Tony Hansen on fri 25 jul 97
We are getting strange cone bending in our gas bisque firing.
The cones curl backward then go down like felled trees. By the
time they do fall the kill in considerably overfired.
I know that reducing during bisque can cause this but
I am positive we are not reducing. Anyone have an idea.
--
T o n y H a n s e n, I M C thansen@digitalfire.com
=========================================================
INSIGHT5/Magic of Fire II demos at http://digitalfire.com
stevemills on mon 28 jul 97
Tony, I'm probably teaching my Grandmother to suck eggs but I check for
reduction by holding a piece of smouldering wood in front of the open
front spy hole: if the smoke goes in it's oxadizing, straight up-
neutral, in the opposite direction-reduction. Cheaper than an analyzer!!
Steve.
In message , Tony Hansen writes
>----------------------------Original message----------------------------
>We are getting strange cone bending in our gas bisque firing.
>The cones curl backward then go down like felled trees. By the
>time they do fall the kill in considerably overfired.
>I know that reducing during bisque can cause this but
>I am positive we are not reducing. Anyone have an idea.
>--
>T o n y H a n s e n, I M C thansen@digitalfire.com
>=========================================================
>INSIGHT5/Magic of Fire II demos at http://digitalfire.com
>
--
Steve Mills
@Bath Potters Supplies
Dorset Close
Bath
BA2 3RF
UK
Tel:(44) (0)1225 337046
Fax:(44) (0)1225 462712
DonKopy@aol.com on tue 29 jul 97
Hi Tony,
I have on rare occasions seen cones exhibit this behaviour. My current theory
is that it is related to the level of sulfur in the clay. It appears as if a
reaction takes place with the surface of the cone creating a skin that
retards the free movement of the cone. The result is either a weirdly twisted
cone or a rapid fall, after the initial resistance is overcome. This should
be rather evident if you break one of the cones and look at the cross
section. I'll bet it has a well melted (gooey chocolate center) interior. You
know what to do if that is the problem.
I came to this conclusion after checking on a bisque firing of some clay
samples I received a few years back. It was a bisque which would have made
Jimmy Hendrix proud, that acrid purple haze overburdening my ventilation
system and filling the room. The cones in that firing were as you describe.
>We are getting strange cone bending in our gas bisque firing. The cones curl
backward then go down like felled trees. By the time they do fall the kill in
considerably overfired.
I know that reducing during bisque can cause this but I am positive we are
not reducing. Anyone have an idea.<
Excuse me...... while I kiss the sky,
Don Kopyscinski
Bear Hills Pottery
Newtown, CT
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