preparing for varnish

[stephen m]

Greetings. I am about to varnish a white oak deck house that has been sanded to bare wood. What should I use to fill cracks up to 1/16 " wide before I seal and varnish ?
Thanks

[John Blazy]

Well, there is the easy way that may get cracks over time, or the right way that might be a little harder to sand. The easy way, since its above the waterline, is to use an off the shelf wood filler like Plastic Wood or Famowood color matched to the oak, then epoxy seal over this, then varnish. The epoxy gives more adhesion, durability and weatherability to the filler, as the filler is soft and porous. The advantage is that one-part filler is easy to sand and can be color matched. The con is that it shrinks upon cure and has fair adhesion.

The best way is to mix a thickened epoxy by mixing fairing filler, or fumed silica like Cab-o-sil - a thixotrope that thickens the epoxy to a gel, and then mix in fine sanding dust of a like colored wood til the goo is like peanut butter and can be puttied in without dripping out.

Then sand flush and seal/varnish.

Or you could just buy a fairing compound that doesn't have color, and simply color the filled cracks with a brown furniture touch up pen.

Or seal the whole thing with epoxy, then caulk the gaps with a brown urethane sealant like 3M 5200 or PL polyurethane door sealant (brown), and then varnish over.

[stephen m]

re: preparing to varnish
Thank you John. I think your easy method will be the best as there are lots of checks but they are very small. Thanks again. Stephen M