Clayton Bailey on fri 10 may 96
What can I add to my clay to increase bloating at cone 10?
John Baymore on sat 11 may 96
Clayton,
Try grinding up some coal into fine chunks and add it to the clay.
.................................john
John Baymore
River Bend Pottery
Wilton, NH
76506.3102@Compuserve.com
Dave Eitel on sat 11 may 96
>----------------------------Original message----------------------------
>What can I add to my clay to increase bloating at cone 10?
An interesting question, and one I've been waiting several months to have
someone ask. I believe one of the major clay suppliers sells a product
called Bloatmore. I have not tried it myself, but I've heard from a number
of my fellow potters that it works great. Otherwise, you could add
powdered coal, I think, to get very similar effects.
Later...Dave
Dave Eitel
Cedar Creek Pottery
Cedarburg, WI
daveitel@execpc.com
http://www.digivis.com/CedarCreek/home.html
Frank A. Pishkur on tue 14 may 96
On Fri, 10 May 1996, Clayton Bailey wrote:
> ----------------------------Original message----------------------------
> What can I add to my clay to increase bloating at cone 10?
>
I always heard that the little bits of your sponge that break off can
cause bloating. Perhaps you could try adding some shredded sponge.
Frank A. Pishkur knarf@adsnet.com
118 Superior St.
Michigan City, IN 46360
.....what a beach.
Hluch - Kevin A. on tue 14 may 96
Bloating can be accomplished by wedging some earthenware clay into your
high temperature clay...Student of mine just made that mistake and it
works fine!?
Kevin A. Hluch
East Seaboard, North America, due West of Dakar, Senegal.
On Tue, 14 May 1996, Frank A. Pishkur wrote:
> ----------------------------Original message----------------------------
> On Fri, 10 May 1996, Clayton Bailey wrote:
>
> > ----------------------------Original message----------------------------
> > What can I add to my clay to increase bloating at cone 10?
> >
> I always heard that the little bits of your sponge that break off can
> cause bloating. Perhaps you could try adding some shredded sponge.
>
> Frank A. Pishkur knarf@adsnet.com
> 118 Superior St.
> Michigan City, IN 46360
> .....what a beach.
>
cape1764@biddeford.com on wed 3 jul 96
Hello again clayarters.
It seems with a new studio there are always problems to sort out. Maybe
one of you can give me some suggestions on this one.
I once fire to cone 9 reduction. It takes me approx. 18 hours to get to
temp. 40 cu. ft. down draft propane fired kiln. venturi b-4a burners. The first
few firings, the kiln was uneven but no bloating. The last 2 firings the pots
on the bottom 2 shelves have bloated. not all of them but many. esp. the large
bowls. It seems as if the glossy glazes don't bloat as frequently. Mugs and
such never bloat. The top of the kiln never bloats. Am I going too fast
through a particular section? Not enough ox at lower temps? No time for
organics to burn out? HELP! Any and all suggestions would be appreciated.
TIA Tracy
Ron Roy on thu 4 jul 96
>----------------------------Original message----------------------------
>Hello again clayarters.
> It seems with a new studio there are always problems to sort out. Maybe
>one of you can give me some suggestions on this one.
> I once fire to cone 9 reduction. It takes me approx. 18 hours to get to
>temp. 40 cu. ft. down draft propane fired kiln. venturi b-4a burners. The
>first
>few firings, the kiln was uneven but no bloating. The last 2 firings the pots
>on the bottom 2 shelves have bloated. not all of them but many. esp. the
>large
>bowls. It seems as if the glossy glazes don't bloat as frequently. Mugs and
>such never bloat. The top of the kiln never bloats. Am I going too fast
>through a particular section? Not enough ox at lower temps? No time for
>organics to burn out? HELP! Any and all suggestions would be appreciated.
> TIA Tracy
Hi Tracy,
You are on the right track re getting the carbon out between 700C and 900C
- slow down and make sure there is extra oxygen around to clear the carbon
out of the clay. The bloating is happening in the thicker pieces because
the cabon can't get out - turns the Fe2O3 into FeO which then over fluxes
the clay which in turn over fires. Fe2O3 is not much of a flux but FeO is a
big time flux.
I suspect the bottom of your kiln lages behind the top and you may even be
into reduction before the carbon is oxidized. Just keep in mind - the
damage is done as the carbon is released from the clay and can be trapped
even in bisque firings. Stephen Hill warns about this problem for once
firing and cauctions to fire slow during the carbon release. You can also
check to see if you are in oxidation by inserting something combustable (I
use a strip of cardboard) if it won't burn inside there is no oxygen. An
oxy-probe startes working about 650C I think (is that right Nils) and that
would certainly let you know what is going on.
If you had some cones in the bottom half which you could peek at you will
find out how far behind it is.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Janet H Walker on tue 13 may 97
I'm sure you've had some answers to this question already but just to
add my experience. Yep, I'm sure this is what is known as bloating.
Textbook bloating. It sounds exactly like my experience. I was using
the same bisque schedule as you are. I finally got so fed up that I
did buy a controller and changed to a very long bisque firing. Since
then I have had zero problems with bloating.
As for firing etc. There is good information in the Hamer dictionary.
Look under "bisque", "black core", and "firing" for info. Also, I
found very explicit information in Harry Fraser's Ceramic Faults and
their Remedies. F.H. Norton's book from the 70's also has detailed
information on the subject of firing schedules.
