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firing glaze tests

updated tue 24 nov 98

 

Chris Schafale on wed 18 nov 98

Hey folks,

I'm firing to ^6 ox, in a Skutt 1027 with controller. Because I'm
just starting to develop glazes, I'd like to do test firings with a
relatively small number of pieces at a time. My question is, will
the results I get with a 2/3 empty kiln be representative of what I
will get when the kiln is full?? I'm firing with all the shelves in
place, tests and cone pack near the middle of the kiln, and using the
controller to provide consistent heating and slow cooling.

Oh, another question -- testing potentially very runny glazes, I'm
sure it would be wise to put a saucer under the piece to catch drips.
Does this need to be a new bisque saucer each time, or could I reuse
saucers that have already been fired to cone 6 unglazed?

Thanks for any thoughts.

Chris
Light One Candle Pottery
Fuquay-Varina, NC
candle@nuteknet.com

Milton Markey on thu 19 nov 98

Hi There!

I usually test glazes in an electric kiln by placing the glaze test tiles in
the same load with wares which have glazes I've already "approved." This way,
the atmosphere in the kiln is the same for the test tiles as it would be, when
I actually fire the glaze in a "normal" load. The placement of the test tiles
in the kiln is unimportant when done this way--in fact, I place test tiles
amongst the wares on all shelves.

Loading test tiles in an otherwise empty kiln requires an unnecessary use of
electricity and may provide inaccurate results.

Good luck to you!

Milton MiltonsLin

In the clear sky Mojave Desert. My, what a meteor shower of the past two
nights!

Karen Gringhuis on thu 19 nov 98

Dear Chris - why not make at least SOME work to fill the kiln AND
fire tests at the same time? Firing tests in a fairly empty kiln
will at leat give you a good first look - the surface may be
affected by a fast rise to temp. but you could soak at the top
to approximate a regular firing? A first look is always just
that only - you would then go on to an interim step anyway.
The surface will amay also be affected as an empty kiln cools
faster than usual but w/ electric I downfire anyway to
gain mattness.

As for recycling the saucers - why not? Just put on some
more kiln wash so you get the test off them provided
they don't have glaze drips etc.

I always try to have tests in every kilnload I fire - and
they\'re what I want to see first - definitely worth
the effort. Good luck. Karen Gringhuis

Dan / Joanne Taylor on fri 20 nov 98

Chris,

Assuming you are using a firing program that your kiln is capable of keeping
up to if fired with a full load, it will fire the same regardless of how few
pieces you have in it. Re a bisque saucer, I've re-used bisque pieces for
the same reason several times with success.

Dan Taylor - in Medalta country

Chris Schafale wrote:

> ----------------------------Original message----------------------------
> Hey folks,
>
> I'm firing to ^6 ox, in a Skutt 1027 with controller. Because I'm
> just starting to develop glazes, I'd like to do test firings with a
> relatively small number of pieces at a time. My question is, will
> the results I get with a 2/3 empty kiln be representative of what I
> will get when the kiln is full?? I'm firing with all the shelves in
> place, tests and cone pack near the middle of the kiln, and using the
> controller to provide consistent heating and slow cooling.
>
> Oh, another question -- testing potentially very runny glazes, I'm
> sure it would be wise to put a saucer under the piece to catch drips.
> Does this need to be a new bisque saucer each time, or could I reuse
> saucers that have already been fired to cone 6 unglazed?
>
> Thanks for any thoughts.
>
> Chris
> Light One Candle Pottery
> Fuquay-Varina, NC
> candle@nuteknet.com

Joy Holdread on fri 20 nov 98

In a message dated 11/18/98 7:03:50 AM US Mountain Standard Time,
candle@nuteknet.com writes:

>
> Oh, another question -- testing potentially very runny glazes, I'm
> sure it would be wise to put a saucer under the piece to catch drips.
> Does this need to be a new bisque saucer each time, or could I reuse
> saucers that have already been fired to cone 6 unglazed?
>
You can reuse the saucer until a glaze fuzes the test tile to it. Try a few
layers of kiln wash on the saucer and use it forever.
Joy in Tucson I attended Berry's sale & what a kick to meet face to face &
check out a colleague who's work and set up is so different.

Caryl W. on fri 20 nov 98

I also have a Skutt 1027 and I don't always have a full kiln. I don't
find any difference in the results, since it's being brought up to
temperature by the controller.I would imagine this could be the case if
you were using only the switches, where the kiln would heat faster with
a small load.Might be a good idea to put a cone pack on the shelves
where the pieces are to check just what cone they fired to.I know I get
differences top to bottom, which can be minimized by incorporating a
soak period(20-30 minutes)at the end of the firing at a slightly lower
temperature(-10C) than your top temperature.

I don't see any problem with reusing glaze temperature fired saucers
under your test pieces.I use small broken pieces of kiln shelf with kiln
wash on them for the same purpose.

