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firing above kiln temp rating

updated thu 27 dec 07

 

John Rodgers on tue 25 dec 07


Why don't you ask Arnold Howard at Paragon? He (and they) at Paragon are
good folk. Bet'cha can get the answer!

Regards,

John Rodgers
Chelsea, AL


Wil Morris wrote:
> I have an old Duncan electric cone 8
>
> Question is: What if I fired it Cone 10 with burners? And , if the bricks
> are under-rated for this kind of temp, what if I lined the inside with
> 2400C fiber blanket to keep the direct heat from the bricks. I was
> considering blanketing anyways for better efficiency.
>
> Im sure the kiln manufacturer (now Paragon) would never divulge this
> kind of info.
>
>

Wil Morris on tue 25 dec 07


I have an old Duncan electric cone 8 that has virtually kicked the bucket.
One of the switches blew, but the elements are old and I always considered
gassing it up and I will like to try reduction for a change. I was
wondering if the Cone 8 max temp that Duncan gave it was relative to the
electrical capacity (which is irrelevant if Im no longer using it) or if
that rating is the maximum temp that the IFB bricks are rated for.

Question is: What if I fired it Cone 10 with burners? And , if the bricks
are under-rated for this kind of temp, what if I lined the inside with
2400C fiber blanket to keep the direct heat from the bricks. I was
considering blanketing anyways for better efficiency.

On a slightly different note,
My mother fired her kiln too high, relying on the sitter to shut it off (I
know,bad idea), she left the house for the afternoon. Well, the sitter
never shut the kiln off and her kiln fired up to she was told an estimated
cone 13. The bricks melted and it almost burned down the house. So now she
has a fancy fully automatic electric. Of course I dont plan to fire that
high, but how high can I go with these bricks, and how do I find out?
Especially where the flame is concentrated, of course that would be
deflected against shelves.
Im sure the kiln manufacturer (now Paragon) would never divulge this
kind of info.

Wil Morris
in snowing Olympia, WA

John Post on tue 25 dec 07


I have fired old electric kiln shells with gas to cone 10 without any
problem.
I wouldn't worry about the kiln too much. Some cone 8 kilns simply
have narrower bricks or less insulation than cone 10 kilns.

Some things to remember...
You may need smaller diameter shelves or half shelves to let the heat
flow through the kiln.
You many want to place the bottom shelf up on some bricks to give room
for the flames to enter the kiln.
Make sure the exit flue is big enough. It needs to be larger than the
burner port.
You can always use a kiln shelf as a damper.
The kiln may also cool too quickly to give you the effects you are
looking for so you may want to try and slow the cooling down by
relighting the burner from 1800 degrees F down to 1300 degrees F.

Steve Branfman has a good section in his raku book about converting old
electrics to other uses.

John Post
http://www.johnpost.us
http://www.wemakeart.org

>I have an old Duncan electric cone 8 that has virtually kicked the bucket.
>One of the switches blew, but the elements are old and I always considered
>gassing it up and I will like to try reduction for a change. I was
>wondering if the Cone 8 max temp
>

William & Susan Schran User on wed 26 dec 07


On 12/25/07 4:20 PM, "Wil Morris" wrote:

> I have an old Duncan electric cone 8 that has virtually kicked the bucket.
> One of the switches blew, but the elements are old and I always considered
> gassing it up and I will like to try reduction for a change. I was
> wondering if the Cone 8 max temp that Duncan gave it was relative to the
> electrical capacity (which is irrelevant if Im no longer using it) or if
> that rating is the maximum temp that the IFB bricks are rated for.
>
> Question is: What if I fired it Cone 10 with burners? And , if the bricks
> are under-rated for this kind of temp, what if I lined the inside with
> 2400C fiber blanket to keep the direct heat from the bricks. I was
> considering blanketing anyways for better efficiency.

Go for it Wil!
I have an old Paragon that's going through the same process.
Mine will be a cross draft design.
Burner at bottom of wall, flame path horizontal.
Shelf right above, then flue above that.
I've put ITC at bottom of kiln in flame path.


I would imagine the brick are K23, so ^10 should be ok.


--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com

Arnold Howard on wed 26 dec 07


From: "Wil Morris"
I was
> wondering if the Cone 8 max temp that Duncan gave it was
> relative to the
> electrical capacity (which is irrelevant if Im no longer
> using it) or if
> that rating is the maximum temp that the IFB bricks are
> rated for.

The firebricks are rated to cone 10.

> Im sure the kiln manufacturer (now Paragon) would never
> divulge this
> kind of info.

Duncan was a serious competitor of Paragon until 1997, when
they stopped making kilns. At that point, Duncan contracted
with Paragon to supply parts for their kilns.

Sincerely,

Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com