Replicating gold wedding bands

Jewelry Discussion
1

Hello All,

I am relatively new to the industry and have come accross a simple
request that I’m not quite sure how to do. I’ve been asked to
replicate 2 14K gold wedding bands for a couple. One has a fancy
design all the way around, the other is plain. I’ve only ever cast
from a wax model so…I know I must start by making a rubber mold.
I’ve searched blogs and forums but all I’ve found is lots of
based on making rubber molds using wax models or mock
pieces. Maybe I’m over thinking it, or not thinking it through
enough, either way, I can’t seem to wrap my head around it. This is
where you experts come in!

My questions are:

  • What material would the sprue need to be made of?

  • Typically the sprue is soldered on, however if I solder it on the
    "original" piece wouldn’t I be damaging it?

  • Where would I place the sprue on the band that has the design all
    the way around without affecting the design in the mold? Any guidance
    you can give me would be most appreciated. Thank you.

Patricia Marrone
TanzMania Gems

2

Hi Patricia,

Yep you are over thinking is a little.

If you want to make a cast copy of the rings that’s easy enough to
do.

Use a cold set rubber, the sprue can a thin dowel and some
mold-a-wax. The mold-a-wax can also attache the wooden sprue to the
ring.

Sprue placement, you can sprue on the inside of the ring, this way
you only have to clean up the inside of the band.

Once you have made your mould, you can remove the sprue from the
ring and store it some place safe.

Now you have rubber mould that you can pour, or inject wax into. You
will need to clean up the wax, for investment and casting.

Regards Charles A.

3

Hi Patricia,

Once you have made your rubber mold you can cut the sprue and or
vents into the rubber with a sharp blade, instead of soldering it to
your model. On the ring with the patterning, if the pattern is thick
enough place the sprue entrance on one of the raised parts of the
design.

The part I would be concerned about is how delicate the patterning is
and if you can get a good mold of it.

Best of luck!
Christine

4

Patricia- When we mold a band with the design all the way around we
sprue to the inside of the shank with a sprue that looks like a
candy cane. We usually use a piece of brass rod. You can solder or
not. If the rod is not soldered and shifts a little away from the
model you can just use a heated wax tool the burn away the little bit
of rubber that is between the sprue and the model.

The hard part is cutting out the mold without scratching too deeply
the pattern on the carved band with the scalpel.

You could also try making an RTV cold mold. It’s clear and easy to
see what you are cutting out the mold and you can use a wax srpue if
you want. RTV molds don’t have the long life that rubber molds do,
but if this is a one time thing an RTV mold will work just fine.
It’ll save you having to buy a vulcanizer.

Have fun and make lots of jewelry.
Jo Haemer
www.timothywgreen.com

5

Patricia,

There are 2 basic types of molds, and lots of mold materials in each
category. One uses a vulcanizer, using heat and pressure to cook the
rubber in a heavy usually aluminum frame. It is fast to do. The
other type is a room temperature mold, which is just poured and
vaccumed. This type will mold anything that can’t take the heat and
temperature. It just takes longer ( sometimes 16 hrs.) to fully
cure. Look for low or no-shrink products.

The vulcanized molds will need an soldered-on sprue to hold up to
the vulcanizing, but the room temp. molds can just have an epoxy
glued-on sprue.

If you’re concerned about messing up the pattern on the outside of
the band you’re needing to mold, why not make a small “L” shaped
bend in your sprue, and solder it into the inside of the band
instead? We use 3/32 brazing rod from a welding supply store for our
sprues, as they will fit perfectly into our sprue formers ( which fit
our model of wax injector ).

Good luck!
Jay Whaley

6

Hi Charles

Actually making a mold of a continuous ring can be challenging. I
have been making molds for 40 years, and sometimes I have to make a
mold several times. Having a wax come out without voids sometimes
takes a bit of work to cut a mold enough to allow the air to escape
for complicated patterns.

I try to make a mold so the wax does not need to be cleaned up, that
usually causes problems.

I use vulcanized rubber molds, I am old school. Disadvantage is a
tiny bit of shrinkage, but no customer has had an issue with
replications I have molds I made 15-20 years ago.

