Resin casting is an exciting and fun craft that allows you to embed or encase almost any object in crystal clear plastic. Coins, shells, rocks, dried flowers, butterflies and insects are just a few of the examples of embedment possibilities. This convenient new package includes catalyst in a clear bubble top cap. Please note that two-part Polyester Resins do not tend to "yellow" as easily as Hard-Surface Epoxy Resins, although it still will "yellow" from any or all of the following: too much UV light, high heat while wet and/or curing, if heated too high afterward.