Varnish over oiled teak?

[Doc_V]

Hello all,

I'm currently working on a 78 Newport 30, the boat has sat since 2008 with no work, but the previous owner was pretty meticulous and it's in pretty good condition. However, all the wood topside, which I'm assuming is teak, appears to have been oiled because there are no traces of varnish. The grain is clearly not smooth anymore and the new owner [a friend] wants to varnish it. Are there any incompatibility issues with applying new varnish over the old oiled wood? If so, any recommendations on what to do to insure a good result would be greatly appreciated.

Thanks!

Doc_V

[CalebD]

Welcome Doc_V to Sailnut.

I always use teak oil prior to using a finish like varnish or Cetol. The oil makes the wood look great. Teak oil is also largely made up of Linseed oil which is one of the main components of most primitive varnishes. There should be no incompatibility between teak oil and varnish.
I stopped using varnish as it is too labor intensive and have switched to Cetol Natural Teak which holds up better. I find that even after oiling the teak and applying Cetol on top I have no problems with the finish coming up.
Of course, I like to let the teak oil seep in for about a week or two before I apply the more durable finish like Cetol. If I am in a hurry and can't wait I wipe the oiled teak down with Acetone on a rag and then start applying the finish coat. Wiping the wood down with Acetone prior to applying any finish is a good idea no matter how long the oil has had to seep in.
A caveat: teak oil will not make wood that has gone gray/silver with age look good unless it has been lightly sanded such that the wood is a more blond color. I have used a razor blade to take down the higher ridges followed by a light sanding with #220 grit sand paper and find that it is sufficient enough to allow the teak oil to soak in and create a nice ruddy (dark red) hue in the teak.
You might be amazed at how good your wood can look with a little prep work and some teak oil applied to it.

[RichH]

Oil and oil based varnishes are compatible. So depends on what type of varnish was used - oil based or urethane, etc. based.
However, an oil finish unless specifically 'loaded' with UV stabilizers will ultimately oxidize and darken to 'black'. Oil finishes arent good surface treatments of exterior teak for this reason.
Better to strip the oil either chemically with TriSodiumPhosphate - TSP or sand it down to flat-grained.
There are too many modern finishes that far exceed the service life of 'varnish'; and, constantly sanding, etc. the surface to constantly re-varnish 'wears out' the wood - faster than letting it go grey and 'eroded'.

[Doc_V]

Thanks for the info. I've been doing some additional digging around based on the Cetol recommendation, and it sounds like that's the way to go...

[juggleandhope]

is RichH's post the consensus - that our good options for exterior teak are;
a. let it go grey or
b. use a modern "finish" like cetol?

or is calebd's point that one should oil and then do cetol better?

since i'm new to this and have someone who would be willing to help with freshening up the exterior teak i'd like to know consensus best practice (or at least the 2-3 dominant perspectives). i'm in brooklyn and don't need to fight the tropical sun.