Taylor from Rockport on mon 11 oct 04
Amanda:
Always a good idea to get one's vocabulary right, but more important here
is to be clear on the concept. When I hear bisque, the concept that comes
to mind is a preliminary firing of my pots to make them easier to handle
when I apply my glazes. For me, it is always lower that my final glaze
firing, but for others the opposite may be true. When I plan on firing a
series of pots to cone 6 in the glaze firing, I plan on bisquing my pots
to 04. For me, when I am talking to myself, "bisque" means cone 04. That
is not so for all the other potters who talk to themselves. In
effect, "bisque" CAN be anything. Better to be clear on your end, what
your needs are. I'm firing a cone 02 clay, so I will need a preliminary
firing (bisque) of cone 0...well now. Now I need to know all kinds of
concepts like vitrification, porosity, yada, yada, yada. Getting in sync
with other potters on what that stuff is called comes much easier when one
knows or is familiar with the concept.
At least that is what I keep telling myself.
Taylor, in Rockport
On Mon, 11 Oct 2004 22:50:42 -0400, Amanda Stickney
wrote:
>Call me an idiot, but every time I ask someone in the studio (I'm a senior
finishing up with my BFA in ceramics - duh) what cone they're going to do a
bisque to, they say "anything is a bisque...
Amanda Stickney on mon 11 oct 04
Call me an idiot, but every time I ask someone in the studio (I'm a senior finishing up with my BFA in ceramics - duh) what cone they're going to do a bisque to, they say "anything is a bisque." HELLO? Then I say, 'well, will my pieces (^04) be able to go in?' They say, 'yeah, I'm doing ^06, is that alright?' (just an example of two weeks ago). Someone want to explain to me why on earth they won't tell me right away what temp they're putting in, or what exactly do they mean by 'anything is a bisque'??? I was never given a definition such as that. And that sure as heck as gotten me confused with the rest of them. I sure would appreciate some info! Thanks!
Amanda
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Lee Love on tue 12 oct 04
Amanda Stickney wrote:
> Call me an idiot, but every time I ask someone in the studio (I'm a
> senior finishing up with my BFA in ceramics - duh) what cone they're
> going to do a bisque to, they say "anything is a bisque." HELLO?
> Then I say, 'well, will my pieces (^04) be able to go in?' They say,
> 'yeah, I'm doing ^06, is that alright?'
When bisque is done in a large woodkiln like my teacher's kiln,
you just bisque until red heat at the top of the kiln. The hottest
bisque is around cone 012, but the ware on the bottom shelves reach a
much lower temperature. The temp is so low, the ware has to be
handled carefully. My bisque in my wood kiln is similar: highest
at 012, but the lowest is warmer than in my teacher's noborigama.
How are variable bisque temps handled? All the ware is
sponged with water. You compensate softer bisque by adding more water
to the ware while sponging it. You accomplish this by the speed at
which you move the sponge over the are (the slower you do it, the more
water gets into the ware. Also, the glaze coat is determined by
scratching the glazed surface and looking at the actual thickness of the
glaze layer. If it is too thick, water is added. If it is too
think, thick glaze is added to the bucket.
--
Lee in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
http://public.fotki.com/togeika/ Photos!
wjskw@BELLSOUTH.NET on tue 12 oct 04
Realizing that I'm not the sharpest tool in the shed, and don't have
the years of experience that others on this list have, I wish to
pose a question:
Is there a relationship between the vitrification temperature of a
clay body (i.e. the cone to which it is "supposed" to be fired) and
the cone to which one should bisque that body? =20
Could one for example, say that "a cone (blank)
(stoneware/porcelain, whatever) should be bisqued to cone
(blank)..." where the bisque cone is a percentage of the final
firing cone? I know this is simplistic (hey, look who it's coming
from) considering that heat work and not simply temperature are
involved. Or is it more a matter of preference, as in the comment
"...anything is a bisque..." (which makes me shudder, thinking of
the outgassing going on during firing, and its reaction to the
glazes...how can one "assume" anything and expect repeatability?)
Could one study the body in question (assuming the manufacturer will
release information on just what is in the damn stuff) and determine
that the body has finished most of it's changing by "X" (temp or
cone) and will still accept (absorb?) a glaze.
