I have an opportunity to handle metal artifacts from a local
museum in order to create replicas or jewelry pieces inspired by
those artifacts. Some of the artifacts are coins, some small metal
hardware, and at least one ring. I also have access to artifacts
in a collector's home to use for this project. Since I have to make
the molds on site, I would like some suggestions of appropriate
materials to use.
If accuracy is required it is not a trivial task that you are facing
with. I have some experience in restoration, so the process as
determine separation line. an object will have at least one or more.
do not rely on flexibility of mold material because when wax is
pulled, things getting distorted. It is fine for production
jewellery, not for museum copies.
Draw separation line and embed object in plasticine leaving exposed
only areas above separation line.
Cover object with even layer of plasticine, and cast a plaster mold
from assembly. Make provisions for keying the mold to other mold that
you will have to make. Lift the mold and remove layer of plasticine
covering the object. Put plaster mold back in place and pour rubber
compound in the space between plaster shell and the object. When set
put it aside.
Repeat the whole process for another part of the object bellow
separation line. if there is more than separation line, you will have
to do it for each and every segment.
When finished, assemble parts into the mold and take wax impression.
It will be exact copy except for wax shrinkage with is less than 1
percent. You can minimize shrinkage even more by painting was on the
inside of the molds with the brush. After 3 or 4 layers, assemble the
mold, pour some wax inside and keep rotating the mold until wax sets.
Since dimensions will be defined by first painted layer, the
shrinkage will be practically zero.
There will be casting shrinkage of course, but that can be
compensated by correct sprue design.