Application of Varnish on Two Sides

[Kovar]

I'm refinishing the mahogany on my 1988 SPORT 13. I've sanded the original parts to bare wood. I've applied the [first of eight] thinned coat of Epifanes clear gloss.

Q1 : should I apply all eight coats on one side then flip?

Q2: or should I apply varnish to both sides with each coat?

Fig. 1. Wooden parts to be varnished.

wood.jpg (38.03 KiB) Viewed 635 times

[jimh]

There is another option: apply one coat to one side, let that coat thoroughly dry, apply one coat to the other side, let that coat thoroughly dry, sand both sides, remove dust, repeat seven more times.

[Palomino]

I was always told not to [apply] varnish [to] both sides [of teak wood parts used on Boston Whaler boats because that] would be encapsulating the wood, and if [the varnish were] ever nicked moisture [would] get into [the wood] and cause [the varnish] to blister.

I've varnished a fair amount of teak on Boston Whaler boats.

I use West System epoxy and then apply three coats of Epifanes. I have never had a problem [with moisture getting into the wood].

I don't leave the wood exposed, I always wash the boat down and put on a cover if the boat will be sitting for more than three days.

[jimh]

I was always told not to [apply] varnish to both sides...

Who gave you this advice?

If you leave one side of the wood unfinished, certainly moisture will be able to get into the wood.

[Palomino]

Think differently of [applying varnish to only one side of wood on a boat]: if you do not varnish the backside then moisture has a way of evaporating.

[Applying varnish to only the exposed side of wood on a boat] is counterintuitive but also makes sense. I think [what makes sense in only applying varnish to the side of wood on a boat that will be exposed to water and weather] has to do with [reducing the work needed] in maintenance [of the varnish finish]: there will be less work if you leave the back unfinished so moisture can evaporate instead of the moisture being encapsulated in the wood when there is a blemish or knick in the varnish.

On a restoration of 1983 Boston Whaler boat, the bow teak hatch top was varnished but the back was not. That was a paid job by a highly reputable person in the sailing and wooden boat world. When I asked [the hired workman] about [only finishing the weather side of the bow anchor hatch] he said something to [what I said above].

I have done it both ways.

I had already done the rest [of the above mentioned 1983 boat restorationI] myself. I stripped everything, [then applied three] coats of West epoxy, [followed with four coats] of Epifanes.

My finish was slightly darker [than the finish done by the hired varnish artisan] because of the epoxy. Both [methods of applying varnish proved to] hold-up equally as well, but only [the totally encapsulated wooden parts] at the bimini connections got water under the varnish and would have needed to be refinished at some point.

Both ways seem to have their places. Maybe [the preference for one-side varnish will be] only with something like an anchor hatch.

[jimh]

…only [the totally encapsulated wooden parts] at the bimini connections got water under the varnish and would have needed to be refinished at some point.

Those holes drilled in the wood should have been better sealed. When a hole is drilled in a wooden part with a varnish finish for a screw fastener to be installed, that hole needs to be sealed against intrusion of water into the wood.