[Katherine Swift]

This question comes through email by R:

I’ve been making stud earrings with sterling silver post and cups that are filled with resin. I mix the resin with different natural materials, clay, gold leaf, dried leaves, etc. Recently I’ve had a couple customers return earrings to me that the resin has fallen out of the bezel.

My first thought was that the resin I was using (clear cast epoxy from the craft store) was not strong enough. Is there any other factors I should be concerned about in my process?

[Katherine Swift]

Assuming the Clear Cast resin cured properly, I don’t think it is the reason it is falling out of the bezel. There could be a couple other possibilities here:

1. If there is a lot of inclusions in the resin, then the epoxy won’t have good adhesion to the metal. Try including a few less if your bezel looks ‘crowded’.

2. If a metal is coated with a lacquer that has not been fully cured or finished with a high gloss coating, the adhesion will not be as good as it should. For your next casting try abrading the metal surface with something like a fine sandpaper. If it still feels slippery, then wipe it with an alcohol. Wipe any other solid pieces with alcohol to remove any residues. If the findings are coated with lacquer, heat cure for 1 hour at 150F prior to casting the resin.

Let me know if these suggestions make it better for the next time. If not, it might be worth trying another resin.

[R]

Hi Katherine, thank you so much for taking the time to respond to my question. Do you think layering a small amount of pure resin at the bottom of the bezel before filling in the resin mixed with the natural materials would make for a better adherence? Or do you think then it would just fall out at the divide between the pure and mixed resins?

[Katherine Swift]

Assuming it is the materials you are adding to the resin that is causing the problem, then yes, a thin layer of resin at the bottom would help. Allow this layer to partially cure, then pour your layer with the inclusions.

[Clinton Gallagher @tapABILITIES]

What one needs to do when resin does not bond (and even when it does) is to create what is called a “key.” That is epoxy something with hard edges and perhaps a hole onto the bottom of the bezel or along the sides of the bezel and such; some type of object that has hard edges that do not allow the resin to move once it is cured. A bezel that has a surface that can be modified to act as one or more keys may work out.

The resin will bond around the edges of the key and the key prevents movement of the resin after it has cured. That’s all the key is used for. It is easy to create such keys if 3D printing a bezel. Adding a key of some sort to an existing bezel may be trickier but if you are going to become adept at crafting these are the tricks of the trade that can be learned.

Using keys to prevent movement of objects that come into contact with one another has been around in manufacturing for like forever.

[R]

Thanks Katherine! I will try this!!

[Author]

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