jonathan byler on thu 19 jan 12
It burns the lungs like sulfur does. And burns off at the temperature
that sulfury compounds would be likely to do (after 800F-900F). And
the only other things that corrode stainless steel to that degree tend
to be chlorine bearing compounds. We don't use salt in this kiln, so
I don't know where we would be getting that level of chlorine vapor in
the kiln atmosphere. Sulfur, however, would be pretty likely, as
either coal contamination or possibly as pyrite (iron sulfide). The
corrosion products of the stainless steel banding have a yellowish
tinge to them which indicates a sulfur compound to me.
Carbonic acid is relatively poor at corroding stainless steel compared
to sulfur compounds, according to what I have read.
On Jan 19, 2012, at 8:48 PM, L TURNER wrote:
> Jonathan, Why do you think it is sulfur? Have you tested the
> emissions for sulfur, or are you just assuming that the corrosion is
> from a sulfur compound?
>
> My suggestion is to get talk to some of the analytical chemistry
> profs/grad students at your university and to some of the materials
> science engineering profs/grad students and see if you can't get some
> hard data on the corrosion mechanism before you go chasing something
> as elusive as sulfur in a clay ingredient.
>
> There are simple tests to the materials that are being corroded that
> will tell you the specific species that is involved at the corroding
> surface. You work back from that to the source. At least that is the
> methond to solve corrosion problems used in the refining, paper, and
> petrochemical industry.
>
> Carbonic acid will also cause steel corrosion - depends on the type of
> steel and the local temperature.
>
> Regards,
>
> L. Turner
> The Woodlands, TX
>
>
>
> On Thu, Jan 19, 2012 at 2:44 PM, jonathan byler
> wrote:
>> We have been having some pretty serious issues with sulfur in our
>> clay
>> eating away the bricks in our bisque kiln. The inside of the kiln is
>> fine, but where the sulfur compounds contact the metal to brick
>> interface on the outside of the kiln, something in the stainless
>> steel reacts with the sulfur and eats up the bricks.
>>
>> Spraying the inside of the kiln with ITC didn't stop the problem. I
>> am thinking that the way to do it right would be to dip the whole
>> brick, or otherwise apply it inside and out so that the ITC might
>> protect the interface between the brick and the metal directly.
>>
>> Another solution that I am going to try on our next kiln is better
>> venting. was thinking that if the kiln were a little tighter that
>> would help direct the fumes away from the metal to brick interfaces,
>> since that is where the problems are coming from.
>>
>> Finally, does anyone have any idea where the sulfur would be coming
>> from? Our clay is made from goldart, ap green fireclay, custer
>> feldspar, and redart. A new coworker thinks that it might actually
>> be
>> our water that is causing the sulfur problems. I suppose we could
>> test this by making a batch of clay using distilled water and fire it
>> off, but there must be a better way.
>>
>> Does anyone have any ideas about this, or has anyone noticed that
>> sulfur problems have come from the water that they use?
>>
>> thanks,
>> jon
jonathan byler on thu 19 jan 12
We have been having some pretty serious issues with sulfur in our clay
eating away the bricks in our bisque kiln. The inside of the kiln is
fine, but where the sulfur compounds contact the metal to brick
interface on the outside of the kiln, something in the stainless
steel reacts with the sulfur and eats up the bricks.
Spraying the inside of the kiln with ITC didn't stop the problem. I
am thinking that the way to do it right would be to dip the whole
brick, or otherwise apply it inside and out so that the ITC might
protect the interface between the brick and the metal directly.
Another solution that I am going to try on our next kiln is better
venting. was thinking that if the kiln were a little tighter that
would help direct the fumes away from the metal to brick interfaces,
since that is where the problems are coming from.
Finally, does anyone have any idea where the sulfur would be coming
from? Our clay is made from goldart, ap green fireclay, custer
feldspar, and redart. A new coworker thinks that it might actually be
our water that is causing the sulfur problems. I suppose we could
test this by making a batch of clay using distilled water and fire it
off, but there must be a better way.
Does anyone have any ideas about this, or has anyone noticed that
sulfur problems have come from the water that they use?
thanks,
jon
John Post on thu 19 jan 12
> Finally, does anyone have any idea where the sulfur would be coming
> from? Our clay is made from goldart, ap green fireclay, custer
> feldspar, and redart.
The culprit is probably the goldart. It is known to have a high
sulphur content. The last time I saw a room full of blue smoke during
a bisque was when a college I was at used a large amount of goldart in
the clay body they made.
John Post
Sterling Heights, Michigan
http://www.johnpost.us
Follow me on Twitter
https://twitter.com/UCSArtTeacher
jonathan byler on thu 19 jan 12
I spoke about this with the cedar heights rep last year at NCECA. he
said that there had been a problem with this once back in the 1970's
(that they got to close to a coal seam), but that they had been very
careful not to let it happen again since... If I remember correctly
he said they had it tested regularly to be sure that there was no
sulfur/coal in the clay. He wanted to blame the fireclay we are
using. everyone wants to blame someone else it seems.
any other current goldart users have this problem? we go through
enough in a year that we clear out our local supplier every so often.
