Dave Finkelnburg on mon 22 jan 01
Hello Priscilla!
Yes, you are correct, if you want to fire to cone 6 you probably need a
small cone 7 in the sitter of your kiln. With a cone 6 there now, you are
likely firing to cone 5. There is only one way to be sure, though. Also
fire with witness cones on the shelves in the load. If your goal is cone 6,
buy a box of cone 6 self-supporting cones and set at least one on the shelf
in the middle of the load.
I don't want this to sound like I am lecturing, but I learned this
lesson the hard way, might never have learned it but for good folks on this
list. If you want to know what cone you are firing to, buy witness cones
and put them in the kiln.
By the way, get your cone supplier to show you how to break the cones
apart without breaking them all up. Whoever at Orton designed those pesky
cones made stuck together should get to spend a century splitting them
apart, with added time for every one inadvertently broken! Sorry about the
rant..... :-)
Sounds like you aren't certain about how high to fire the clay body. If
you are getting what you want now, you may not want to fire a cone higher.
If you look in the archives, there should be many posts about testing clay
bodies for maturity after firing. Look under "absorption" for testing you
can easily do yourself.
Dave Finkelnburg in frosty Idaho where the visibility today was 70
miles, minimum
vince pitelka on tue 23 jan 01
> Yes, you are correct, if you want to fire to cone 6 you probably need
a
> small cone 7 in the sitter of your kiln.
Dave -
This all depends on where the kiln sitter is located. On our L&L kilns the
sitter is near the top of the kiln, and in a glaze fire it is a good idea to
place a cone which is one step higher, so that the lower parts of the kiln
will indeed get to the desired temperature. On the other hand, we have a
Skutt toploader which has the sitter near the bottom, and in that case you
need to place a cone which is one step lower, or else the top of the kiln
will over-fire.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dekalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Susan Shaffer, SBR Inc. on tue 23 jan 01
Dave:
Amen on those Orton cones! Recently returned to the world of clay after
a 20 year "sabbatical", and couldn't believe their "new" casting approach.
I know there must be a tried and true method for separating those little
buggers! What's the trick? Tried scoring, using two rulers to break along
the line, and of course my thumbs - and the loss ratio is still pretty
ridiculous. Any clues out there?
----- Original Message -----
From: "Dave Finkelnburg"
To:
Sent: Monday, January 22, 2001 10:31 PM
Subject: Re: Firing kilns comparatively
> Hello Priscilla!
> Yes, you are correct, if you want to fire to cone 6 you probably need
a
> small cone 7 in the sitter of your kiln. With a cone 6 there now, you are
> likely firing to cone 5. There is only one way to be sure, though. Also
> fire with witness cones on the shelves in the load. If your goal is cone
6,
> buy a box of cone 6 self-supporting cones and set at least one on the
shelf
> in the middle of the load.
> I don't want this to sound like I am lecturing, but I learned this
> lesson the hard way, might never have learned it but for good folks on
this
> list. If you want to know what cone you are firing to, buy witness cones
> and put them in the kiln.
> By the way, get your cone supplier to show you how to break the cones
> apart without breaking them all up. Whoever at Orton designed those pesky
> cones made stuck together should get to spend a century splitting them
> apart, with added time for every one inadvertently broken! Sorry about
the
> rant..... :-)
> Sounds like you aren't certain about how high to fire the clay body.
If
> you are getting what you want now, you may not want to fire a cone higher.
> If you look in the archives, there should be many posts about testing clay
> bodies for maturity after firing. Look under "absorption" for testing you
> can easily do yourself.
> Dave Finkelnburg in frosty Idaho where the visibility today was 70
> miles, minimum
>
>
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Dave Finkelnburg on wed 24 jan 01
Vince,
Your post is great! Thankyou!
You point out exactly why witness cones are so necessary, even in
electric kilns with kiln sitters. How could you have determined, without
witness cones, what part of the kiln gets hotter, or not so hot, and by how
much, relative to the cone in the sitter?
Obviously my experience with my Olympic is more like your L&L's, and not
like your Skutt. Thanks for the additional information!
Dave Finkelnburg
From: vince pitelka
>> Yes, you are correct, if you want to fire to cone 6 you probably need
a
>> small cone 7 in the sitter of your kiln.
>
>Dave -
>This all depends on where the kiln sitter is located. On our L&L kilns the
>sitter is near the top of the kiln, and in a glaze fire it is a good idea
to
>place a cone which is one step higher, so that the lower parts of the kiln
>will indeed get to the desired temperature. On the other hand, we have a
>Skutt toploader which has the sitter near the bottom, and in that case you
>need to place a cone which is one step lower, or else the top of the kiln
>will over-fire.
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