How much varnish is too much...

[Andy Rosser]

I'm having a hard time knowing when to stop applying coats of varnish to my chestnut restoration (note... it is my first restoration!) Each coat improves the look of the boat! I'm very careful to apply thin layers, and I've been thinning about 25% which makes it go on very smoothly in our current weather. Since I know you are dying to know, 6 coats so far. Planning to stop soon. Besides weight, what are the issues? Are there some parts you do more? Thank you for your input.

*edit: I am using Epifanes high gloss clear varnish.

 

[Dave Wermuth]

Or perhaps, how much is not enough? I usually quit at four, but I thin things differently than you. It's like the eggs, salt to taste.

 

[Todd Bradshaw]

Some of the modern finishes have definite maximum coating thickness specs and going beyond those amounts can cause a finish which is too brittle, prone to cracking, etc. It is generally quoted in mils of cured finish thickness rather than the number of coats. This is to get past different builders thinning the stuff in different ways. Traditional varnishes don't seem to share that problem. As long as the instructions on the can aren't giving you a maximum desired thickness or a warning about building it up too thickly I think it's up to you and what you like the look of.

 

[Tim Belcher]

I'm about to put on my first coat (ever) on the exterior. The instructions on my Epifanes varnish can says to apply three coats, thinning 50%, 25% and 15% and then "complete the varnish system by applying at least 4 more coats, thinning 5%" . That would make 7 coats at a minimum, and two more if you're in the tropics. Seems like a lot. I'm thinking I'll follow Dave's advice.

 

[MGC]

Tim,
I looked back to see what you have previously posted and it looks like you are dealing with a typical wood and canvas boat.
I'm wondering if you mistyped and meant to say that you are preparing to apply this "first ever coat" on the inside of the hull? There it makes sense to use a thinned Epifanes and gradually build it up to the depth of coverage that you think is adequate.
On the outside of the hull....putting any varnish on the exterior will generate some animated discussion. I have heard of anecdotal stories of restores using varnish on the hull, but I do not know anyone who actually does that. I personally use a warmed blend of turpentine, mineral spirits and BLO on the hull (after the inside has a been coated with spar). I know others use warmed BLO, tung oil, other blends of BLO and....but definitely not layers of varnish.

 

[Tim Belcher]

MGC - Thanks. No, I meant on the outside, after painting. Before canvassing I coated both the interior and exterior with a mixture of LBO, turpentine and varnish, then coated the interior with a couple of coats of slightly thinned varnish. I then put on the canvas, filled it and let the filler cure, and have now put on 5 coats of paint. I thought the next step was to put varnish over the paint. I responded to another post earlier today because the canvas started to wrinkle. Should I not varnish over the paint?

 

[MGC]

Tim, if you are using a high quality paint on the exterior and if you have achieved a satisfactory finish, call it done. It would be daunting to touch up any scratches if you varnish over the paint.
It is common to apply varnish over the epoxy finish on a stripper, but not on canvas, at least not in the last century.
If you look at some catalogs from the early 1900's you might find some reference to a coat or two of varnish applied over the one or two coats of color they applied. That practice ended with modern paints.
I'm pretty curious if anyone who is following this thread applies varnish over paint. I'd be very surprised to learn of it.
Mike

 

[Tim Belcher]

Thanks Mike. That's the best news I've had all day.

 

[Todd Bradshaw]

It is EXTREMELY difficult to get decent, even looking layers of varnish over paint - even by spraying. It may look great at first but give it a bit of time and the varnish will probably start to yellow a little bit. As that happens you will start to see the variations in varnish thickness - yellower where it went on a little bit thicker. Depending on what color paint you started with, this can be really obvious and look awful after a while.