Page 21 - ArtMolds Journal June-July 2103 Mod 4
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the alginate even at his wrist. Looking into the mold, I couldn’t see any damage to the alginate. (Photo #2). However, once Alastair had removed his arm, the algi- nate compressed under its own weight, settling about an inch. (Photo #3) We went ahead and filled the void with plaster. As I had suspected, when we took the plaster arm and hand out of the mold (Photo #9), the fingers   Proving that chaining your block molds can prevent ‘duck beak’ syndrome. were flattened. What was needed was a way to lock the alginate in place so that it didn’t slide down in the mold and com- press. My first idea was to construct baffles inside the tube, and I may still try this. But it occurred to me that there was a simpler solution that just might work. What I did was suspend three lengths of chain in- Photo 8. If you look at the edge of the tube where the alginate  side the tube from top to bottom. “Three” was a guess; meets, it is almost level with the rim. Compare this with photo  just seemed like the right number. I suspected that the number 4 and you see that with the chains installed the alginate  alginate would flow between the lengths of the chains did not compress  down  into the tube mold even with the arm  and lock the alginate in place. (See photos 5 — 9.) As removed.  you can see from the last photos, the alginate did not compress and the fingers were that much the better. I didn’t try this system on a leg. Although I am confi- dent it will work, I see three problems. The first is that the bottom of the mold will have to be large enough to contain the foot, making the construction of the tube more complex. The second is that because the foot will be more difficult to be extracted through the ankle void than a hand is through the wrist, it may be necessary to make a cut in the alginate from the heel up to about mid calf. The last problem is that there is such a difference in cross section between the ankle and the thigh that it will take a great deal of alginate to do a leg casting this way. So legs, I would probably use a skin mold. If I need- ed to make multiple copies, I could either make the skin mold of the model in skin safe platinum cured silicone rubber or I could make a plaster, in the alginate mold and make a rubber skin mold from it. The type of rubber Photo 9. Note the distortion of fingers on the hand on the left. It is  in this case; latex, urethane, platinum or tin cured sili- even more noticeable when viewed in person. Distorted  fingers  cone, is mostly just the preference of the sculptor are the result of the weight of the alginate mold pressing down on  though each has advantages and disadvantages. Decid- and collapsing the cavities that the fingers occupied after the hand  is removed from the mold. This  is a common occurrence when a  ing on the perfect rubber for a particular application is a hand casting goes beyond the wrist and up the fore arm as the  discussion for another time.  weigh of the alginate builds the more of the arm that is captured  in the mold.  The  hand on the right was cast in the mold using the  Dave Parvin is a Denver area sculptor who may be reached supporting chains and show no distortion as the chains supported  at [email protected] but who much prefers to talk the alginate in the tube prevented its weight from collapsing the  than type (720) 971-0824. fingers.  June | July 2013 ARTMOLDS JOURNAL | 21 
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