The
tack fuse range is around 730C – 780C. This will give a graduation
in profile from the very sharp, almost barely laminated, to one very
rounded almost flat. Choosing the right heat for the right profile
is one of balancing several elements: temperature, time, speed.
Low temperature, high tack fuse |
If
there were no other considerations, you could go slowly up in
temperature and peek in at infrequent intervals until the right
profile had been achieved. However this tack fusing is happening in
the devitrification range, so slow rises in temperature are not
advisable.
Medium temperature, mid tack fuse |
So
an alternative strategy would be to go quickly through the
devitrification range (700C to 760C) and soak for a bit longer above
that range. However, often the desired profile may has disappeared
by the time you get to 770C.
High temperature, rounded tack fuse |
It
would seem that you can attempt to balance the temperature, time and
speed equation by firing quickly (such as 330C/hr) to your desired
temperature and soak there for 10 minutes only.
To
ensure you get the profile that you want you should begin to observe
from at least 10C below your chosen temperature. If you do not get
the profile you want, you can extend the soak until the desired
effect is achieved. On a subsequent firing, you can set the top
temperature a bit higher, but with the 10 minute soak and again
observe. This can be repeated until the desired combination is
achieved.
Each
of these attempts needs to be completely recorded so that the results
can be used in later firings if slightly different profiles are
needed.
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