
Originally Posted by
David G
OK - it's time for an overview and some definitions.
Overview --
Most finishes consist of some proportion of three primary components: oil; solvent; resin. Some small bits of additives are often included to achieve certain traits - like flowability, quick skinning, UV resistance, etc. But the types and proportions of the 3 primary components determine how to accurately label any product.
Definitions --
'Oil Finish' is - in my working lexicon - comprised precisely of the following percentages of oil/solvent/resin: 100/0/0. That is - oil only. The two most common used as wood finishes are Linseed Oil (usually boiled linseed oil), and Tung Oil. They're dead simple to apply, though tedious, and offer minimal protection. There are all sorts of hoary myths and old wives tales about why these "simple, pure, traditional finishes" are preferable - but in fact... they very, very, rarely are.
'Varnish' contains all three primary components, plus additives. For marine grade or spar varnish the oils are typically tung, BLO, soy, and/or safflower. The resins typically are phenolic, acrylic, and/or polyurethane. The solvents vary, but usually include mostly mineral spirits. This is applied by brushing or spraying - which isn't nearly as easy as wiping on some oil - but protects far better when complete.
In between those two are a pair of products - similar, but not precisely equivalent: wiping varnish and oil/varnish blends
'Wiping Varnish' is simple to conceptualize. Take any varnish, and thin 50/50 with mineral spirits. It can be applied with a rag. Wipe on. Let sit briefly. Wipe off. Repeat as many times as you'd like. Because it's so heavily thinned, the film build will happen more slowly, and typically ends up far thinner than a brush-on varnish finish. Therefore... it offers less protection. But it's easier to apply and re-apply. Daly's makes one of these which is very good, called Pro-Fin. I'm not aware of any commercial versions with UV protection - but it's simple to make your own, starting with a good brand of spar varnish. Application of this type usually stops once a minimum level of gloss is achieved, but you could go on for days, slowly adding film depth and gloss... if you were so nutsy as to want to <G>
'Oil/Varnish Blend' is more variable - depending upon the mfgr. Basically - you start with oil, add a bit of resin, then a good bit of solvent, and maybe some additives. This is the product that Mr. Girouard mentioned. Daly's SeaFin Teak Oil. Best of its ilk. I use it myself, quite happily. Typically, the resin content of this type of finish is less even than wiping varnish. So film build is slower, and protection less. One usually stops applying this before any gloss starts to happen. It's quite matte looking. Since it's also a wipe-on/wipe-off product... it's also quite easy to apply and touch up.
So - I'd say you have four options.
First - do nothing. I'd leave oil out of the mix, since it does require some time/expense... and you get essentially zero protection from it. Bad return on investment. The only finish that's be more of a waste of time for your application would be wax.
Second - oil/varnish blend, like the Daly's SeaFin Teak Oil.
Third - make up some wiping varnish using mineral spirits and some good spar varnish.
Fourth - brush on varnish.
Given the finishes on the rest of your boat, one could easily make the aesthetic case for spar varnish. It matches the level of gloss of many of the rest of the components, and, practically, it's the best protection. But - it'll be the most work.
OTOH - one could also make the aesthetic case that some matte components would provide some welcome contrast to all that existing gloss. In which case - nothing, or oil/varnish blend, or wiping varnish.
I hope this helps you visualize your choices, and I hope it reduces the level of confusion about the terminology that is common when one discusses finishes.
And for further reference - if anyone wants to learn more - my two favorite wood finishing bibles are Jeff Jewitt's book (I think it's just called 'Finishing'), and Bob Flexner's book, 'Understanding Wood Finishing'.