The second assignment for this class was to create a mold out of alginate and cast a finger. I chose to do the beginner level assignment as I had no previous experience casting and molding.

Creating the alginate was fairly easy, it just required a 1:1 ratio of alginate powder to cold water. I stirred the mixture in a plastic cup until the mixture was lump free. I then went on to make my plaster by mixing the powder with water in a 2:1 ratio.

After waiting about 30 minutes, as per the instructions, I went to check on my mold to see if I could remove it. However, the plaster was definitely not set yet. I decided to wait over night.

I think my mold came out well; the wrinkles of my fingers were well defined. However, on the underside, there were a couple of air bubbles. This surprised me as I took a lot of care to swirl the plaster mixture around to coat the fingers and tap out the air bubbles.

For my next attempt at molding, my goal was to avoid any air bubbles.

Unfortunately, the only powder left for me to use was cement. Additionally, I had to use a different type of alginate which required a water to powder ratio of 4 to 1 by volume.

I struggled with this cement mixture as it was much more viscous than the plaster mixture. I struggled with the ratio, but a student who had used this mix before me gave me a few tips. This time around, I took care to very slowly pour the mixture in. I made sure to swirl and tap between each pour in hopes of avoiding air bubbles.

Then tragedy struck.

When trying to pull my finger out, it snapped in half. The top of the finger had seemed dry, but upon inspecting the now split-in-half finger, I realized that the cast had not fully dried.

Take 3:

This time around, I used the same alginate powder from my second take, but had to use quick drying concrete instead, as once again, all the other powders were used up. This time, the concrete mix required a 5 to 1 powder to water ratio. This was the directions on the packaging, so I trusted it and followed. However, the mixture was closer to a paste than a liquid of any sort. It almost felt like clay. So against my better judgement, I dared to add small drops of water until the mixture was closer to a very thick liquid. this time, I was forced to use a glove and scrape small amounts of the mixture into the opening of my mold and tap my cup until the mixture had traveled ( very slowly) to the bottom of the mold. I repeated this process until the mold was filled.

When I went to pull out my mold ( after 48 hours), I saw that my cup had accumulated water in between the outside of the alginate and the cup. This did not give me high hopes for my mold. I suspected that the drops of water I had used in order to lower the viscosity of the cement mixture was to blame. But when I pulled my mold out, it was not terrible. I did notice that in some regions, the cement still needed to set and had a slick, clay like texture. In other parts, the wrinkles and lines of my finger showed up nicely. There were a few air bubbles here and there, but I was not surprised as I had not expected the thickness of the mixture to create an air bubble-free cast. 

   

Overall, this was a very fun, if some what frustrating, experience for me. I learned a lot and realized that trial and error along with the right materials are necessary to create a perfect mold.

Labor Cost:

Trial 1:

10 minutes to prepare and mix the alginate

8 minutes of alginate setting

5 minutes to prepare and mix the plaster mix

= 23 minutes * 3 –> approximately 1h 9m 

Various times for waiting to set

Cost:

Alginate : $ per pound

3 ounces per finger ( 9 ounces –> .56 lbs)

Plaster:

Around $1.50 per pound

6 ounces –> .375 lbs x $1.50 = Approximately $0.56