Neon-Cat on thu 12 aug 10
Hi David =3D96 how exciting to be thinking about building a soda kiln!
I=3D92d like one, too. You=3D92ll have to keep us updated on your successes=
.
I don=3D92t have studies for you =3D96 how about some fundamental basics th=
at
cut to the chase? If you need help before you talk to the inspector
again just post me off list.
At the desired kiln temperature (somewhere between 1150 =3D96 1310 C/2102
- 2390 F) depending on your clay body and the desired glaze effects)
for your soda firing several things happen in very, very rapid
succession when you introduce sodium bicarbonate. The reactions
involved are as follows:
Sodium bicarbonate is thermally decomposed into sodium carbonate,
water vapor and carbon dioxide:
2NaHCO3 ---> Na2CO3 + H2O + CO2 (1)
Immediately heat converts the sodium carbonate into sodium oxide plus
carbon dioxide:
Na2CO3 ---> Na2O + CO2 (2)
The sodium oxide, as it does when evolved during sodium chloride
(NaCl) firings, reacts with the surface of the clay ware to form a
sodium-alumina-silicate glaze (the goal):
2Na2O + xAl2O3.ySiO2 ---> 2Na2O.xAl2O3.ySiO2 (3)
Alternately, but not likely (the melting point of sodium hydroxide is
318 C/604 F and its boiling point is 1390 C/2534 F), some sodium oxide
that has not reacted with either the kiln walls or the clay ware may
combine with water vapor in the kiln atmosphere to produce sodium
hydroxide fumes:
Na2O + H2O ---> 2 NaOH (4)
The low levels of these fumes, if created, would just harmlessly
disperse in the surrounding atmosphere after discharge from the kiln.
More likely, at kiln temperature any sodium hydroxide fumes formed
will almost instantaneously decompose to form more sodium oxide and
evolve additional water vapor:
4NaOH + heat ---> 2Na2O +2H2O (5)
This will then beautifully glaze the ware as in equation 3 above.
Or any sodium hydroxide fumes formed could combine in a carbonation
reaction with CO2 to form a low-density =3D93light=3D94 soda ash (sodium
carbonate) and water vapor:
2 NaOH + CO2 ---> Na2CO3 + H2O (6)
This in turn (as in equation 2) forms more sodium oxide with which to
glaze the ware or there could be a reaction with carbon dioxide gas
and water vapor that returns the original reactant sodium bicarbonate:
Na2CO3 + CO2 + H2O ---> 2 NaHCO3 (7)
Reaction 6 most often occurs in aqueous solutions, not extremely hot,
gaseous atmospheres like we have in a kiln, besides this carbonization
reaction is a slow one involving the diffusion of atmospheric carbon
dioxide into an aqueous solution.
These cycling reactions from the thermal decomposition of sodium
bicarbonate are so very unlikely at kiln temperatures that about all
in the way of possible nuisance that will be produced during a success
firing are those fumes associated with normal reduction or oxidation
firing. A stalled kiln or a misfiring might possibly produce some
light fumes of NaOH. But really, just stick with equations 1,2 and 3
above.
Fearless firing!
(take the inspector one of your first-born pots from the new kiln...)
Marian
Neon-Cat
www.neon-cat.com
http://www.flickr.com/photos/neon-cat/
David Beumee on thu 12 aug 10
I'm very interested in building and firing a small soda kiln. The city
official who I contacted for permission to build is not convinced of the
evidence of environmental safety that I presented, namely Ruthann Tudball's
quotes from Gail Nichols book "Soda, Clay, and Fire." That the Pollution
Inspectorate in the UK deemed that effluent from studio potters' sodium
vapor kilns "trivial and insignificant" in relation to other forms of
pollution (Tudball 1995) is not convincing enough to our city building
inspector. He wants updated assurance of the environmental safety of
injecting sodium bicarb into a kiln. Ruthann Tudball argues that any sodium
hydroxide vapor emitted from the chimney would convert back to to soda ash,
(sodium carbonate), and that the environmental effects from a studio
potter's kiln would be minimal, but our city inspector argues that soda ash
is caustic and therefore unsafe. When I made a comparison between the
pollution produced by an occasionally fired 16 cu. ft. soda kiln and the
pollution produced by driving a car for a year, or to that of a jumbo jet
taking off and landing, that argument got nowhere with him. Does anyone kno=
w
of evidence of environmental safety of firing a soda kiln that relies on
research done in the US since 1995?
David Beumee
Porcelain by David Beumee
Lafayette, CO
Vince Pitelka on thu 12 aug 10
In response to David Beumee's post below, the safety GOOD guy, Jeff Zamek
(in comparison to the wacko safety Nazi who writes for a popular magazine),
has done the research, and has shown that the worst thing produced by a sod=
a
kiln is the slow corrosion of ferrous surfaces in the immediate area. Jeff
can be reached via his website at www.jeffzamek.com. Do not let paranoid
local officials stop you from building a soda kiln. Jeff can probably help=
.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
-----Original Message-----
From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of David Beumee
Sent: Thursday, August 12, 2010 10:03 AM
To: Clayart@LSV.CERAMICS.ORG
Subject: soda and environment
I'm very interested in building and firing a small soda kiln. The city
official who I contacted for permission to build is not convinced of the
evidence of environmental safety that I presented, namely Ruthann Tudball's
quotes from Gail Nichols book "Soda, Clay, and Fire." That the Pollution
Inspectorate in the UK deemed that effluent from studio potters' sodium
vapor kilns "trivial and insignificant" in relation to other forms of
pollution (Tudball 1995) is not convincing enough to our city building
inspector. He wants updated assurance of the environmental safety of
injecting sodium bicarb into a kiln. Ruthann Tudball argues that any sodium
hydroxide vapor emitted from the chimney would convert back to to soda ash,
(sodium carbonate), and that the environmental effects from a studio
potter's kiln would be minimal, but our city inspector argues that soda ash
is caustic and therefore unsafe. When I made a comparison between the
pollution produced by an occasionally fired 16 cu. ft. soda kiln and the
pollution produced by driving a car for a year, or to that of a jumbo jet
taking off and landing, that argument got nowhere with him. Does anyone kno=
w
of evidence of environmental safety of firing a soda kiln that relies on
research done in the US since 1995?
David Beumee
Porcelain by David Beumee
Lafayette, CO
John Britt on thu 12 aug 10
Check out Phil Rogers book:
http://www.amazon.com/Salt-Glazing-Phil-Rogers/dp/0812236890/ref=3D3Dsr_1_9=
=3D
?s=3D3Dbooks&ie=3D3DUTF8&qid=3D3D1281652321&sr=3D3D1-9
He has a section on testing.=3D20=3D20
I would think that they would have to have proof of toxicity (e.g. chlori=
=3D
ne
gas) rather than you prove that there is toxicity (no chlorine gas)? The=
=3D
n
you would have to prove every conceivable possibility is not happening.
