The better marine varnishes contain about 3% UV filtering components. These components act in the same manner as Neutral Density filters used in photography, i.e, thicker coats don't give you more protection. The filters (coats) have to be stacked. For optimum UV protection with varnish, you should have an equivalent of 12, or 4 coats of varnish. More than 4 coats is probably guilding the lily--more cosmetic than protection from UV exposure. At this level (4 coats), you will probably be refinishing to repair dings, dents, and scratches long before the UV has any appreciable affect on the underlying epoxy.

: Hi all! The kayak's sanded, and I've got my Z-Spar Flagship varnish and T-10
: thinner, but never having varnished before, I'm wondering how many coats I
: can get from a 32 ounce can with 10% thinning? It seems that I should put
: more coats on the deck and gunwales for UV protection (maybe 3 topside and
: 2 on the keel), does that seem about right? Also, the websites that the BB
: has directed me to have conflicting information about sanding between
: coats. 320-400 grit versus 150 - 180 grit, any thoughts?

: David