Yes, centrifugal casting machines are more violent, but with
dental high heat investments it is a moot point! In fact I have
never experienced a problem with the investments meant for low
heat burnout either. I regularly cast gold alloys and
palladium/silver/gold alloys in dental castings to .2 mm
thinness! Always! The pal/sil/gold needs to be thicker or
have multiple sprues.
Are you using that Ransom and Randolph investment? It is an
o.k. investment in pre-weighed packets but in bulk form it
goes bad faster than a hornet can find a Coke can at a picnic!
The packets also go bad quickly but not as fast. It is not wise
to mix techniques unless you really know what you are doing.
If you are going to use the dental burn out schedule than use
dental investment.(You don't need to cool the flask to 925 F
before casting. Put the hot ring in the cradle before you start
to melt the metal(2 1/2 oz. or less of silver). Melt it then
bring it to casting temp. and let her fly.
Have you ever taken into consideration your melt? It's really
easy to under heat the metal when using a bulk of several
ounces. If you have metal left in the crucible, you never
reached casting temp. and thin areas won't cast. On the other
hand a small amount of metal can be overheated and burned and
IN-GASSED producing sub-surface porosity and possibly a brittle
I have been doing this for so long it is second nature to me.
There are so many variables in any casting process that you need
to actually have control of, or have experienced first hand that
it is difficult if not impossible to diagnose on this forum. If
you or anyone else wishes, E-mail me and I'll send you my phone
number and you can call me. I'll be happy to spend as much time
as you need. I work from my home so you can call me at most
times. I'm usually up at 9 am central and go to bed at 1-2 am.
Please don't call after midnight:).
NRA Endowment and