John Britt=3D20
www.johnbrittpottery.com
ivor and olive lewis on fri 13 aug 10
Dear David Beumee <
Get hold of a copy of P. J Durrant, "General and Inorganic Chemistry.",
Longmans, Green and Co Ltd. 1956. P. 319. Durrant states "Anhydrous Sodiu=
m
Carbonate is prepared by heating hydrated salts, or by heating Sodium
Bicarbonate. It melts at 852 deg C and is not decomposed by heat.Asterisk t=
o
a Footnote. (Quote)
"Sodium carbonate loses weigh at a rate of 1 milligram per minute if heated
above red heat in a platinum crucible in air. The loss is due partly to
decomposition, whereby Carbon Dioxide is expelled leaving a residue of oxid=
e
and hydroxide, and partly by volatilisation. If Sodium carbonate is heated
in a porcelain crucible considerable loss of weight is observed, as silica
from the porcelain expels Carbon Dioxide.
SiO2+ Na2CO3 =3D Na2SiO3 +CO2 "
You might read "Ninety Sixth report on the Alkali and Chemical Works in
England and Wales, 1959". P46 concerns Salt Glazing and states that the
total acid content is between 3 and 4 grains per cubic foot. They also foun=
d
Potassium, Ammonium, Lithium, Calcium and Magnesium compounds in the
effluent.
I doubt if you will find defining experimental evidence gathered in the pas=
t
fifteen years that is scientifically controlled. There were no scientific
controls applied to work done before 1950 on the Salt Glaze Process. Who in
Industry would waste money researching an obsolete technology ?
Best regards,
Ivor Lewis,
REDHILL,
South Australia
KATHI LESUEUR on fri 13 aug 10
On Aug 12, 2010, at 9:06 PM, Robert Harris wrote:
> Oh, I should add that I realize that Zinc Oxide can only be used in
> oxidation.>>
I'd like to hear the opinion of some of our glaze gurus on this =3D
statement. I have two cone 10 glazes that have zinc. I've tried them =3D
with and without the zinc. There was a difference. I've never heard that =
=3D
zinc can only be used in oxidation. Comments, please?
KATHI LESUEUR
http://www.lesueurclaywork.com
> =3D20
Edouard Bastarache on fri 13 aug 10
Welcome back Neon-Cat.
clap, clap, clap!!!
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://www.facebook.com/edouard.bastarache
----- Original Message -----=3D20
From: "Neon-Cat"
To:
Sent: Friday, August 13, 2010 12:32 AM
Subject: Re: soda and environment
Hi David =3D96 how exciting to be thinking about building a soda kiln!
I=3D92d like one, too. You=3D92ll have to keep us updated on your successes=
.
I don=3D92t have studies for you =3D96 how about some fundamental basics th=
at
cut to the chase? If you need help before you talk to the inspector
again just post me off list.
At the desired kiln temperature (somewhere between 1150 =3D96 1310 C/2102
- 2390 F) depending on your clay body and the desired glaze effects)
for your soda firing several things happen in very, very rapid
succession when you introduce sodium bicarbonate. The reactions
involved are as follows:
Sodium bicarbonate is thermally decomposed into sodium carbonate,
water vapor and carbon dioxide:
2NaHCO3 ---> Na2CO3 + H2O + CO2 (1)
Immediately heat converts the sodium carbonate into sodium oxide plus
carbon dioxide:
Na2CO3 ---> Na2O + CO2 (2)
The sodium oxide, as it does when evolved during sodium chloride
(NaCl) firings, reacts with the surface of the clay ware to form a
sodium-alumina-silicate glaze (the goal):
2Na2O + xAl2O3.ySiO2 ---> 2Na2O.xAl2O3.ySiO2 (3)
Alternately, but not likely (the melting point of sodium hydroxide is
318 C/604 F and its boiling point is 1390 C/2534 F), some sodium oxide
that has not reacted with either the kiln walls or the clay ware may
combine with water vapor in the kiln atmosphere to produce sodium
hydroxide fumes:
Na2O + H2O ---> 2 NaOH (4)
The low levels of these fumes, if created, would just harmlessly
disperse in the surrounding atmosphere after discharge from the kiln.
More likely, at kiln temperature any sodium hydroxide fumes formed
will almost instantaneously decompose to form more sodium oxide and
evolve additional water vapor:
4NaOH + heat ---> 2Na2O +2H2O (5)
This will then beautifully glaze the ware as in equation 3 above.
Or any sodium hydroxide fumes formed could combine in a carbonation
reaction with CO2 to form a low-density =3D93light=3D94 soda ash (sodium
carbonate) and water vapor:
2 NaOH + CO2 ---> Na2CO3 + H2O (6)
This in turn (as in equation 2) forms more sodium oxide with which to
glaze the ware or there could be a reaction with carbon dioxide gas
and water vapor that returns the original reactant sodium bicarbonate:
Na2CO3 + CO2 + H2O ---> 2 NaHCO3 (7)
Reaction 6 most often occurs in aqueous solutions, not extremely hot,
gaseous atmospheres like we have in a kiln, besides this carbonization
reaction is a slow one involving the diffusion of atmospheric carbon
dioxide into an aqueous solution.
These cycling reactions from the thermal decomposition of sodium
bicarbonate are so very unlikely at kiln temperatures that about all
in the way of possible nuisance that will be produced during a success
firing are those fumes associated with normal reduction or oxidation
firing. A stalled kiln or a misfiring might possibly produce some
light fumes of NaOH. But really, just stick with equations 1,2 and 3
above.
Fearless firing!
(take the inspector one of your first-born pots from the new kiln...)
Marian
Neon-Cat
www.neon-cat.com
http://www.flickr.com/photos/neon-cat/
Robert Harris on fri 13 aug 10
Zinc oxide is easily reduced to Zinc metal in a reduction atmosphere.
The boiling point of Zinc metal is 907C (1664F), so generally speaking
in a reduction kiln the zinc just boils out of your glaze before you
even get a good melt going. I suppose it may depend on what
temperature you start to reduce at, but if the zinc hasn't fully
incorporated into the melt then it's just going to disappear up you
chimney and onto your kiln lining.
I have heard rumours of zinc doing nasty things to your glaze in a
reduction atmosphere too. Perhaps others on this list have more
experience.
Robert
Edouard Bastarache on fri 13 aug 10
Kathi,
I tested that in reduction at cone 9=3DBD. Ron Roy is right when he says zi=
=3D
nc
oxide is reduced to metallic zinc and expelled from the glaze, therefore
useless.
------------------------------------------------------------------
Check out the following results and you will see what I mean,
no important differences between the 2 series, taking into account the fa=
=3D
ct=3D20
they were baked in 2 different firings.
Chromium Brown Greens
Bruns Verts de Chrome
http://chromiumgreens.blogspot.com/
----------------------------------------------------
C/9-10 Redux Zinc-Chromium Browns
C/9-10 R Bruns de Zinc-Chrome
http://chromiumbrowns2.blogspot.com/
-----------------------------------------------------=3D20
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://blogsalbertbastarache.blogspot.com/
http://cerampeintures.blogspot.com/
http://www.facebook.com/edouard.bastarache
----- Original Message -----=3D20
From: "KATHI LESUEUR"
To:
Sent: Friday, August 13, 2010 9:26 AM
Subject: Re: soda and environment
On Aug 12, 2010, at 9:06 PM, Robert Harris wrote:
> Oh, I should add that I realize that Zinc Oxide can only be used in
> oxidation.>>
I'd like to hear the opinion of some of our glaze gurus on this statement=
=3D
. I
have two cone 10 glazes that have zinc. I've tried them with and without =
=3D
the
zinc. There was a difference. I've never heard that zinc can only be used=
=3D
in
oxidation. Comments, please?
