The Process
For this homework assignment, we were tasked with creating finger hooks made out of Plaster of Paris. To do so, we had to create molds using alginate, the same materials used to make dental molds.
To make the mold, we began by mixing the alginate with water. I used 33g of alginate powder in 125 mL of water, and made sure to mix this thoroughly. Next, I placed my finger in the cup and waited approx. 5 min for the mold to cure. Once I felt some resistance in trying to remove my finger, I knew it was ready, and continued to slowly retract my finger from the mold. I was able to appreciate a well-formed, finger-shaped left behind in the space my finger occupied.
Next, I prepared the plaster by mixing 40g of Plaster of Paris into 20 mL of water. Once this became a more consistent solution, I poured it into mold, ensuring the plaster solution filled the hole to the top and with slight overflow. After tapping the cup on the table a few times to knock loose any air bubbles that may have been present, I lowered in my screw head approx. 0.5 cm below the surface of the plaster. The screw tip was then taped to a 3D printed jig that was provided at the beginning on the workshop (thank you TAs!).
After repeating the same set of steps for my second finger, I set the plaster and molds aside to cure and returned the following day to remove them from the alginate molds. I was happy to see that they both turned out very well!
For post-processing, I broke off the excess, unwanted plaster and gently sanded the bases of the finger to smooth out the edges. I then used purple/violet spray paint to add color to my creations, followed by a clear coat of spray paint to give it some final gloss.
Overall, my pieces turned out great! I am still unsure where I may put them, but I will have fun in trying to figure that out.
Before leaving the OEDK, I made sure my workspaces were clean and ready to be used by the next person.
Reflection
This was my first time casting and molding, and I am already looking forward to the next time I get to do something similar (the final project, I suppose). For the finger, I created in class during the tutorial, it did not turn out, as there was a pretty significant defect of hole at the tip of my finger where it curved up the most. I believe there was an air pocket got trapped when pouring in my plaster. In making my subsequent molds, I made sure to tap the cup to the table to try tp knock loose any air bubbles, and also used a popsicle stick to try and push the plaster to the distal tip to the mold. I also had less a curve to my finger when recreating new molds to help prevent.
Another challenge I encountered when during cast removal once the plaster had cured. The first time, my alginate mold ripped, forcing me to make other one which took additional time. Again, I think this was caused by the aggressive curve of my finger when creating my initial mold. In the subsequent times, when the less curved finger, they did not rip.
Therefore, the things I would/will continue to do differently include:
- Less curve of the finger to prevent air bubble trapping and mold ripping.
- Tap the plaster down during and after pouring into the mold.
- Use the smaller cups (as they better fit the 3D printed rigs and added less strain to my positioning when placing my finger in the alginate)
- Explore other painting/staining/coloring methods!
Cost Estimate
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | Alginate mold powder
Plaster of Paris
Spray paint |
$13.99/bag
$7.99/tub
$5.98/can |
Joann
|
1 bag
1 tub
2 Cans |
$13.99
$7.99
$11.96 |
| Labor | Casting, Molding, and Post-Processing Engineer (me) | $20 /hr | Zip Recruiter | 2 Hour | $40.00 |
| Total | $73.94 |
As I gain experience, I would be able to make more finger hooks in a given period of time, as familiarity with the process will help make me more efficient. Additionally, this process it easily scalable, with the limiting factor being the number of fingers available to create molds from. The quality will also increase, as I will be able to better identify which parts of the process create flaws and may be addressed with other techniques.