It seems that the generalizations I have been reading (such as
bisque to ^05) can't be the best course of action for all clay
bodies. I also realize that experience is a great teacher, and in
time, one gets to know (intimately?) one's own clay body (again,
assuming the manufacturer doesn't start monkeying with the formula)
but I feel it would be nice to have a formula, or a baseline from
which to start.
Just curious.
Wayne Seidl
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Taylor
from Rockport
Sent: Monday, October 11, 2004 11:45 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: come on with the bisque vocab already!
Amanda:
Always a good idea to get one's vocabulary right, but more important
here
is to be clear on the concept. When I hear bisque, the concept that
comes
to mind is a preliminary firing of my pots to make them easier to
handle
when I apply my glazes. For me, it is always lower that my final
glaze
firing, but for others the opposite may be true. When I plan on
firing a
series of pots to cone 6 in the glaze firing, I plan on bisquing my
pots
to 04. For me, when I am talking to myself, "bisque" means cone 04.
That
is not so for all the other potters who talk to themselves. In
effect, "bisque" CAN be anything. Better to be clear on your end,
what
your needs are. I'm firing a cone 02 clay, so I will need a
preliminary
firing (bisque) of cone 0...well now. Now I need to know all kinds
of
concepts like vitrification, porosity, yada, yada, yada. Getting in
sync
with other potters on what that stuff is called comes much easier
when one
knows or is familiar with the concept.
At least that is what I keep telling myself.
Taylor, in Rockport
On Mon, 11 Oct 2004 22:50:42 -0400, Amanda Stickney
wrote:
>Call me an idiot, but every time I ask someone in the studio (I'm a
senior
finishing up with my BFA in ceramics - duh) what cone they're going
to do a
bisque to, they say "anything is a bisque...
steve baker on tue 12 oct 04
To me a "bisque" firing is designed to do a few things. First of all, it allows for all the combustible components in the body (which may react with some glazes chemically and physically - pinholes, etc.) to be removed prior to glazing. These gases include organics, sulfur compounds, and chemical water from the decomposition of the clay minerals. In many clay bodies, this can amount to 10% of the mass, and a huge volume of gas. The second reason is to mature the piece to a degree of vitrification where it can be handled and possibly extensively decorated without the fear of breaking the green piece. Some bodies soften so readily that they must be bisgue fired to allow them to be glazed. The term bisque generally refers to the first firing of the piece without the glaze. This firing can be higher or lower than the actual glaze firing, though in most ceramics the glaze firing is higher. If you want to know what is going on with your clay body, take a bisqued piece, weigh it,
then put it through the glaze firing unglazed, and weigh it again. If it continues to lose weight in the second firing, then you know that decomposition is still taking place. This is especially helpful if one suspects the body is causing pinholing in a glaze firing. Most decomposition reactions have been completed by about 1400 degrees F, with the exception of pyrites. But at 1400 degrees the piece has no strength, so a higher temp or cone is needed. The next thing is to make certain the body has enough strength to be handled. Then the next thing is to make certain the body has the right absorptive qualities to receive the proper decoration. If the body is too porous, it may suck the water from the glaze too fast. Too tight, and it may not take up the water at all. The cone is not as important as what is going on with the body. Usually the higher temp the body is, the higher temp the bisque will be. 04 possibly for a high fire stoneware, cone 08 maybe for an earthenware.
There are no constants.
Amanda Stickney wrote:Call me an idiot, but every time I ask someone in the studio (I'm a senior finishing up with my BFA in ceramics - duh) what cone they're going to do a bisque to, they say "anything is a bisque." HELLO? Then I say, 'well, will my pieces (^04) be able to go in?' They say, 'yeah, I'm doing ^06, is that alright?' (just an example of two weeks ago). Someone want to explain to me why on earth they won't tell me right away what temp they're putting in, or what exactly do they mean by 'anything is a bisque'??? I was never given a definition such as that. And that sure as heck as gotten me confused with the rest of them. I sure would appreciate some info! Thanks!
