Tom Buck on thu 4 jul 96
Eric Lingren, others, have established the position of pyrometric cones
at full maturity, yet as Tony Hansen discovered, getting a consistent
cone positioning and therefore a consistent heat-work from firing to
firing is most difficult. Hansen did a series of tests, and consulted
with Orton specialists during same, and found some real problems with
cones as such. To read Hansen's report see his book, Magic of Fire 2,
either in paper or elecronic form. Go to URL
http://digitalfire.com/index.htm and follow the appropriate links for
data on the book, etc.
Cheers Tom.Buck Hamilton Canada
Mitchell Sewall on sat 9 sep 06
Maurice,
By reading your post to Tom Witman I realize you know something about cones.
Hence this question:
How come both large cones and the small ones use the same numbering system
and yet as I understand it, they go down at different temperatures?
Mitch
Maurice Weitman on sat 9 sep 06
At 16:35 -0400 on 9/9/06, Mitchell Sewall wrote:
>Maurice,
>By reading your post to Tom Witman I realize you know something
>about cones. Hence this question:
>How come both large cones and the small ones use the same numbering
>system and yet as I understand it, they go down at different
>temperatures?
Hi, Mitch,
I apologize if I gave you the impression that I knew something about
cones. Nevertheless, here comes my take on your question... I'm sure
others will pipe up as they see fit.
I assume you mean the difference between the large (full-size --
"classic" heh) cones and the small ones that one uses in a kiln
sitter.
If you mean the diff between the large cones and self-supporting,
they should be identical, but the self-supporting are, I believe,
more accurate since they are always at the proper angle. Large cones
put in a clay "cone pack" are more difficult to place and keep at the
proper angle, and angle influences the rate of drop.
Now then, my understanding is that the small cones were designed for
one purpose: to be used in kiln sitters. As such, they are meant to
be used horizontally, AND with the added weight of the sensing bar.
Therefore, if used as witness cones, they will "report" that the heat
work experienced was less than was the case. I don't really know to
what extent this would be, but it would not surprise me if a cone 6
small cone put in a cone pack wouldn't drop until cone 7 or 8, maybe
even higher.
The bottom line is, they should not be used as a reliable indication
of heat work. They may be used in that way once you've established
that you're happy with the results when a small cone X is at Y
o'clock, but the number stamped on them will not represent the true
heat work associated with that number.
I hope that was clear, and would be happy to clarify any murkiness.
Regards,
Maurice
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