Here's the scoop. Red clays contain organics and sulphur compounds
that are not in porcelains. RedArt clay is notoriously sulphurous.
Those compounds have to burn out completely in the bisque or else
they will be trapped inside under the glaze skin during the glaze
fire and cause the blobs and bubbles. The organics burn out between
700C and 900C. The sulphurs go above 900C.
This has several implications.
- Fire slowly between 700C and 900C. "Slowly" is rarely put into
numbers. I have done 50C and 60C per hour heat rise. This seems to
accord with Fraser although some books do define "slowly" as 100C
per hour rise. "It depends" as do so many things. Cast pieces that
are evenly thin can probably go more quickly (i.e. 100/hr) than
pieces whose walls exceed 1 cm.
- Fire to cone 04 to get the sulphur out.
- Soak the bisque load for an hour or two at top temperature.
Some may think this is ridiculous overkill. It does, however,
result in bloat-free pieces at the end of the glaze firing.
By the way, I have a hypothesis about the practice of soaking a
bisque load overnight on low. That practice is for the sake of the
person doing the switching, not anything to do with the needs of the
bisque load. If you didn't leave it on low overnight, you would
have to either start it on medium (anyone tried this?) or get up
several times during the night to turn the switches. I can't think
of many better arguments in favor of getting a controller...
Regards,
Jan Walker
Suzanne Storer on wed 14 may 97
Jan asked about firing schedules for bisque overnite. I use a cone 6 red
claybody and begin firing the bisque about 8 or 9PM for an hour or two, then
all switches go to medium or "6" on my L&L kiln for the night. In the
morning all switches go to "high" for a couple of hours or so 'til cone 04
is reached. Works slick!
Suzanne Storer
Roger Bourland on wed 14 may 97
A blown fuse interrupted a recent ^6 glaze firing at about 1800"F. . I
caught it going down at about 1100' F and started things going again.
However I found that there was severe bloating, raised "bubbles" all over
the pots (many of them) when I opened the kiln. I presume the bloating was
related to the mid-firing problem.
Are these a lost cause, or is refiring a possible remedy?
Roger Bourland
Christian R. Eberle on thu 15 may 97
> A blown fuse interrupted a recent ^6 glaze firing at about 1800"F. . I
> caught it going down at about 1100' F and started things going again.
> However I found that there was severe bloating, raised "bubbles" all over
> the pots (many of them) when I opened the kiln. I presume the bloating
was
> related to the mid-firing problem.
>
> Are these a lost cause, or is refiring a possible remedy?
>
> Roger Bourland
It sounds like a problem I've had with larger pieces. The bubbles are from
gas that doesn't finish escaping through the liquid glaze (when it reaches
^6). My solution was to add a 45 minute hold time at the end of the
firing.
Chris
Cheryl L Litman on tue 11 nov 97
I just started using a dark brown clay (#266) from Standard Ceramic
Supply and made a bunch of bowls. The clay is rated cone 4-6. After a
cone 7 glaze fire I noticed that half of the bowls had one of more raised
spots on them, always toward the inside of the bowl, never on the
outside. I've never used this clay before so I don't know what is
normal. I do a 06 bisque 3 hours on low, 3 on medium and then the cone
shuts it off about 1 hour later. I use the same firing schedule for the
^7 glaze and after I turn all the switches to high it usually takes
another 4.5-5 hours to shut off.
I'm sure that I'm not wedging that much air into that many pieces so the
problem is coming from overfiring the clay I would guess? When a clay is
rated as vitrifying at ^4-6 would firing one cone higher cause all these
problems? I fired to ^7 because I was using a glaze I like which is
rated for ^7. Any suggestions? Anyone else ever have this problem? I'm
planning to fire the next batch to ^6 and see what happens.
I see people referring to slow and fast firings - anyone care to put a
number to those term? Is my glaze firing to ^7 over 11 hours slow,
medium or fast?
Cheryl Litman
Somerset, NJ
email: cheryllitman@juno.com
Ray Carlton on thu 13 nov 97
it's called bloating and is caused by overfiring//Yes cheryl your 11 hour
firing is quite slow i would suggest using a higher firing body// bloats
will start where an air pocket is but is not necessarily required for a
good sized bloat
cheers
At 10:41 11/11/97 EST, you wrote:
>----------------------------Original message----------------------------
>I just started using a dark brown clay (#266) from Standard Ceramic
>Supply and made a bunch of bowls. The clay is rated cone 4-6. After a
>cone 7 glaze fire I noticed that half of the bowls had one of more raised
>spots on them, always toward the inside of the bowl, never on the
>outside. I've never used this clay before so I don't know what is
>normal. I do a 06 bisque 3 hours on low, 3 on medium and then the cone
>shuts it off about 1 hour later. I use the same firing schedule for the
>^7 glaze and after I turn all the switches to high it usually takes
>another 4.5-5 hours to shut off.
>
>I'm sure that I'm not wedging that much air into that many pieces so the
>problem is coming from overfiring the clay I would guess? When a clay is
>rated as vitrifying at ^4-6 would firing one cone higher cause all these
>problems? I fired to ^7 because I was using a glaze I like which is
>rated for ^7. Any suggestions? Anyone else ever have this problem? I'm
>planning to fire the next batch to ^6 and see what happens.
>
>I see people referring to slow and fast firings - anyone care to put a
>number to those term? Is my glaze firing to ^7 over 11 hours slow,
>medium or fast?
