besides making new models altogether,, does anyone have any
methods to enlarge silver or brass masters, for casting, like
painting them with something thick, and then making the mold?? I
You may be able to do Silastic E RTV Silicone Rubber Kit put out by
the Dow Corning Corp. Midland, MI 48686-0994, USA (517)469-6000 --
basically about 1 lb base and 0.1 lb curing agent (Rio has the
Silastic J which seems to take a lot longer to cure, but remains
workable longer, but I haven't worked with Silastic E since 2000 so
it could simply be their new line with little difference). You have
your frame for the mould, with a little cone for where the molten
metal will be channelled, use one of the wax wires you can pick up,
lay out four corners with other pieces of wax or what have on hand.
The wax piece, plastic piece, metal work, whatever it is that you
are trying to make a mould of gets heated onto the wax wire, or
crazy glue to a piece of wire proper if it's, too, heavy a piece
(this is called brass sprue formers and rods in Rio Grande) . . .
mix the curing agent and base, pour out into mold until model is
half covered. Take out the corner holders, a light amount of
petroleum jelly then lay out the rest, let cure and take apart the
moulding frame and pull apart the mold, remove you original.
Because of it's room temperature vulcanizing there is no heat
involved, nor any expensive vulcanizers. You could most likely add
careful layers to your piece before making the mold. Making things
smaller is easier with the Reduc-It Mold Compound (Also from Rio),
you pour it into your mold and it will shrink to 50% volume -- it's
a positive casting material.
Also, how workable/carvable is the silicone rubber inside the
mold, so as to make parts of pieces larger, for rework? thankyou!
the vulcanized stuff that I've worked with is hard as all heck, the
RTV stuff would take to a knife fairly well, you might be able to
get the results you need from working it. My carving blows so I
couldn't do it, but with patience and a sharp knife I think it is
possible. Also you chop up RTV molds you don't need anymore and
fill up a lot of the lost space in new molds with those, they'll
integrate pretty much fully into the mold so you inject wax or what
Fredericton, New Brunswick, Canada