william schran on mon 30 dec 02
John Hesselberth wrote about 15-20 minutes being a sufficient soak
time for the correct development of glazes and prolonged soaking time
being perhaps unproductive. Several years ago I ran a series of tests
with a couple of glossy & mat glazes where I altered the soak times
from no soaking to about 2 hours. Can't lay my hands on the written
results at the moment, but I do remember as soak time increased, all
of the glazes became glossier and some began to run when I let the
soak go beyond an hour.
I agree that a short soak is beneficial for all glazes. When we speak
about firing we are discussing temperature AND time to produce work
heat. It is the work heat after all that produces the good/bad
results. One can produce apparent similar glaze melt at lower
temperatures with extended firing time.
I do wonder though, when the cones bend to their proper position and
the proper firing cycle has been followed to produce the proper work
heat, why that shouldn't be sufficient. Perhaps the soak is necessary
to allow the work heat in, around and through all parts of the
pot/sculpture? Is it like cooking, where one can shut off the heat
and the interior of the food continues to cook?
Bill - finally unpacked in Fredericksburg, Va. where the temperature
is due to get up to 60=B0 tomorrow and I can get up on the roof to
complete some needed repairs.
J. B. Clauson on mon 30 dec 02
As it was explained to me by one of my mentors whose name was also Bill, the
glazes outgas a when they reach maturing temperature. The soak is to assure
that this process is complete and you are not left with bubble spots on the
surface of your glaze. Too long will cause the glaze to get all melty (my
word, not Bill's) and run off the pot. He recommended a 20 minute soak.