that so I'll have to let
that slide."
Hi Sojourner -
Thanks for that message and some good solid information, except for your
sentence above. It is irresponsible to keep saying that, because there is
no evidence to support it. There are no chlorine fumes produced by salt
firing, for the simple reason that there is plenty of water vapor present t=
o
combine with the chlorine to form hydrogen chloride gas.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net
http://iweb.tntech.edu/wpitelka/
Randall Moody on fri 25 nov 11
It is my opinion that if you don't want to do salt/soda firings then don't.
--
Randall in Atlanta
http://wrandallmoody.com
ivor and olive lewis on sat 26 nov 11
Dear Sojourner Forspam,
I would appreciate seeing a PDF of that article on Salt
glazing.
In particular I would appreciate a description of the Chemistry that is use
by the Author. Does he use the Lawrence and West equations\, or describe ho=
w
the kiln effluent was collected and analysed.
By the way, the earliest description of the reaction of clay with salt at
high temperatures I have found in the literature was published in English,
translated from German in(1670) is to be found in the Works of Rudolph
Glauber, the Dutch Alchemist
Thanks,
Ivor Lewis,
REDHILL,
South Australia.
Bonnie Staffel on mon 28 nov 11
For whatever it is worth, speaking of fumes from salt kilns and when I
attended Cranbrook, we had small experimental gas kilns in the kiln room
with chimneys that went outside. After the groundskeeper noticed some
changes in the copper clad roofs, salt firing was eliminated from the
program. If anyone remembers Catherine Choy, a student there at the time,
she was always experimenting in reduction and salt firing in these small
kilns. They may have been the old Revelation Kilns developed by Pewabic
Pottery in its early days.
Bonnie
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
DVD Throwing with Coils and Slabs
DVD Introduction to Wheel Work
Charter Member Potters Council
| |
|
