Bob Masta on thu 30 dec 04
Hi, all. This is really a question for Ron Roy regarding
his "Answers" column in the Jan 2005 CM, but I'm
guessing the answer will be of interest to others.
Ron says in his final sentence that "The very least you
should do is keep a peephole open during the bisque
firings and the last 220F (100C) of your glaze firings."
Ignoring the discrepancy on the F-and-C conversions,
I don't understand the motivation for keeping the peep
open at the end, except possibly to keep an eye on the
cones. I assume that all the volatiles are long gone
well before then, and if they weren't we would want
the peep open until they were. Is there something I am
missing here?
Thanks!
Bob Masta
potsATdaqartaDOTcom
Ron Roy on thu 30 dec 04
Hi Bob,
This is what I sent to CM - "The very least you should do is keep the spy
open during your bisque firings and up to 200F of the end of your glaze
firings."
Somewhat different from what showed up.
Many of the problems potters experience in electric kilns are due to
reduction effects - I am trying to make a point - make sure you are in
oxidation if that is what you want - especially if firing zinc oxide, lead
................
I do not think all the volatiles are gone at the end of a glaze firing by
the way - I do believe there is a more or less steady stream of volatiles
from the beginning to the end of our firings.
I spent many hours in the company of firing kilns during my life time in
clay - and I actually think I have developed some kind of sensitivity to
the volatiles produced - and I know of others who have it - one at least
who cannot be in a room with a kiln firing.
I have a small electric in my studio now - mostly for bisque firing. When
ever I enter that room - even though I have a vent running and plenty of
resupplied oxygen - I still have an uncomfortable feeling.
That article is really a plea for having a kiln vent running during firings
- and I do agree that elements will last longer if reduction is reduced -
whoops - can I say that?
Thanks for catching that Bob - I was definitely uncomfortable till I got
the original out because I could not imagine myself saying it that way -
and getting the conversion temp wrong as well.
I'm sending a copy of this to CM - RR
>Hi, all. This is really a question for Ron Roy regarding
>his "Answers" column in the Jan 2005 CM, but I'm
>guessing the answer will be of interest to others.
>
>Ron says in his final sentence that "The very least you
>should do is keep a peephole open during the bisque
>firings and the last 220F (100C) of your glaze firings."
>Ignoring the discrepancy on the F-and-C conversions,
>I don't understand the motivation for keeping the peep
>open at the end, except possibly to keep an eye on the
>cones. I assume that all the volatiles are long gone
>well before then, and if they weren't we would want
>the peep open until they were. Is there something I am
>missing here?
>
>Thanks!
>Bob Masta
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ivor and Olive Lewis on fri 31 dec 04
Dear Bob Masta,
Twill be at least six weeks before I can read all of what RR has
written but yes, there is a very good reason why it is advisable to
keep a peep open for the whole duration of a bisque firing.
In a word, Volatiles. Not only is there free water but also water
derived from the OH groups in the original clay that must be disposed
of. These chemical reactions may not cease as quickly as people might
assume. That created in the interior of the clay has to diffuse out of
the pots into the atmosphere. Then you have Volatiles from residual
minerals in your clay, Sulphides, Sulphates, Chlorides, Carbonates and
Fluorides, nor should we forget the "Organics". Sulphates are
notorious for persisting in the clay to beyond 1000=BA C.
Retention of Volatiles can lead to Bloating during a glost firing, so
you read wise words form Ron.
My own experience is that any kiln made from porous refractories and a
metal casing should be vented properly to discharge these corrosive
gases. Though this may be done, in the long term you will have severe
corrosion problems as the gases diffuse into and through your
insulation. Even Stainless Steel and Nichrome corrode. My fibre kiln
of fifteen years and 375 firings is under repair for this reason. A
main member of the roof, 1/4 inch thick steel as well as Nichrome wire
which retained the ceramic studs have corroded to failure.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
John Rodgers on fri 31 dec 04
Some of my very old "electric kiln" guru's have told me often that I
should always fire both bisque and glaze with the bottom plug out. That
this ensures a more uniform heat throughout, and helps continue to burn
out contaminants, etc, right to the last. I have followed their
recommendations and seem to have better success by following the
procedure. Not sure about some of the logic, but it seems to work.
