BLOG 3 – Concrete Fingers

For this week’s homework assignment, our goal was to mold and cast two fingers.

The first step, molding my fingers, is done by mixing one 140g of alginate with 560g of water in a mixing container for 4 minutes and pouring it into a paper cup, then placing my finger into the mixture for approximately 4 minutes, waiting for it to set. After the alginate has set, I slowly removed my fingers.

The second step is mixing the quick setting concrete to pour into the mold. For each finger, I used about one and a half tablespoons of concrete and some water to make it the consistency of pancake batter. After it is well mixed, I poured it into the alginate mold. After around 3 hours, the concrete would set, and I could remove the concrete finger from the alginate to completely dry.

Failures/Imperfections

The first one went well.  For the second one, I mixed in a little extra water into the concrete to help reduce the air bubbles. The concrete broke apart when I tried to remove the mold. The next two went wrong as I tried to mix two molds worth of alginate at once. The alginate started to set before I was able to pour it into the cup, making the mold have poor quality. The last one went reasonably well.  For all of the concrete fingers, I observe some small air bubbles. I aggressively tapped the mold and thinned out the concrete mix to remove as much air as I could. Therefore I don’t think that I did much wrong, and it was inevitable when casting concrete into small irregular molds like a finger. Overall my success rate was 2/5, which isn’t good but could be expected from a person who only cast a soap once.

 

Costs

In total, I used 8 paper cups ($6.58/ 40pcs), 8 mixing sticks ($5/ 80pcs), 2 mixing containers ($11/12), roughly 700g of alginate($28.05/ 2lb), 150g of concrete mix ($2.28/10 lbs), and 2 screws ($6.98/35 ). The total cost of materials for the project is $60.16. The cost of materials actually used is $24.13. The time it took was 2 hours spread out over a few days, so approximately $20 for labor cost. The total cost for this project including labor is $80.16, assuming you own a scale.

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