Casting

Casting involves pouring a liquid material, typically a metal or polymer, into a mold cavity and allowing it to solidify. The solidified object, known as a ‘cast’, retains the shape of the mold.

Casting Process

Here I’m trying two types of materials for explaining the workflow. Here’s the overall step by step workflow of casting:

• Prepare the cast mixture

  Gypsum:

  

  Eggshell composite:

  

  _for a more detailed guide on how to make the mixtue of this eggshell composite, please visit my week 15 page: wildcard week.

• Pour the cast mixture into the mold

  Before pouring, you want to put baby powder in the mold just slightly not too much, to help your cast easily removed once it’s dried and also remove bubbles.

  

  !!! quote” “”

  Ideally, you want to make a 'thin stream' when pouring the mixture, to minimize air bubble. this image above is actually not a good example, because the stram is too thick and wide, ther emight be some bubbles trapped in there
  

  

• Wait for the cast to cure

  This process can take 2 hour-ish. FOr the biomaterial, it might take longer time, but we accelerate the process by putting it in the freezer.

  freezing biocomposite to accelerate setting process:

  

• Demolding

  The process of demolding is not that hard. The result of our silicone mold is medium-hard but still flexible.

  For the gypsum, once it’s out of the mold, no need to further dry it. But for biomaterials, you still need to dry it further. It usually takes 1-2 day for the composite to be fully dried without additional dryer / dehydrator.

  Demolding freezed eggshell composite before drying

Casting Results

For this assignment, I would like to test casting different types of materials. From the common casting materials, to the experimental ones. Since I play with biomaterials quite a lot. I would love to also explore how my biomaterial recipes would turn out with the mold that I made.

Gypsum

Wax

Biomaterials

For this, I will cast bio-composites. I refer to this Eggshell Biocomposite recipe by Sofia as a starting point. However, the recipes I ended up using here have been improved and adjusted based on my personal experiences. I provide more in-depth explanations of the complete recipes and process in the upcoming Wildcard Week Assignment.

Eggshell Biocomposite

Eggshells-based Composite

• Eggshells waste (powder) : 24 gr –> thi is the amount that’s required to fill my mold
• Gelatin : 6 gr (datasheet)
• Palm Wax: 1 gr
• Water : 12 gr

❗ Important! Learn the technical specification of your ingredients!

Gelatin bond breaks easily in high temperature. I learned this through experience, but actually there is an explanation for that. It’s because each ingredient/material, especially biomaterial has their own specifications, such as melting point, gelling point, boiling point temperatures. Basically, you want to know their phase-state changes considerations & requirements

Each gelatin might be different according to manufacturer/producer, but in general the melting point of gelatin is quite low, falls in the range of 30-40 degree celcius. Below that point, it will set to gel, and above that point it will melt and eventually break its bond (meaning it will split in water) at 100 celcius (boiling point).

What this implies? So that you know how to handle and manage / manipulate the heat when dealing with this ingredient. There are multiple occasions when I made material with gelatin and then I dried it under the sun in Indonesia, it turns out it’s melting..... You know, when working with agar or other binder, the melting point might be higher, thus can withstand such heat.

For a more detailed specification of gelatin, you can check/refer to this datasheet

It’s better to be aware of this prior to making biomaterials so you can mitigate / minimize errors and also you know what to expect out of your material.

Seashell Biocomposite

Seashells-based Composite

• Seashells powder: 24 gr –> thi is the amount that’s required to fill my mold
• Gelatin : 6 gr (datasheet)
• Palm Wax: 1 gr
• Water : 12 gr

Sawdust Biocomposite

Sawdust-based Composite

• Sawdust powder: 24 gr –> thi is the amount that’s required to fill my mold
• Gelatin : 6 gr (datasheet)
• Palm Wax: 1 gr
• Water : 12 gr + additional water to wet the sawdust first

Comparing Casting Results & Reflections

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Obviously, biomaterials need additional process to prepare the mixture, which you can check on my Wildcard Week page. However, in terms of the process, everything just run smoothly. The only difference I would say is more if you would like to casting gypsum make sure the inner surface of the mold is smooth enough (you may want to swipe a slight amount of baby powder to ease the demolding process. Meanwhile, for the biomaterial .. you dont want that… because it will stick to the mixture and I’m not sure what will happen, but maybe the finish wouldn’t be as great (?)

On the other hand, in terms of the casting results, we can see the main difference here:

• Biomaterials tend to shrink, resulting in smaller size

especially because I took the approach of freeze it first before demolding, so when it went to drying process, there’s no ‘scaffolding’ that holds the shape and size in place. So it will shrink from 360 degree direction. Resulting in smaller size.

This might be also due to some unprecise measurement in the recipe or process when making the biomaterial itself. But assuming the composition was right, as you can see the sawdust is the one that shrinks the most… probably because it is basically fibres so it contracts a lot when drying.

• Biomaterials: the texture is amazing!

What I mean by this is.. with gypsum or the wax, I believe if there’s some dirts, or still there are printing line in your mold, it will be much more visible. BUt in the case of biomaterial, such slight bumps would not affect much.

• Always learn and understand the datasheet of the material you’re working with!

Gladly biomaterials ingredients I’m working on are not that hazardeous, because basically they are all kitchen and cooking ingredients.. which supposed to be safer. But if you’re working with material hat you’re not sure of… especially biological material that might need special disposal system, always check for the specifications in the datasheet, so you know how to handle it and protect yourself from harmful situation