An old lapidary taught me an excellent trick for sealing cracks in gemstones. Some gems are inherently unstable. If a client of mine wants one of these gems for inlay, or to be cut or set, I will often use this technique – with full disclosure, of course – to make the stone suitable for use in these applications. Also, with the growing trend of repurposing old jewelry, I am seeing more sentimental gems coming across my counter that require repair rather than replacement. Enter the epoxy technique.
To get epoxy deep into a crack in a gemstone, mix it as you normally would and then mix that compound in a 50:50 ratio with acetone. (I generally use water–clear Epoxy 330, which is specifically formulated for use with gemstones.) You can simply paint this new mixture on the crack and it will penetrate very well. As the acetone evaporates, it leaves epoxy in the crack, which cures normally once the acetone is completely evaporated. This curing process may take a few days rather than the normal 24 hours for this particular epoxy, so don’t rush it!
To get even better results, immerse the gem in the epoxy–acetone mixture and then place it in a vacuum chamber to boil the mixture, which draws the solution even deeper into the cracks. A formerly unstable gemstone will be ready to set, inlay, or cut after this treatment—and your client will be glad you knew this handy trick.