KATHI LESUEUR
http://www.lesueurclaywork.com
>
Neon-Cat on fri 13 aug 10
Thanks, Edouard!
It was a pleasant respite from kitchen remodeling. If the upcoming
solvent fumes make me loopy maybe I'll venture into zinc oxide, a very
interesting ceramic material. It is not hygroscopic but it can by a
process termed chemisorption adsorb gas phase species (H+. OH-, etc.)
on its surfaces. It has a fondness for adsorbing the ions associated
with carbon dioxide and water but can adsorb a wide variety of ions.
This makes for some interesting thoughts about fired zinc oxide, kiln
atmosphere during firing, glaze companion ingredients, the changes in
zinc oxide surface porosity before and after calcining, etc. If I were
to use zinc oxide I'd not bother calcining it. It's interestingly
complicated and widely studied in recent years.
Laboring is hard -- maybe fumes *will* help...onward.
You all have a good day!
Marian
On Fri, Aug 13, 2010 at 11:03 AM, Edouard Bastarache w=
rote:
> Welcome back Neon-Cat.
>
> clap, clap, clap!!!
>
> Gis,
>
> Edouard Bastarache
> Spertesperantisto
>
> Sorel-Tracy
> Quebec
>
> http://www.flickr.com/photos/30058682@N00/
> http://edouardbastarache.blogspot.com/
> http://blogsalbertbastarache.blogspot.com/
> http://cerampeintures.blogspot.com/
> http://www.facebook.com/edouard.bastarache
Ron Roy on fri 13 aug 10
Hi Kathi,
When zinc is reduced - and it is easily reduced - the metal boils away
at our temperatures - leaves the mix - maybe does some melting in some
glazes that seal over before reduction starts.
I'd like to see the recipes of those two glazes to see if they are the
kind that would seal over before reduction.
This can even happen in oxidation firing because of organics in clays
that are not burnt out properly.
It is also true that some glazes will look the same with and without
zinc in a reduction firing - David Hendly did some tests - wrote an
article for CM on copper reds with and without zinc - most were the
same without zinc.
If glazes do work without zinc it is a pure waste - and zinc is not
cheap - and fumed zinc is associated with metal fume fever - flu like
symptoms.
RR
Quoting KATHI LESUEUR :
> On Aug 12, 2010, at 9:06 PM, Robert Harris wrote:
>
>> Oh, I should add that I realize that Zinc Oxide can only be used in
>> oxidation.>>
>
> I'd like to hear the opinion of some of our glaze gurus on this
> statement. I have two cone 10 glazes that have zinc. I've tried them
> with and without the zinc. There was a difference. I've never heard
> that zinc can only be used in oxidation. Comments, please?
>
> KATHI LESUEUR
> http://www.lesueurclaywork.com
>
>>
>
John Hesselberth on fri 13 aug 10
Hi Kathi,
Zinc oxide is easily reduced to zinc metal which boils at 907 Celsius =3D
(1665 F). That is why it can often be a waste to use zinc oxide in a =3D
reduction glaze. However, if the glaze seals over before reduction is =3D
started I would guess that much of the zinc oxide would be trapped in =3D
the glassy melt that is forming--the reducing gases couldn't get to it-- =
=3D
and would be effective in altering the glaze characteristics. David =3D
Hendley did some experiments several years ago--I think they were =3D
published in CM or Clay Times--where he made several glazes with and =3D
without zinc. In some there was no difference; in others there was a =3D
difference.
So my working hypothesis is that it depends on how soon and how strongly =
=3D
you reduce compared to the sealing temperature of the glaze.
Regards,
John
On Aug 13, 2010, at 9:26 AM, KATHI LESUEUR wrote:
> On Aug 12, 2010, at 9:06 PM, Robert Harris wrote:
>=3D20
>> Oh, I should add that I realize that Zinc Oxide can only be used in
>> oxidation.>>
>=3D20
> I'd like to hear the opinion of some of our glaze gurus on this =3D
statement. I have two cone 10 glazes that have zinc. I've tried them =3D
with and without the zinc. There was a difference. I've never heard that =
=3D
zinc can only be used in oxidation. Comments, please?
>=3D20
> KATHI LESUEUR
> http://www.lesueurclaywork.com
>=3D20
>>=3D20
ivor and olive lewis on sat 14 aug 10
In the late 1800's and early 1900's Borax was a favoured adjunct flux used
on the process employing Sodium Chloride.
Ivor Lewis,
REDHILL,
South Australia
ivor and olive lewis on sat 14 aug 10
Dear KATHI LESUEUR .
In a nutshell....
Regarding the use of Zinc Oxide.
In the presence of a reducing atmosphere at red heat Zinc oxide is converte=
d
to metallic Zinc. Metallic Zinc melts at 419 deg C and boils at 907 deg C.
Zinc vapour escapes from the kiln and reoxidises, making no contribution to
the CHEMISTRY of the Glaze.
If the kiln atmosphere is controlled to ensure an excess of Oxygen, Zinc
oxide will not decompose. Having a melting point of 1975 deg C (3587 F ) i=
t
makes no contribution to melting of a glaze. As it dissolves into a Silicat=
e
melt it will modify certain Physical properties such as Viscosity and
Surface Tension, assisting with flow and smoothing and in large proportions=
,
the genesis of Crystalline Inclusions.
An indication of the break down of Zinc Oxide in a reduction firing is the
presence of a yellow coloured incrustations around cracks where gases escap=
e
from the kiln. When the kiln is cold,these yellow deposits change to white.
Best regards
Ivor Lewis,
REDHILL,
South Australia
David Beumee on sat 14 aug 10
Thanks very much Marion. Please if I could just try to get this straight:
The sticking point with the inspector is that sodium hydroxide is also a
product of the thermal decomposition of sodium bicarb, as Ruthann Tudball
acknowledged in the quotes given from Gail Nichols "And What About The
Environment?" section of Chapter 1 of her book " Soda, Clay, and Fire,"
which Ruthann said is converted back to sodium carbonate (soda ash) in the
presence of carbon dioxide when the hydroxide vapor leaves the stack. At
this point the inspector said "and soda ash is caustic." I said, "I don't
know. I know that in a shino glaze, soda ash can be caustic to your hands."
He said "yeah, it eats your skin." So his issue is caustic soda ash being
dispelled into the environment.
You are saying that initially, sodium hydroxide is NOT a byproduct of the
thermal decomposition of sodium bicarb, and that "alternately, but not
likely", some sodium oxide may combine with water vapor in the kiln
atmosphere and produce sodium hydroxide fumes.
"The low levels of these fumes, if created, would just harmlessly
disperse in the surrounding atmosphere after discharge from the kiln."
"More likely, at kiln temperature any sodium hydroxide fumes formed
will almost instantaneously decompose to form more sodium oxide and
evolve additional water vapor."
" These cycling reactions from the thermal decomposition of sodium
bicarbonate are so very unlikely at kiln temperatures that about all
in the way of possible nuisance that will be produced during a success
firing are those fumes associated with normal reduction or oxidation
firing. A stalled kiln or a misfiring might possibly produce some
light fumes of NaOH."
This is truly great news, Marion, but the obvious next question from this
Alfred trained potter turned city building inspector will surely be, "Says
who?" "Where's your evidence?"
