Reika is mostly correct, with some added details in fact, but there is also two elements that influence Aetherial Sparking, this was all explained in:

http://lodestone.finalfantasyxiv.com...f271d7a0a84d5f

Some notes:

Hand of the Gods will heavily lessen the loss of durability from any element that goes chaotic while under its effect.

Grand Design will always be +30% Progress on normal and good success, even under Ice and Lightning unstable.