Caryl

>Date: Wed, 18 Nov 1998 09:03:07 EST
>Reply-To: Ceramic Arts Discussion List
>From: Chris Schafale
>Subject: Firing glaze tests
>To: CLAYART@LSV.UKY.EDU
>
>----------------------------Original
message----------------------------
>Hey folks,
>
>I'm firing to ^6 ox, in a Skutt 1027 with controller. Because I'm
>just starting to develop glazes, I'd like to do test firings with a
>relatively small number of pieces at a time. My question is, will
>the results I get with a 2/3 empty kiln be representative of what I
>will get when the kiln is full?? I'm firing with all the shelves in
>place, tests and cone pack near the middle of the kiln, and using the
>controller to provide consistent heating and slow cooling.
>
>Oh, another question -- testing potentially very runny glazes, I'm
>sure it would be wise to put a saucer under the piece to catch drips.
> Does this need to be a new bisque saucer each time, or could I reuse
>saucers that have already been fired to cone 6 unglazed?
>
> Thanks for any thoughts.
>
>Chris
>Light One Candle Pottery
>Fuquay-Varina, NC
>candle@nuteknet.com
>
>


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Janet H Walker on fri 20 nov 98

...firing to ^6 ox, in a Skutt 1027 with controller...
...will results with 2/3 empty kiln be representative of full...
...using the controller for consistent heating and slow cooling...

I've had conflicting answers on this question from experts on this
list. One camp says that since the controller is doing everything
the same in the test as in the actual firing that the results will
be the same. The other camp says that the actual thermal load in
the kiln will affect how the glazes come out.

In going with the recommendations of the camp that says it matters,
I put in various extra posts on the levels where there aren't any
pots, in order to simulate the thermal effects of a full load. In
the absence of any other guidance, I took the "usual" load of pots
that would be on a shelf and weighed them. Then figured out the
weight per inch of my kiln posts. Then subbed about 0.8 lb of kiln
post for each pound of finished pot...

I'm not saying that anyone else SHOULD do this. I'm just telling
Chris what I did! Advice is worth what you pay, etc.

Jan Walker
Cambridge MA USA

Chris Schafale on sat 21 nov 98

Thanks for your thoughts. The problem is that as yet I have no,
count em, zero, tried and true glazes to work with, since I just got
my kiln. Don't misunderstand -- I have gazillions of recipes, but
until I've tested them, I'm not putting them all over pots that I put
a lot of work into. So until I get to at least one good recipe that
works and that I like, (hopefully soon), I'll be firing half-empty
kilns with a bunch of little glaze tests in them. I think that the
controller should take care of the problem of the kiln heating and
cooling at a different rate when full or half-empty, but I wanted to
see what others' experience might be.

As for the saucers, I had some vague, perhaps mistaken memory of a
warning about firing stoneware to maturing temp. repeatedly.
Something about explosions, perhaps?? Cristobalite? Did I dream
this? or just misunderstand (more likely) or misremember (most
likely)?

Chris

Having a hectic but wonderful time trying to prepare for Christmas
shows and develop new glazes at the same time.




> ----------------------------Original message----------------------------
> Dear Chris - why not make at least SOME work to fill the kiln AND
> fire tests at the same time? Firing tests in a fairly empty kiln
> will at leat give you a good first look - the surface may be
> affected by a fast rise to temp. but you could soak at the top
> to approximate a regular firing? A first look is always just
> that only - you would then go on to an interim step anyway.
> The surface will amay also be affected as an empty kiln cools
> faster than usual but w/ electric I downfire anyway to
> gain mattness.
>
> As for recycling the saucers - why not? Just put on some
> more kiln wash so you get the test off them provided
> they don't have glaze drips etc.
>
> I always try to have tests in every kilnload I fire - and
> they\'re what I want to see first - definitely worth
> the effort. Good luck. Karen Gringhuis
>
>
Light One Candle Pottery
Fuquay-Varina, NC
candle@nuteknet.com

Ron Roy on sun 22 nov 98

Hi Chris,

As usual - it depends. If you are firing with a sitter the kiln will fire
faster and you will get less melt. If you are firing with a controller the
speed will remain the same and you will get approx the same amount of heat
work.

However in both cases - because the load is less than usual the kiln will
cool a little faster - which may affect some crystal (matte) development.

I suggest you add in a few empty kiln shelves to simulate a normal firing.

You can reuse the saucers.

RR

>----------------------------Original message----------------------------
>Hey folks,
>
>I'm firing to ^6 ox, in a Skutt 1027 with controller. Because I'm
>just starting to develop glazes, I'd like to do test firings with a
>relatively small number of pieces at a time. My question is, will
>the results I get with a 2/3 empty kiln be representative of what I
>will get when the kiln is full?? I'm firing with all the shelves in
>place, tests and cone pack near the middle of the kiln, and using the
>controller to provide consistent heating and slow cooling.
>
>Oh, another question -- testing potentially very runny glazes, I'm
>sure it would be wise to put a saucer under the piece to catch drips.
> Does this need to be a new bisque saucer each time, or could I reuse
>saucers that have already been fired to cone 6 unglazed?
>
> Thanks for any thoughts.
>
>Chris

Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849

Web page: http://digitalfire.com/education/people/ronroy.htm

Arturo M DeVitalis on mon 23 nov 98

I cannot emphasize enough the value of "learning" via the techniques
given by Robin Hopper in "The Ceramic Spectrum". Like the
spices/herbs/seasonings available to us in the kitchen they become "best
friends" only after you have tried them out yourself in various
combinations on our own foods cooked on our own stoves. Check out
Robin's approach and see what you think.

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