David
On Thu, Aug 12, 2010 at 10:32 PM, Neon-Cat wrote=
=3D
:
> Hi David =3D96 how exciting to be thinking about building a soda kiln!
> I=3D92d like one, too. You=3D92ll have to keep us updated on your success=
es.
>
> I don=3D92t have studies for you =3D96 how about some fundamental basics =
that
> cut to the chase? If you need help before you talk to the inspector
> again just post me off list.
>
> At the desired kiln temperature (somewhere between 1150 =3D96 1310 C/2102
> - 2390 F) depending on your clay body and the desired glaze effects)
> for your soda firing several things happen in very, very rapid
> succession when you introduce sodium bicarbonate. The reactions
> involved are as follows:
>
> Sodium bicarbonate is thermally decomposed into sodium carbonate,
> water vapor and carbon dioxide:
> 2NaHCO3 ---> Na2CO3 + H2O + CO2 (1)
>
> Immediately heat converts the sodium carbonate into sodium oxide plus
> carbon dioxide:
> Na2CO3 ---> Na2O + CO2 (2)
>
> The sodium oxide, as it does when evolved during sodium chloride
> (NaCl) firings, reacts with the surface of the clay ware to form a
> sodium-alumina-silicate glaze (the goal):
> 2Na2O + xAl2O3.ySiO2 ---> 2Na2O.xAl2O3.ySiO2 (3)
>
> Alternately, but not likely (the melting point of sodium hydroxide is
> 318 C/604 F and its boiling point is 1390 C/2534 F), some sodium oxide
> that has not reacted with either the kiln walls or the clay ware may
> combine with water vapor in the kiln atmosphere to produce sodium
> hydroxide fumes:
> Na2O + H2O ---> 2 NaOH (4)
> The low levels of these fumes, if created, would just harmlessly
> disperse in the surrounding atmosphere after discharge from the kiln.
>
> More likely, at kiln temperature any sodium hydroxide fumes formed
> will almost instantaneously decompose to form more sodium oxide and
> evolve additional water vapor:
> 4NaOH + heat ---> 2Na2O +2H2O (5)
> This will then beautifully glaze the ware as in equation 3 above.
>
> Or any sodium hydroxide fumes formed could combine in a carbonation
> reaction with CO2 to form a low-density =3D93light=3D94 soda ash (sodium
> carbonate) and water vapor:
> 2 NaOH + CO2 ---> Na2CO3 + H2O (6)
> This in turn (as in equation 2) forms more sodium oxide with which to
> glaze the ware or there could be a reaction with carbon dioxide gas
> and water vapor that returns the original reactant sodium bicarbonate:
> Na2CO3 + CO2 + H2O ---> 2 NaHCO3 (7)
> Reaction 6 most often occurs in aqueous solutions, not extremely hot,
> gaseous atmospheres like we have in a kiln, besides this carbonization
> reaction is a slow one involving the diffusion of atmospheric carbon
> dioxide into an aqueous solution.
>
> These cycling reactions from the thermal decomposition of sodium
> bicarbonate are so very unlikely at kiln temperatures that about all
> in the way of possible nuisance that will be produced during a success
> firing are those fumes associated with normal reduction or oxidation
> firing. A stalled kiln or a misfiring might possibly produce some
> light fumes of NaOH. But really, just stick with equations 1,2 and 3
> above.
>
> Fearless firing!
> (take the inspector one of your first-born pots from the new kiln...)
>
> Marian
> Neon-Cat
> www.neon-cat.com
> http://www.flickr.com/photos/neon-cat/
>
James Freeman on sat 14 aug 10
On Sat, Aug 14, 2010 at 2:00 AM, David Beumee wrote=
=3D
:
>
> The sticking point with the inspector is that sodium hydroxide is also a
> product of the thermal decomposition of sodium bicarb,
David...
Just some outside perspective, and a few thoughts:
It seems as though you are trying to counter the inspector's
speculation with your own speculation, and as you note at the end of
your post, that simply won't work. The phrase "Sez who?" comes to
mind.
My first question would be whether or not there are any local
regulations regarding the small-scale discharge of caustic soda.
Since it is a product that you can buy over the counter in a grocery
store, I'm guessing there aren't any. If there are no such
regulations where you live, under what authority is he banning your
kiln? Absent regulations, it seems that there is no need to even
speculate on what is produced in your kiln fumes.
The next thing I would think about is the minute quantities that would
be produced, assuming that the speculations are correct and that any
would be produced at all. How many pounds of soda ash will you pump
into the kiln during a firing? A couple (I don't remember, as I only
fired with soda once)? Out of that couple of pounds, how much caustic
soda could theoretically be produced, if any? A teaspoon? Half a
teaspoon? Maybe one of our chemists can do the math, but I'm guessing
it would be insignificant.
When we were planning the salt kiln at the local college, there was
much ado about the supposed HCl discharge. They wanted us to fire
with soda instead, for imagined environmental reasons, so I did some
research. Most of the "knowledge" regarding what was being produced
and discharged from salt and soda kilns turned out to be old wives'
tales; sorry, old significant others' or domestic partners' tales. I
found reference to the only study and analysis of actual kiln
effluent, at least at that time. As I recall, a chemistry professor
at a UK university heard all of the speculation and potters' wisdom,
and it didn't make sense to him. He captured and analyzed the actual
fumes from the college's salt kiln, and found them to be harmless, and
containing insignificant amounts of HCl. He determined that most of
what comes from the salt kiln flue, aside from normal combustion
exhaust, is just reconstituted precipitated salt. Does anyone
remember the name of the gentleman who conducted the study, or where
it was published? It is years since I read it.
I also remember reading an article comparing the theoretical effluent
of salt versus soda firing, and contrary to common knowledge, it
turned out that soda firing was far worse for the environment than was
salt firing. Again, I cannot remember where I read it, but believe it
was referenced in a book on salt and soda firing. Anyone recall?
Anyway, given this, and the above, why not just tell the inspector
that it is a salt kiln rather than a soda kiln. If you locate the
above mentioned salt kiln study, you can "prove" that nothing terribly
bad will spew from your flue, so problem solved. After you have
obtained approval for your salt kiln, fire with whatever sodium source
tickles your fancy at the moment. In my youth, I was very interested
in Volkswagen-based sand rails and dune buggies. Rather than jumping
through flaming hoops trying to register and license a "hand built"
automobile for the street, folks would simply register it as a
Volkswagen of whatever year, referencing the VIN from the engine. Not
precisely kosher, but it worked.
If you really want to know what spews forth from a soda kiln, why not
capture some effluent from an operating soda kiln or from a little
temporary test kiln that you build, and have it analyzed? Again,
problem solved, and all hypothetical chemical speculation rendered
moot.
Just a few random thoughts. Perhaps there is a useful morsel
somewhere in the heap.
Good luck with the project.
...James
James Freeman
"All I say is by way of discourse, and nothing by way of advice.=3DA0 I
should not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
Vince Pitelka on sat 14 aug 10
As I understand it, the only gaseous effluent from a soda kiln other than
water vapor and carbon dioxide is sodium hydroxide, which precipitates on
adjacent surfaces as dilute lye, and will cause slow corrosion over time.
