Hi everyone. Last week, I made an alginate mold of my finger and cast two models using rockite. Here are the steps I followed to execute this project.
Preparing the Alginate Mold
The first step for this project was to make a negative impression of my finger using alginate. Using a scale and silicone measuring cups, I weighed out my water and alginate in a 4.5:1 ratio. I used 6.8 ounces of water and 1.5 ounces of alginate.
Next, I poured the water into the alginate and mixed until all the clumps were removed.
Alginate mixture
After a few minutes, the mixture became harder to stir. At this point, I put my finger in the mixture in the desired position I wanted the cast finger to be in and waited roughly 7 minutes for the alginate mixture to set.
Waiting for the alginate to set
Casting the Finger
Now that the mold was created, I prepared the rockite mixture used to cast the finger. Using the same measuring cups and scale, I measured water and rockite in a 1.3:5 ratio. I used 10 grams of water and 35 grams of rockite. Once again, I mixed the water and rockite and stirred until the clumps were removed.
Once this mixture was ready, I poured it into the mold I had just created. As I poured, I tapped the measuring cup against the table to try to remove all the air bubbles that may have accumulated in the rockite mixture.
The last step before letting the rockite set was to place the screw about a half inch into the mold. There were 3D printed jigs set up to hold the screws in place in the mold, but there wasn’t enough space in measuring cup I used for the jig to fit into, so I fixed together my own setup instead. Using tape and string, I assembled a makeshift rig to hold the screw in place as the rockite set.
Makeshift setup
De-Molding and Casting the Second Finger
After around 16 hours, I came back to take the first finger out of the mold. It turned out really well and had very fine details! There weren’t really any major protrusions or anything that I needed to sand or file. Even the bottom where the screw was attached came out essentially perfectly flat and had smooth edges.
While the finger looked great, the mold had ripped slightly when I pulled the finger out, likely because the finger was curved and the alginate was releasing water.
Ripped mold
Despite this small damaged area, the rest of the mold appeared to be intact. I decided to prepare another mixture of rockite using the same measurements as the first finger’s and follow through the same steps up until this point.
The resulting finger came out nearly identical, aside from the part corresponding to the damage on the mold. The damage turned out to be present in both finger joints, however I couldn’t see the second joint because I curved my finger and the upper side of the negative mold wasn’t easily visible.
Second finger
To remove the excess material, I used the edge of a file to take away the bumps while also defining the joints. Though I was not able to recover every detail of the joints present in the first finger, I made the second finger better resemble the first. Though they don’t look identical on the joints, they feel similar to the touch.
First and second fingers, side by side
Finishing the Models
With both fingers cast, the last step was to finish them with spray paint and clear coat. I chose white spray paint for the fingers.
After the spray paint dried fro 24 hours, I applied a clear coat. However, I noticed that when I applied the clear coat, the spray paint coat bubbled up and peeled off in some places. This may have been because the clear coat was too thick or the spray paint coat wasn’t fully dried. Regardless, I unfortunately didn’t have enough time to re-apply spray paint and clear coat, so there are a few places with a damaged paint coat.
Overall, the molding and casting part of the project went well. Aside from the mold chipping off after removing the first finger, both fingers came out nearly identical and in great detail. The finishing with spray paint and clear coat could have gone better, but I can touch up the bad spots in the future.
Cost Analysis and Cleaned Workspace
Total Cost Estimate: ~$36.02
- Silicon Measuring Cups = $1.29
- Popsicle Sticks = $3.99
- Alginate Molding Powder = $11.99
- Rockite = $6.79
- Spray Paint = $5.98
- Clear Coat = $5.98
The cost analysis is a rough estimate as many of the material costs listed are in bulk and do not reflect the actual amount of materials I used.
Below is an image of the cleaned table where I cast my fingers.
Cleaned workspace