>
>Cheryl Litman
>Somerset, NJ
>email: cheryllitman@juno.com
>
>
raycarlt@valylink.net.au
Ray Carlton
McMahons Creek Victoria Australia 3799
Cheryl L Litman on thu 13 nov 97
Thanks to all for the replies re the bloating problem. I'm planing on
firing the next batch to ^6 and I'll see how things turn out. I love the
clay, it throws well, handbuilds well and looks great with the glaze I'm
using.
Cheryl Litman
Somerset, NJ
email: cheryllitman@juno.com
Ron Roy on thu 13 nov 97
Hi Cheryl,
I make a lot of clay bodies and I recommend they be fired at a (one)
specific cone. There are just too many variables in our raw materials for
me to feel safe recommending a firing "range." It's tough enough to keep
things working properly at one cone.
So what has happened here - the body is more open at 4 than at 6. But if it
is to be water tight at 4 then the absorbency needs to be under 3% - I
prefer 2% - so at cone 6 the clay is almost certainly - at least some of
the time - completely vitrified - so at cone 7 the clay is likely to be
overfired (too soft.)
At lower temperatures clays and glazes need more flux to make them melt -
the net result of this - the firing "range" is usually shorter. The reason
for this is - the more flux you have the faster the rate of melting. It's a
generalization but you better believe it. The implication here is that
higher fire clay and glazes have a better "range" cause they need less flux
to melt. There are plenty of exceptions to the rule here as well -
unbalanced - overfluxed high fire glazes don't have much range at all - I
suppose I could use some porcelain bodies as an example of a high fire body
with less range - they need lots of flux to melt all that kaolin.
The moral of this particular story - don't fire clay higher than the
manufacturer recommends - and - whatever you fire it to - check the
shrinkage and absorbency to make sure you are getting what you pay for. If
you are mixing your own clay - better check your raw materials before you
mix em.
>----------------------------Original message----------------------------
>I just started using a dark brown clay (#266) from Standard Ceramic
>Supply and made a bunch of bowls. The clay is rated cone 4-6. After a
>cone 7 glaze fire I noticed that half of the bowls had one of more raised
>spots on them, always toward the inside of the bowl, never on the
>outside. I've never used this clay before so I don't know what is
>normal. I do a 06 bisque 3 hours on low, 3 on medium and then the cone
>shuts it off about 1 hour later. I use the same firing schedule for the
>^7 glaze and after I turn all the switches to high it usually takes
>another 4.5-5 hours to shut off.
>
>I'm sure that I'm not wedging that much air into that many pieces so the
>problem is coming from overfiring the clay I would guess? When a clay is
>rated as vitrifying at ^4-6 would firing one cone higher cause all these
>problems? I fired to ^7 because I was using a glaze I like which is
>rated for ^7. Any suggestions? Anyone else ever have this problem? I'm
>planning to fire the next batch to ^6 and see what happens.
>
>I see people referring to slow and fast firings - anyone care to put a
>number to those term? Is my glaze firing to ^7 over 11 hours slow,
>medium or fast?
>
>Cheryl Litman
>Somerset, NJ
>email: cheryllitman@juno.com
Ron Roy
93 Pegasus Trail
Scarborough,Canada
M1G 3N8
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/people/ronroy.htm
David W McDonald on fri 20 aug 99
Donn Buchfinck,
In response to your question, I have been using "Amador", but
also experienced bloating with Soldate 60. Sounds like from the others
I've heard from though that "LB Blend" is even worse, although I don't
see how anything could be worse than what I've seen coming out of my
kiln. In my experience this clay cannot handle even a fraction above cone
10.
Yes I do use wax resist, but my glaze firings are 18 to 20 hours
long due to the size of the work I'm firing (15" to 25" slab built and
wheelthrown platters, 1/4 to 3/8 inch wall thickness), and I think the
wax has plenty of time to burn off and out of the kiln. Thanks for your
timely response. David McDonald
On Thu, 19 Aug 1999 12:24:41 EDT Nudefigure@aol.com writes:
>HI
>I teach at the walnut creek civic art center here in the San Francisco
>bay
>area, and we have had problems with laguna clays
>send them back to them
>develop a clay body and buy a mixer and make it yourself
>I know this is a problem, but this is how we remedied it in my
>personnel
>studio
>and don't let laguna tell you that you are the only one
>
>the only thing I could tell you is that if you are using wax resist
>and you
>are firing fast in the beginning and that does not let the wax burn
>off and
>get out of the clay body, then that might bloat the clay
>what kind of clay are you using???
>
>Donn Buchfinck
>San Francisco
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Shelley Potter on mon 5 jun 00
----- Original Message -----
From: Shelley Potter
To: clayart
Sent: Saturday, June 03, 2000 10:05 PM
Subject: bloating
Hi,
I have just read much that was written about bloating in the archives. I'm
still not quite sure what the cause is of all the raised bubbles in my last
batch of pieces.
I am working with cone 5 clay for the first time. I hand build vessels with
several different colored clays. In this instance, I'm using :
Hagi Porceline
Cassius Black
Electric Brown
I wedged some paper clay into each of them (a lot of wedging), rolled them
out with a rolling pin, and built cylinders with alternating slabs of the
different clays. I sanded them at bone dry. . So each pot has all three
clays . The clays did not separate from each other in the firing, so that
went well.
Then I fired them (no glaze) in my computerized Skutt. I set the controlls
at cone 5 at medium speed with one hour of soak at the end. ( I thought this
would give me a more smooth porceline finish.(?))
