Tips for Carving wax 2.  Lost wax Casting of your carved wax Ring. 

By Jason Bellchamber www.bellchamber.net/old

Lets go through the steps to create a simple ring design with a pattern going around the band.  I’ve decided on making a design from an art history.  It’s a symmetrical pattern that goes all the way around the band.

1. I decide on the thickness of the band, in this case 7mm and cut a section of the wax tube 9mm wide using a coping saw. 

2. Then I ream the inside of the tube out to the exact finger size I desire, on a mandrel or, in this case my own finger.  This is the only time you should try the ring on a finger.  Once the walls of the ring are less than 2mm thick, it becomes very fragile.

3. Then I use a rasp or very coarse file to bring the edges of the ring down to a thickness of 1.5mm.  I like to make the thickness uniform; it makes for a more comfortable ring. 

4. Once the desired thickness is achieved, I then turn to a finer bastard file to make the edges smooth so that no scratches are visible.   Now the fun begins!  We can start carving our design into the wax.

5. As recommended if this is your first attempt keep it very simple, or even plain, that way you will get a feel for carving the wax and then polishing the cast metal piece.  I have chosen a pattern that repeats itself every three steps, it’s called a Triskele.  I begin by using a compass to lightly score the lines where the pattern will repeat itself.  Then move to a ball burr (or empty mechanical pencil end) to mark the pattern in dots.  Then I connect the pattern using the mechanical pencil scoop.

6. Once the pattern is carved completely, and I’m satisfied, I decide what metal to cast it in.  In this case I decide to make Sterling Silver.  Sterling silver is traditionally 92.5% Silver alloyed with 7.5% Copper.  Fine silver can be purchased at pawn shops or coin stores in 1 oz. wafer or coin form.  Pure Copper can be had from old pipes and fittings. 

7.  Weigh the wax on a scale to a 10^th of a decimal.  Multiply the wax by the specific gravity of the metal you are casting with.  In this case I use 10.5 x weight for Sterling Silver.  Add another 10gms final metal weight for the sprue base.  This excess metal will push all of the molten metal during the cast into the empty mold.

8.  The first part of setting up a wax is to attach/melt a sprue to the ring in order for the molten metal to flow into the hot mold.  The sprew attaches the ring to the Base of the mold and provides an opening for the metal to flow into.  The sprew is a 1.2-2mm round stick of wax that should be a max of 1.7cm long.

9. Once the sprew is attached to the ring the other end is melted onto the Rubber sprue base. 

10.A steel flask is placed onto the mold so that the piece to be cast sits basically in the center of the inside space.  A special plaster commercially known as investment is mixed with water and poured over the wax and fills the flask.  Once it is prepared and hardened it is smoothed at the top and the rubber base is removed from the mold.  Now the wax sprue is the only part visible.

11. The flask Is placed in a Kiln and slowly heated to 1350 degrees and held there for 1 hour.  This nearly gurantees that all the wax is melted or at least sublimated inside the investment.  The Temperature is lowered slowly to the proper casting temperature ~900 for Sterling Silver.

12.  In this case we are using a Centrifugal casting arm which uses a spring to spin.  The centrifugal action quickly forces the metal into the flask.  Before the modern era a cuttlefish bone mold was used on the end of a chain and spinning it by hand would force the metal into the mold.

13. The Metal is metled into the clay cruscible which takes less than a few
minutes. ONce it is completely melted, the hot flask is quickly removed from
the oven and placed in the centrifugal arm. The pin is dropped and the arm
spins the liquid metal into the mold. The visible part of the metal or button
solidifies first since it is the only section exposed to the air. The metal
actually takes about 10 seconds to solidify if it is silver or gold. When the
arm stops swinging the flask is allowed to cool for ~10 minutes to guarantee uniform solidifying.

14. When ready the flask is immersed into a bucket of water and the investment
, explodes off into the water, leaving your metal casting.

12. Clean off the investment from the casting and use a jewellers coping saw to
cut off your piece from the sprue. The Spure can be used over with newer
material next time you cast.

13. Now you are ready to follow the steps in hand polishing your peice. Using
a rough bastard file on a wooden surface, cut the sprue down to the surface of
the ring. Next use your rough sandpaper to clean off the oxidized layer on the
inside and outside of the ring. Next step is using your fine sandpaper to
smooth off any scratches. I find when finishing the pieces by hand that the
grit of the smoother sandpaper comes off and the paper underneath provides a
shiny finish. For a final polish on the cheap I suggest getting the coarsest
paper towel you can find, ie. the industrial brown stuff they use in public restrooms,
it makes an excellent final polish. It's at this point that the surface will start
to gleam and you are finished.  In all set aside 3-4 hours to hand finish your work.

Your initial few pieces should be finished by hand because it will provide you with a feel for the metal that you are polishing.  Metal has a aura of being hard, but when you get a sense of each elements malleablities and properties you will see which one you prefer.

All photos by Jason Bellchamber

2006