I’m the person who posted earlier about being taught to use a
reflective surface to check for moisture in the kiln before casting.
Thanks all for your I burn out at 300 degrees for one
hour, 700 for one hour, 1350 for two hours and then slowly ramp down
to 900 to cast and I do this using a little homemade device that I can
set to ramp up or down to these temps at the rate of 300 degrees an
hour (I set it about 10 pm and cast in the morning) so it also would
seem to me that there could be no moisture in the molds. However
darned if there isn’t often condensation on the mirror when I check.
As someone suggested it’s probably fumes. I could never determine any
harm was done when I cast, even with the condensation still there. I
gave up checking and just ignore it. I generally have very good
results and feel that spruing is of great importance. Usually only
when it really matters do I find a little porosity on a piece exactly
where I wouldn’t want it to be. Annette
Annette,
Is your kiln gas fired? if so water is a byproduct of combustion of
hydrocarbons so you will see moisture from a gas flame. Otherwise it
could be water vapor in the air that is hitting the cool mirror and
condensing but it is not going to be water from the flasks if you
follow the burn out schedule you provided.
Your burn out schedule sounds good but one thing to remember is that
the flask temp will lag behind the kiln temp by a long time. On the
4" dia. flasks we used it was about a 1 hour lag. That is it takes a
dry flask one hour to reach the kiln temp after the kiln temp has
stabilized. This is due to the low thermal conductivity of dry
investment. This is the reason many people cast at too hot a flask
temp. They think that the flasks are ready to go as soon as the kiln
reaches the casting temp.
Jim –
James Binnion Metal Arts
Phone (510) 533-5108
Toll Free (877) 408 7287
Fax (510) 533-5439
@James_Binnion
Member of the Better Business Bureau
Hi all, What causes these carbon residues ? Would this be from an
incompleat or inproper burnout ? Thanks Jimmy…