The actual firing took 8 hours with one hour of hold at the end. the temp
went to 2165F. Blebs only happened in the porceline and to a lesser extent
in the Cassius Black. None in the brown clay.
My questions: was this firing just too fast? Did the soak at the end play
any part in this so that maybe there was an overfire? Why didn't the brown
clay bleb and the porceline bleb so much? Any chance that the paper clay
had
anything to do with it since I didn't mix it with dry clay but only wedged
it in?
This never happened at medium speed in my high fire clays. Does cone5 clay
have less leeway than cone10?
So far I'm thinking I will set the kiln in ramp/hold mode going very slowly
at the beginning to let carbon, etc burn out sufficiently. Any other
suggestions?
Other than the blebs, I was actually quite happy with the creamy texture of
the porceline considering it was only cone 5.
Thanks, Shelley
Paul Taylor on wed 7 jun 00
Dear Shelly
You are right cone five clay has less leeway than cone ten because it
fluxes at a lower temperature which shortens the time impurities have to
burn out.
As usual there could be several things happening to cause this fault.
Porcelain is completely vitrified so even the cone ten porcelains can
take a little longer to biscuit fire, cone five even longer still.
To prevent bloating you have to get all the carbon out and that includes
the stuff in the paper( clay). the paper will open up the clay which
compensates for the extra carbon.
The cone five glaze may also be causing problems.
Because the clay vitrifies earlier there is less time for the carbon to
escape so a soak on the way up to temp at 700c to 800c , an hour will
probably do.
Carbon trapped in the body has three opportunities to escape, the
biscuit firing and cooling plus the glaze firing. If you biscuit fire the
cone five porcelain too high you can inhibit carbon escape in the cooling
and the second firing. If you have had trouble getting the glaze on the
biscuit porcelain lower the temperature- try 945 centigrade .
Slowing down the glaze fire helps, in so much that the pots right up to
the burners especially in gas kilns sometime heat up before the others.
Although it all evens up by top temperature, it seals in carbon and bloats
next to the burners or elements. It looks like over firing at the burners or
near the elements but it is bloating
Make sure your kiln is exchanging a little air especially between 750 and
850.
Too tight a packing does not help. That usually does not matter, but cone
five porcelain needs all the help it can get so biscuit lids separately.
The glaze could also be fluxing quite early. On the old stone ware it did
not matter the body is open enough to have thrown off the carbon, but the
porcelain was struggling. so the glaze firing could be a little slower
especially before that glaze melts.
A very good thing to do is to put some test rings in your kiln and draw
them out at fifty degree intervals or more after 945 c to see what is
precisely happening, when the body fluxes and when the glazes fluxes- you
will be surprised. You only have to do it once. Try not to electrocute your
self. turn the kiln off to with draw the test. That sounds so obvious but in
the worry of getting a red hot ring out of the kiln you can so easily
forget. You would not be the first to get a jolt for forgetting.
Regards Paul Taylor
> From: Shelley Potter
> Reply-To: Ceramic Arts Discussion List
> Date: Mon, 5 Jun 2000 21:57:21 -0700
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: bloating
>
>
> This never happened at medium speed in my high fire clays. Does cone5 clay
> have less leeway than cone10?
>
> So far I'm thinking I will set the kiln in ramp/hold mode going very slowly
> at the beginning to let carbon, etc burn out sufficiently. Any other
> suggestions?
> Send postings to clayart@lsv.ceramics.org
Alisa and Claus Clausen on wed 7 jun 00
Hi Shelley,
Sorry about your unsatisfactory firing.
When I experienced bloating in one of my firings, Ron Roy described =
bloating defects and causes as below:
-Air bubbles in vitrifeid clay can look like bloating.
-Large bubbles can occur if bisquewear is dirty, black coring. Looks =
like bloats but is is actually from iron=20
in over fluxed clay bodies.
- Small bubbles over the entire body (mine where inside and out) means =
the clay is overfluxed at the
temperature the clay was fired to.
My particular kiln load was fired first to about 900c but hung up there =
for many hours before I caught on that the old kiln was not going to get =
hotter. A particular hope of mine when it reaches around 900c because I =
need minimal 1220c.
The pieces were refired to 1250c. I think the long "hold" in the first =
failed firing is what overfired my claybody. I usually hold only 10 =
minutes. Do your glazes need an hour soak at the top? Especially if =
your pieces were unglazed, this does not sound necessary, maybe the =
culprit.
I am sure the experts like Ron can better help you, but my gut idea due =
to my own experience is that your hold is too long for unglazed work. =
Secondly, I fire slow bisques, but have not noticed any difference in my =
glaze surfaces when I slow down the initial ramps. Lately I fire 100c =
per hour up to 600c, then full speed up to 1100c (200c per hour) and =
slow down to 100c again up to top temp. 1250c., hold 10 minutes and off. =
Hope you work it out.
Best regards,
Alisa in Denmark
-----Oprindelig meddelelse-----
Fra: Shelley Potter
Til: CLAYART@LSV.CERAMICS.ORG
Dato: 6. juni 2000 22:44
Emne: bloating
>----- Original Message -----
>From: Shelley Potter
>To: clayart
>Sent: Saturday, June 03, 2000 10:05 PM
>Subject: bloating
>
>
> Hi,
> I have just read much that was written about bloating in the =
archives. I'm
> still not quite sure what the cause is of all the raised bubbles in my =
last
> batch of pieces.
