Frederich, Tim on tue 15 jan 02
Hello,
I would like to make a couple of suggestions for looking at cones inside the
kiln. The first would be to wear a good pair of colored safety glasses
(shade 2.5 or better) to block the harmful wavelengths of light. The next
would be to place a target piece of soft brick behind the cone pack. You
can paint some horizontal lines of Red Iron Oxide on the brick to help see
the end point of the cone as it begins to fall.
Please do not blow in the peephole. You can blow dust in on your ware, you
can burn your face if there is any back pressure from the kiln chamber, and
you can cause the cones to stop working in the proper manner. If the cone
is in the beginning of the melting stage and hit with a blast of cold air
(what we call "freezing") it can form a shell on the cone and stop the
deformation of the cone. The cone may have to go to a much higher
temperature to begin deforming again. What usually happens is that the next
higher cone will begin to deform and the lower cone number will remain
standing.
Another suggestion is to pull the peephole plug and wait for several seconds
before looking in to allow the chamber to clear.
Please use caution at all times when working around the kiln. We would like
everyone to remain safe and well.
Best regards,
Tim
Frederich, Tim on thu 17 jan 02
Snail, Craig, Jonathan and everybody,
I will try to answer some of the questions that have been asked. First
Snail asked about "cone freezing" if the kiln holds at a temperature just
below the equivalent temperature of that cone. If a kiln holds at a
temperature just below the end point of a cone, that cone will eventually
fall due to the amount of heatwork (time and temperature) that it recieves.
This is not "cone freezing". If the cone does not fall even when the
temperature starts to rise again, then some other variable is affecting the
cone.
Craig asked about the affects of fly ash and different atmospheres on the
cones. The ash and/or a reducing atmosphere can cause the cone to act
differently than it normally would. The ash could flux the cone and the
atmosphere could cause a bloating problem. There are many variables that
can affect the cone and these same variables are also affecting your ware in
the same manner. A suggestion to protect the cones, especially in a wood
firing,is to build a type of shelter house out of your clay body over the
top of your cone pack to stop some of the ash from settling on the cones.
Even if the cones cannot give you an exact reading in these situations,
through experience you will learn to judge what is right for your ware in
your kiln in these types of firings.
Jonathan thought that you might be able to calculate the heatwork and not
use the cones at all. You could come up with a time/temperature equation
but it still would not show you the actual heatwork that is taking place.
It could not account for the physical variables that change inside the kiln
at any given moment such as changes in atmosphere, heat radiation or load
variation. It would not account for power fluctuation from moment to moment
or the outside atmosphere at that given time. All of these variables can
affect any given firing. Logs and math cannot account for all these
changes.
Cones are still the most accurate and most reliable source of measuring
heatwork that we have. They can be used to calibrate thermocouples and
controllers. They are still the best indicator of what is happening inside
the kiln chamber including the unwanted variables.
If you have further questions, please ask. I will be at NECCA and will be
glad to talk to you. If you have firing problems or cones that did not
react the way you thought they should, please bring them along and we will
evaluate them. You can also send cones and questions to Orton . Mark them
to the attention of Tim Frederich and include information on how I may reach
you. I prefer a phone number so that I may call you direct.
Best regards,
Tim
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