John Rodgers
Chelsea, AL
Bob Masta wrote:
>Hi, all. This is really a question for Ron Roy regarding
>his "Answers" column in the Jan 2005 CM, but I'm
>guessing the answer will be of interest to others.
>
>Ron says in his final sentence that "The very least you
>should do is keep a peephole open during the bisque
>firings and the last 220F (100C) of your glaze firings."
>Ignoring the discrepancy on the F-and-C conversions,
>I don't understand the motivation for keeping the peep
>open at the end, except possibly to keep an eye on the
>cones. I assume that all the volatiles are long gone
>well before then, and if they weren't we would want
>the peep open until they were. Is there something I am
>missing here?
>
>Thanks!
>
>
>
>
>
>Bob Masta
>
>potsATdaqartaDOTcom
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
>
Kim Lindaberry on fri 31 dec 04
John,
So what about kilns with vent fans installed with the bottom? My
understanding is that you are supposed to keep all peeps in so the vent
fan can draw hot air downward from the small holes in the kiln lid. If
there were any peep holes open this would cause the air to be drawn
from their locations and thus not even out the kiln temps from top to
bottom.
Kim
On Dec 31, 2004, at 7:12 AM, John Rodgers wrote:
> Some of my very old "electric kiln" guru's have told me often that I
> should always fire both bisque and glaze with the bottom plug out. That
> this ensures a more uniform heat throughout, and helps continue to burn
> out contaminants, etc, right to the last. I have followed their
> recommendations and seem to have better success by following the
> procedure. Not sure about some of the logic, but it seems to work.
>
> John Rodgers
> Chelsea, AL
Louis Katz on fri 31 dec 04
In my school studio we dry out our kilns with the top spy out and fire
with all the plugs in. We have a bailey kiln vent that works better
than 95% of the time. The down time is becasue we do dry in the kiln
and this has a very corrosive effect on the kilns, vent blowe and
piping. In ten years I have replace the vent pipe partially once and
completely twice. I have replaced the blower once and I think it is due
again. I would fire with the top spy out for the whole firing except
that this makes the smell of the kiln quite noticable. I identify this
smell as like dirty vanilla smelling . BTW Vanilla is an aldehyde.
This leads me and others to assume that this smell I am picking up is
an aldehyde or combination of them.
also , We recently had the air quality people through and passed our
airborne silica test with flying colors. Hose the floor, make broom a
four letter word. Keep tables and other horizontal surfaces washed
down.
I am in favor of well ventilated bisques although some sulphur problems
seem to be worse in them. I tell people on not to cool with the bottom
spy holes plugs out. (Cool with them in).
Louis
On Dec 31, 2004, at 7:12 AM, John Rodgers wrote:
> Some of my very old "electric kiln" guru's have told me often that I
> should always fire both bisque and glaze with the bottom plug out. That
> this ensures a more uniform heat throughout, and helps continue to burn
> out contaminants, etc, right to the last. I have followed their
> recommendations and seem to have better success by following the
> procedure. Not sure about some of the logic, but it seems to work.
>
> John Rodgers
> Chelsea, AL
>
> Bob Masta wrote:
>
>> Hi, all. This is really a question for Ron Roy regarding
>> his "Answers" column in the Jan 2005 CM, but I'm
>> guessing the answer will be of interest to others.
>>
>> Ron says in his final sentence that "The very least you
>> should do is keep a peephole open during the bisque
>> firings and the last 220F (100C) of your glaze firings."
>> Ignoring the discrepancy on the F-and-C conversions,
>> I don't understand the motivation for keeping the peep
>> open at the end, except possibly to keep an eye on the
>> cones. I assume that all the volatiles are long gone
>> well before then, and if they weren't we would want
>> the peep open until they were. Is there something I am
>> missing here?
>>
>> Thanks!
>>
>>
>>
>>
>>
>> Bob Masta
>>
>> potsATdaqartaDOTcom
>>
>> ______________________________________________________________________
>> ________
>> Send postings to clayart@lsv.ceramics.org
>>
>> You may look at the archives for the list or change your subscription
>> settings from http://www.ceramics.org/clayart/
>>
>> Moderator of the list is Mel Jacobson who may be reached at
>> melpots@pclink.com.