How the mold is cut to allow air to escape is crucial to eliminate
mold lines. That is when having to remake a mold is the solution.

Sometimes I have to use hard solder and very, very carefully build
up the edge of the band, and then I use easy solder on the sprue, and
very, very carefully solder the sprue only allowing the easy solder
to melt.

Sometimes I solder the top of the sprue to the underside of top of
the ring, and solder the bottom edge of the ring so there are two
points of contact.

Richard Hart G.G.
Denver, Co.

7

Hi Richard,

I was trying to remove the demon from the job :wink:

I use cold set, and probably would use vilcanised rubber as well, if
I had access to the proper tools.

Today there are many cold set rubber formulations, for a multitude
of purposes that would suit our industry.

The main issue with the cold set rubbers is that they cost more than
vulcanised rubbers. The main advantage is that heat sensitive
materials can be moulded as well.

Correct me if I’m wrong (my time making moulds isn’t as long as 40
years), but I would think that for the ring in question the mould
lines would be on the edge of the ring, maybe a three part mould.
Because I make my moulds in sections I don’t cut the original out of
the mould, so I can place the parting lines where I want them to be.

When I make a mould from an artefact I can’t afford to damage the
original.

I liked the two points of contact, that’s nifty, and I hadn’t
thought to do that myself.

Regards Charles A.

8 
Sometimes I solder the top of the sprue to the underside of top of
the ring, and solder the bottom edge of the ring so there are two
points of contact.

Don’t think this part of my post was clear,

Sometimes I solder the top of the sprue to the underside of top of
the ring, and solder the bottom edge of the ring to the side of the
sprue so there are two points of contact.

Richard Hart G.G.
Denver, Co.

9 
Correct me if I'm wrong (my time making moulds isn't as long as 40
years), but I would think that for the ring in question the mould
lines would be on the edge of the ring, maybe a three part mould.
Because I make my moulds in sections I don't cut the original out
of the mould, so I can place the parting lines where I want them to
be.

When I make a mould from an artefact I can't afford to damage the
original.

A couple of points. First, making a mold of a wax is not the best
idea if you are making a model for production, a wax model can not be
cleaned up and polished like a metal model.

When cutting the vulcanized mold with a metal model in it (I have
only made a vulcanized silicone mold about 3 times in 40 years and I
think one or two room temperature molds) it is very important that the
cut from the object be a strait line toward the outside edge for at
least the first 1/2 inch, then do the zig zag mold locks to the
outside edge of the mold. This and proper air vents will reduce the
mold lines to barely perceivable for most pieces.

Most people do not understand how many air vents are needed to get a
clean wax model. Any recessed areas need a way for the air to escape,
and there needs to be enough cuts to allow air to escape to the
outside.

I have made a few three piece molds, but three piece molds are rare
for jewelry. Usually it is a core for a hollow piece and it is
actually a piece of rubber that is prepared with silicone spray and
talc and stuffed into the space in a coil that when vulcanized can
be pulled and removed without destroying the wax model. Think
filigree ring where the top of the ring is like an upside down bowl
and the material in the shank is cut in a spiral. Open the mold
after filling with wax, and the rubber in the center of the shank
pulls out first, the last part of the core goes up into the upside
down bowl and spirals around to the top of the inside of the bowl.

To me, mold making is an art form and as important as the wax
carving skills. After much time is spent being so accurate in the
carving, reproducing that model as accurate is important. No mold
lines and no flashing.

Why this is do important is that the clean up of a wax from a well
made mold is minimal.

And I love the process of how the mind has to approach picturing the
model in the mold and figure out what needs to be cut so the stress
of pulling the wax out of spaces does not pull the wax apart. To me
it is a form of meditation. On some items I have to meditate twice.

Richard Hart G.G.
Denver, Co.

10

IF this is for a “one of” have you thought of using Delft Clay? I
viewed the videos on using it on YouTube.

I’ve also viewed a Delft video at
http://www.ganoksin.com/gnkurl/ep7z3l

which shows casting a ring and placement of sprue holes. Seems
faster, quicker and more accurate than lost wax casting.

Michele