Amanda
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Anne Webb on tue 12 oct 04
hey amanda....
i have no idea why they wouldnt give you a straight answer. ...didnt know,
didnt care or were just trying to get a reaction out of you...?
the *typical* guideline for bisquing, as i was originally told, was
somewhere in the range of ^08 to ^03. the temp you choose is dependent on
your claybody and the glazes you use. theoretically in a bisque you are
removing the water on a molecular level, burning out gasses, and making the
body strong enough to handle. The subtleties of a few degrees difference in
bisquing can mean the difference of whether you have pinholes/bloating or
not, whether you get the desired thickness of glaze, etc..
we use a native clay body we dig locally and we bisque it to 04 to burn out
more of the gasses, etc. consequently i have less problems with pinholes,
bloating, etc. later in the glaze firing.
when i bisque porcelain i usually bisque cooler like ^06. there is less crap
in the claybody to burn out and the glazes just look better ... body is more
porous and consequently the glazes go on slightly thicker.
if we are rakuing, we usually bisque to 04 then glaze fire to around 06.
burns out crap from clay and offers a stronger body to raku with.
if you know for sure you have to be particular with a given claybody, and
they dont know or care what temp they're firing to, be insistent.
good luck amanda :)
anne
>Call me an idiot, but every time I ask someone in the studio (I'm a senior
>finishing up with my BFA >in ceramics - duh) what cone they're going to do
>a bisque to, they say "anything is a bisque." >HELLO? Then I say, 'well,
>will my pieces (^04) be able to go in?' They say, 'yeah, I'm doing ^06, >is
>that alright?' (just an example of two weeks ago). Someone want to explain
>to me why on >earth they won't tell me right away what temp they're putting
>in, or what exactly do they mean >by 'anything is a bisque'??? I was never
>given a definition such as that. And that sure as heck as >gotten me
>confused with the rest of them. I sure would appreciate some info!
>Thanks!
>Amanda
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Antoinette Badenhorst on tue 12 oct 04
No Amanda, for sure you are not an idiot! I am going to give you my
thumb sucking answer to what I see as bisque. Of cause there are many
book (academic) answers available, but here goes. The word bisque must
have a universal word of some kind from where it stems. In Afrikaans we
have a word "beskuit" and in Italian there is the word "biskoti". Both
are a type of sweet bread that is double baked and dried out. That makes
it dry enough so that if you dip it in coffee (or wine), it sucks up
enough moist to become soft enough again to eat without killing the
inside of your mouth. I bet you there are more words with a similar
translation.
When we talk of bisque, in my view, we prepare the clay to be able to
suck enough water (in the glaze) in so that enough glaze can stick on
the surface of the pot. Different clays and different glazes will have
different requirements. I originally learned that a ^08 is a bisque, but
when I experienced trouble with transparent glazes that craze on pots, I
learned that if I bisque at a higher temperature and thin the glaze out
to a "skim milk look" I will eliminate the problem. Different
temperatures can be bisque, but not all bisque temperatures can suit
your clay body. That is why it is handy to know what is in your clay and
also to know what ingredient melts at what temperature. If you can not
control that, the next best thing is to do tests to see at what
temperature your clay will start vitrifying.
Nice day.
Antoinette Badenhorst
105 Westwood Circle
Saltillo, MS 38866
(662) 869-1651
www.clayandcanvas.com
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Amanda
Stickney
Sent: Monday, October 11, 2004 9:51 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: come on with the bisque vocab already!
Call me an idiot, but every time I ask someone in the studio (I'm a
senior finishing up with my BFA in ceramics - duh) what cone they're
going to do a bisque to, they say "anything is a bisque." HELLO? Then
I say, 'well, will my pieces (^04) be able to go in?' They say, 'yeah,
I'm doing ^06, is that alright?' (just an example of two weeks ago).
Someone want to explain to me why on earth they won't tell me right away
what temp they're putting in, or what exactly do they mean by 'anything
is a bisque'??? I was never given a definition such as that. And that
sure as heck as gotten me confused with the rest of them. I sure would
appreciate some info! Thanks!
Amanda
_____
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with MSN Messenger! Download today - it's FREE!
________________________________________________________________________
______ Send postings to clayart@lsv.ceramics.org You may look at the
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who may be reached at melpots@pclink.com.
Snail Scott on tue 12 oct 04
At 10:50 PM 10/11/2004 -0400, you wrote:
>...every time I ask someone in the studio...what cone they're going to do
a bisque to, they say "anything is a bisque."
...what exactly do they mean by 'anything is a bisque'?
<<<<
Technically, any work fired without glaze is being
bisqued, and it isn't a temperature-dependent
condition. If there's no glaze, it's a bisque firing,
even if it's to ^12. It's not conventional in studio
practice, but it is the correct use of the term.
Sounds like they're giving you the full latitude to
decide on your process. If you want to bisque to ^8,
then ^8 is a bisque. And just because they're going
to put glaze in a firing, doesn't mean you might not
be able to bisque work in the same firing - their
glaze firing could be your bisque.
