Resin Casting to Create Unique Materials

Resin is a material of plasticity (the quality of being easily shaped or molded) and can be manipulated to create different visual effects and forms. In this instructable I'll introduce you to some casting techniques you can use to create your own unique materials with epoxy resin.

Although there're types of epoxy resin with less harmful content and smaller environmental impact, it is generally a good idea to work with epoxy resin in a cautious manner. Epoxy resin can cause skin irritation and dermatitis through skin contact. Epoxy resin dust is very harmful when inhaled, especially when it is not fully cured. Over-exposure to epoxy resin usually causes allergy in about 2% of users. (Me included unfortunately!)

The kind of resin I'm using is Entropy Super Sap CCR. Entropy resin replaces petro-chemicals with renewable, bio-based materials, thus is less harmful to your health and the environment. Epoxy resin comes in two parts: part A resin, and part B hardener. You can mix by either weight or volume, and I recommend mixing by weight (more accurate) when you're working with a smaller volume.

Here're a few safety tips to follow:

1. Always wear gloves.

Skin contact with epoxy resin (part A, part B, and uncured mixture) can cause skin allergy. Do NOT use latex gloves since latex will absorb chemicals in epoxy resin. For better protection, use barrier cream ("invisible glove") and then wear gloves.

A complete guide on skin protection when working with epoxy resin

2. Make sure resin is FULLY cured before you proceed to other steps.

It's very important to keep track of your casting time. The time that epoxy resin takes to harden is NOT the time it takes to fully cure. Usually it takes longer to become chemically stable (fully cured). Uncured resin dust is very harmful.

3. Vacuum all the dust.

Don't let epoxy resin dust fly around, especially if you're working in a workshop where other people are vulnerable without awareness.

Have ready the dimensions of your project and design your casting boxes accordingly. Plan ahead how you'll remove the box afterwards. Here I'm using 3/16'' plywood, which can be easily removed later by cutting (bandsaw or table saw) or machining.

Use tape to seal the edges to avoid leaking. Plastic packaging tape works better than blue tape ( although that's that I used in the photo).

Epoxy resin can be easily colored with resin pigments, and by using different techniques, you can create a wide variety of patterns.

1. Solid color

Mix pigment thoroughly with epoxy resin part A first, and then add part B. You can also add pigment to A&B mixture, but it will require more vigorous mixing. Here I used TAP Plastics resin pigment.

2. Layered effect

By pouring a thin layer, let it cure, pour the next layer, and repeat this process, you can eventually get a material block with many layers of different colors of your choice.

- You can alter the thickness of each layer, to get intentional consistent or inconsistent layered effects.

- Let the last layer fully cure before you pour the next layer, to get straight lines between layers. Let the last layer cure halfway (gel state) and pour the next layer, to get wiggled lines between layers.

- Tilt casting boxes to get tilted layer effects.

3. Marbled effect

Prepare two different colored resin mixtures (black and white in example) , wait until they gel a little bit, and then mix the two. Since the resin is no long thin liquid, the final mixture will not become a pool of grey, but instead forms a marbled effect with black, white and grey. Depending on how gel the resin is, you can get a range of different effects.

If you're going for the layered effect, be prepared that it will be a lengthy process. The fast hardener will harden the resin in 24 hours, while the slow hardener hardens the resin in 48-72 hours. If your layer is more than 1 inch thick, you'll have to use the slow hardener since the fast one will generate too much heat and produce unpredictable results (irregular surfaces, resin coming out of the casting box, etc.)

It's good practice to keep track of your casting because once you pour in one layer, you can't see the previous layer. To make things accurate, you can either put marks on the inside of the box so you have a reference when you pour, or keep a casting log of how much material you used for each layer. In my experiment I was casting 15 boxes all at the same time, so keeping a casting log has been very helpful in the process.

By embedding things in the casting, you can create very interesting results. Here I cut the solid color castings into small pieces using the bandsaw, and then embed them in another casting. The possibilities are really endless, although it's a little bit labor intensive. And one important fact about this technique is that, however different the casting looks, it is ONE material only. This can be very helpful if material consistency is important for your next steps (such as milling).

You can of course embed other materials / objects in the casting as well. This instructable by artist Julie Kumar can give you more inspirations on that direction.

Once the casting is done, you can work with your unique material however you want! I machined a few samples on the 5-axis CNC milling machine at Pier 9 workshop, and it was very satisfying to see the layers of colors revealed by the machine. Hope you enjoyed this instructable and are ready to make your own materials now!