I have a set of fine silver pieces that need to be thicker for
casting purposes. My caster suggests that I build up the backs with
wax. I’m not familiar with this process - what kind (color?) of wax,
and could someone give me a few pointers on the process? Many thanks.
Hi Cheryl, I have heard of many casters suggesting building up models
with wax and a number of other lower melting products, but, I , as a
caster do not suggest doing this at all … specifically if you plan
on making more than a dozen or so pieces. The reason I say this is
that what will have to be used is an RTV based low shrink mold…
which costs a bit more to make and the other reason is this…
Should the wax fall of the model or become cracked and another mold
needs to be made… when you redo the wax, you will never get the
same weight … so now, the item from mold to mold will weigh a
different amount … In silver, this may not be a problem… however,
in gold, this could add $10 -$20 easily.
A more permanent solution is to use plumbers solder (no Lead)
plumbers flux , and a soldering Iron… you simply flux the area to
be built up, then heat it with the soldering iron… add the
solder… and continue to build it up until you achieve the desired
thickness… then, wash off with warm soapy water to remove the
flux… now, you can sand the back side down, texture the back,
stamp your logo… Stamping logo’s do not require a hammer in this
typoe of solder as it can be pressed in by hand… Plumbers solder
has a heat resistance of around 400oF and will easily go through
mold making without any adverse effects … and regular molds can be
made for a lower price.
If the item is flat, solder a thin brass sheet to the model and cut
out your pattern. It is always better to have a fully working model
than something that requires special molding processes or careful
attention afterwards.
Hope this helps some of you. Daniel Grandi Racecar Jewelry Co. Inc.
We do casting, finishing, model and mold making, cnc, assembly and a
whole lot more for people in the trade.
Cheryl, on a broad expanse, you can use a soft wax like sprue wax.
Warm the piece and “puddle” it on, or roller the wax into a thin
sheet and press it on – warm hands work better. With sprue wax,
you can press it to smooth it out. On small areas, you may have
trouble keeping the wax stuck on the metal. A small, polished
surface will want to let go almost immediately. Abrading the
surface can help. “Sticky” wax will hold on better, but is
difficult to work when cool.
If at all possible, you would want to have a perfect original all in
metal, with well-soldered joints (no gaps). If that’s not
happening, though, wax can do miracles.
The fact that it’s an RTV mold shouldn’t scare you. RTV molds can
be used for hundreds of good wax injections. It depends on the
piece. It doesn’t have the tear resistance that regular rubber
molds have. Consequently, it may not be a good choice for things
with deep undercuts or very thin cutouts.
There many RTV formulas and there are some dramatic differences in
perfo rmance.
Dana Carlson