Monday, May 21, 2007


The Open Studio Weekends were happily successful in terms of attendance, pace & sales. I used the castings to demonstrate the process verbally which I can now share from the photographs I've made as I have polished & molded them in the week since.

I spent a great deal of time & care in the finishing processes to develop the "complexion" of their surfaces without disturbing delicate details. Much attention was paid to the interiors, which will help the mold quality as well as sweeten the sound by fining the proportions in a way almost impossible to perceive in the wax.

I can actually hear the resonance now that they are translated into metal... but that is affected unduly by the fact the sprues add considerable weight which will ultimately be gone.

Polished interior surfaces will allow smoother release of the wax injection from the mold...

[Note: Click on the photographs to view at larger size...]

Notice the tidy new buttons replacing those crude ones used for the first casting... These will connect tightly to the nozzle of the injector shown at the bottom of this post, if your curiosity is impatient. They will build that capability into the molds which are next to be made in this series of rather technical processes bringing the designs into production.

I use a silicone rubber, which comes in strips protected by sandwiching layers of slick thick paper which curls as it is peeled off the soft unvulcanized sheet .25 inches thick... it resembles putty in texture. It cuts easily with scissors to fit inside the aluminum mold frames, stacking & mushing around the polished master suspended inside but still connected to the outside via the button & sprue.

Since one cannot write on the silicon rubber with any permanence, I embed a tag of brass or aluminum thin enough to emboss identification of the design, which becomes then part of the surface of the mold during the vulcanization process, which takes place under the heat & pressure between the plattens of this press.

At just above 300 degrees... & all the pressure I can build with the screw... the rubber solidifies into a tough flexible solid block surrounding the master inside.

Out of the mold frame the molds await my attentions with a scalpel to cut this block open in such a manner that it will release the metal master & then fit tightly back together again.

Beginning at the cavity left by the button I follow the sprue into the block with my knife... cutting the keys which will lock the two halves back together. I must "think inside out" as I prepare this solid rubber version of what is negative space in the normal world.

This becomes a birthing process of sort... leaving the space shaped by that master, ready & waiting to become filled, with melted wax this time... again & again... making production copies of this design in wax. A wax which makes the plaster waste mold, as described in the previous post. Remember that a wax is melted for each metal bell, hence: "lost wax casting".

I used toothpicks to keep the springy rubber half cut mold open enough to make the photograph.

The wax injector is simply a tank of molten wax with a tight lid & under pressure from an air compressor or even a bike pump... it only uses about 4 psi. By inserting the pressure sensitive nozzle into the button/receptacle of the mold which is held tightly together with both hands, one pushes to allow the wax to enter & fill the mold. After several minutes to cool & harden the mold is opened to release the wax, which must next be touched up to repair the parting lines left by the mold seams.

The bell mold has three pieces... one pulls out of the core of the bell first, while it is being hugged securely by the outside halves.

Here the molds lay open to expose the injections...

This is the resulting production wax, prematurely assembled for one more portrait of thois stage in the new life becoming the SEA HORSE Bell.

The molds are now at the foundry & I am anxiously waiting for the first prototypes in silver... savoring my anticipation to actually hear its voice at last. Because all these processes change the bell's size & proportion due to shrinkage, from hot to cold in both wax & metal, this then holds the final mystery!

Friday, May 11, 2007


The new designs, of which I've shown the waxes in recent posts, have been cast in sterling silver to become the masters from which I will make the vulcanized rubber production molds. It is always such a relief to see that translation securely made... many disasters can befall this process.

Ordinarily the foundry would saw off the conical buttons from the sprue, that connecting rod, which was the channel that allowed the molten metal to flow into the "waste-mold", made by pouring plaster around the wax inside a cylindrical stainless steel flask. That flask is put into a kiln to melt out the wax, thus effectively destroying my carving! The work, however, is temporarily retained as a negative cavity inside the plaster. There is only one opportunity to replace it with metal... hence the term 'lost wax casting"...

When the process fails I am required to start all over again on a new wax!

The buttons in this position demonstrate how their weight helps push metal into all the details & furnish a reservoir while the metal shrinks during cooling. Being the last to solidify, that mass takes the stress & distortion inherent in the changing states from liquid to solid. They will be replaced later with smooth buttons for the molding process...

As we look into the interiors of the bells, anticipating the sounds they might make when relieved of all the extra weight in the buttons & sprues, we can enjoy the show of fiery visuals involved in the moments of the actual casting process. These photos show James, proprietor of OutCast & Company, during a pour for a vacuum cast. [We also use a centrifuge for some castings.]

After bringing the metal to melting temperature inside the blast furnace, one sees him taking the flask out of the oven with tongs & placing it on the vacuum table . The crucible is then lifted out to pour fiery metal into the cavity of the plaster mold flask while the vacuum draws the air out ahead of its passage to prevent loss of detail & encouraging a dense casting.


All looks good, but one never knows until the flask is broken open to reveal the result. A period of glowing meditation &/or nervous anticipation is required while the last of the flame keeps the button molten until the interior metal has safely solidified...

I leave you with the knowlege that the process was successful since you saw the masters at the top of this post. Next I will polish the masters & make the molds, hopefully taking time to make photographs to continue sharing these technical aspects of my work.

Being a Double Leo explains my joy in such fire!