>>
>>
>>
>>
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
Louis Katz
http://www.tamucc.edu/~lkatz
Sam Hoffman on fri 31 dec 04
This is a difficult theory to convince people of; neutral-reducing
atmospheres in electric kilns. I fire my crystalline glazes in a Skutt
1224P with at least half of the peeps open. Crystalline glazes are
loaded with zinc oxide, and without a truly oxidizing atmosphere, the
crystals grow VERY slowly. The colors are less brilliant, as well.
I find the Envirovent to be a very good addition to any electric kiln
being used for glaze firing. It ensures an oxidizing atmosphere, and a
more even firing. With the vent, no peeps should be open. (four small
holes are drilled in the lid)
Happy firing!
-Sam
S.L. Hoffman Pottery
Corvallis, Oregon
www.samhoffman.com
On Dec 30, 2004, at 8:09 PM, Ron Roy wrote:
> Hi Bob,
>
> This is what I sent to CM - "The very least you should do is keep the
> spy
> open during your bisque firings and up to 200F of the end of your glaze
> firings."
>
> Somewhat different from what showed up.
>
> Many of the problems potters experience in electric kilns are due to
> reduction effects - I am trying to make a point - make sure you are in
> oxidation if that is what you want - especially if firing zinc oxide,
> lead
> ................
>
> I do not think all the volatiles are gone at the end of a glaze firing
> by
> the way - I do believe there is a more or less steady stream of
> volatiles
> from the beginning to the end of our firings.
>
> I spent many hours in the company of firing kilns during my life time
> in
> clay - and I actually think I have developed some kind of sensitivity
> to
> the volatiles produced - and I know of others who have it - one at
> least
> who cannot be in a room with a kiln firing.
>
> I have a small electric in my studio now - mostly for bisque firing.
> When
> ever I enter that room - even though I have a vent running and plenty
> of
> resupplied oxygen - I still have an uncomfortable feeling.
>
> That article is really a plea for having a kiln vent running during
> firings
> - and I do agree that elements will last longer if reduction is
> reduced -
> whoops - can I say that?
>
> Thanks for catching that Bob - I was definitely uncomfortable till I
> got
> the original out because I could not imagine myself saying it that way
> -
> and getting the conversion temp wrong as well.
>
> I'm sending a copy of this to CM - RR
>
>
>> Hi, all. This is really a question for Ron Roy regarding
>> his "Answers" column in the Jan 2005 CM, but I'm
>> guessing the answer will be of interest to others.
>>
>> Ron says in his final sentence that "The very least you
>> should do is keep a peephole open during the bisque
>> firings and the last 220F (100C) of your glaze firings."
>> Ignoring the discrepancy on the F-and-C conversions,
>> I don't understand the motivation for keeping the peep
>> open at the end, except possibly to keep an eye on the
>> cones. I assume that all the volatiles are long gone
>> well before then, and if they weren't we would want
>> the peep open until they were. Is there something I am
>> missing here?
>>
>> Thanks!
>> Bob Masta
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
> Phone: 613-475-9544
> Fax: 613-475-3513
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
John Rodgers on fri 31 dec 04
Never used a power vented kiln......and I don't think my old guru's did
either, so the issue was never addressed. If you have power vents on
the kiln I would definitely follow the instructions for use of the vent,
regardless of guru's perspective.
Regards,
John Rodgers
Chelsea, AL
Kim Lindaberry wrote:
> John,
>
> So what about kilns with vent fans installed with the bottom? My
> understanding is that you are supposed to keep all peeps in so the vent
> fan can draw hot air downward from the small holes in the kiln lid. If
> there were any peep holes open this would cause the air to be drawn
> from their locations and thus not even out the kiln temps from top to
> bottom.
>
> Kim
>
> On Dec 31, 2004, at 7:12 AM, John Rodgers wrote:
>
>> Some of my very old "electric kiln" guru's have told me often that I
>> should always fire both bisque and glaze with the bottom plug out. That
>> this ensures a more uniform heat throughout, and helps continue to burn
>> out contaminants, etc, right to the last. I have followed their
>> recommendations and seem to have better success by following the
>> procedure. Not sure about some of the logic, but it seems to work.
>>
>> John Rodgers
>> Chelsea, AL
>
>
> ______________________________________________________________________________
>
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
Ron Roy on sun 2 jan 05
Hi Sam,
Thanks for posting this.
