COUNTING TO 12 | ENGI 210: Prototyping and Fabrication

new fingers

In molding and casting my fingers, I first needed to measure an appropriate ratio of alginate to water (1:4.5 by weight). Following the provided instructions, I used a scale to measure 1.5 ounces of alginate and 6.75 ounces of water.

Image 1: The Measured Water (Left) and Alginate (Right)

After these quantities were measured, I then proceeded to mix the two, adding water to the alginate. After I decided the two formed a solution, I stuck my right index and middle fingers in and waited.

Image 2: My Fingers In the Alginate Solution

After a short talk with a friend, I decided that it had been enough time and took my fingers out of the mold.

Image 3: The Alginate Mold Without My Fingers

To cast my fingers, I measured out 53 grams of Rockite and 15 grams of water (preserving the 3.5:1 by weight ratio). Before mixing the two, I used a screwdriver to drive two screws into the provided 3D-printed mixture. Afterward, I mixed the Rockite and the water and poured the solution into the finger holes.

Image 4: The Alginate Mold With the Rockite Solution Poured In (And Screws and Fixture In Place)

-2, +2

When I came back, the Rockite solution was set, allowing me to take out my fingers. Unfortunately, due to how I placed my fingers, they weren’t exactly identical. Moreover, the screws were terribly off-center, causing them to protrude out of the mold.

Image 5: My Initial Finger Attempt

Given that my alginate solution was beginning to release water, I decided to throw my Rockite fingers and alginate solution out and start again. After I repeated the whole process, I decided to use two fixtures this time- one for each finger. I hoped that this idea would help me center my screws more accurately, as I could independently control the position of each screw. However, when I took my Rockite fingers out again, I discovered the heads of the screws were still showing, leading me to conclude that it was due to my finger placement in the alginate (weirdly diagonal) that led to this mishap.

Image 5: My Second Attempt

Nevertheless, I continued, sanding down the bottoms of the fingers. With the bottoms now smooth (or smoother, anyway), I spray painted my fingers with light blue spray paint and left them to dry for the night.

Image 6: The Fingers Drying

Coming back, I gave them a light sanding to remove spray painting artifacts and gave them another coat of spray paint. Unfortunately, while doing so, I accidentally sprayed a glob of paint onto one of my fingers. Thus, in an attempt to fix this, I sanded off the excess paint before applying an actually good coat of spray paint. As you may expect, this sanding also removed a lot of the detail of my fingers, which was saddening.