Typically, caps on cosmetics are plastic and/or have a plastic disk or a liner made of a plastic-coated paper, foam, or foil that is nonrecyclable waste. A barrier between a formula and cap is important to protect the formula. We prefer that our packaging is truly 100% recyclable, but for a cap to go without a liner or disk, it needs to have a resin coating.
The resin we use for coating our caps is safe, BPA-free, and approved for food contact. It’s the same type of resin used inside soup cans and metal water bottles, for example. Just like you don't want BPA in your water bottle, you don't want it in your cosmetic packaging, especially for formulas like ours that are designed to maximize bioavailability. Our resin is important to protecting the formula as it prevents oxidation with water (rust) and prevents leaching of the metals of the cap into the formula. Aluminum leaching is not necessarily unsafe, but it does have an adverse effect on stability of the formula.
When recyclable metals, like our cap, are reclaimed at the recycling center, they are melted down to be repurposed into new products. As the metals melt, the resin burns off, ensuring the reusability of the material.