Question about varnishing a table

D Swanson · Apr 19, 2020

Unless there is significant degradation of the existing varnish, I would de-grease first, sand it, wipe clean and apply. May also consider sanding with 400 + grit between subsequent coats.

BigEasy · Apr 19, 2020

Yes, you're on the right track.....degrease, and sand very lightly with 400 grit, vacuum & wipe, and apply a couple coats of your favorite sealer.
You got this before you needed to completely refinish!

rgranger · Apr 19, 2020

... and that is why varnish is better than polyurethane...

Also, polyurethane can be vapor tight.... so wood out in the sun with a coat of urethane can form a blister under the urethane as the wood out-gases ... Varnish can breath .... so urethane is a no-no for exterior wood that will be in direct sunlight.

dlochner · Apr 19, 2020

If you want to get rid of the gray streaks the only way is to strip all the old finish, sand and maybe bleach the wood. Then start over.

FWIW, I've grown fond of Epifanes Wood Gloss finish. It seems to hold up well to sun and can be recoated after 24 hours. If recoated within 72 hours no sanding is necessary between coats.

Will Gilmore · Apr 19, 2020

rgranger said:
and that is why varnish is better than polyurethane...

Read your specs carefully. Epifanes is "Formulated with tung oil, phenolic and alkyd resins and U.V. filters" from the Jamestown site.

But, Rust-Oleum (for example) "Spar Varnish, Resin Type Polyurethane,"

The big difference between a polyurethane "varnish" and a spar varnish is the addition of U.V. filters to the solution.

Some people like a completely sealed base-coat of epoxy filling the wood pores, sand to wood and coat with your favorite spar-varnish. I'm afraid I don't have the experience with many products to be helpful. I like the newer water-based spar-varnish because it's so easy to apply a build-up of many coats and re-apply every so often. Really, it's as easy as a quick buff and wipe on, not much harder than using a furniture polish. However, it's definately not as durable as oil-based varnishes. They are getting close though.

What I like the best about it is the clarity. As a woodburning artist, water-based varnishes don't have that darker patina.

-Will (Dragonfly)

dlochner · Apr 20, 2020

Spar varnish does indeed contain UV blocking properties, however, the big difference between a spar varnish and a regular varnish is it flexibility. When used outside, wood will swell and contract with moisture, heat, and cold. Spar varnish is more flexible than a non spar varnish so that it can accommodate changes in the wood and maintain good adhesion.

Spar varnish - Wikipedia

en.wikipedia.org

TomY · Apr 20, 2020

Captain Larry-DH said:
My cockpit table is starting to look a little beat up and the finish is degrading in some spots, and I'd like to freshen it up. I have some spar varnish on hand. My question is whether I can just scuff sand it and degrease before giving it a new coat, or should I sand it all the way down?
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Just give it a good flat sanding with 220 or 320 (320, more time = better finish). Use a block and make the old finish an even fog or mat sheen. If you want the best finish with no more work, use a 4" foam roller and plastic pan to apply and even coat. Roll and lightly tip (with a throw away foam brush) the top, brush the small bits.

As you have time, let it dry at least 24 hours, flat sand with 320 or finer (or just a 3M wood finishing pad) to an even fog again, and roll and tip again(using your pan of varnish, roller and brush that you covered and left in a cool place).

It's not likely the under side needs recoating but do that last after the top has dried. There's very little time and effort in this. The time is in the drying.

Will Gilmore · Apr 20, 2020

dlochner said:
Spar varnish is more flexible than a non spar varnish

Leave it to the knowledgeable members of SBO to expand and hone my limited knowledge. Thanks d.

-Will (Dragonfly)