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Finial casting question

Hello Orchid Friends - About a month ago I asked a question
regarding materials used for Japanese cloisonnE9 vases. I had been
asked to create missing lids for two of them. At that time I
received many good Orchid suggestions that sent me in the right
direction for my answer. [Centuries ago Chinese vases were enameled
on bronze or brass but they later switched to copper. When the
Japanese began enameling vases, copper was firmly established as the
base metal in the finer pieces.]. Now that the project has become a
reality I find myself in need of additional

The little lids that I will be producing each have a small finial
shaped like a tiny chrysanthemum bud approximately .32" x .37". I
was given a finial from another vase to use for reproduction
purposes. I have 2 issues:

The finial / vase is over 100 years old. This small item has a
patina that I can’t mess with. It also has definite gunk that I know
must be carefully removed or I will be reproducing that antique gunk
in the new finials. This is the lessor of my problems.

Secondly, I’ve been told by the castor that if he uses vulcanized
rubber for the mold, we will get shrinkage and the surface of the
original will probably have a color change. I can’t live with that!!

The original seems to be made of a pinkish bronze or copper. There
are small areas visible where gold plating has been worn away.

Below are snips from the archives mentioning materials that may do
the job [small amount of shrinkage] but my main question of a
possible color change to the original metal doesn’t come up.

HELP! What is the answer?

I have taken some liberties in editing:

From Bill Mull, Zero-D Products, Inc: You can accelerate a
platinum cure silicone’s set time dramatically with the application
of heat. You will give up a little in shrink, but you can cure a
mold in 1/2 hour or less… The shrink of platinum cure RTV is under
1/10 of 1% if cured at room temperature,

silicone. Shrinks less than vulcanized rubber, for the most part…
It doesn’t oxidize silver masters… You need a vulcanizer that will
get hot enough. You need a metal master.

Silicone RTV] Silicone RTV is initially costly, but it makes a
permanent mold (unlike the less costly urethane RTV which tends to
revert over time, especially in moist regions). RTV molds do have
some small percentage of shrinkage…

shrinkage, item # 160-135 from Swest, 15 min cure time, and works
well, but don’t think anything reproduces detail like Exaflex. You
can use QS in a mold frame and cut out like vulcanized rubber.
Thomas Blair

silicone mold materials] All have virtually no shrinkage and are
contaminated by sulfur and gum rubber contact. Shelf life of about
two to three years… L RTV - Light green silicone. The best jewelry
mold making silicone available. Pours, cuts and injects great. My
silicone standard to compare all other silicones to. I guarantee if
anyone tries this silicone they won’t go back to anything else.

a kind carved waxes and pieces that need a mold with 0% shrinkage
(keep in mind that some injection waxes can cause more shrinkage
than some mold rubbers).

Michael Knight at CASTALDO…We have a excellent RTV rubber
[CASTALDOAE LiquaCast 0% Shrinkage RTV Liquid Jewelry Molding
rubber] similar to Silastic but not thick as tar, not frightfully
expensive, not easily torn and lacking in strength, not hard to mix,
hard to de-bubblize and not hard to use. And not a silicone - a
newer technology.

And from a different post from Michael speaking of Quick
Sil…Firstly, the rubber is not a liquid and thus is not wet and
will not wet. It is a clay-like putty. Secondly it sticks to
nothing, not even itself.

Karla you need to talk to a metals conservator before doing anything
to the piece. This sounds like it may be a historically important
item and it should not be cleaned or otherwise messed with without a
through understanding of what you are doing. A simple cleaning of
the “gunk” could possibly reduce the value of the item
significantly. Don’t apply any molding compounds or do any cleaning
without talking to a conservator.

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160

Member of the Better Business Bureau