For some folks, especially those doing production,
absolute consistency is needed to reproduce results
across time, and firing to the same bisque temp is
essential. For others, though, the choice may vary
with circumstances - maybe ^04 if some work in the
kiln is destined for low-fire red glazes, or maybe
^06-08 if not, or even ^010-012 if some of the work
will be drilled or ground after the bisque firing.
In many cases, the exact temperature just doesn't
matter much.
The person who didn't specify a cone for their
firing may actually have been open to suggestions,
and if you'd said, " I'd like to go to ^04", they
might have said, "Sure."
-Snail Scott
>>>>
Craig Clark on tue 12 oct 04
Amanda, first of all, unless things have changed dramatically since
I was in school, art students often times know very little about the
technical end of things. Especially if they are fresh out of high
school. Do what you are doing and turn to the professional community for
answers or suggestions about these matters. Once you have found these
answers continue knowing that you have expanded your knowledge base and
act accordingly. Try and explain, calmly, to those who don't understand.
If the students in your clay room somehow think that an 06 bisque is
going to be the same as an 04 bisque then they do not have even a basic
understanding of what they are doing. As a reference, 04 is hotter than
06. This is basic stuff that is available in any of the introductory texts.
I may be mistaken but I believe the greater ceramic community, when
discussing firing, would refer to a bisque or bisquit firing as the
first firing of the ceramic object to take it through quartz inversion
therby imparting a more substantial permanancy to the object. The
intention of a bisque firing, generally speaking, is to alter the
physical state of the pot so that it is easier to handle for the
application of glaze. The glazed bisque piece is then fired a second, or
multiple, times in what is generally refered to as a glaze firing. The
glaze firing is the general name given to the firing of pots after glaze
has been applied.
There are obvious variations on this simple theme. I am explaing
that which is generally meant, not the esoteric. One may indeed apply a
glaze to an unfired pot and fire the pot to the maturation point of that
glaze and then after cooling, apply another glaze that matures at a
lower temp than the original and fire the pot again. All of this may
occur in the realm of the 04, 06 range. There may be many multiple
firings. Each being cooler and cooler. There may be arguments about what
to call these. I would refer to all of them as glaze firings for
clarity. Just my opinion here.
Glaze fire temps vary greatly depending upon the type of glaze that
is used and the intention of the artist/craftsmen. Bisque fire temps, at
least those in standard discussions, both verbal and in numerous texts,
are generally either cone 04 or cone 06. I have started bisqueing to 04
in the past coupla years because of what I consider to be vey sound
advice from a number of members of this list.
For definitive explanations of many of these questions consult, among as
many books on pottery as you are able (read, read, read!!!), "The
Potter's Dictionary of Marterials and Techniques," often refered to as
Hamer and Hamer. Written by Frank and Janer Hammer.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Ivor and Olive Lewis on tue 12 oct 04
Dear Amanda,
It sounds to me as though there is a serious lack of management in the =
studio which serves you.
Who has the responsibility, the Professor? the Technician? or is it left =
to the students to decide?
I can understand your frustration if you are unable to get consistency =
in your work because of ignorance.
Hope you succeed with Honours.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Ivor and Olive Lewis on wed 13 oct 04
Dear Wayne Seidl,
My opinion is that there are no technical or scientific relationships
between optimum temperatures for firing to achieve bisque and firing
to vitrification, though each clay will have optimum time temperature
relationships for the achievement of both processes. There may also be
an optimum amount of heat to make this happen but this will vary with
local conditions: Kiln fabric, Furniture Density, Packing Density,
Style of Firing and so on.
I have written about the optimum temperature range for ensuring that a
clay has dehydroylated, converting Kaolin to Metakaolin and become a
coherent fabric. The article is in Ceramics :Technical Vol 12. p 52
"Terra Sigillata" . Here, I give a Tamman Point of Kaolin as 952=BA C at
which sintering of that material will be proceeding to create a
reasonably strong coherent material. This is not to impose limits on
people who are willing to work to a lower temperatures. Felspars and
some other fluxing materials sinter well below 700=BA C so Cone 08 may
not describe the lower limit to fire a bisque. I suggested a firing
range of 950=BA-1050=BA C for Terra Sigillata.
You suggest <(such as
bisque to ^05) can't be the best course of action for all clay bodies.
