My church has asked me to refinish a baptismal font. It is a light colored burl. I plan to strip what is left of the old finish and sand it. It has some water damage and may need to be filled in places. Is spar varnish the best finish to use where water is a constant?
From contributor M:
It's my understanding that spar varnish is only different from regular varnish by the addition of more long oils in the mix. The word "spar" refers to the old ship masts that it used to be used on. The masts would flex and bow under the force of wind in the sails, and so the varnish on these spars needed to be flexible to keep from cracking and breaking off of the ship's timbers. As such, it's not any more resistant to water's action, despite what the advertising fluff says on the can (Helmsman... yuck). You may want to use something a little more like clear fiberglass resin or other clear epoxy if this'll be used in the bowl of the font. Better yet, go to a boat shop and find the products that they recommend for use under the waterline.
I've had very good luck with Waterlox. Their long oil is phenolic and tung oil (the best of the best) and their short oils can be gloss with a rub out or they have a nice semi-gloss. I usually thin the product with 25% naptha or mineral spirits and apply it like a wiping varnish. 24 hours between coats with 4 or 5 coats should do it. One of the nice things about this approach is that it is very easy to refresh - just wipe on a fresh coat. This is not a waterproof solution and you will have to go back and work on it once in awhile, but if you stay ahead of it , it should work well.