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Masters for rubber molds


Via a bankruptcy case I have acquired many jewelry molds by a famous
artist. Most of these molds are “production” molds i.e. rubber. I am
forced to sell the molds and the licensing to produce the jewelry to a
manufacturer to recover my investment. I am being told that not
having the “masters” severely detracts from the value of this mold
collection since masters are extremely time consuming and costly to
re-produce. I can understand that it must be difficult to make a
master from scratch, but how difficult or costly is it to "re-master"
from an existing mold. Your comments will be appreciated. this is a
many sided question but i’ll try to keep it simple! the process to
create your molds required an original metal model to make the rubber
mold. through normal production cycles the molds you have will
eventually wear out. in the normal course of events you would then
take the model master and cook a new mold. this is where you have the
problem . without the original master you can’t make the exact same
mold as you had before. there are two main reasons for this ; #1
SHRINKAGE is that when you cast metal a natural part of the process
is for the casting to shrink as the heated metal cools and contracts.
a rough rule of thumb is the shrinkage is about ten percent. there
are people that would dispute the exact amount of shrinkage but the
casting are measurabally (by wt. ) smaller regardless of amount #2
LOST DETAILS you loss an amount of detail when you cast . this is
partly due to shrinkage and partly due to the whole process that
produces the casting. the original models should have had extremely
sharp detail almost overdone to compensate for this. now before you
panick all is not lost , not even close. there are many ways to
recreate the master models without resorting to handbuilt copies. it
depends on what you want to accoplish. #1 would be to establish a
whole new mold line by cleaning up one casting from the mold to
master qaulity detail. you would then make all new molds based on the
new masters from the old molds. the upside is this is fairly cheap /
but the downside would be smaller casting with a lighter wt and
reduced sizing . #2 you could invest in a small electroforming unit
and “grow” new masters. the process is this -you take the casting
off of the original mold and clean up - wiegh the piece- you then
place in electroforming unit- the process can be dicey but basically
you leave the casting in long enough to add a little over ten percent
of the total wt. -you do this by removing from unit periodically and
wieghing check against original wt until you hit the wt desired -
then clean thoroughly as cynide gas isn’t to good to breath!-then
redetail as needed - the neat thing is that electroforming tends to
add more material to the high spots which you want anyway- then make
new mold – a small note: unless you’re really good with the torch
just cut in the spru as electroformed metal can bubble like plate if
you’re to long soldering i think thats enough for now lots of other
ways to fix but these two were the first general ones that came to my

good luck and any questions feel free to e-mail i’ll try to answer in
timely fashion

Talk to you later Dave