For this week’s assignment, I embarked on a unique and creative journey—making two identical wall hooks using molds of my own finger. This hands-on (pun intended) project required precision, patience, and a touch of artistry. Here’s a step-by-step breakdown of my process and the lessons learned along the way.

Step 1: Creating the Alginate Mold

The process began by preparing the mold material, alginate, known for its quick-setting and skin-safe properties. I mixed 33 grams of alginate with 115 grams of water in a silicone mixing cup, stirring continuously for about five minutes. The consistency was key here, ensuring it was smooth and lump-free.

Once the alginate was ready, I submerged my index finger into the mixture, holding it steady until the mold hardened. This step required patience, as any movement during the setting process could compromise the mold’s detail. Once solidified, I carefully removed my finger, leaving behind a detailed impression ready for casting.

Step 2: Mixing and Pouring the Plaster

With the mold prepared, it was time to create the plaster. Using a 3:1 ratio of plaster of Paris to water by volume, I mixed the ingredients until achieving a consistency slightly thicker than pancake batter. It’s crucial to ensure the mixture is lump-free for a smooth finish and when holding the popsicle stick out of the mixture there would be no drips.

I then poured the plaster into the alginate mold and inserted a screw into the center of the mold. The screw served as the mounting mechanism for the wall hook. To keep the screw in place during the setting process, I taped it to a popsicle stick and balanced it atop the mixing cup. This setup ensured the screw remained securely positioned.

Step 3: Repeating the Process

After allowing the plaster to set overnight, I carefully removed the first plaster finger mold. Unfortunately, removing it caused some degradation to the alginate mold, resulting in flakes that affected the surface of subsequent casts. Despite this, I repeated the process to create a second finger mold, following the same steps as above.

Step 4: Post-Processing the Plaster Fingers

Once both plaster fingers were ready, I moved on to post-processing. I sanded the sharp edges and imperfections using 400-grit sandpaper, smoothing out areas where the alginate mold had caused surface irregularities. After sanding, I wiped each piece with a damp paper towel to remove plaster dust, preparing them for the final finishing touches.

Step 5: Painting and Sealing

The final step was to give the wall hooks their finished look. I applied three coats of blue spray paint to each finger mold, allowing 20 minutes of drying time between coats. To protect the paint and provide a matte finish, I added three coats of matte clear coat, again with adequate drying time between layers.

Step 6: Clean Up

Lastly, I ensured to clean up any areas that I used to complete this assignment. I used loading dock space for spray painting, and I made sure to clean my mixing cup and return it to the BIOE 555 table. See images below for clean workspaces.

Final Thoughts

This project was a fascinating exploration of molding and casting techniques. While the process was straightforward, it taught me the importance of precision in mixing materials, patience during setting times, and problem-solving when imperfections arise. The result: two custom wall hooks that are not only functional but also uniquely personal—a literal extension of myself.

Cost Analysis

Cost Type	Cost	Price	Source	Quantity	Total
Materials	Alginate	$18.99 /1.5 lb.	Amazon.com	0.073 lb	$0.92
	Plaster of Paris	$22.55/8 lb.	Walmart.com	0.2 lb	$0.56
	Screws	$9.47/153ct.	HomeDepot.com	2 screws	$0.13
	Sandpaper	$6.98/ 4ct.	HomeDepot.com	1 sheet	$1.75
	Blue Spray Paint	$5.98/can	HomeDepot.com	0.1 can	$0.60
	Matte Clear Coat	$5.98/can	HomeDepot.com	0.1 can	$0.60
Labor	Injection Molding Operator	$18.00/hr	Ziprecruiter.com	1 hr	$18.00
	Prototyping Engineer (You!)	$13.00/hr	Personal Charge	1 hr	$13.00
Overhead	Facility Cost (Machine Time)	–	–	–	–
	Quality Control	$34.07/hr	Zippia.com	5 min	$2.83
Design	Engineering and Development	$37.08/hr	Zippia.com	5 min	$ 3.09

 

Total Cost for BOTH Finger Wall Hooks: $23.48

Total Cost of SINGLE Finger Wall Hook: $11.47

 

The cost analysis presented considers the materials used for the product and incorporates a labor charge comparable to the hourly rate of an injection molding operator. Facility costs were excluded, as this project could feasibly be completed at home without the need for specialized infrastructure.

From a manufacturing perspective, where injection molding is the primary production method, the cost structure would differ. While initial machine costs are significant, the efficiency of mass production would significantly lower the per-unit cost. Additionally, the engineering and development time for this assignment was minimal—limited to the selection of a finger for the mold and calculated at approximately five minutes. In a large-scale manufacturing scenario, however, the design process for an injection molding machine would require considerable time and resources to ensure optimal production efficiency.