The second assignment of ENGI 210 was to clone my finger by creating a mold out of alginate, then casting it with plaster.
first attempt
On my first trial, all the steps seemed pretty straightforward. I mixed alginate powder with water at a 1:1 ratio, stirred it for a few minutes to get rid of all lumps and extra powder on the surface of the cup. It was interesting to see the white mixture turn pink, then come back to white again! After that, I stuck my index and middle finger in the mixture and let it sit to create a mold.
For plaster, I mixed plaster powder and water at a 2:1 ratio and carefully poured it into the mold, making sure to get all air bubbles out by coating the surface first. I was unsure if I mixed the plaster correctly because I did not feel it get warm as I stirred the mixture, but decided to wait and see how it turns out. As I was rather busy for the rest of the day, I chose to let it sit overnight and came back the next morning.
When I attempted to remove the plaster from the mold, I was immediately disappointed because the screw fell off of the plaster. It seemed as if the plaster didn’t solidify entirely. Still, I removed the remainder by cutting open the mold. As the plaster was still rather soft, it ended up breaking in the middle as you can see in the picture. Yet, I was happy that there were almost no air bubbles and also impressed with the details that it managed to clone.
second attempt
My goal was to make at least three attempts and I set aside multiple time slots throughout the week to work on it. However, I wasn’t able to make it due to floodings and bad allergies, unfortunately. In the end, unfortunately, my second and last attempt came rather close to the deadline.
For the second attempt, I used a different orange-ish powder (unsure if it’s alginate) for the mold and used cement instead of plaster as they were the only remaining material. I used the same ratios for all mixtures to recreate the process.
There were some clear differences that I noticed: the alginate(?) mixture seemed less viscous than the initial alginate mixture and seemed a bit more gelatinous, while the cement mixture was much more viscous than the plaster mixture.
I feel that the results from the second trial were somewhat similar in a sense that the cement also turned out not fully solidified. It was much softer than the first trial in fact, as you can see by the residue on the mold as shown in the picture. This caused the object to break in the exact same places as the previous trial: in the middle, and at the head of the screw. I believe that this might have been a result of a different mold; the mold was much more watery compared to the mold in the first trial, which made me think it must be mixed with water at a different ratio.
After all, I ended up with two failed attempts at cloning my finger. I was rather surprised by how difficult or finicky the molding and casting process is. On the bright side, I believe that the first trial might be repairable using glue: I will update this blog once I give it a try.
Cost analysis
For each trial, I tried to use the same amount of material:
- 3 oz of alginate
- approximately 1.5~2 oz of plaster/cement.
Considering the prices of each material:
- Alginate: $7 for 13 oz
- Plaster: $1.50 for 1 lb
The cost of material for the two molds come out to about $3.50~$4.00
In addition, it took me about 25 minutes per mold to produce and finish up each object. Using a $20/hr rate, that amounts to about $16.50
In total, the cost of two casted fingers adds up to about $20.
