I cast Argentium a few times a week without any of your experience.
I am not sure about why you have the problem. Let me point out some
things that I do different.
Over 40 years of casting I have never seen flames in my oven. I used
to dewax at 300f for an hour and let the wax melt into a tray that
was removed before increasing the temperature. I now use boiling
water to dewax. (I use a rice cooker) There is nearly nothing to
I use a short burnout time, my flasks are smaller than yours. They
are 2 1/2 diameter and 3 inch occasionally a 4 inch flask diameter
and never more than 4 inches tall. I most often have only 4 flasks in
the oven. My temperature control is very good.
My burn out time is
start -15 min at 300f
then - 30 min at 500f
then - 30 min at 900f
then - 1hour 45 min at 1350
cool to temperature to cast the first flask 45 min.
cool to each successive temperature 30 - 45 min depending upon the
I use a torch to cast and cannot tell you the temperature of the
metal. I can tell you for filigree I will cast with a flask temp of
1100f. The metal is melted untill it balls up and will swirl when the
arm of my centrifugal cast is moved and it is then released.
I usually do not quench, I break out when fully air cooled. If I do
not wait until fully air cooled, the flasks are broken out in water,
but the flask is probably not more and 200f - 300f. (cool for 1/2
hour before breakout)
Things that you wrote that concern me…
the flames in your oven the low flask temp for filigree and perhaps a
high metal temp to compensate if the reused metal is compromised
because it has been cast and has come out as you described, I would
not reuse any of it in another cast. It sounds like it is ruined.
Below is a copy of a recent post that I made about casting
I am usually casting 2 1/2 inch flasks, sometimes 4 inch flasks (all
custom work, small items)
- centrifugal casting - torch (propane & oxygen) to melt and I use a
somewhat hotter flame than I use for regular silver (for regular
silver the flame I use is somewhat reducing, I use more oxygen in the
flame when casting Argentium) The usual amount I cast is from 10 to
60 grams in a flask
i) I find that I need a mix of new grain to old buttons of 60% new
and 40% old (50/50 shows some signs of a poorer cast on occasions,
but not always) I make very sure the old material is very clean
ii) I coat the material to be cast with boric acid dissolved in
alcohol, then burn off the alcohol, I use no other flux The boric
acid solution is about 30 – 40 % saturated
iii) I am careful to not over heat the metal (molten Argentium looks
different from molten sterling) I cast shortly after the metal has
become fully melted. The Argentium 935 pro appears to have a large
slush area. It does not roll as easily like molten sterling silver. I
notice that I have a few bits still adhered to the flask after
iv) the flask temperature I use is slightly higher than what I use
for regular sterling (1100f for very fine items down to 850f for
v) I always let the flask cool to about 250f - 300f or right to room
temperature and I break out the cast, I do not quench. (I have
quenched hot flasks in water, the casting will crack!)
vi) The just cast material is very white. I ultrasonic clean off
investment for a few minutes only, pickle in hot pickle for a few
minutes, then ultrasonic again about one minute.
My castings are always free of porosity, never have surface pits
from contamination and work and polish well. I very often fuse (weld)
pieces together and will use Argentium hard solder and medium only. I
have never had a need to use easy solder.
I always heat treat in a small kiln holding the temperature at about
500 – 550F for an hour.
The finished cast jewellery is very white in colour, reasonably hard
and has a very good polish. Never has fire scale been a problem and
when doing torch work, I do not coat with anything at all.
My customers tell me that their items remain bright and they are
pleased. I have a little bit of evidence that those that can turn
sterling silver black when worn have much less of an issue with the
Argentium sterling silver.
I hope that I have been helpful and certainly welcome any question
that you have.