My first foray into the world of molding and casting was (very literally) cut short. While the entire process was brief and relatively unsuccessful, I feel that I’ve learned from failure enough to mold and cast an object given the chance in the future.
I knew my molding and casting experience was going to start off rough when I ended up missing the demonstration class due to feeling under the weather. At the time of writing this, we’re still in the midst of the COVID-19 pandemic, so feeling even a little out of it is a sentence to stay in your room for at least one whole day. My experiences going forward were influenced by the (very kind) aid of classmates and the TA.
I started the process by mixing the alginate together in the predetermined ratios. Though Dr. Wettergreen would later mention that this material was too old to create a suitable mold, I didn’t notice during the mixing process. The mixture very quickly turned very batter-like and quickly became difficult to mix together. Once mixed, I stuck two of my fingers in the mixture and held for the full 5-minutes. As the alginate cured, I could feel it tightening around my fingers – when removed, there was a certain pressure that was relieved.
After letting the alginate sit for a few minutes, I began to mix the casting mixture. Instead of the cement (which was apparently used for the in-class demonstration), I opted to use a quick-setting concrete mixture. Concrete, of course, has a larger aggregate mixed with the cement in order to provide more structural support for larger projects. While this should have theoretically helped for strength, I now believe it wasn’t conducive to fine details such as the finger patterns targeted with this project. Regardless, I mixed the concrete until it was a thick paste. I knew from previous experience that the goal with concrete was to avoid a “soupy” mixture. I poured the concrete over the top of the alginate mold, ensuring a good amount reached all the way to the fingertips by constantly tapping the sides of the cup. Hitting the sides of the cup allowed for the concrete to settle, so to speak, and completely fill the mold. Once the concrete was fully in the mold, a screw was carefully placed at the top, and the entire cup was allowed to sit for a full 48 hours.
The problems with the materials didn’t present themselves fully until attempting to demold the fingers. After sitting for a couple of days, the alginate was visibly purple where high concentrations of water occurred – this was visible even from the outside of the cup. When trying to take the top of the concrete off (the “base” of the two fingers) it immediately snapped off, leaving the fingers embedded in the mold. Upon inspection, it was clear that the concrete was too wet to fully cure, as it easily crumbled apart. The fingers were the same way upon removal and were easily broken up by applying even light pressure. I decided to throw everything away, as there was really nothing left to present to the class, other than this blog post and pictures. It seemed that the moisture contamination and retention by the older mold material caused these parts to fail, just as Dr. Wettergreen suspected.
In conclusion, I’m glad I learned the rough process of molding and casting, even though the outcome wasn’t ideal. At the time of writing, I currently have three flowerpots curing using a new mold and casting material that Dr. Wettergreen provided the class – I’m hoping this time things go better!
Costs:
– Labor: 2 hours at $12/hr = $24
– Alginate: $49.99 for 3 lbs., 1 lbs. used = $16.66
– Concrete: $5.25 for 50 lbs., 1lbs. used = $0.10
– Auxiliary materials: paper towels, nails, popsicle sticks, etc. = ~$1
Total cost: $41.76
