Will resin discolour over time and why?

As previously discussed, we know that resin is a polymer. During its lifetime the resin piece or product will undergo a natural process called polymer degradation. This includes changes in both the chemical structure and the physical properties of the resin.

Environmental factors such as light, heat and exposure to chemicals lead to the breakage of polymer molecules which lead to changes in the colour, shape and tensile strength of the polymer.

For example: When your resin product is exposed to UV rays, its chemical structure is altered and free radicals form. These free radicals react and bond with oxygen in a process called oxidation which causes the resin to develop a yellowish or amber-like tone over time.

Disclaimer: As you can see, the yellowing is a natural, inevitable process that forms part of the ageing of your product for which we cannot be held responsible.

We do, however, use a high-quality UV stabilised resin that minimises ageing and yellowing.

My personal experience:
I have been using my current brand of UV curable resin for over two years now and I have not experienced any yellowing in my jewellery pieces. That being said, discoloration may still occur and is greatly influenced by how well you take care of your resin product.

The epoxy resin that I use for products such as keychains, bookmarks and larger items do discolour slightly over time. I have found that a slight yellow-tone develops which might not be obvious but it is more visible when you compare it to a newly casted resin product.
Please see the below resin care instructions which will help maintain the beauty of your resin product for years to come.

Reference: https://compositeenvisions.com/document/yellowing-or-clouding-of-epoxy-how-to-protect-against-it/