I’m back for our first foray into the world of casting and molding. To start this assignment, Anjitha and I mixed our individual alginates. To do this we took our ratio of 1:4 alginate powder: water. We then stirred up our cups until the mixture was at the desired viscosity (visually determined) and placed our fingers in. Instead of doing two individual hooks, I opted for one hook with two fingers for a sturdier support. I held my fingers into the alginate until it solidified enough that nothing came off when I touched the top of it, and then I slowly removed them using a back and forth motion to not mess up the mold.

We next began working with the casting material, which was a plaster. This powder to water ratio was 2:1. Before mixing the components, we each secured a screw (or two) into the finger holes which would give us the ability to use it as a coat/purse hook once the plaster solidified around it all. The securement method was tape, through with the screw was placed before the tape edges were adhered to the outer cup edge to stay in place. We made enough to share the plaster between four of us, and quickly filled in our molds before leaving them to set.

When I came back to remove my casted piece from the mold a few days later, it broke coming out of the mold because it was so wet. It had begun leeching liquid from the alginate hydrogel which made it pretty fragile. I brought my piece in to let it dry for a couple of days, then came back to finish it off.

 

 

 

 

 

To finish the piece I had to do a bit of sanding on the rough edges (and to get the rust dots off) and had to glue the finger back on at the broken junction. The plaster sanded pretty easily with the 100 grit so I quickly moved to a higher grit for the fine touch post-processing required for the delicate piece. It was crazy to see the fine detail produced in the mold that transferred to the casting- finger wrinkles were clearly visible which was not something I expected. There were also a number of air bubbles on the underside (inside of fingers) that I’m still unclear as to how they came to be. Perhaps when the plaster was poured I didn’t tap the cup down quite enough times to remove all the air bubbles and they settled in the inner curve of the fingers. While sanding the dots of rust off the piece, I did my best to preserve the detail while still finishing the piece well. To glue the finger back on I used standard super glue and was able to sand the glue overflow a little too to maintain the uniformity of the piece as much as possible after it had dried.

I finished my piece with a clear gloss spray coat, which I was able to get on the whole piece with a homemade foil stand I fashioned before going out to the back deck area to spray and ta-da: it was done! It was interesting messing around with the ratios of materials while we were still figuring out what would be ideal and getting to see the level of detail that can be preserved through these molds. I’m excited to get started on the final where we will get to dig deeper into molding/casting and get some more practice!

 

 

 

Cost: $23.09 for the dual-finger hook

Material: $4.34

Alginate- $8.99 for 454g @ 40g = $0.79 ; Plaster- $10 for 1lb @ 150g = $3.3; Gloss coat- $6.19 for 12 oz @ ~0.5oz = $0.25

Labor: $7.5/hr @ 1.5 hrs = $11.25

Overhead: $5/hr @ 1.5 hrs = $7.5