I'm pretty sure it's neigh impossible that we are getting bags from
the 1970's, and I think they are getting theirs direct from cedar
heights? would have to check up to confirm that they are.
I forget if this has been discussed, but who would we send a sample to
for testing? does anyone have a company that they use and are happy
with?
thanks,
jon
I guess I should have some sent to an independent lab to be tested,
just to see.
On Jan 19, 2012, at 4:09 PM, John Post wrote:
>
>> Finally, does anyone have any idea where the sulfur would be coming
>> from? Our clay is made from goldart, ap green fireclay, custer
>> feldspar, and redart.
>
> The culprit is probably the goldart. It is known to have a high
> sulphur content. The last time I saw a room full of blue smoke
> during a bisque was when a college I was at used a large amount of
> goldart in the clay body they made.
>
>
> John Post
> Sterling Heights, Michigan
>
> http://www.johnpost.us
>
> Follow me on Twitter
> https://twitter.com/UCSArtTeacher
>
>
>
William & Susan Schran User on thu 19 jan 12
On 1/19/12 3:44 PM, "jonathan byler" wrote:
> We have been having some pretty serious issues with sulfur in our clay
> eating away the bricks in our bisque kiln. The inside of the kiln is
> fine, but where the sulfur compounds contact the metal to brick
> interface on the outside of the kiln, something in the stainless
> steel reacts with the sulfur and eats up the bricks.
I note that the IFB at the outer edges of the sections of our top loaders a=
t
school have this issue. It's not real bad, but it is there. We do have
direct downdraft vents for the kilns and I think that certainly helps keep
it from being much worse. I think the problem is a combination of moisture
and sulfur condensing on the stainless steel skin where it meets the IFB.
Our kiln are located in a non-conditioned building so more exposed to
heat/cold and humidity. These kilns are used only for bisque firing. My kil=
n
at my home studio also has some of this, but it is inside a somewhat
conditioned garage and is now 20 years old, so I would expect some of this.
> Another solution that I am going to try on our next kiln is better
> venting. was thinking that if the kiln were a little tighter that
> would help direct the fumes away from the metal to brick interfaces,
> since that is where the problems are coming from.
Definitely, you need direct venting on the kiln. This will probably not
eliminate the problem but will certainly slow it down.
> Finally, does anyone have any idea where the sulfur would be coming
> from? Our clay is made from goldart, ap green fireclay, custer
> feldspar, and redart. A new coworker thinks that it might actually be
> our water that is causing the sulfur problems. I suppose we could
> test this by making a batch of clay using distilled water and fire it
> off, but there must be a better way.
> Does anyone have any ideas about this, or has anyone noticed that
> sulfur problems have come from the water that they use?
I think there is probably some sulfur in most all clays, just some more tha=
n
others. Combine the sulfur with the moisture, there's the problem. Good
direct venting will be the best route to go.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
John Britt on thu 19 jan 12
Jonathan,
Fire clay, a.k.a. goldart and AP Green, probably have lots sulfur. (Fire =
=3D
clay is=3D20
mined between coal seams. Read "Out of the Earth into the Fire" -Obstler)=
=3D
I think=3D20
but cannot check for sure, that redart has sulfur too.
So either change your body or put in a vent and know that it will corrode=
=3D
fast. So=3D20
you will have to change the vent motor and the metal hose - maybe yearly=3D=
20=3D
depending on your volume.
john britt pottery
Ben Shelton on thu 19 jan 12
I'd say that the source of the sulfur is most likely the clays as others ha=
=3D
ve said.=3D0A=3D0AIf you have the option bisque with gas.=3D0AIf not, vent.=
=3D0A=3D0A=3D
John Britt worries about corrosion in your vent motors but I think that can=
=3D
be avoided. If you set up a venturi based siphon this shouldn't be a worry=
=3D
.=3D0AKinda hard to describe... Imagine 2 air passages. One starts in the k=
il=3D
n, the other at a fan motor. The fan air is introduced into the vent pipe w=
=3D
ith an elbow that points towards the chimney exit. There should be a length=
=3D
of pipe on this elbow. The fan air blowing out of the opening expanding in=
=3D
to the pipe causes a venturi effect sucking air from behind it.That should =
=3D
avoid having vent gasses in the fan unit. Of course, you will have to play =
=3D
around with vent pipe sizes and air flow rates but that is half the fun isn=
=3D
't it?=3D0A=3DA0=3D0ABen
mudduck on thu 19 jan 12
Jonathan
I'm having this problem with my kiln also. Didn't know what the problem was=
.
I use standard 119 clay and during bisque the sulpher smell stinks to high
heaven. It's my under standing that 119 has Goldart in it also.
I was wondering why my kiln appeared to be rotting from the out side in.