The only gaseous effluent from a salt kiln other than water vapor and carbo=
n
dioxide is hydrogen chloride gas, which precipitates on adjacent surfaces a=
s
dilute hydrochloric acid, causing faster corrosion over time. I remember
being surprised by the claim that soda kilns are actually more
environmentally harmful than salt kilns, and I do not understand the
reasons. Does anyone know why the very slight amount of sodium hydroxide
coming out of a soda kiln would be more harmful than the slight amount of
hydrogen chloride coming out of a salt kiln? It is also a matter of degree=
s
of harm, and as James Freeman pointed out, a soda kiln is generally only
charged with a few pounds of soda, and of that amount, the quantity of
sodium hydroxide released into the atmosphere is very slight.
It is important to point out that the salt spray present along all coastal
areas that have surf is at least as corrosive in the immediate area as the
effluent coming out of a salt or soda kiln. This inspector's concern about
a soda kiln because soda is caustic is unfounded, especially in
consideration of all the far more-harmful chemicals we use in, on, and
around our homes and gardens. He is afraid of an unknown entity, and of th=
e
possible liability concerns in our current "age of litigation," as Garrison
Keillor calls it. This climate of fear is so destructive in so many ways,
and this inspector needs to understand that he cannot deny the soda kiln
based on his on inexpert speculation.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Neon-Cat on sat 14 aug 10
David, perhaps by jerking your chain a little bit your inspector is
training you in soda kiln fundamentals by making you stretch and
reach. I like him; maybe I=3D92ll send him something.
Left to my own devices I=3D92d have skipped sodium hydroxide entirely but
since it appears in so much written by potters for potters in
conjunction with soda firing I thought I=3D92d find some slight
justifications for its mention and the cloud that follows it.
Asking me to provide =3D93evidence=3D94 or references to that which is comm=
on
knowledge and generally accepted is like asking for
evidence/references for 2 + 2 =3D3D 4. There is no =3D93hypothetical chemic=
al
speculation=3D94 (to use the words of James Freeman) for what occurs when
sodium bicarbonate is fired at high temperatures. To scientists,
government, and regulatory agencies it is not a mystery. Hello! We are
in the year 2010.
But here=3D92s something that might help you =3D96 remember good old MSDS
sheets? Handy references. Inspectors and fire departments make use of
them for disaster planning =3D96 in case you set your studio on fire they
like to know what products are likely to form during a fire so they
can stay safe, the city stays safe, and you stay safe while the
problem is addressed. MSDS information is like gold sometimes. Trained
professionals of all sorts make good use of them.
In the US, OSHA deals with hazardous combustion products -- chemicals
that may form when a material burns. These chemicals may be toxic,
flammable or have other hazards and these chemicals formed during
combustion may be quite different from those formed during thermal
decomposition. As potters and clay workers firing a variety of
materials at low to high temperatures we should concern ourselves with
both thermal decomposition products and the products of combustion.
Here follows an example of what is in a fancy sodium bicarbonate MSDS.
Your inspector has access to up-to-date MSDS sheets, OSHA regulations,
and other great information as part of his profession. Some MSDS
sheets will give us what we as studio artists need. Most MSDS sheets
for sodium bicarbonate just list carbon dioxide, and sometimes carbon
monoxide as hazardous decomposition products.
http://www.delta-education.com/msds/Sodium_Bicarbonate.pdf
Hazardous Decomposition or Byproducts: Heating above 100 C may cause
dangerous levels of carbon dioxide gas to be present in confined
spaces. Yields sodium oxide if exposed to temperatures above 850 C.
Avoid inhalation, eye and skin contact with sodium oxide.
Special Fire Fighting Procedures: Carbon Dioxide may be generated
making necessary the use of a self-contained breathing apparatus
(SCBA) and full protective equipment (Bunker Gear). Carbon dioxide is
an asphyxiant at levels over 5% w/w. Sodium oxide, another thermal
decomposition product existing at temperatures above 1564 F is a
respiratory, eye and skin irritant. Avoid inhalation, eye and skin
contact with sodium oxide dusts.
Good luck. The only reason you might not get your soda kiln would be
if you shoot yourself in the foot. And do keep it honest. Please.
Marian
Neon-Cat
(back to the sanity of good, honest labor =3D96 my kitchen floor looks
great and will be better with one more coat of finish. Low VOCs with a
slight, pleasant energizing kick. Ah, this is the life...)
On Sat, Aug 14, 2010 at 1:00 AM, David Beumee wrote=
=3D
:
> This is truly great news, Marion, but the obvious next question from this
> Alfred trained potter turned city building inspector will surely be, "Say=
=3D
s
> who?"=3DA0 "Where's your evidence?"
>
> David
Michael Wendt on sat 14 aug 10
My wife Barb and I went white water rafting with Salmon
River Excursions a few weeks ago and since the trip was over
6 hours, the guide at orientation brought up the need to
pee.
He said the Department of Environmental Quality has a
saying:
"The solution to pollution is dilution."
We were told to jump into the water and let'er rip.
The same is true for your soda kiln issue.
Have him show you the pertinent regulation in writing that
applies.
If he can't, go to the EPA web site and get their emission
limits for your effluent.
If there are regulations in place for your emissions, do
the math!
Calculate the total volume of air and gas emitted during a
firing cycle that includes the soda injection.Figure how
much the concentration per unit volume would be if the
entire charge went airborne (which we know it won't do).
Show that you will fall below any standard for release and
you are home free.
You can prove you will comply.
All you are talking about is a flyspeck of meaningless
release and why you ever brought it up in the first place
with the inspector is the real mistake.
It is important to understand his position. It is easier and
safer for him to say "NO!"
and to place the burden of proof upon you so accept that
burden and prove your case.
Good Luck!
Michael Wendt
ivor and olive lewis on sun 15 aug 10
I see no reason why Sodium Bi-Carbonate (NaHCO3) should be substituted for
Sodium Carbonate (Na2CO3) though I am concerned that Potters, in discussing
their raw materials commonly refer to the Sodium content of some of their
glaze ingredients as being in the form of Sodium oxide, Na2O and firmly
believe (a good example of "Common knowledge" that is erroneous) that it
is created when extreme heat is applied to several common Sodium compounds.
Yet Durrant tells us "Sodium Monoxide combines with water with extreme
violence to form Sodium Hydroxide and explosively with acids to form salts"=
.
Sodium Monoxide (Na2O) may be prepared by heating Sodium Peroxide with
metallic Sodium or by burning metallic Sodium in a limited supply of Air. I=
t
is very reactive towards water and Carbon dioxide.
Sodium Hydroxide has been mentioned. Durrant again "When heated, Sodium
Hydroxide does not lose water to yield Sodium oxide.; at temperatures above
1300 deg C it dissociates to a slight extent into its constituent elements,
Sodium, Oxygen and Hydrogen."
Ralph H. Petrucci and Robert K.Wisner give interesting information. Knowing
there is a need for a procedure for converting resistant materials into a
soluble form, they propose combining a sample of their unknown substance
with a mixture of Sodium and Potassium Carbonates in a crucible. The
crucible is covered with a lid and strongly heated to fuse the carbonates
and dissolve the sample. As some of you will know, porcelain crucibles are =
a
common commodity in a chemical lab. Recall what I told you about the
behaviour of Sodium Carbonate as elated by P. J. Durrant , when it is heate=
d
in a porcelain crucible. Petrucci and Wismer chose to use a Nickel Crucible=
.
No need to wonder why !
