This past week, we worked on molding and casting. We used alginate and plaster to mold our fingers into wall hooks!
- Creating the mold: For the mold, I used 33 g of alginate and 125 g of water to start off my negative. I used a popsicle stick and a silicone cup to create the mixture. I placed two of my fingers inside the alginate for 5 minutes as it hardened. I carefully removed my fingers which resulted in the mold.
2. Creating the cast: I used a 2:1 ratio of plaster to water for creating the positive of my fingers. I estimated how much plaster to used and poured it into the mold. I also placed a jig with two screws into the paster so that it would be connected and would allow me to screw it into the wall. I removed the plaster from the mold about 1.5 days later to allow for it to dry as much as possible. I removed it from the alginate by carefully breaking apart the mold around the plaster and got the fingers shown below.
3. Post-processing: When I removed the fingers from the alginate, I saw that the fingertips were still wet. Part of the fingernail also was chipped while I removed it since it was still wet. I let it dry for a day before spray painting them blue shown below.
Clean Table:
Reflection: The first time I tried to mold and cast my fingers, the alginate dried much quicker than I realized and I had to stick my fingers into the gel very quickly. It dried very soon after and I didn’t have any issues pouring the plaster. However the next day, when I was trying to remove the plaster, I was pulling on the screws and the jig and the screws broke off the plaster. I then realized I needed to remove the alginate from the cup first before breaking away the alginate. This helped me better understand the best methods for demolding plaster from alginate and I was much more successful the second time around.
Cost Analysis:
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | Alginate | $19.99/450 g | Amazon.com | 33 g | $1.47 |
| Plaster of Paris | $10.19/8 lb | Amazon.com | 30 g | $0.08 | |
| Silicon cups | $9.99 for 4 | Amazon.com | 1 | $2.50 | |
| Popsicle sticks | $7.59 for 60 | Amazon.com | 2 | $0.25 | |
| Screws | $11.99 | Amazon.com | 2 | $0.24 | |
| Spray Paint | $5.95/can (12 oz) | Homedepot.com | 0.25 oz | $0.12 | |
| Labor | Prototyping Engineer (You!) | $36/hr | ziprecruiter.com | 2 hrs | $72 |
| Overhead | Outdoors | None | myself | 2 hrs | $0 |
| Total for one round of molding and casting: | $76.66 |
