Ask the Staff
Question:
I am making a pair of Adirondack chairs out of cypress for my daughter. The chairs will live in the Seattle area. What finish would you recommend for this wet climate?
Thanks,
Jay
Answer:
Hello Jay,
Thank you for your question.
Because cypress can sometimes have some extraction bleeding of oil, it can make some film finishes a little fussy to adhere to the wood. If the wood is good and dry, you can probably prep the surface by wiping it off for your first coat of varnish using some naphta. You can then use a thinned coat of varnish for your first coat to aid pentration / adhesion.
5+ coats of a
marine (spar) varnish
, assuming you want a clear finish would give good protection, otherwise a high quality paint could work. And if the chairs live outside year round without overhead cover, expect to sand lightly and apply another coat of varnish about every year to maintain them. The idea is to encapsulate the wood and have enough surface build to keep water completely off the wood. Marine varnish should have UV inhibitors to help block the sunlight from degrading the wood (the UV protection diminishes with time, even though you still have a good film present for water protection.) When you reapply the varnish, you add back the UV protection (insert joke here about Seattle's lack of sunshine) (and the lack of need for serious UV protection).
A good intact amount of film barrier also fills the surface crannies of the wood surface. Those crannies more easily allow mold and algae growth to take hold. Thin wipe on oil coatings cannot give the smooth film protection you get from coats of a brushed on varnish (though you can find oil finishes that claim to have mildew inhibitors).
Here are some exterior oil finishes to consider:
Some folks say that an oil finish on cypress makes it darker than they like. This is a personal preference issue. When using any finish for the first time, be sure to do some test on scraps so you can know your methods and know your results (don't experiment on your mother-in-law's piano bench!)
An advantage with oils is that they don't end up "peeling" when the finish finally degrades enough like with brushed on varnish. Everything is a trade off. 4-5+ coats of varnish to really get good protection, but in a number of years the varnish will let go. Oil finishes can be reapplied numerous times and as they age, they don't degrade to a place of needing to be scraped or sanded away before refinishing. The trade off is that the multi coats of varnish will be a more solid barrier than an oil finish would be.
Regards,
Highland Woodworking
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