>
> I am working with cone 5 clay for the first time. I hand build vessels =
with
> several different colored clays. In this instance, I'm using :
>Hagi Porceline
>Cassius Black
>Electric Brown
>
> I wedged some paper clay into each of them (a lot of wedging), rolled =
them
> out with a rolling pin, and built cylinders with alternating slabs of =
the
> different clays. I sanded them at bone dry. . So each pot has all =
three
> clays . The clays did not separate from each other in the firing, so =
that
> went well.
>
> Then I fired them (no glaze) in my computerized Skutt. I set the =
controlls
>at cone 5 at medium speed with one hour of soak at the end. ( I thought =
this
> would give me a more smooth porceline finish.(?))
>
> The actual firing took 8 hours with one hour of hold at the end. the =
temp
> went to 2165F. Blebs only happened in the porceline and to a lesser =
extent
> in the Cassius Black. None in the brown clay.
>
> My questions: was this firing just too fast? Did the soak at the end =
play
> any part in this so that maybe there was an overfire? Why didn't the =
brown
> clay bleb and the porceline bleb so much? Any chance that the paper =
clay
>had
> anything to do with it since I didn't mix it with dry clay but only =
wedged
> it in?
>
> This never happened at medium speed in my high fire clays. Does cone5 =
clay
> have less leeway than cone10?
>
> So far I'm thinking I will set the kiln in ramp/hold mode going very =
slowly
> at the beginning to let carbon, etc burn out sufficiently. Any other
>suggestions?
> Other than the blebs, I was actually quite happy with the creamy =
texture of
> the porceline considering it was only cone 5.
> Thanks, Shelley
>
>________________________________________________________________________=
______
>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 thu 8 jun 00
Hi Shelly,
The first question is - did you have a large cone in the kiln - it's the
only way to know what temperature you really fired to.
Small blebs are a sign of overfired clay - this is my guess. At first I
thought - not enough time for all that carbon from the paper to get out and
the reduced iron caused the overfiring - but that is not likely with
porcelain - not much iron.
If you really want the answer you should test all 3 clays for absorbency at
cone 5 - not hard to do.
What was the recommended firing temp of the paper clay?
What does your clay supplier have to say?
RR
> I have just read much that was written about bloating in the archives. I'm
> still not quite sure what the cause is of all the raised bubbles in my last
> batch of pieces.
>
> I am working with cone 5 clay for the first time. I hand build vessels with
> several different colored clays. In this instance, I'm using :
>Hagi Porceline
>Cassius Black
>Electric Brown
>
> I wedged some paper clay into each of them (a lot of wedging), rolled them
> out with a rolling pin, and built cylinders with alternating slabs of the
> different clays. I sanded them at bone dry. . So each pot has all three
> clays . The clays did not separate from each other in the firing, so that
> went well.
>
> Then I fired them (no glaze) in my computerized Skutt. I set the controlls
>at cone 5 at medium speed with one hour of soak at the end. ( I thought this
> would give me a more smooth porceline finish.(?))
>
> The actual firing took 8 hours with one hour of hold at the end. the temp
> went to 2165F. Blebs only happened in the porceline and to a lesser extent
> in the Cassius Black. None in the brown clay.
>
> My questions: was this firing just too fast? Did the soak at the end play
> any part in this so that maybe there was an overfire? Why didn't the brown
> clay bleb and the porceline bleb so much? Any chance that the paper clay
>had
> anything to do with it since I didn't mix it with dry clay but only wedged
> it in?
>
> This never happened at medium speed in my high fire clays. Does cone5 clay
> have less leeway than cone10?
>
> So far I'm thinking I will set the kiln in ramp/hold mode going very slowly
> at the beginning to let carbon, etc burn out sufficiently. Any other
>suggestions?
> Other than the blebs, I was actually quite happy with the creamy texture of
> the porceline considering it was only cone 5.
> Thanks, Shelley
>
>______________________________________________________________________________
>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
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Tom Wirt/Betsy Price on tue 25 sep 01
You can also get bloating in oxidation if the clay is being
overfired....a secondary sign would be that you are seeing slumping
and deformation. This can happen if the clay body has too much flux
(usually feldspar). Make a bar and do an absorption test. If you are
getting zero absorption, the clay is probably overfluxxed. This can
happen even with long bisque firings.
Tom Wirt
mel jacobson on tue 25 sep 01
one of the best lessons that i learned from ron roy
was to SLOW down the bisque firing. i have tripled
the time i bisque, and i make sure all my clay is very
well mixed. no bloating for almost 8 years.
of course, i use my walker pug mill for all of my clay...
even that clay i buy ready to go. i add more sand and
fine grog, and my lake superior iron sand. a couple
of runs through the pug mill, then bisque slow.
i never get bloating.
did before, and i know it was my sloppy, fast bisque firing.
(just on occasion.)
that little hint, and some extra care has served me well.
not all have a walker, or pug mill, but i truly believe it is one
on the most valued of tools for any studio.
mel
first frosts are starting in minnesota. jackets are coming out
of closets. we stand in front of mirrors admiring our winter
clothes.
red and orange, yellow in the trees. the wonder of nature.
From:
Minnetonka, Minnesota, U.S.A.
web site: http://www.pclink.com/melpots
Brad Sondahl on tue 25 sep 01
Some clays (particularly containing the brown clay Redart) are more
susceptable to bloating due to their sulfur content. When I had trouble
with it many years ago, someone suggested raising the bisque
temperature. I now bisque to Cone 05, which coincidentally contributes
to the longer firing time Mel is talking about. I haven't had any
bloating since doing that. Occasionally when I'd onefire lamps, I'd get
some bloating when I put a glaze on that was shiny--I assume the glaze
melted at a point when it was still offgassing some sulfur fumes,
creating a similar situation to baking pocket bread...