>> I would agree. As you say, local experience, accounting for all
factors, is the best teacher.
Sincere Regards,
Ivor Lewis.
Redhill,
S. Australia.
Ron Roy on thu 14 oct 04
Hi Wayne,
I got way behind in my email so I am late with this - but.
This can be a complicated question and answer because there are several
factors that need to be taken into account. Understanding those factors is
the key to finding the right solution.
In my case the "right" solution is the one that works for all the things I
do. I fire all bisque to 04 - because I fire porcelain in a gas kiln. In
order to stop bisque dunting - which is the main problem that we are
talking about.
Certain forms are susceptible to this kind of cracking - and it happens as
the rim of a platter or bowl reaches the quartz inversion temperature of
573C before the rest of the pot - tries to get smaller and can't.
The key factors to consider are - the kind of clay, the forms and how big
they are and how fast your kiln cools - how tight you can close your kiln
after a firing and even how thick your shelves are.
Susceptible clays are any with free quartz in them - particularly in bisque
ware. Keep in mind - all clay have some - and porcelains have a lot. Keep
in mind - I have never seen (in a dilatometry chart) any clays without free
quartz - even after the top firing, never mind bisque.
Susceptible forms are bowls and platters because the rims cool faster than
the bottoms.
You seldom have the problem with small pots by the way - but if you intend
to make larger pots - my best advice - in all that you do is - learn
techniques that will work with large pots - the small ones will take care
of themselves.
Kiln cooling rates are very important in all this.
Solid fuel kilns (wood and coal) stay hotter longest - because of the heat
from the fire box - so I would expect the problem would be less with bisque
fired in them.
Some gas kilns cool slowly because of the kinds of refractories used - but
if the damper is left open - you can imagine how that would cool rims
faster and cause the problem. Many cool fast - like the fiber kilns -
firing bisque in them is going to be tricky if not impossible for some
forms.
Some electric kilns cool even faster than fiber kilns - but you can slow
them down through the quartz inversion temperatures.
The tighter the kiln is stacked the slower the load will cool - but that
should not be thought of as a cure - the rims will still cool first - in
fact it might even make it worse. Thick shelves will hold heat longer and
make dunting harder to control.
So why does firing bisque at the more or less maximum temperature of cone
04 help solve the problem? More free quartz in melted so that it does not
go through the inversion on the way down and the ware winds up stronger.
Making rims thicker also helps a lot by the way - they hold heat longer and
are stronger.
Firing bisque higher also has other benefits - it's easier to handle
because it's stronger, glazes need to be a bit thicker because the ware is
less absorbent but that also means they don't need to stirred so often
during glazing. The one exception I can think of would be for earthenware -
some is bisqued even higher to help avoid chipping and leaking.
Understanding the reasons for dunting will always lead to how to avoid it.
Answers that say - "I've always done it that way" or "because my teacher
said so", and "I've never had any problem" - ignore the differences each of
us has to work with.
This is getting a little too long so I will stop for now and try to answer
any questions this brings up as they come.
RR
>Realizing that I'm not the sharpest tool in the shed, and don't have
>the years of experience that others on this list have, I wish to
>pose a question:
>
>Is there a relationship between the vitrification temperature of a
>clay body (i.e. the cone to which it is "supposed" to be fired) and
>the cone to which one should bisque that body?
>
>Could one for example, say that "a cone (blank)
>(stoneware/porcelain, whatever) should be bisqued to cone
>(blank)..." where the bisque cone is a percentage of the final
>firing cone? I know this is simplistic (hey, look who it's coming
>from) considering that heat work and not simply temperature are
>involved. Or is it more a matter of preference, as in the comment
>"...anything is a bisque..." (which makes me shudder, thinking of
>the outgassing going on during firing, and its reaction to the
>glazes...how can one "assume" anything and expect repeatability?)
>
>Could one study the body in question (assuming the manufacturer will
>release information on just what is in the damn stuff) and determine
>that the body has finished most of it's changing by "X" (temp or
>cone) and will still accept (absorb?) a glaze.
>
>It seems that the generalizations I have been reading (such as
>bisque to ^05) can't be the best course of action for all clay
>bodies. I also realize that experience is a great teacher, and in
>time, one gets to know (intimately?) one's own clay body (again,
>assuming the manufacturer doesn't start monkeying with the formula)
>but I feel it would be nice to have a formula, or a baseline from
>which to start.
>Wayne Seidl
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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