It depends on the type of vent system used by the way - mine (Baily) exits
at the back near the bottom and requires the front top spy to be open.
Fresh air flows through at a very low rate from front top to bottom rear.
RR
> This is a difficult theory to convince people of; neutral-reducing
>atmospheres in electric kilns. I fire my crystalline glazes in a Skutt
>1224P with at least half of the peeps open. Crystalline glazes are
>loaded with zinc oxide, and without a truly oxidizing atmosphere, the
>crystals grow VERY slowly. The colors are less brilliant, as well.
>
> I find the Envirovent to be a very good addition to any electric kiln
>being used for glaze firing. It ensures an oxidizing atmosphere, and a
>more even firing. With the vent, no peeps should be open. (four small
>holes are drilled in the lid)
>
>Happy firing!
>
>-Sam
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Bob Masta on sun 2 jan 05
Thanks to Ron and everyone for your responses.
I expected that there would be plenty of volatiles
from a bisque firing, but I figured they would be
tapering off toward the end. For a glaze firing,
I expected the same general initial volatile output as
the glaze materials released their carbonates, etc,
but imagined the overall volume to be lower due to
the smaller amount of glaze compared to body clay,
and to the fact that glaze materials generally have less
organics and sulfates, etc. But I assumed this would
all be pretty much gone by the end of the firing.
Of course, after more thought I realized that any glaze
that shows bubbles must have been giving off gasses
at the end of the firing!
It sure would be interesting to see a plot of the various
emissions versus time/temperature in a typical firing.
I guess we need to find a potter with a gas chromatograph
that s/he can hook to the kiln vent. Or maybe rig up a
way to insert a filter to collect stuff from the vent for a few
minutes, and run a new one every hour. Then send the
stack of filters to some clever analytical chemist.
Or maybe infrared absorption or some other exotic
technique. Anyone?
Best regards,
Bob Masta
potsATdaqartaDOTcom
Ron Roy on mon 3 jan 05
Hi Bob,
I agree - time to get emmissipns tested - surely there must be a university
somewhere that has a science and a pottery department.
I hope we - as a group - are ready for some unpleasant information however
- we have been avoiding this for a long time.
RR
>Thanks to Ron and everyone for your responses.
>I expected that there would be plenty of volatiles
>from a bisque firing, but I figured they would be
>tapering off toward the end. For a glaze firing,
>I expected the same general initial volatile output as
>the glaze materials released their carbonates, etc,
>but imagined the overall volume to be lower due to
>the smaller amount of glaze compared to body clay,
>and to the fact that glaze materials generally have less
>organics and sulfates, etc. But I assumed this would
>all be pretty much gone by the end of the firing.
>
>Of course, after more thought I realized that any glaze
>that shows bubbles must have been giving off gasses
>at the end of the firing!
>
>It sure would be interesting to see a plot of the various
>emissions versus time/temperature in a typical firing.
>I guess we need to find a potter with a gas chromatograph
>that s/he can hook to the kiln vent. Or maybe rig up a
>way to insert a filter to collect stuff from the vent for a few
>minutes, and run a new one every hour. Then send the
>stack of filters to some clever analytical chemist.
>Or maybe infrared absorption or some other exotic
>technique. Anyone?
>
>Best regards,
>
>
>
>Bob Masta
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
May Luk on thu 6 jan 05
Hi all;
I would like to know what's the rationale of closing the vent completely?
A friend close their vents completely at 200C. After 6 months, new set of
elements needs to be change. Then the technician told them to close the vent
at 600C. I asked her:'what is the hurry?' Sometimes, I had my top vent open
all the way even during cooling for glossy glaze, I didn't notice any big
difference in Kw usage. If slow cooling is not needed, why close the top
vent the whole time?
Thanks
May
London, UK
Lee Love on fri 7 jan 05
May Luk wrote:
>Hi all;
>
>I would like to know what's the rationale of closing the vent completely?
>
It occurred to me the other day, while my wood kiln bisque was
cooling, was that folks might get cracking during the bisque in a
softbrick wood kiln, like the Olsen fastfire, because they cool too
quickly, especially if they don't close up the fireboxes at the end of
the firing. It also occured to me, that this could also be true of
softbrick electric kilns.
--
in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
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