Resin Casting Natural History for Teachers

Resin Casting Natural History for Teachers

Natural history is an important part of Ohio’s story, but it can be a challenge bringing nature into the classroom. Natural history objects are usually made of organic material that can be fragile or can decompose, causing sanitary problems. One simple solution for preserving these items for use in your classroom is to encase them in polyester resin!

This is a process that is relatively inexpensive (especially compared to the pre-enameled specimens that you can buy online), easy to do, and can ensure items will be protected and safe for handling. Recently, I had the experience of enameling some of the insects in the Ohio History Center’s Education Collection. There was a bit of a learning curve, but if you are interested in enameling specimens for use in your classroom I will run through the steps that we took enameling our insects.

Of course before you start the process you need to have specimens to preserve. At the Ohio History Center we are fortunate to have a large collection of dried insects already at our disposal. You can order dried insects from different websites online, but, before you go out and try to gather your own specimens you should be aware of collecting laws in the state and remember that it is always best to leave living animals in their natural habitat.

Other than the specimens to enamel, you will also need casting molds and the resin itself. We used a silicone mold. This worked fine, and since the silicone is flexible it doesn’t allow any of the resin to stick to the sides. The actual resin we used was the Castin’ Craft brand clear polyester resin, one canister should be enough to make about 10-12 smaller casts.

The first step of the process is to mix the liquid resin with the catalyst. The catalyst, which comes in a small bottle along with the resin, is the chemical that reacts with the resin to make it harden. This first step can be a little bit tricky because if you mix in too much of the catalyst then your resin will be too brittle and if you do too little of the catalyst then the resin will never fully harden. So this part can take a little testing.

We filled the bottom half inch of a plastic cup with the resin, this should fill the first layer of 4-5 molds, and then added about 40-45 drops of the catalyst. When you find the proper mix you should stir the mixture for about one minute. This will create a lot of bubbles, so before you pour the resin into your mold make sure you wait for another minute or so for some of the larger bubbles to disperse (many of the smaller bubbles will go away on their own). Also make sure when you do your mixing you do it in a well ventilated area or outdoors since the chemicals are very strong smelling.

When you are ready to pour the resin mixture into the mold only pour a small layer, just enough so the specimen doesn’t touch the bottom, into the mold and then add whatever specimen and tag you are enameling. You need to let the specimen and tag dry in the resin until they are firmly in place. If you try to pour another layer before the specimen and tag are solidly in place then they will float to the top of the new layer of resin. We would usually leave the first layer to dry for an entire night. It would also be helpful to try and remove any larger bubbles that are in the mixture while the resin is still liquid.

After your first layer is done you can add a second layer of resin mixture to make sure the specimen is fully immersed. Let these dry in their molds for at least a couple days until they are solid. We’re finding out that there is a lot of trial and error to this process so if your first few resin cast don’t turn out how you expect you should keep trying and find out what works best for you!

Here is a website and that also might be helpful if you want to try resin casting natural history objects.

Posted April 5, 2018

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