For my first attempt at this project, I used alginate to create the mold of my finger then poured concrete to cast the shape. The mold was mixed in a ratio of 2 parts water to 3 parts alginate powder. Then, I stuck my finger into the mold and held it there until I felt the algniate harden. After mixing the concrete according to the instructions on the package, I poured the concrete in. I held the screw in the concrete until it hardened, since I knew it would harden relatively quickly (Figure 1). Later in the day, I returned to remove the finger from the mold. However, I found that the shape was still wet from the alginate releasing the water over time. I tried to remove the finger still but the screw broke off from the rest of the finger. So, I repeated the process but decided to use Plaster of Paris as my casting material instead.

Figure 1. Concrete in Alginate Mold

I repeated the same process described earlier with Plaster of Paris instead of concrete (Figure 2).

Figure 2. (top) Ingredients For Mold, (bottom) Shaping the Mold

I had much better success with removing the part with this material. However, on one of my fingers I did not ensure that all the bubbles were removed so I ended up with a divot under the ends of one of the tips of the finger along with small bubbles (Figure 3). To avoid this in the future, I could use a vacuum to remove the air from the plaster, swirl around a small amount of plaster in the bottom before filling the mold, or bounce the cup against the table to bring the air up.  After removing the fingers from the mold, I left them out for a couple hours to dry completely. Lastly, I spray painted the shapes blue because I thought the fingers looked creepy and I wanted them to look less real. 🙂 

 

Figure 3. (Top) Fingers after removing shapes from mold, (Bottom) Final Shapes

It took me approximately 2 hours to create the mold, pour the plaster, remove the shape, and post process the shape (not including waiting time). Working at $12/hour labor costs would be $24. A large tub of Plaster of Paris costs $6. I used a small fraction of this, but will estimate the plaster cost to be $0.50. A can of spray paint costs $4. I used a small fraction of paint, but will estimate it to cost $0.50. 20, 8oz disposable measuring cups costs $9, so the 3 cups I used costs $1.35. There was no machine time required for this project. The total cost of this project is $24 + $0.50 + $0.50 + $1.35 = $26.35.