Skutt KilnMaster Kilns Manufactured after March 1 2006 - Manual (Page 43)

43
a
ppendix
3 —
h
eatwOrK
Heatwork is the measurement of the effects of time and temperature. In Ceramics, this
measurement is gauged through the use of Pyrometric Cones. They are composed of materials
which are carefully measured and compressed into the shape of a tetrahedron. The cones are
placed in the kiln on a shelf with your ware and, when they have received the proper amount of
heatwork, they bend over indicating that it is time to turn off the kiln.
Pyrometric Cones come in a variety of shapes and sizes. Each size and shape has a different
temperature chart associated with it. The chart below is based on a Large Self-Supporting Cone
and has become the standard for commercial clay bodies, glazes and controller software.
All clay bodies and glazes are designed to fire to a certain cone value. In a KilnMaster Kiln the
computer calculates the heatwork and shuts the kiln off at the proper heat and time combination.
This is called Cone Correlation. ConeFire Mode programs all are controlled by Cone
Correlation, Ramp and Hold Programs are not
Skutt Kilns are designed to fire a range of cone values from 022 to 10. As you can see by the chart below, the
temperature associated with each cone value gradually increases from 022 to 10. It is very important not to forget
to add the leading zero when entering a cone value (if it is required) or the kiln
will fire much hotter than you want it to.
Remember that heatwork is the combination of time and temperature. This is most
important during the last 200 °F of the firing. If the kiln is firing very slow during
this period, the controller will automatically adjust the temperature down to ensure
the ware does not receive too much heatwork. The cone values listed in the chart
are only valid if the kiln is firing at exactly 108 °F/hr. during the last 200 °F of the
firing. That is why it is very important to know the capabilities of your kiln when
writing Ramp Hold Programs or entering Hold times.
We recommend that you still use Self Supporting Witness cones on every firing
to monitor the accuracy of your kiln. Place the appropriate cone on a shelf
approximately 2 inches from the kiln wall and two inches from the tip of the
thermocouple. Make sure the space
between the thermocouple and cone is
unobstructed.
The Cone Measuring Template shown
here can be used to determine the exact
bend measured in degrees of angle. A
perfect bend is considered to be at 90
degrees.
Remember that cones can vary slightly
and are meant to be a general indicator
of the heatwork within the kiln. Bends
between 20 degrees and the tip of the
cone just above the shelf are acceptable
for most projects. If you fine your
bends are consistently low or high you
can usually fine tune the heatwork by
adjusting Hold times.
a
PPendiCes
Cone
No.
◦F ◦C
022 1087 586
021 1112 600
020 1159 626
019 1252 678
018 1319 715
017 1360 738
016 1422 772
015 1456 791
014 1485 807
013 1539 837
012 1582 861
011 1607 875
010 1657 903
09 1688 920
08 1728 942
07 1789 976
06 1828 998
051/2 1859 1015
05 1888 1031
04 1945 1063
03 1987 1086
02 2016 1102
01 2046 1119
1 2079 1137
2 2088 1142
3 2106 1152
4 2124 1162
5 2167 1186
51/2 2197 1203
6 2232 1222
7 2262 1239
8 2280 1249
9 2300 1260
10 2345 1285