Can you put the flasks in a refridgerator sealed in plastic
to help slow the drying process?
Good day Marjorie Lord-
Yes, any place where there is more humidity will help retard the
investment setting up, but even better I think would be to do as
we usually do and as I’ve been told by Skip Meister that dental
techs do also. Say you invest late in the day and want to burn
out tomorrow, or you’ve already burned the flask out but can’t
cast that day for whatever reason. Leave it, and the next day you
can take the whole flask and drop it into a pail of water, count
to 10 or so seconds and take it out. It will now be sufficently
hydrated to put back into the oven and bring up to casting
temperature and cast with no problems, or to burn out, but don’t
leave in the water too long as the investment starts to break
down. It works very well and if I had a nickle for every time I
done this, I could retire.:^) By the way- Where is Skip lately?
Rick
Can you put the flasks in a refridgerator sealed in plastic
to help slow the drying process?
I doubt the fridge would make much difference. The plastic is
what would help. But it’s best not to wait at all if you can.
Invest, wait an hour after gloss off, and start your burnout.
With those ovens having computerized controllers, you set the
flasks in the oven as soon as they’re set up enough to remove
the bases, clean up the tops if needed, and mark as desired.
Then set the burnout controller to start only after the
appropriate delay… If casting has to be delayed, set the oven
to hold the flasks at the correct casting temp after the burnout
cycle has run. The flasks can stay in the oven at the casting
temp for days, if needed, with no harm.
Or, if you need to invest and then start the burnout later, one
way we used to do it when I was a graduate school T.A., where
students needed to invest one class session and cast the next,
which would be a several days later, is to let the flasks dry
normally. When it’s time to burnout, of course, they’ll be way
too dry to put in the oven. The moisture, by the way, is
required to help conduct heat into the mold, minimizing the heat
shock to the investment in the low temp range where it’s most
succeptible to thermal shock, as well as to generate steam which
helps force the wax out of the mold instead of soaking into the
investment, which then would require a much longer burnout to
really clean up. So we’d simply take the dried flasks and put
them in a bucket of water to soak for an hour, then put them in
the kiln to burnout. The failure (cracking) rate of the molds is
somewhat higher than with the proper procedure, but still quite
low.
You could also seal the set up flasks in plastic, but remember
that the investment is chemically binding the water as well as
drying. Even sealed, after a while it will still be too dry.
Peter Rowe