P.J. Durrant, M.A.. Ph.D., "General and Inorganic Chemistry". 2nd. Edition,
fourth reprint with minor corrections, 1956.
Ralph H. Petrucci and Robert K.Wisner , "General Chemistry with Qualitative
Analysis" ISBN 0-02-394970-8, 1983
Regards,
Ivor Lewis,
REDHILL,
South Australia
Louis Katz on sun 15 aug 10
Borax added to soda smooths out the surface in my limited experience. It
also interferes with the salmon colored flashing. According to the Borax
Handbook written for one of the borax selling companies in the 70's it
lowers the temperature necessary for a salt glaze surface. I have do not
know what comes out of the chimney.
I work about 100 yards from the salt water. The galvanized metal near our=
=3D
soda kiln corrodes a bit faster than further away. If salt is used in the=
=3D
kiln the effect is almost immediate. Garbage/saggar firings cause even
quicker corrosion.
Lee Love on sun 15 aug 10
On Sun, Aug 15, 2010 at 2:18 AM, ivor and olive lewis
wrote:
> I see no reason =3DA0why Sodium Bi-Carbonate (NaHCO3) should be substitut=
ed=3D
for
> Sodium Carbonate (Na2CO3)
I use a mixture of baking soda, soda ash and whiting. She does it in
"solid form." I just add water and spray with a garden sprayer. Her
recipe below.
Gail Nichols Soda Mix
Light Soda Ash=3D85=3D85=3D85=3D85=3D85..=3D85=3D85=3D85.....20
Sodium Bicarbonate (baking soda).=3D85.......30
Calcium Carbonate..................................50
100%
Add 9 U.S. fl. oz. of water per 1 lb. (600 ml of water per 1 kg) of
dry mix. Wearing gloves, mix the dry ingredients thoroughly, then add
the water all at once. Stir until the mixture begins to set, then
break it into small pieces.
As this mixture breaks down in the heat of the flame, water vapor is
released along with the vaporizing soda. Water vapor helps to carry
the soda through the kiln chamber, enabling good glaze distribution
and evidence of flame movement on the work. Water vapor also appears
to assist with soda dissociation and glaze formation.
--
=3DA0Lee, a Mashiko potter in Minneapolis
http://mingeisota.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
ivor and olive lewis on mon 16 aug 10
The most authoritative account measuring the components of the effluent fro=
m
a Salt (Sodium Chloride) Glaze Kiln was recorded in a private investigation
by the British Ceramic Research Association in 1960. This confirmed
information give in the records of the 1959 Alkali and other Chemical Works
Inspectorate that almost as much Potassium chloride as Sodium chloride was
discharged as well (listed from memory) as Ferric Chloride, Aluminium
Chloride and Silicon Tetrachloride.
It was already known in WW 1 that Potassium Chloride could be collected
during the smelting of Iron if the fluxes contained common salt.
I have never read any accounts of a salt firing where Kilnmeisters noted
dense green fumes (Chlorine.) issuing from a stack. Mr. Anderson, who was
M.D of Eltringham Pipe Works, Co Durham told me of Brown Fumes being vented
during saltings. He advised against hanging around a salt glaze kiln (1967)=
.
I do not wish to contradict Mel since my observations mirrior his. Quoting
Mel "... people have no way of knowing what is heat, what is steam and wha=
t
is smoke. ??
what is pure white and comes from a stack...???? water." Mel, it does not
need a brilliant imagination to design controlled experimental procedures
for collecting and analysing Kiln Effluent (Controlled in the Scientific
Sense), and little more than simple arithmetic to do the thermodynamic
analysis of the proposed Hypothetical (read Dan Rhodes) Chemical Equations.
All the best,
Ivor Lewis,
REDHILL,
South Australia
David Beumee on mon 16 aug 10
Hi Ivor,
Can you help me with a bit of calculation?
A soda kiln kiln is charged with 2574.5 grams of soda ash at cone 9, and
67.15 grams of sodium reacted with the clay surfaces. This produced 1332.26
grams of carbon dioxide, 1665.8 grams of sodium peroxide and 1094.26 grams
of sodium hydroxide.
How much of each of these chemicals is produced if the original amount of
soda ash is 681 grams (1 1/2 pds) instead of 2574.5 grams (5.6 pds.)?
David Beumee
Lafayette, CO
On Mon, Aug 16, 2010 at 12:43 AM, ivor and olive lewis <
iandol@westnet.com.au> wrote:
> The most authoritative account measuring the components of the effluent
> from
> a Salt (Sodium Chloride) Glaze Kiln was recorded in a private investigati=
on
> by the British Ceramic Research Association in 1960. This confirmed
> information give in the records of the 1959 Alkali and other Chemical Wor=
ks
> Inspectorate that almost as much Potassium chloride as Sodium chloride wa=
s
> discharged as well (listed from memory) as Ferric Chloride, Aluminium
> Chloride and Silicon Tetrachloride.
> It was already known in WW 1 that Potassium Chloride could be collected
> during the smelting of Iron if the fluxes contained common salt.
> I have never read any accounts of a salt firing where Kilnmeisters noted
> dense green fumes (Chlorine.) issuing from a stack. Mr. Anderson, who was
> M.D of Eltringham Pipe Works, Co Durham told me of Brown Fumes being vent=
ed
> during saltings. He advised against hanging around a salt glaze kiln
> (1967).
> I do not wish to contradict Mel since my observations mirrior his. Quoti=
ng
> Mel "... people have no way of knowing what is heat, what is steam and
> what
> is smoke. ??
> what is pure white and comes from a stack...???? water." Mel, it does not
> need a brilliant imagination to design controlled experimental procedures
> for collecting and analysing Kiln Effluent (Controlled in the Scientific
> Sense), and little more than simple arithmetic to do the thermodynamic
> analysis of the proposed Hypothetical (read Dan Rhodes) Chemical Equation=
s.
>
> All the best,
>
> Ivor Lewis,
> REDHILL,
> South Australia
>
David Beumee on tue 17 aug 10
Ivor,
Thank you very much for the calculations. For a 20cu. ft. soda kiln,
according to Vince, I'll need a pound and a half of soda ash in solution to
get the glazed surface I'm seeking, and I needed some help to get exact
figures of hydroxide release for a pound and a half of soda ash, instead of
the five and a half pounds listed in the calculations of Chapter 8 of Phil
Rogers book "Salt Glazing."
Apparently it's the hydroxide release, "condensing first to liquid droplet=
s
as a mist, reacting with carbon dioxide and water vapor to form a mixture o=
f
sodium hydroxide and sodium carbonate that solidifies as a submicron fume.
The fume plume may be invisible if the concentration is low,'' that present=
s
a problem for the local city building inspector in approving the building o=
f
this new soda kiln. His claim is that soda ash in the environment is causti=
c
and therefore unsafe environmentally, and the burden of proof has been
placed on me to prove otherwise. From what I can gather, the main argument
is that yes, it is caustic, but the amount of release is so small as to be
safe, at least in comparison to the amount of carbon dioxide and monoxide
produced as a byproduct of normal combustion.
You say, "if either salt or soda firings are performed under the protocols
that I was trained to use there will only be marginal emissions. The
majority of the vapours and aerosols will be adsorbed by the fired ware,
kiln furniture or the internal refractories. Carbon dioxide, when it is
present, being transparent and colourless would go unnoticed." What were
these protocols please Ivor, and is it possible that such protocols could
present proof to our building inspector that hydroxide/soda ash release is
relatively safe in a residential neighborhood environment?
