Varnish over Poly?

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Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
I built a cockpit table this year and have so far applied 5 coats of oil based poly. No matter how I thin it I cannot seem to get all the bubbles out. Can I sand it and apply varnish over the poly? Does anyone have a better suggestion? Tim R.
 
Feb 26, 2004
179
Hunter 260 Sophia, NC
What I do

after each coat I use fine sandpaper, and at the final coat I use a very very fine (almost plain paper) waterproof sandpaper with large amounts of water to get the last bubbles and dust out of the finish product. Hope this helps John B Baums Rush :)
 
D

Dennis

NO

I learned the hard way. Stick with the same product. I had to strip my table and start over because I changed poly to urathane or vise versa - either way it does not work.
 
Mar 21, 2004
343
Hunter 25.5 Carlyle, IL
When all else fails...

follow the directions. Most decent products will a detailed description of how to apply their finish over previously finished material.
 
Dec 2, 2003
4,245
- - Seabeck WA
I did this test last fall

I put varnish over urethane on outside wood. It worked well except where Hunter has seams in the teak such as the cheap cabin top handrails. The seams are letting the base urethane fail. The varnish isn't peeling though. Still, I'm gonna change to white starboard, like Ron Mills did.
 
K

kj

Try this

Seal with two coats slow curing West System epoxy. Let it soak into the wood. Sand with a medium grit sand paper 5 coats of varnish sand between second and forth coat Wet send final coat with a very fine sand paper Rub to a mirror like Finish with metal polisher such as Brasso or Noxon I used this technique when I refinshed wooden rowing shell about 8 years ago. This finish is just beginning to age this year.
 
C

Chris Burti

Gad, I hate writing this...

It's so much easier to 'show and tell'. First let's get straight on terms. Varnish is oil/alklyd paint...without pigment. Poly is polyurethane...a different beast modified in many ways by manufacturers. If you have 'oil-based poly'... you have some kind of hybrid that I am not familiar with. But it sounds suspiciously like some kind of marketing wiz's idea. Application is the same for either of the more traditional finishes...poly is more forgiving (and I believe more durable). The following 'rules' are for a 'perfect'finish (yeah...Santa Claus, Easter bunny and check's in the mail kinda thing)...you can still get a decent 3-foot finish while breaking most of them. Dont mess with the stuff if temps are below 65 degrees or above 80 degrees. Too low...won't flow, too high...fast dry. Never paint from the can. The brush introduces air bubbles into the medium that dry without bursting between uses, might as well sprinkle sand in there. Take a small clean can, punch a couple of holes in the side near the top so that you can fix a wire across the top about one-third of the way from the side. This is a 'striker'...use it to strike excess finish from the brush. Pour a small amount of finish into this can and work from it cleaning thoroughly between coats. Oh yeah, never pour leftovers back into the main can...bubbles and dust. I digress a bit here...I drag out my rakes, hoes, shovels, etc. when I am vernishing at home. I brush out the leftovers onto the handles, makes 'em last longer and reduces blisters. Speaking of brushes, invest in a good china bristle brush... we're talking at least $20 for a 1.5" brush. Cheap brushes simply won't get the job done. When applying the finish stroke in one direction only, wet to dry and don't go back over where you've laid the coat down. This is why a top finish requires 6-12 coats sanded between each coat. When you drag your brush over a section that is starting to skim over, you introduce new bubbles and you interefere with the finish's ability to flow out the bubble initially left there. You get the idea now why it is easier to 'show and tell' than trying to write out forty years of experience concisely.
 
G

Gord May

Good description Chris

Tho' show is easier than tell - Chris did a creditable job of 'telling'. Well done Chris; clear, concise yet complete.
 
Jan 22, 2008
519
Sundance Sundance 20 Weekender Ninette, Manitoba, Canada
further to the excellent directions

Two more points you may want to consider when applying this stuff. Point one: Make sure the varnish is warmer than the table you are applying it to. [If the table is warmer, it heats the varnish and expands microscopic bubbles to visibility] You can ensure a better finish if you let your varnish sit in the sun or pan of warm water for thirty miutes, but apply it to the table that is sitting in the shade. Any potential bubbles are absorbed. Point two: Always apply varnish (and epoxy) on a cooling temperature. Usually after two in the afternoon when the temperature has reached it's high for the day. Same principle, if the material and varnish are cooling, microscopic bubbles are less likely to expand. Any that do form , can be 'tipped off' with a dry foam brush at the gel stage of drying. Hope these additional tips help.
 
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robert taylor

great product

home depot sells a brand of spray poly (fast drying). it leaves a flawless finish. i just finished an enclosure over the nav table for my wife's computer/printer. i had the same problem...always bubbles no matter what. wet sand your final coat of brush on poly, then spray lightly with the spray product. the spray is not like regular spray paint....it is like a fog. do it on a day with no wind and you will have a perfect finish. my finish was satin...i can't take my eyes off of it.
 
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