I am casting sterling silver filigree. Most of my pieces have aprox
a 1 mm framework either around them or running through them
somewhere, and filigree wires which are generallly 1x 0.5 mm, at
least in the originals. I do the standard burnout, but on the cooling
side, I stop at 1150 deg F for casting. I am using vacuum casting,
however. I used to do centrifugal, and that did not require as much
upward temperature adjustment. I have an electromelt, and usually
have the temperature of my sterling at between 1900 and 1920 for
filigree. If you do heavier work at this temperature, it does create
porosity, but the filigree type work has to be hot enough to fill as
it cools so quickly in such small dimensions.
Other things to consider:
Your design.....you always have to think of the flow of your
silver...can it get from the main sprue to the end of your design
easily or does it have to turn back and go against the flow. just
remember the old expression :go with the flow....when it comes to the
is your tree set up correctly? check the angle on your pieces you
are casting to take advantage of either the vacuum or centrifugal
forces at work.
If you are vacuum casting, is there too much plaster between the
ends of your pieces and the vacuum? you need just enough plaster
between the ends of your pieces in the mold, and the vacuum that the
mold will not blow out, but not so much that it impedes the vacuum.
If you are using vacuum, I strongly recommend using Wax web liners
for the flasks. This allows your vacuum to reach up into the sides of
the flask, allowing stronger pull on the pieces lower in the trees.
Again with vacuum, leave an air space when you invest. I think I got
this from Tim McCreight's book, Practical Casting, but it said if
you leave a space of up to about 1/4 inch on your flask, it allows
for a more even pull than if your top it off, and then the pull is
only on the center of the flask.
Size does matter! I do much better with my 3x5 inch flasks than my
6x4 inch flasks with my vacuum casting of filigree. It takes longer
for me to get the flask to 'grip' to the pad and every second counts
when you have to cast extra hot! In addition, the bigger the flask,
the more plaster..and you have to keep that distance from the tips of
your pieces in mind.
If this helps, I photographed some of the wax trees and finished
castings a while back so you can see how they are set up
I didn't photograph the flasks, but you usually don't want more than
half an inch- an inch between the top of your tree and the end of the
Hope that helps