Thank you,
David Beumee
Lafayette, CO
On Mon, Aug 16, 2010 at 8:18 PM, ivor and olive lewis u
> wrote:
> Not sure what the question is David or where you are going with this
> information once you get it. I would round up the figures to the nearest
> whole unit (Gram)
>
> <<....If 2574.5 grams of soda ash, meaning Sodium Carbonate is admitted
> into the kiln and the total mass of the products were found to weigh 4159=
.47
> grams of which only 67.15 grams of Sodium ( a Metal not an oxide !) has
> assisted in forming a glaze then there are problems. What was the weight =
of
> the glaze ?
> How much of each of these chemicals is produced if the original amount o=
f
> soda ash is 681 grams (1 1/2 pds) instead of 2574.5 grams (5.6 pds.)? ...=
.>>
>
> 17.761175 gms Na Sodium
> 352.38277 gms CO2 Carbon dioxide
> 440.6041 gms Na2O2 Sodium Peroxide
> 289.43177 gms NaOH Sodium Hydroxide
>
> By the way, if either salt or soda firings are performed under the
> protocols that I was trained to use there will only be marginal emissions=
.
> The majority of the vapours and aerosols will be adsorbed by the fired wa=
re,
> kiln furniture or the internal refractories. Carbon dioxide, when it is
> present, being transparent and colourless would go unnoticed.
>
> Best regards,
> Ivor Lewis,
> REDHILL,
> South Australia
>
>
>
> ----- Original Message -----
>
> Hi Ivor,
> Can you help me with a bit of calculation?
> A soda kiln kiln is charged with 2574.5 grams of soda ash at cone 9, and
> 67.15 grams of sodium reacted with the clay surfaces. This produced 1332.=
26
> grams of carbon dioxide, 1665.8 grams of sodium peroxide and 1094.26 gram=
s
> of sodium hydroxide.
> How much of each of these chemicals is produced if the original amount o=
f
> soda ash is 681 grams (1 1/2 pds) instead of 2574.5 grams (5.6 pds.)?
>
> David Beumee
> Lafayette, CO
>
>
>
>
>
>
> On Mon, Aug 16, 2010 at 12:43 AM, ivor and olive lewis <
> iandol@westnet.com.au> wrote:
>
>> The most authoritative account measuring the components of the effluent
>> from
>> a Salt (Sodium Chloride) Glaze Kiln was recorded in a private
>> investigation
>> by the British Ceramic Research Association in 1960. This confirmed
>> information give in the records of the 1959 Alkali and other Chemical
>> Works
>> Inspectorate that almost as much Potassium chloride as Sodium chloride w=
as
>> discharged as well (listed from memory) as Ferric Chloride, Aluminium
>> Chloride and Silicon Tetrachloride.
>> It was already known in WW 1 that Potassium Chloride could be collected
>> during the smelting of Iron if the fluxes contained common salt.
>> I have never read any accounts of a salt firing where Kilnmeisters noted
>> dense green fumes (Chlorine.) issuing from a stack. Mr. Anderson, who wa=
s
>> M.D of Eltringham Pipe Works, Co Durham told me of Brown Fumes being
>> vented
>> during saltings. He advised against hanging around a salt glaze kiln
>> (1967).
>> I do not wish to contradict Mel since my observations mirrior his.
>> Quoting
>> Mel "... people have no way of knowing what is heat, what is steam and
>> what
>> is smoke. ??
>> what is pure white and comes from a stack...???? water." Mel, it does no=
t
>> need a brilliant imagination to design controlled experimental procedure=
s
>> for collecting and analysing Kiln Effluent (Controlled in the Scientific
>> Sense), and little more than simple arithmetic to do the thermodynamic
>> analysis of the proposed Hypothetical (read Dan Rhodes) Chemical
>> Equations.
>>
>> All the best,
>>
>> Ivor Lewis,
>> REDHILL,
>> South Australia
>>
>
>
John Britt on tue 17 aug 10
David,
What if you used sodium bicarbonate?
It is not toxic. Pretty close to Alka-Seltzer.
John Britt
www.johnbrittpottery.com
ivor and olive lewis on tue 17 aug 10
Not sure what the question is David or where you are going with this =3D
information once you get it. I would round up the figures to the nearest =
=3D
whole unit (Gram)
<<....If 2574.5 grams of soda ash, meaning Sodium Carbonate is admitted =3D
into the kiln and the total mass of the products were found to weigh =3D
4159.47 grams of which only 67.15 grams of Sodium ( a Metal not an oxide =
=3D
!) has assisted in forming a glaze then there are problems. What was the =
=3D
weight of the glaze ?
How much of each of these chemicals is produced if the original amount =3D
of soda ash is 681 grams (1 1/2 pds) instead of 2574.5 grams (5.6 pds.)? =
=3D
....>>
17.761175 gms Na Sodium
352.38277 gms CO2 Carbon dioxide
440.6041 gms Na2O2 Sodium Peroxide
289.43177 gms NaOH Sodium Hydroxide
By the way, if either salt or soda firings are performed under the =3D
protocols that I was trained to use there will only be marginal =3D
emissions. The majority of the vapours and aerosols will be adsorbed by =3D
the fired ware, kiln furniture or the internal refractories. Carbon =3D
dioxide, when it is present, being transparent and colourless would go =3D
unnoticed.
Best regards,
Ivor Lewis,
REDHILL,
South Australia=3D20
----- Original Message -----=3D20
Hi Ivor,
Can you help me with a bit of calculation?
A soda kiln kiln is charged with 2574.5 grams of soda ash at cone 9, =3D
and 67.15 grams of sodium reacted with the clay surfaces. This produced =3D
1332.26 grams of carbon dioxide, 1665.8 grams of sodium peroxide and =3D
1094.26 grams of sodium hydroxide.
How much of each of these chemicals is produced if the original =3D
amount of soda ash is 681 grams (1 1/2 pds) instead of 2574.5 grams (5.6 =
=3D
pds.)?
David Beumee
Lafayette, CO
On Mon, Aug 16, 2010 at 12:43 AM, ivor and olive lewis =3D
wrote:
The most authoritative account measuring the components of the =3D
effluent from
a Salt (Sodium Chloride) Glaze Kiln was recorded in a private =3D
investigation
by the British Ceramic Research Association in 1960. This confirmed
information give in the records of the 1959 Alkali and other =3D
Chemical Works
Inspectorate that almost as much Potassium chloride as Sodium =3D
chloride was
discharged as well (listed from memory) as Ferric Chloride, =3D
Aluminium
Chloride and Silicon Tetrachloride.
It was already known in WW 1 that Potassium Chloride could be =3D
collected
during the smelting of Iron if the fluxes contained common salt.
I have never read any accounts of a salt firing where Kilnmeisters =3D
noted
dense green fumes (Chlorine.) issuing from a stack. Mr. Anderson, =3D
who was
M.D of Eltringham Pipe Works, Co Durham told me of Brown Fumes being =
=3D
vented
during saltings. He advised against hanging around a salt glaze kiln =
=3D
(1967).
