This is a bit like looking for a forever-young person—we have not found such a material yet. What you are looking for is UV-resistant resin. Epoxy resin will yellow over time because it is not fully resistant to ultraviolet light.
The most effective way to remove air bubbles is vacuum degassing or pressure casting, but both require specialised equipment. A practical alternative is a utility lighter or heat gun. Warming the resin makes it thinner so bubbles rise more easily.…
The resin has likely absorbed moisture from the air, or there is water in the surrounding environment. Avoid using epoxy when relative humidity is above 75%.
Several factors can prevent proper curing: low temperature, off-ratio mixing, insufficient mixing, high humidity, poor ventilation, or using the wrong resin or hardener. Epoxy hardener is not a catalyst—adding more hardener will not speed up curing. Follow the correct mixing…