Brad Sondahl
--
For original art, music, pottery, and literature, visit my homepage
http://pages.about.com/bsondahl
Pottery homepage http://sondahl.freeyellow.com
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Randy Peckham on tue 11 dec 01
I use ^6 clay, and glazes, and never have a problem with bloating with
"new" clay, fresh out of the bag. Sometimes sporadically I do have a
problem with bloating with my recycled clay. I also have a low fire
recycle bucket, and a 3 yr old who loves to play in the goopy buckets. I
have found pieces of a 3M scouring pad, tools, pieces of pencil, sticks,
chamois, toys, food, etc. It seems that if something that is volatile just
below ^6 is embedded in my clay it will form a bloat. Most of the stuff I
find is organic, or plastic, and I don't think that is the problem. I am
not sure what is in the 3M scouring pad. I think if it is cantamination,
it is from the scouring pad at the moment. Is it just contamination that
I am dealing with?
I heard someone say that bloating can be caused by improperly wedging
clay. This doesn't make alot of sense to me, but maybe the clay is
outgassing, the outer edge of an air pocket vitrifies, and seals off air
escape from the pocket, and expanding air causes the soft clay to bubble?
I sometimes am lax in my wedging duties.
Snail Scott on tue 11 dec 01
At 08:18 AM 12/11/01 -0500, you wrote:
> I heard someone say that bloating can be caused by improperly wedging
>clay...I sometimes am lax in my wedging duties.
I haven't wedged in years, but it's never caused bloat.
-Snail
Tony Ferguson on tue 11 dec 01
My experience is: Bloat is from too fast firing--organics buring out and
getting trapped in the layer between the clay and the glaze--the glaze seals
over before the gases escape--at least with my work.
Slow down, a slow bringing up the kiln and down is best--your work will love
you for years to come--you can set up stresses that will wreak havoc years
later.
Tony Ferguson
315 N. Lake Ave. Apt. 401
Duluth, MN 55806
USA
218.727.6339
Stoneware, Porcelain, Raku
http://www.AquariusArtGallery.com
----- Original Message -----
From: "Snail Scott"
To:
Sent: Tuesday, December 11, 2001 9:39 AM
Subject: Re: Bloating
> At 08:18 AM 12/11/01 -0500, you wrote:
> > I heard someone say that bloating can be caused by improperly wedging
> >clay...I sometimes am lax in my wedging duties.
>
>
> I haven't wedged in years, but it's never caused bloat.
>
> -Snail
>
>
____________________________________________________________________________
__
> 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.
>
_________________________________________________________
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Anthony Allison on tue 11 dec 01
Dear Tony
I only get bloating when i drink too many linies. Or is it the pretzles i
eat with this fabled beer? Anyway, i wanted to ask if this timed delayed
destruction is like corporate planned obsolescence? A bean counter would no
doubt be saying rush them firings lol
Good thing for beer, pretzles, and slow stuff. Life is good. cheers Tony
Tony
----- Original Message -----
From: "Tony Ferguson"
To:
Sent: Tuesday, December 11, 2001 3:19 PM
Subject: Re: Bloating
> My experience is: Bloat is from too fast firing--organics buring out and
> getting trapped in the layer between the clay and the glaze--the glaze
seals
> over before the gases escape--at least with my work.
>
> Slow down, a slow bringing up the kiln and down is best--your work will
love
> you for years to come--you can set up stresses that will wreak havoc years
> later.
>
> Tony Ferguson
> 315 N. Lake Ave. Apt. 401
> Duluth, MN 55806
> USA
> 218.727.6339
>
> Stoneware, Porcelain, Raku
> http://www.AquariusArtGallery.com
>
>
> ----- Original Message -----
> From: "Snail Scott"
> To:
> Sent: Tuesday, December 11, 2001 9:39 AM
> Subject: Re: Bloating
>
>
> > At 08:18 AM 12/11/01 -0500, you wrote:
> > > I heard someone say that bloating can be caused by improperly wedging
> > >clay...I sometimes am lax in my wedging duties.
> >
> >
> > I haven't wedged in years, but it's never caused bloat.
> >
> > -Snail
> >
> >
>
____________________________________________________________________________
> __
> > 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.
> >
>
>
> _________________________________________________________
> Do You Yahoo!?
> Get your free @yahoo.com address at http://mail.yahoo.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.
>
>
Tony Ferguson on tue 11 dec 01
Dear Tony,
he he. The only time I get bloating is when I eat too much tofu or mock
duck. I think taking the few extra hours to go slow saves a lot of money
and hassle in the long run. Bean counters fart too!
Tony
----- Original Message -----
From: "Anthony Allison"
To:
Sent: Tuesday, December 11, 2001 4:14 PM
Subject: Re: Bloating
> Dear Tony
>
> I only get bloating when i drink too many linies. Or is it the pretzles i
> eat with this fabled beer? Anyway, i wanted to ask if this timed delayed
> destruction is like corporate planned obsolescence? A bean counter would
no
> doubt be saying rush them firings lol
>
> Good thing for beer, pretzles, and slow stuff. Life is good. cheers Tony
>
> Tony
> ----- Original Message -----
> From: "Tony Ferguson"
> To:
> Sent: Tuesday, December 11, 2001 3:19 PM
> Subject: Re: Bloating
>
>
> > My experience is: Bloat is from too fast firing--organics buring out
and
> > getting trapped in the layer between the clay and the glaze--the glaze
> seals
> > over before the gases escape--at least with my work.
