Product
Well, for this one, there’s actually no product to deliver. I’ll write this blog post to show what work I did complete, but in the end I was unable to complete the molding and casting process and thus don’t have anything to show.
Procedure
We made our first finger mold and cast in class. Unfortunately, when I tried to pull this out after leaving it out to set, the screw broke right off from the rest of the finger.
The result of pulling the first attempt at a cast out
This was probably because I tried to pull it out straight up – I didn’t break the mold or try to wiggle it out gently. The good news about that was that since the mold was intact, I could go right into another try.
I used a balance to put 22g of plaster of Paris and 16g of water into a beaker (it was supposed to be 11g to make a 2:1 ratio, but I poured a bit too much. I didn’t think at the time it was too watery, so I went with it. In retrospect, it very well may have been too thin, causing the cast to crumble when I tried to remove it.)
Weight of the plaster mixture for the second cast attempt
This was stirred with a popsicle stick for a few seconds, then poured into the mold. I used another popsicle stick, laying horizontally across the beaker, and a makeshift tape string to suspend the screw.
Screw suspension contraption
After an hour, I went to check up on it. I tried to get it out using the same method as before – and, surprise surprise, I got the same result. The screw broke off from the rest of the finger. Again, I was able to slide the broken finger out of the mold and retry.
Since both times the screw broke off, I decided for the third try to make sure the screw got inserted deeper. This time, I used 37g of plaster of Paris and 18g of water and poured it in.
Weight of the plaster mixture for the third attempt
I adjusted the screw to hang lower off of my makeshift tape-popsicle stick contraption. This time, for whatever reason, the plaster refused to set. I left it outside for 2 hours, and it still wasn’t dry. Maybe it was too humid outside? Either way, at this point I couldn’t get the finger cast out anyway. I decided to leave it at that and document my work so far in the interest of time.
Challenges
The largest challenge was definitely getting the fingers out of the mold. Most of this was just due to my carelessness with taking them out, but it was also partially due to not inserting the screws in deep enough. Next time, I would allow extra time to set, and I would also break the mold to get the finger out instead of pulling.
Cost Analysis
I did the cost analysis assuming that the third attempt worked, and I was able to post-process it.
Plaster of Paris: 37g = $0.19 (based off of $9.48 for 4lbs at Lowe’s)
Tap water: negligible
Alginate: 50g (estimated) = $1.65 (based off of $14.95 for 1lb on Amazon)
Popsicle stick for stirring: negligible
Spray paint: $1.58 for a 10-oz bottle at Lowe’s
Time: 15 min. making mold, 90 min. wait time for 3 mold attempts, 15 min. for post-processing all at $15/hr =$30
Total cost: $33.42