I do not wish to contradict Mel since my observations mirrior his. =3D
Quoting
Mel "... people have no way of knowing what is heat, what is steam =3D
and what
is smoke. ??
what is pure white and comes from a stack...???? water." Mel, it =3D
does not
need a brilliant imagination to design controlled experimental =3D
procedures
for collecting and analysing Kiln Effluent (Controlled in the =3D
Scientific
Sense), and little more than simple arithmetic to do the =3D
thermodynamic
analysis of the proposed Hypothetical (read Dan Rhodes) Chemical =3D
Equations.
All the best,
Ivor Lewis,
REDHILL,
South Australia
ivor and olive lewis on wed 18 aug 10
Dear John Britt,
The objections being raised by the environmental inspector to David's
proposal is due to the belief that Sodium Hydroxide, a known caustic
material, is being disposed in the atmosphere.
Looking at Standard Thermodynamic values for Delta H of Formation leads me
to suspect that formation of Sodium Hydroxide will be suppressed in favour
of the creation of Sodium Silicate
I would always favour Carbonate before bicarbonate. More Sodium Bang for th=
e
Buck . Anyway, the EPA inspector would raise the same objections and say
that Sodium Hydroxide will be there.
Regards,
Ivor Lewis,
REDHILL,
South Australia
David Beumee on wed 18 aug 10
John,
Yes, absolutely, I plan on using only the most benign type of sodium
available, but I have to prove the environmental safety of the introduction
of sodium, and the only research I can find with actual figures was done
with soda ash; Chapter 8, Phil Rogers book, "Salt Glazing."
I'm getting good help from Dr. Carty at Alfred and Pete Pinnell at UNL.
We're going to dispell the fears of this building inspector and get this
kiln approved and built.
Thanks for your help.
David Beumee
On Tue, Aug 17, 2010 at 6:26 PM, John Britt wro=
te:
> David,
>
> What if you used sodium bicarbonate?
>
> It is not toxic. Pretty close to Alka-Seltzer.
>
> John Britt
> www.johnbrittpottery.com
>
>
David Beumee on wed 18 aug 10
Ivor,
I got the idea that sodium hydroxide is formed at the introduction of a
soda ash solution into a kiln at cone 10 from the list of reactions, page
112 of Chapter 8, Phil Rogers book "Salt Glazing." Extreme heat is required
of course, and, according to this list, the sodium carbonate is split into
sodium oxide and carbon dioxide, further dividing into sodium ions and
sodium peroxide. The reaction list states that sodium peroxide is unstable
and converts into "any number of substances," and that some of the sodium
ions combine with the clay to form glass. "The remaining sodium ions combin=
e
with water created in combustion to form sodium hydroxide (caustic soda) an=
d
hydrogen." The author states that no soda ash recombines to its original
form "as it exits the kiln in the way that salt does." Phil goes on to use
this hypothesis to prove that soda firing is more polluting to the
atmosphere than salt firing.
Dr. Carty's contention is that once volatilized, The Na will condense on
any cool surface. "In the kiln, this is the pot, (believe it or not), but
once it leaves the kiln chamber it will likely condense on the inside of th=
e
stack or chimney. This means you will likely coat the inside of your kiln
exhaust but that the emission of Na is very unlikely."
Finally we're getting somewhere!
David
On Tue, Aug 17, 2010 at 11:57 PM, ivor and olive lewis <
iandol@westnet.com.au> wrote:
> Dear John Britt,
>
> The objections being raised by the environmental inspector to David's
> proposal is due to the belief that Sodium Hydroxide, a known caustic
> material, is being disposed in the atmosphere.
>
> Looking at Standard Thermodynamic values for Delta H of Formation leads m=
e
> to suspect that formation of Sodium Hydroxide will be suppressed in favou=
r
> of the creation of Sodium Silicate
>
> I would always favour Carbonate before bicarbonate. More Sodium Bang for
> the
> Buck . Anyway, the EPA inspector would raise the same objections and say
> that Sodium Hydroxide will be there.
>
>
> Regards,
>
> Ivor Lewis,
> REDHILL,
> South Australia
>
John Britt on wed 18 aug 10
David,
Have you gotten the article from Ceramics Review on Soda and the environm=
=3D
ent?
Around 1999?
Johnbrittpottery.com
John Britt on wed 18 aug 10
I remember now, that article was called "Somethings in the Air".
Johnbrittpottery.com
David Beumee on wed 18 aug 10
I'll look for the article, thank you.
David
On Wed, Aug 18, 2010 at 2:15 PM, John Britt wro=
te:
> I remember now, that article was called "Somethings in the Air".
>
> Johnbrittpottery.com
>
>
David Beumee on mon 7 mar 11
To Vince and everyone,
I'm still needing help proving to our local building inspector that soda
firing is relatively benign to ill effects on the environment, so that my
partner and I can obtain a building permit to build a soda kiln with 12 to
13 cu. ft. of stacking space.
From the advice of Dave Finkelnburg, I contacted an environmental engineer
in Boulder, and through him I'm on the right track as far as
obtaining the kind of info that our local building inspector is requiring,
but here's what I need from anyone who may fire soda. I need top-of-stack
thermocouple
temperature readings at the time that the soda/water solution is being
introduced at cone 10.
Thanks to everyone for your help,
David Beumee
Lafayette, CO
David Beumee on wed 11 may 11
Last year I received a lot of help from the scientists on Clayart
concerning the safety of soda firing, and I was able to gather much valuabl=
e
information for which I am extremely grateful. I wanted to share the
conclusions that have been found, namely that introducing sodium bicarb or
soda ash solution into a kiln at cone 10 introduces no significant exposure
of harmful chemicals to the environment, because potentially harmful
chemicals condense as liquid inside the kiln and stack before leaving as
gases in the exhaust fumes.
With the help of an environmental engineer in Boulder Colorado, referred
to me by Dave Finkelnburg, the engineer's task to me was to measure stack
exhaust temperature readings at the time sodium bicarb or soda ash solution
is introduced into a kiln at cone 10. Vince Pitelka and the troops at the
Appalachian Center for Craft were able to take readings for two consecutive
firings, measuring exhaust temperatures for a 20 cubic foot soda kiln at
cone 10, stack height approx. 13'. Vince reported an average temp. reading
of 481 C (898 F), rising to 521 C (970 F) when the damper was mostly closed=
.
The boiling point for sodium carb is 892 C (1689 F) and for sodium bicarb i=
s
851 C (1563 F), meaning that most of the sodium carb would condense as a
liquid before leaving the kiln in the exhaust. The more reactive and
dangerous components, formed from baking soda or soda ash at high
temperature, such as sodium oxide and sodium hydroxide, have boiling points
of 1950 C (3542 F) and 1388 C (2530 F) respectively, and have liquified on
the cooler surfaces of the pots to form a glaze with the silicates present
in the clay, the inside of the kiln and the stack. One would not expect
these chemicals to remain in the exhaust fumes when the exhaust temperature
is 481 C, 1469 C (2676 F) below the boiling point of sodium oxide and 907 C
(1664 F) below the boiling point of sodium hydroxide.
Our local building inspector gave me the task of "proving" that soda
firing is safe for the environment as a precursor for granting a building
permit for a small soda fired kiln here at the studio. I'm hoping this
evidence will be convincing.
--
David Beumee
Porcelain by David Beumee
806 East Baseline Road
Lafayette, CO 80026
www.davidbeumee.com
303-665-6925
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