> >
> > Slow down, a slow bringing up the kiln and down is best--your work will
> love
> > you for years to come--you can set up stresses that will wreak havoc
years
> > later.
> >
> > Tony Ferguson
> > 315 N. Lake Ave. Apt. 401
> > Duluth, MN 55806
> > USA
> > 218.727.6339
> >
> > Stoneware, Porcelain, Raku
> > http://www.AquariusArtGallery.com
> >
> >
> > ----- Original Message -----
> > From: "Snail Scott"
> > To:
> > Sent: Tuesday, December 11, 2001 9:39 AM
> > Subject: Re: Bloating
> >
> >
> > > At 08:18 AM 12/11/01 -0500, you wrote:
> > > > I heard someone say that bloating can be caused by improperly
wedging
> > > >clay...I sometimes am lax in my wedging duties.
> > >
> > >
> > > I haven't wedged in years, but it's never caused bloat.
> > >
> > > -Snail
> > >
> > >
> >
>
____________________________________________________________________________
> > __
> > > 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.
> > >
> >
> >
> > _________________________________________________________
> > Do You Yahoo!?
> > Get your free @yahoo.com address at http://mail.yahoo.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.
> >
> >
>
>
____________________________________________________________________________
__
> 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.
_________________________________________________________
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Marsh Pottery on fri 14 dec 01
One more reason for bloating : the clay is being fired past vitrification
to it's boiling point. The bigger the pot, the bigger the bloats...
I fired a Cone 06 black "art" clay (meant for small decorations, not full
pots) to Cone 4 and the walls bloated. I was trying for a Native American
look... The clay had no air bubbles in it when I threw the pots.
Marsha K
Ron Roy on sun 16 dec 01
Hey Randy - sorry to be so late with this - I'm suddenly a publisher and
the weight is on me.
You have to say what colur your clay is so we can guess which it is or both.
Best to describe what the bloats look like - all over or just in certain
places - what shap are they - like that.
Clay with iron - could be carbon not properly oxidized during the bisque.
Most likely it's air bubbles - if the clay is well vitrified - it seals the
air in but it is still expanding so you get a bubble because the clay is
pyroplastic at the end of your firings.
Sounds like it would be better not to wedge if there are things in it like
pencils - you could get a nasty wound in your hand from that sort of thing.
>I use ^6 clay, and glazes, and never have a problem with bloating with
>"new" clay, fresh out of the bag. Sometimes sporadically I do have a
>problem with bloating with my recycled clay. I also have a low fire
>recycle bucket, and a 3 yr old who loves to play in the goopy buckets. I
>have found pieces of a 3M scouring pad, tools, pieces of pencil, sticks,
>chamois, toys, food, etc. It seems that if something that is volatile just
>below ^6 is embedded in my clay it will form a bloat. Most of the stuff I
>find is organic, or plastic, and I don't think that is the problem. I am
>not sure what is in the 3M scouring pad. I think if it is cantamination,
>it is from the scouring pad at the moment. Is it just contamination that
>I am dealing with?
>
> I heard someone say that bloating can be caused by improperly wedging
>clay. This doesn't make alot of sense to me, but maybe the clay is
>outgassing, the outer edge of an air pocket vitrifies, and seals off air
>escape from the pocket, and expanding air causes the soft clay to bubble?
>I sometimes am lax in my wedging duties.
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Barbara Francis on thu 8 dec 05
Hey does anybody have any ideas about my problem with bloating? I am firing cone 6 with a cone 5 body, but have been for years. Just a couple pieces were effected, but I am afraid to go ahead and fire this other work. I am afraid that some low-fire clay might have gotten into my scraps by accident, that's all I can figure out. Any advice would be appreciated. Thanks. Barb
---------------------------------
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Taylor from Rockport on thu 8 dec 05
Oh Barb,
You know very well that at your age, you are prone to bloating. Nothing
any of us can do for you, if you refuse to go vegitarian. Hehe
How did your holiday sale go? Haven't you had it already?
Are you still having problems with Armadillo's Cinco Blanco bloating or is
it one of the other clays? We never did figure that one out when it
happened awhile back, but have you lengthened your bisque time any to see
if that helped? As an experiment, I made some test chits with their
lowfire body, Lonhorn Red, fired them with glazes to cone 5, and they all
bloated like crazy but didn't melt on the shelves. Some of them looked
like flattened baloons, Barb.
You know that I just go ahead and fire to cone 5 now. Can't be too hard to
reformulate your glaze book. Ask Berry to get you a glaze program for
Christmas.
Still hoping to have a big pit firing in February. Be making some roundish
raku pots, bisque 012.
Taylor, in Rockport TX
http://www.wirerabbitpots.blogspot.com
On Thu, 8 Dec 2005 11:38:05 -0800, Barbara Francis
wrote:
>Hey does anybody have any ideas about my problem with bloating? I am
firing cone 6 with a cone 5 body, but have been for years. Just a couple
pieces were effected, but I am afraid to go ahead and fire this other
work. I am afraid that some low-fire clay might have gotten into my
scraps by accident, that's all I can figure out. Any advice would be
appreciated. Thanks. Barb
William & Susan Schran User on thu 8 dec 05
On 12/8/05 2:38 PM, "Barbara Francis" wrote:
> Hey does anybody have any ideas about my problem with bloating? I am firing
> cone 6 with a cone 5 body, but have been for years. Just a couple pieces
> were effected, but I am afraid to go ahead and fire this other work. I am
> afraid that some low-fire clay might have gotten into my scraps by accident,
> that's all I can figure out.
