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Soldering model for vulcanizing

Hi all Can somebody tell me how to solder the sprue to certain non
precious metal models prior to be vulcanized? can it be glued or soft
soldered without getting separated during the vulcanization process?
Thanks in advance. Jonathan

if you are using RT V. silicone you can put the sprue on with wax,
since no heat is needed. Yours truly, Larry Paul

Larry Paul casting Co. Inc.
740 Sansom Street
Philadelphia PA 19106
215. 928 – 1644
fax 215. 574 – 1943

Hi Jonathon, Assuming your model is made of pewter or brass the best
way to attach your sprue would be to soft solder it using 60/40
solder. Do not use low-melt solder as it will come apart from the
heat of the vulcanizer. Hope this helps!

Susanne Roberts
East Side Concepts, Inc.
Providence, RI 02906
401 861-5176

sprues for models in rubber! don’t glue it! you can use soft solder,
but not lead!.. remember that the hot vulcanized rubber will reach
up to about 225+F. so with this in mind, use anything you want…but
there is another idea,…why don’t you ‘burn’ in the hole after the
model has been removed?..gerry, the cyber-setter/teacher


This is second hand advice, as, when it comes to molds, I have mainly
watched. The people I know who make them slip a very small shred of
paper or a matchstick into the mold rubber where the sprue is going
to go. They then cut a sprue “nozzle” when cutting open the mold.
This opening is used mainly to insert the wax injector, although it
does produce a sprue. When spruing up to a tree you might want to
add to the injected sprue or modify it. This is easy to do if you
keep a wax pen and some sprue wire and a little “pot” of melted wax
(use a cut down Coke can on a coffee cup warmer) set up where you are


first a question what kind of metal? second a possible off hip
solution mold the model and sprue loose in the rubber. when you cut
and vent the mold cut the small bit between the sprue and model out,
being careful to be very neat (use a sharp blade) this was the
solution typically used by molders when we had occasaion to mold up
white metal models. if its copper or brass you can use easy or
easy-flo silver solder if you know the models history. alot of older
models i wouldn’t do this with as you can’t be sure that easy solder
or even lead solder might have been used. hope this helps.

Talk to you later Dave Otto :-{)-

Hi Marcos, I use a heat cured silicone rubber (vulcanized) It is
better to solder the sprue onto the model, But if you have no idea
what the material is, then, with silicone heat cured powder seperated
molds, it is easier to place the sprue in the mold about 1/16" away
from the model and cut , grind or burn the connection to the model
after the mold is cured.

Daniel Grandi

Marcos: I often make a vulcanized mold without attaching the spue to
the master model. Place it where it touches the sprue and then place
the rubber in position. When vulcanized it may shift a little but not
much. Cut the mold as usual and the with a hot wax tool or a piece of
sprue material heated red hot burn out the blockage between the model
and the sprue. I have done it a number of times with good
results on pieces that I could not solder on. Frank Goss

If you use silicone rubber to make the mold, YOU control where the
rubber flows. What this gives you is control over the mold line and
the amount of pressure exerted on your piece and sprue. If you pack a
mold correctly, you can place the two pieces (the master and sprue)
closely together, and then as others have said, cut or burn the small
amount of rubber that flows between the two away. The idea is to keep
this area as smooth and clean as possible to keep the resistance and
obstructions to a bare minimum. Remember, wax and metal flow cleanest
when there is little to no resistance. Of course the most ideal
situation is to use a good solid master (silver or bronze, plated
piece) that you can solder the sprue to that will avoid this problem
entirely. Good luck and feel free to contact me with questions.


Hi All To fix a sprue without solder , drill a small hole in the model
and then screw in a woodscrew. Regards David Sheard
L A Sheard England