This week, I learned molding and casting and used these newly acquired skills to make finger hooks.
First, I made an alginate mold using 28 g of Perfect Mold Mold Making Material (Figure 1) and 4 oz of water. To combine, I stirred the mixture vigorously to remove most of the clumps (Figure 2). Once the mixture was relatively smooth, I stuck my middle and pointer fingers into the mold (Figure 3).
Figure 1: Perfect Mold Mold Making Material package
Figure 2: Stirred alginate mold
Figure 3: My fingers in the mold
After letting the mold solidify for about 5 minutes, I carefully removed my fingers to reveal a negative mold.
Next, I prepared the Plaster of Paris by creating a 2:1 solution of Plaster of Paris to water by volume. I combined roughly 30 mL of water with 60 cm^3 of Plaster of Paris (Figure 4). I then poured the mixture into the alginate negative. Lastly, I rested two flat-head sheet metal screws at the top of the cast such that the hook could be screwed into a wall in the future (Figure 5).
Figure 4: Stirred Plaster of Paris mixture
Figure 5: Poured cast
On my first iteration of these hooks, I let the Plaster of Paris sit in the mold overnight. When I came back the next day, the alginate was wet and the plaster was very brittle. As a result, the fingers broke into several pieces. Additionally, I noticed divots on the finger pad areas, indicating the presence of large air bubbles while the plaster was hardening (Figure 6).
Figure 6: Failed first iteration
On my next iteration, I decided to make some procedural changes in response to the problems with my first iteration. First, I decided to slowly pour the Plaster of Paris into the mold to prevent the formation of large bubbles and to gently tap the filled mold on the table after pouring tap out any air bubbles that may have formed. Additionally, I decided to de-mold the plaster after 30 minutes, since this is how long the instructions said it took for the plaster to set. I figured that the less time the cast sits in the mold, the less time the alginate has to release water onto the cast; in theory, the drier the cast, the less brittle it’ll be.
While my slow pouring idea did help mitigate the formation of large bubbles, I still struggled immensely to keep my casts from breaking as I removed them from the molds. Some other problems I encountered were the screw hanging half out of the finger (Figure 7) and the screw falling into the finger (Figure 8). It took me 3 additional attempts (8 fingers total) to create 2 presentable finger hooks.
Figure 7: Finger hook with poorly-placed screw
Figure 8: Screw fell into cast while hardening (right)
After finally creating two successful casts, I sanded them to buff out some imperfections and round out the nailbeds (Figure 9). After a nice manicure, it was time for spray painting.
Figure 9: Sanding out imperfections
First I primed the hooks (Figure 10), then spray painted them. I was inspired by Sully from Monster’s Inc., so I painted the hooks with a blue undercoat with purple spots on top (Figure 11). With that, my project was complete!
Figure 10: Priming spray paint
Figure 11: Completed finger hooks
Edit: As I was on my way to drop off my fingers at the grading table, I dropped one of them, and it split in half. After taking some deep breaths, I successfully super glued it back together and sprayed it with a little more spray paint to minimize the appearance of the crack. It is now as good as new(-ish).
Clean work station after re-spray painting 🙁
Molding and Casting Cost Analysis