Gene
mudduck@mudduckpottery.net
www.mudduckpottery.net
Rimas VisGirda on fri 20 jan 12
I would venture it is Goldart that has the sulfur. From about 1987 to 98 we=
used a clay 1/3 each of Goldart, Hawthorn fireclay and OM-4 ball at IL Wes=
leyan U. We fired to cone 10-11 and encountered a bloating problem where th=
e bloats when broken open had a yellow residue. We tracked it down to sulfu=
r in Goldart and sometime during that time I talked with a Goldart rep that=
affirmed Goldart had sulfur... Our bloating was caused by too low a bisque=
(cone 010) that didn't burn out all the sulfur; when we switched to cone 0=
5 bisque the bloats went away. However, that's not your original query. In =
my experience, our unvented electrics were used primarily for bisquing and =
there was corrosion at the top spy hole but I never noticed any problems wi=
th the bricks. The strap that circled the lid would get funky and start to =
slip up so I took a piece of sheet steel about 6 inches long and bent it in=
to an L that supported the bottom edge of the lid; the handle screws
were screwed through the upright part of the L. My studio kilns are all ven=
ted and the aluminum ducting deteriorates, but I think that is due more to =
moisture than sulfur as I don't use stoneware much any more...
A way to test which clay had sulfur might be to tale a chunk of the clays i=
n question and put each under an inverted cup and firing to cone 04; the cl=
ay with sulfur should have a yellowish residue/deposit on the inside of the=
cup...
Sulfur can be a problem in shared studio situations where an electric kiln =
is used for bisque as well as low fire (c/05) glazes. The sulfur given off =
during the bisque can impregnate the soft brick of the kiln and be given of=
f into the atmosphere during a c/05 glaze firing. Some 05 glazes are sensit=
ive to this and can get funky. At IWU, we would fire the kiln empty to c/6 =
the day before the 05 firing to clean the sulfur out of the brick...
-Rimas
William & Susan Schran User on fri 20 jan 12
On 1/19/12 11:10 PM, "jonathan byler" wrote:
> It burns the lungs like sulfur does. And burns off at the temperature
> that sulfury compounds would be likely to do (after 800F-900F). And
> the only other things that corrode stainless steel to that degree tend
> to be chlorine bearing compounds. We don't use salt in this kiln, so
> I don't know where we would be getting that level of chlorine vapor in
> the kiln atmosphere. Sulfur, however, would be pretty likely, as
> either coal contamination or possibly as pyrite (iron sulfide). The
> corrosion products of the stainless steel banding have a yellowish
> tinge to them which indicates a sulfur compound to me.
In doing a search about kiln corrosion, I came across this page by Skutt:
http://www.skutt.com/resources/articles/ar3_corrosion.html
In the page I note this statement:
"Sulfur is another mineral which is commonly found in many clay bodies whic=
h
will also wreak havoc on your kiln in the form of sulfuric acid."
So it is most likely sulfuric acid causing your issues with corrosion.
This acid, H2SO4, is the result of the sulfur in the clay combining with
water. The compound condenses on the colder stainless steel skin as it
escapes from any small opening, such as between the sections.
Best solution - change formulation of clay to clays with low sulfur content=
.
2nd best - direct vent the kiln - should do this anyway.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Bonnie Staffel on fri 20 jan 12
I mixed my own clay mix using Jordan, APGreen and Iron Oxide. I then =3D
used
Goldart to replace the Jordan when that became unavailable. I had =3D
extensive
problems when using the new mix. I deduced it was from the Goldart clay. =
=3D
The
studio was filled with a blue haze and my single pane windows in the =3D
winter
became etched from the sulfur smoke and the moisture on the windows. I =3D
had
to plan my firings so that the smoke occurred during the nighttime when =3D
no
one was in the studio.=3D20
At a separate time, I used some clay dug from a mid Michigan area where =3D
they
made stoneware sewer tiles and I was after the effect of the mottled =3D
pattern
for a special project. That clay was rank with the sulfur. I don't know =3D
of
any coal being mined in that area, but must contain the sulfur anyway.
Regards,
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
Des & Jan Howard on fri 20 jan 12
Jonathan & Mel
We use tanked stored rainwater. No sulphur there.
The local materials for the bodies we dig & use contain
no sulphur compounds. That said, the ochre slip we use
extensively, on nearly every pot, is made from another
local material. A witch's brew of limonite, siderite,
haematite, magnetite & iron sulphide. Calcining a
spoonful of this stuff soon displays the sulphur content.
Des
On 1/20/2012 7:44 AM, jonathan byler wrote:
> We have been having some pretty serious issues with
> sulfur in our clay
>
> Finally, does anyone have any idea where the sulfur
> would be coming
> from? Our clay is made from goldart, ap green fireclay,
> custer
> feldspar, and redart. A new coworker thinks that it
> might actually be
> our water that is causing the sulfur problems. I
> suppose we could
> test this by making a batch of clay using distilled
> water and fire it
> off, but there must be a better way.
>
> Does anyone have any ideas about this, or has anyone
> noticed that
> sulfur problems have come from the water that they use?
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
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