Actually there are many possibilities around which do go from classical natural sealing with shellac or Urushi Laquer (mostly done on Jnats)...i prefer synthethic clear coating.
For Jnats check Keiths page:
http://www.tomonagura.com/jnats/japa...ng-a-jnat.html
I use a clear coating (Hobby Line Acrylic Clear Coating) which is UV stable....
I also used Dupli Color Clear Coating on some of my stones which till now works well...