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Casting Epoxy Resin for Beginners

Anna is an artist who enjoys collecting and repurposing old objects to turn into special things.

Learn to make these beautiful geodes.

Learn to make these beautiful geodes.

How to Make Resin Geode Art

If you've ever wanted to try using epoxy resin for an art project, you might wonder: Is it easy to do, especially for someone who hasn't had any experience with this material before? The answer is yes! This particular resin is easy to use and produces a strong and clear product. It is very shiny and a joy to work with.

For this article, I will be featuring a geode pour for beginners.

What You'll Need

Here are things you would need to start:

  • epoxy resin (it comes in two parts: resin and hardener)
  • plastic crystals
  • mica powder
  • plastic mixing cups
  • paper towels
  • mixing sticks
  • measuring cups or weighing scale
  • mold (silicone or homemade)
  • table cover
  • heat gun/torch (optional)
Example of epoxy resin (resin and hardener)

Example of epoxy resin (resin and hardener)

Epoxy Resin

There are a few brands of epoxy resin on the market. Take note that this kind of resin is quite expensive. Both epoxy resin and regular epoxy require mixing before use; they are are both adhesives. The difference between epoxy resin and regular epoxy, though, is the drying time. Epoxy hardens quickly between 6 to 20 minutes, while the epoxy resin hardens in about 8 to 24 hours, depending on the thickness of the cast.

Pictured above is epoxy resin I used for the geode project, and I give it five stars! It is a 3:1 ratio, meaning three parts resin to one part hardener. (That is why the hardener comes in a smaller bottle.) This type of epoxy resin hardens into a clear and smooth surface. It is perfect for river tables, jewelry, and crafts. It is easy to use and odorless, and you do not need a torch to remove bubbles.

Usually when the resin is poured into a mold, small air bubbles form, especially on the top of the piece. You would then use a torch or a heat gun to skim over the top and burst these bubbles. But for this particular epoxy resin—with a bit of care in the mixing process and by slowly stirring the mixture—bubbles do not form. Because of this, the pour is smooth as glass.

Pour three parts resin to one part hardener.

Pour three parts resin to one part hardener.

Tips for Measuring the Resin

For small projects, you can use the small measuring cups that come with syrup medicine or milk/whey power measuring cups. You can also measure using a weighing scale. I do not suggest mixing too much resin at one time. Mix only what you need. You can always add resin on top and not worry about it separating.

Depending on the epoxy resin that you use, mix the ratio in the product instruction. In this example, I measured three parts of the resin to one part of the hardener. This is a very sticky product, so make sure you cover your work surface with enough tarp or plastic. I do not suggest covering your work surface with porous materials like fabric or paper. The resin will seep through it. This product will get everywhere. Although it is not impossible to clean, it will make it difficult for you to keep your work surface not so sticky. You can also wear gloves.

Molds (Silicone or Homemade)

You can use silicone molds or make your own. I usually make my molds using PVC or Sintra boards. Because of the nature of my work, I make use of this material quite a lot, so there is a lot of scrap PVC around at all times. I cut out the shape that I want and glue on the sides. I make sure that I use the glossy side of the board, so I can remove the resin cleanly and efficiently from the mold once it dries. You can also make use of other materials that are similar to these boards. Just make sure to line it with plastic cling wrap so it will be easy to unmold.

If you don't want to make your own mold, try these geode-shaped silicone ones. All you need to do is pour your resin. Once your piece has dried, it will be easy to unmold.

Mica powder comes in a variety of colors.

Mica powder comes in a variety of colors.

Mica Powder

Mica powder is readily available and comes in a variety of shimmery colors. It is perfect for the geode project since it will mimic the colors of the stone/crystals. These mica powders usually come in 10-gram packs and are not expensive. If you are on a budget and want to try casting or pouring resin for the first time, purchase only the colors you would need with the final look of the project or object in mind. For the geode, I would suggest blue, pink, green, white, and gold. You can then add a few more colors to the mix as accents.

Try these mica powders for your geode and other pieces. You don't need a lot of pigment so these would go a long way. These come in so many shades and colors.

Colored Resin With Glitter

This is how your mixture would look like after adding the mica powder or pigment. Some people add glitter for added effect, but take note that the glitter tends to sink to the bottom, so use it sparingly.

Plastic Crystals

Plastic Crystals

Plastic Crystals

For the geode project, I recommend using clear plastic crystals in different shapes. This will add a bit of dimension to your project.

Now that you have everything ready, let's begin!

Step 1: Prepare Your Mold, Resin and Pigments

  1. Once you have your mold ready, rest it on top of a level surface protected by plastic (on the off chance your mold has any leaks).
  2. Mix your resin and divide it into several cups.
  3. Add pigment to each cup and mix each one for at least five minutes.

Step 2: Begin Pouring the Resin

  1. For the geode design, you need to pour the resin into the mold in a circular fashion. Make sure that you pour it in thin lines.
  2. Do not pour too high. Stay close to the mold as possible.
  3. The tricky part is estimating just how much resin you need for the size of the mold. Follow the guidelines below.

How to Estimate How Much Resin You'll Need

For square or rectangular molds, multiply length by width by height (in inches) to give the volume of the mold in cubic inches. For this geode mold, I calculated it the same way, assuming the geode mold as a rectangle.

I also calculated the area of the center hole, assuming its shape as a rectangle, and subtracted that number to the total cubic inches for the entire primary mold. The excess resin will not be too much; it will add minimal height to the finished piece.

You can run a stick in the mixture to create some organic patterns.

You can run a stick in the mixture to create some organic patterns.

Step 3: Layer the Colors

  1. Layer your colors any way you want, alternating between lights and darks.
  2. With a stick, you can create more shapes by cutting into the mixture and swirling the colors to create some organic patterns.
  3. Keep on layering until you get the thickness and look that you want.
Let the piece dry for 24 hours.

Let the piece dry for 24 hours.

Step 4: Remove Bubbles and Let Dry

  1. After all the colors are poured, inspect to see if you need to torch or use a heat gun to remove bubbles. You can also use your heat gun to move some of the pigmented mixtures in any direction if you would like to get a smokey or wispy effect. Just make sure you do not go too near the resin with your gun. Test it at a distance of 20 inches above the resin, then go near it gradually.
  2. You can add the crystals to the outer sides of the geode; just arrange them in clumps to give it a natural look. However, you need to reserve a few crystal pieces for the inside of the center hole; you can only attach these once the resin has thoroughly dried.
  3. Let the entire cast dry. I recommend leaving it overnight.
  4. After 24 hours, touch the resin to make sure everything has fully cured. If it is no longer tacky, you can unmold it.
Add the plastic crystals to the center of the geode.

Add the plastic crystals to the center of the geode.

Step 4: Add Crystals

  1. To add the crystals in the center, you can use a hot glue gun. This is very beginner-friendly. Attach the crystals in clumps and make it uneven. Your piece will look a lot more dynamic this way.
  2. Do not attach the crystals in a single line following the shape of the hole like a necklace. Layer it so it looks natural.
  3. This last step is optional: You can mix a tiny amount of resin, tint it with a little bit of color and pour it on top of the crystals to break the monochromatic plastic crystal look.

Tips for Casting Your Geode

  • Keep in mind that this particular resin doesn't dry into a stiff, glass-like structure. It has a bendable and somewhat rubbery feel, so even if you drop it, it will not shatter.
  • For added effect, you can also draw thin lines going around the mold with a metallic sharpie to give the surface a bit more color and depth. As you continue casting, you will find more techniques that will make your piece come out even more beautiful.
  • Remember: Practice makes perfect!

© 2020 Anna Javier