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calcining epk

updated mon 31 oct 05

 

Paul Lewing on fri 28 oct 05


on 10/28/05 4:06 PM, Carole Fox at silverfoxpottery@COMCAST.NET wrote:

> Does it make a difference whether you calcine epk at cone 04 or 06? If you
> do it at one temp one time and the other the next time, will it make a
> difference in the glaze?
No, you just need to get it past where the chemically combined water is
driven off. I've done it at cone 08 and at cone 016, and noticed no
difference.
Paul Lewing, Seattle

Carole Fox on fri 28 oct 05


Does it make a difference whether you calcine epk at cone 04 or 06? If you
do it at one temp one time and the other the next time, will it make a
difference in the glaze?
Carole Fox
Silver Fox Pottery
Elkton, MD
silverfoxpottery@comcast.net

Michael Wendt on sat 29 oct 05


Calcining Kaolins is touchy. If you fire them above a
certain point, they begin to sinter and form a hard, difficult
to use mass. Larger agglomerated chunks will mean
refractory spots in a glaze so you want the calcine to be
as fine a particle size as the original clay grind since it
won't slake like regular kaolin does when added to
water.
The kaolins I have tested have turned to metakaolin a little
above red heat. Firing past that point, whether cone 06
or 04 will probably not be hot enough to cause sintering,
which usually starts at high fire ranges if there are no fluxes.
I calcine to 1125 Fahrenheit (cone 020 is 1175 F)
and it works fine and is completely free flowing rather
than lumpy.
YMMV
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Carole asked:
Does it make a difference whether you calcine epk at cone 04 or 06? If you
do it at one temp one time and the other the next time, will it make a
difference in the glaze?
Carole Fox
Silver Fox Pottery
Elkton, MD
silverfoxpottery@comcast.net

Taylor from Rockport on sat 29 oct 05


I've not had a problem with my calcined epk. The calcination was in a
regular 04 bisque load. Nice and fluffy calcined epk was the result, nary
a sintered clod (besides me).

Taylor, in Rockport TX, who has hear the first of the sand hill cranes
overfly our property this weekend. Winter has arrived with a honk and a
flap.

William & Susan Schran User on sat 29 oct 05


On 10/28/05 7:06 PM, "Carole Fox" wrote:

> Does it make a difference whether you calcine epk at cone 04 or 06?

Nope, makes no difference with that minor temperature change.


-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu

Kathy Stecker on sun 30 oct 05


Ok I'll jump at the bait hook in mouth now-so what is the advantage or
reason to calcine the epk?


Thanks

Kathy Stecker
Winter Springs, FL



Date: Fri, 28 Oct 2005 22:45:07 -0700
From: Paul Lewing
Subject: Re: calcining epk

on 10/28/05 4:06 PM, Carole Fox at silverfoxpottery@COMCAST.NET wrote:

> Does it make a difference whether you calcine epk at cone 04 or 06? If you
> do it at one temp one time and the other the next time, will it make a
> difference in the glaze?
No, you just need to get it past where the chemically combined water is
driven off. I've done it at cone 08 and at cone 016, and noticed no
difference.
Paul Lewing, Seattle

Carole Fox on sun 30 oct 05


Kathy-
It was recommended that I use it in a glaze that was giving me problems with
crawling. I thank Tom Buck for explaining to me that calcining the kaolin
cuts down on the swelling that usually occurs causing a bigger drying
shrinkage. Less shrinkage helps with the crawling problem. Jeepers, Tom- I
hope I got that right!
Carole Fox
Silver Fox Pottery
Elkton, MD
silverfoxpottery@comcast.net

----- Original Message -----
From: "Kathy Stecker"
To:
Sent: Sunday, October 30, 2005 12:07 PM
Subject: Re: calcining epk


> Ok I'll jump at the bait hook in mouth now-so what is the advantage or
> reason to calcine the epk?

William & Susan Schran User on sun 30 oct 05


On 10/30/05 12:07 PM, "Kathy Stecker" wrote:

> Ok I'll jump at the bait hook in mouth now-so what is the advantage or
> reason to calcine the epk?

To prevent it from shrinking so much when used in a glaze.
Removes all the chemically combined water.


-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu

Paul Lewing on sun 30 oct 05


on 10/30/05 9:07 AM, Kathy Stecker at KSteck@AOL.COM wrote:

> what is the advantage or
> reason to calcine the epk?
If you have too much clay in a glaze, it can shrink too much and pop off or
crawl. You then calcine some of the kaolin (or whatever clay you're working
with) and add that as part of the recipe instead of the raw clay.
The other step in the process is that since the calcined clay has lost the
chemically combined water, if you add straight across calcined for raw,
you'll end up with too much alumina and silica. So you have to compensate
for the LOI (loss on ignition) when you make the substitution.
Paul Lewing, Seattle
PS. You never want to calcine all the clay in the recipe, because then it
will not stay suspended in water. You just want to add only enough calcined
clay to solve the crawling or flaking problem.