Arnold Howard on thu 30 may 02
Charles Moore kindly mentioned this post about witness cones, so I
am sending it again:
How to Position Cones on the Shelf
Most people have difficulty seeing the witness cones on the kiln
shelf during firing. But if you position them just right, you can
see them even at cone 10, when the kiln interior turns white-hot.
Being able to see the cones during firing is your assurance that
the kiln is firing normally. If the kiln takes longer than usual to
fire and you cannot see the cones, you may worry that something has
gone wrong. Maybe the kiln is even over-firing.
In formulating these guidelines, I tested a welder’s facemask,
mirror, and high intensity flashlight. You don’t need those items,
even for cone 10 viewing.
1) Place the cones 8” - 12” away from a peephole. Positioning them
closer makes them difficult to see.
2) Have enough space around the cones to keep them from touching a
piece of ware when they bend.
3) Position cones so that when viewed from the peephole, they are
silhouetted by an element on the opposite kiln wall. (Keep cones at
least 2” from an element.) The element that silhouettes the cones
should be level with the lower part of the cone. If the element is
in line with the upper part of the cone, you won’t be able to see
the cone when it bends.
4) If you use the three-cone system, always have the higher
temperature cone on the same side in every firing. Otherwise you
can lose track of which cone is which.
5) Wear firing safety glasses when viewing the cones through the
peephole. I have experimented with didymium glasses. I found that
they were no better at improving the view of the witness cones than
the less expensive green firing safety glasses.
Arnold Howard
Paragon Industries, Inc.
--- Tim O'Neill wrote:
> I'd appreciate some expert advice regarding safety glasses for
> looking in
> my peeps. I went to Home depot to purchase some welding glasses
> & they
> don't carry them (darn lawyers) so I went online. The folks at
> BIGCERAMICSTORE.COM have a pair of UV & INFRARED A&B safety
> glasses for
> $15. They advertise them as "for looking in kilns."
> I purchased a pair & now have some concerns because the box only
> mentions
> ANSI Z80.3 regarding UVA & UVB. No mention of IR.
>
> Can somebody out there tell me definately that I'm using an
> adequate filter
> to look in the kiln at cone 6? I make my living driving big
> airplanes &
> these eyes are good for more than cone watchin'
>
> Thanks in advance,
> Timo
>
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