Just ran into this in a refinishing article... See the last sentance.
Marine "spar varnish" is much softer than furniture or floor varnish, particularly in the sun or when it is very hot. Some spar varnish brands feel "sticky" when they are hot even after they are fully cured. This is a perfectly natural effect that allows the spar varnish to expand and contract along with the wood in the extreme marine environment. Modern spar varnishes also have UV inhibitors added to block the damaging effects of ultraviolet radiation from the sun. For both of these reasons, you should never use floor varnish outside on your boat and it is not recommended to use spar varnish on the floors of your house or on furniture that will be subjected to long periods of sitting unless you don't mind seeing the seat of your pants permanently imprinted in your priceless heirloom.
Hmmm, that's good to know!
I am actually in the process of using the Boiled Linseed oil. On chair 1 I've applied the first coat of 50/50 boiled linseed oil / paint thinner mix.
It darkened the wood up a little. Still waiting for it to dry. Next coat I'm going to go a little heavier on the linseed oil, I think maybe 60/40....
Not sure how many coats I'll end up doing.
I think on another forum, I found where someone said...
Apply 1 coat per day for 1 week
Then 1 coat each month for a year
Then 1 coat each year after that...
I'm sure that would provide incredible protection and looks, I'm just not sure I have the motivation to be doing all that....
Probably will just do 3 coats. Then a year later if they need a refresher, I'll pressure wash and apply more oil.