Is all of the clay from the same batch?
Clays are a naturally occurring material, mined from the earth.
One would expect some variation in these materials.
It may be that this specific batch contains some variation of one of the
clays used in this body that is more prone to out gassing at the temperature
your using.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
primalmommy on thu 8 dec 05
Are you firing with witness cones? Your kiln may be overfiring, or you
may have a hot spot on one shelf.
Are you bisquing long and slow?
I once drove Alisa crazy with emails (she was very nice about it) when a
predictable black glaze bubbled and blistered only in the BOTTOMS of
some pots. It seemed to be the wrong place for a glaze to bubble. They
were casseroles which I threw bottomless, then threw a floor and
"stretched" it oval, and assembled the two pieces. Well, it turns out I
had used a lowfire clay to make the bottoms! Yeah, they bloated, too...
just the bottoms. I am currently growing herbs in them ;0)
Good luck with your problem!
Yours
Kelly in Ohio
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mel jacobson on tue 25 jul 06
it is always a combination
of very back luck, and materials
within the clay that gets trapped.
gas expands, and the layer of clay lifts.
i talked to joe koons today.
just to chat about bloating.
he said the same thing.
it is nature at work.
the potter watches.
i have made a quarter a ton of new clay.
we shall see.
pugged it three times.
potters just get on with it.
that is all we can do.
from: mel/minnetonka.mn.usa
website: http://www.visi.com/~melpots/
Clayart page link: http://www.visi.com/~melpots/clayart.html
clennell on wed 26 jul 06
Sour Cherry Pottery
> it is always a combination
> of very back luck, and materials
> within the clay that gets trapped.
> gas expands, and the layer of clay lifts.
>
> i talked to joe koons today.
> just to chat about bloating.
>
> he said the same thing.
> it is nature at work.
> the potter watches.
>
> i have made a quarter a ton of new clay.
> we shall see.
> pugged it three times.
>
> potters just get on with it.
> that is all we can do.
>
>
Mel: We just had some problems with bloating at the very back of the chamber
in the wood kiln. I tried to call the bloats art but thought the better of
it and took them to the dump. We had used our studio body that contains 4%
Redart. We never had that problem when our body contained yellow ochre as a
colourant. I think I have narrowed it down to that. We have switched to 5%
Redstone as a colourant in the clay. Redstone is a stoneware clay from
Plainsman Clays in Alberta.
Another woodie coming up soon, so I'll find out.
Best,
Tony
Tom at Hutchtel.net on wed 26 jul 06
I Think Jon Pacini just addressed this a month or two ago. I would guess
that since Redart vitrifies at such a low temp...essentially stoneware, at
Cone 10 plus it is past glaze and starting to boil. Makes the body
disintegrate. Unless the clay maker is using the high energy mixing
equipment, and even sometimes still, you get pockets of concentrations of
the ingredients.
We now use Highwater clays who put in the high energy system last summer..
Before that I could see streaks of color that I would assume were streaks of
various clays. That's almost nonexistent now.
Had lots of bloating problems with Continental which is one of the primary
reasons we switched. Is your bloating from the Laguna, the continental or
both.
One thing I have noted over the years...the higher tech you're
system...clay, glaze, firing, the lower the tolerance you have for changes.
Mel, I think we could say your old home blended clay was low tech...wide
tolerance. I suspect every clay component in a highfire body must have a
maturity point at or above the firing temp.
Tom Wirt
----- Original Message -----
Subject: Re: bloating
>> it is always a combination
>> of very back luck, and materials
>> within the clay that gets trapped.
>> gas expands, and the layer of clay lifts.
>>
>> i talked to joe koons today.
>> just to chat about bloating.
>>
>> he said the same thing.
>> it is nature at work.
>> the potter watches.
>>
> Mel: We just had some problems with bloating at the very back of the
> chamber
> in the wood kiln. I tried to call the bloats art but thought the better of
> it and took them to the dump. We had used our studio body that contains 4%
> Redart. We never had that problem when our body contained yellow ochre as
> a
> colourant. I think I have narrowed it down to that. We have switched to 5%
> Redstone as a colourant in the clay. Redstone is a stoneware clay from
> Plainsman Clays in Alberta.
Lee Love on fri 28 jul 06
On 7/27/06, Tom at Hutchtel.net wrote:
> One thing I have noted over the years...the higher tech you're
> system...clay, glaze, firing, the lower the tolerance you have for changes.
Maybe. I fire several kinds of natural clay, which are only
minimally processed. My iron usually comes from natural ochre clay
and not by adding a refined iron bearing clay.
The most frequent cause of bloating I experience in my woodkiln,
is from over firing iron bearing clays. A high iron glaze over an
iron bearing clay makes it more likely.
--
Lee in Mashiko, Japan
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Rimas VisGirda on sat 22 may 10
What do the bloats look like when you break them open? If they are yellowis=
h, it is probably sulfur in the clay that hasn't been driven off in the bis=
que. We had that problem with a Goldart based clay that we bisqued to c/010=
. Bisquing to c/05-04 solved the problem. -Rimas
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