My Finger, But Made out of Plaster

This project was pretty straightforward and a good intro to casting. However, it took me many more than two tries to get two good finger hooks. The problems that I had included poorly-made alginate casts (not well mixed, bad proportions, or poor finger placement in the mold), plaster mixing that was too watery or too bubbly (leading to improper setting and/or indents in the finger), and problems taking the final plaster product out (either due to impatience or trying not to break the mold while taking it out). These fails weren’t all for nothing, though, as I was able to find strategies to minimize these errors while also becoming better at casting in general.

I began by using a 1:4 weight ratio of alginate casting material to water. To fill the measuring cup with the mixture, I used about half a cup of alginate (58 g). I then made sure to mix thoroughly, especially in mixing the bottom of the mixture as my first attempt didn’t adequately do this. I then put my pointer finger into the mixture for about 15 mins, and I determined when to take it out based on when the cast mixture on the stirring stick hardened:

After making the mold, I measured out a 1:2 mixture by volume of water to plaster. This ended up being about 50 mL of plaster and 25 mL of water. I stirred this for about two minutes, as I found that stirring it slowly and for a long time minimized the bubbles in the final setting mixture. After pouring the plaster to the top of the finger, I used a tape contraption to place the screw into the hardening plaster, as this takes about 30 minutes minimum.

Once it set, I experimented with different removal procedures, and I found that splitting through the mold. The unfinished product looked like this, and depended greatly on the depth of the mold:

To finish the pieces, I used a dark blue paint through all parts of the finger hook. I experimented with this finish on one of my failed pieces (that had cut in half) to make sure that it looked good. 

I then let the paint on my actual pieces dry for about 15 minutes, and I made sure to wipe away excess paint to make sure that the marks of the finger were maintained in the final plaster product.

I then finished the plaster wall hook using a clear gloss finish after doing a second coat of the paint:

I let these clear coat layer dry for about 15 minutes, reapplied it, then I had my finished product! Due to my different casting sizes, the hooks were different sizes, but I kind of liked it that way, as both had their own uniqueness despite having the same finger markings.

 

Cost Analysis:

The time for this project was about 3.5 hours, and at a rate of $15 an hour for moderately skilled labor, the labor cost was $52.50. The only material costs incurred in this project were the screws, alginate casting powder, Plaster of Paris, and finishing paint/clearcoat. The paint, clear coat, and 5 screws used were negligible in cost. The plaster and casting powder combined were about $10, as I had to do multiple takes of the molds [1,2]. Overall, therefore, this project cost about $62.50.

References:

  1. Homedepot.com. [cited 2022 Apr 3]. Available from: https://www.homedepot.com/p/DAP-25-lbs-White-Dry-Mix-Plaster-of-Paris-10312/100123682
  2. Make-a-Mold Alginate Impression Material – Box, 4.5 lb [Internet]. Google.com. [cited 2022 Apr 3]. Available from: https://www.google.com/shopping/product/16295099378903551282?q=alginate+casting+powder+cost&prds=eto:15804354545292299566_0;10680113310730360500_0&sa=X&ved=0ahUKEwi_ycGB-fb2AhXvkokEHSMABw0Q9pwGCAU
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