Nonsense.
Haven't they ever seen a fine yacht, like a Hinckley B-40 yawl, for example, with miles of gorgeous varnished teak brightwork? How can anyone say that?
I take it personally, because I've been varnishing teak on various fine yachts for nearly thirty years. Once a guy approached me as I was in mid-brushstroke varnishing the toe rails on a Sou'wester 42, and berated me for telling his uncle how to varnish teak, because everybody "knows" you can't varnish teak.
As I said, I was varnishing teak when he launched into his tirade! It's what I do for a living, every workday.
And then there's the perennial debate about varnish versus teak oil. Unless your vessel resides in a far northern latitude like Scandinavia's, you'd better forget about using teak oil on your exterior teak.
If you think varnish is high maintenance, just try using teak oil. You will be quickly disabused of the idea that it's less work, and besides the hassle of continual re-application, it's a magnet for pollutants and dirt. It's difficult to keep an exterior oil finish looking presentable, and people who say teak oil lasts for months or even a year outside are sadly mistaken.
I've always advised prospective customers that the secret of maintaining beautiful varnish is to apply enough of it from the get-go, meaning at least eight coats of varnish, with two top coats of Cetol Gloss (clear) on bare wood in Maine, and at least ten coats of varnish, with two top coats of Cetol Gloss in Florida. I also tell them to ignore anyone who insists that the teak needs two maintenance coats every three or four months. That's nonsense.
If I had to recoat my customers' varnish that often, I wouldn't have any customers. There's no reason a properly applied finish shouldn't last a year, even in south Florida, as long as it's not abused, and kept clean. Letting crud build up on it by not bathing it frequently, at least once a week, can compromise its integrity, no surprise there.
Once I've done the initial ten or twelve build-up coats the first year, I do two annual maintenance coats of Cetol Gloss over the varnish thereafter. I've had people challenge me on this, expressing disbelief, but my customers will verify it.
Even with the best application of the best UV-resistant products, the wood will show color changes over time (usually lighter, not darker– sunlight bleaches wood, no matter what some "experts" say), and will lose some of the clarity and life of its grain. Even so, a properly maintained brightwork finish can look very good for 6-8 years, without stripping and revarnishing.
