Magmatic Emergence By James W. Garthe Anticipating the arrival of our third grandchild, I decided to produce a sculpture to symbolize her worldly existence and to create a piece that hopefully will become a meaningful part of her life as she grows and develops. Overview of the Piece The artwork that came about combined a cast aluminum hand with a highly polished rock sphere. Called Magmatic Emergence, the two-piece sculpture depicts the near perfect fetus of our granddaughter being caressed in her paternal grandfather’s seemingly indestructible hand as he releases her from the earth’s viscous magma that has served as the amniotic fluid of her creation. The Epidosite Sphere The sphere was made from a mineral, called epidosite, found in Warren County, New Jersey. The area near a reservoir was scoured looking for the rock, which I wanted to exhibit a pistachio-green color; it also had to be solid and free of extraneous cracks. The heavy stone I found stretched my daypack to its limit, yet despite this weight clawing at my shoulders I was in rockhound heaven. Epidosite is a type of granite which is fine-grained, igneous (volcanic…or one could say magmatic) and rich in silicon, which gives it its shine. This sample is over 500,000,000 years old. Looking at the piece, the mottled green mineral is called epidote; the black is hornblende, a type of amphibole; the white to gray is quartz; and the salmon-pink spots are feldspar. The sphere-making process started by using an 18-inch diameter diamond saw to cut the rock into a cube. Clear mineral oil was used as a cutting fluid to lubricate the blade and keep it cool. Corners of the cube were sliced off with 12 additional cuts, forming a geometric shape called a chamfered cube. Next, remaining corners were smoothed using a high-speed diamond grinder until by eye a spherical shape emerged. The rough sphere was next inserted into a machine having two motor-driven spindles with a cast iron pipe cap on each end which partially encircled the sphere. A coarse silicon carbide abrasive (36 grit) and dripping water were applied to the rotating caps. Successively finer silicon carbide grits (80, 220, 600 and 1200) and more water were used until the rock was perfectly spherical. Polishing was done with optical grade cerium oxide, the same material used to polish eyeglass lenses. Cerium oxide and water were mixed into a paste that was applied to diaposed polishing caps, leather on one side and a PVC pipe fitting on the other. Making this sphere took about five hours from start to finish. Producing the Cast Hand To start with, a pattern in the likeness of the finished piece was made using Accu-Cast 570-PGV alginate. Having used this material a year earlier on another hand casting project gave me the confidence to mix the alginate and plunge my right hand in without trepidation. After the cure period, my hand came out and molten candle wax went in. Once the solidified wax hand was freed from the alginate, a plywood form was fashioned around the wrist to create a puddle-looking base. Webs were built up between fingers, drips were added to the underside of the hand, and the hand was again dipped in hot wax to coat the finger tips. I’ve long wanted to practice lost wax casting and now was my chance. I purchased 10 pounds of castable ceramic powder, and after mixing the powder with its liquid activator, I coated the wax sculpture with this paste. After a couple days the entire piece was placed upside down in an oven to melt the wax and fully cure the coating so it would withstand the 1400ºF temperature of molten aluminum. In my coal-fired furnace, I melted scrap aluminum castings and poured the liquid metal into the cavity left by the wax. After the aluminum cooled, the ceramic mold was chiseled off and discarded. Adding finishing touches to the casting took about six hours. Several rotary burrs, rifflers (small files) and emery cloth were used to refine and shape the casting. To help create the impression that lava was clinging to the uplifting hand, I dripped oil-based paint on the outside of the casting, while the iridescent look was created by sponging acrylic paint over much of it. Fingertips were polished with a cloth buffing wheel and rouge. Lastly, the title and other information was stamped into its underside, while a piece of black polyester felt was glued to the base to make a scratch resistant surface. Closing Comment Thank you for taking the time to read this and thank you also for a terrific casting product…I have enough alginate remaining to make one more sculpture (but no grandchild to present it to yet), so stay tuned! James W. Garthe 4774 Eberle Road Petersburg, PA 16669 (814) 667-2409 firstname.lastname@example.org
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