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Old 05-08-2013, 14:39   #1
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Varnish over Polyurethane? And PU over Varnish?

Well, I wouldnt be putting this question on the Wooden Boat forum

but....

My boat interior is Duka with polyurethane and with some bits of varnish in some spots by previous owner.

The laminates used are extremely thin and I really dont want to sand anything back cos it wont be 'back', it will be 'through'...

Please dont answer as a purist...

a) Can I put Varnish over Polyurethane without a devastatingly bad result?
b) Can I put Polyurethane over varnish without a devastatingly bad result?
c) Can I put 3 layers: Polyurethane: Varnish: Polyurethane?



One of the reasons for being able to use varnish is colour matching/contrasting.
I am in Grenada so I can buy one type of Polyurethane and one type of varnish. I can not order from overseas etc.



Thanks for your help.


Mark
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Old 05-08-2013, 14:43   #2
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Re: Varnish over Polyurethane? And PU over Varnish?

You can color the poly! Fair warning though, the surface MUST be roughed up a bit otherwise it will peel. Learned that the hard way with floors. Some more, poly is much harder than varnish and there are many who consider poly to be a form of varnish.

Now what you did not state is whether the poly is oil or water base. Water base will not have the orange color most think of with poly and you can apply oil base over water base although I believe you run a risk of peeling if you go water over oil.
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Old 05-08-2013, 14:51   #3
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Re: Varnish over Polyurethane? And PU over Varnish?

Yes, I'm roughing up the surface with 220, just not sanding back to the original wood.

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Old 05-08-2013, 15:34   #4
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Re: Varnish over Polyurethane? And PU over Varnish?

Mark, 2 component Poly cant be over 1 comp varnish , now there is regular 1 part Polyurethane and this one is compatible with regular varnish,


a) Can I put Varnish over Polyurethane without a devastatingly bad result?


YES YOU CAN, NO PROBLEM.

b) Can I put Polyurethane over varnish without a devastatingly bad result?


SAME,, NO PROBLEM IF THE POLY IS 1 COMPONENT. 2 PARTS POLY SOFT AND PEEL OFF 1 PART VARNISH.


c) Can I put 3 layers: Polyurethane: Varnish: Polyurethane?

IF IS MONOCOMPONENT YES...


To bad you cant strip the old coating, i mean if you dont want to take the risk , with a heat gun and a wood scraper is a piece of cake for me , 4 months agoo we strip all the cabin sole , take 1 week, and i use west system , 3 coats with the thin hardener to seal the teak sole , and after 4 coats of Perfection 2 part varnish , the result is amazing , and i hope last for many years....
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Old 05-08-2013, 15:43   #5
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Re: Varnish over Polyurethane? And PU over Varnish?

Just completed my interior. Used Minwax had rubbed polly over Minwax varnish not a problem used fine bronze wool to roughen a bit between coats. Applied 5 coats. Can apply 2 to 3 coats a day depending on weather looks great.
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Old 06-08-2013, 08:26   #6
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Re: Varnish over Polyurethane? And PU over Varnish?

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Originally Posted by casual View Post
Just completed my interior. Used Minwax had rubbed polly over Minwax varnish not a problem used fine bronze wool to roughen a bit between coats. Applied 5 coats. Can apply 2 to 3 coats a day depending on weather looks great.
I'd be interested in knowing a few more details about what process and materials you used. As you probably know, repairing or refinishing a Cabo Rico interior is a challenge because the original finish is such a big secret. I've heard it was a french polish, but that finish is not very water proof and I can't imagine it would work well on a boat.
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Old 06-08-2013, 12:24   #7
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Re: Varnish over Polyurethane? And PU over Varnish?

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I'd be interested in knowing a few more details about what process and materials you used. As you probably know, repairing or refinishing a Cabo Rico interior is a challenge because the original finish is such a big secret. I've heard it was a french polish, but that finish is not very water proof and I can't imagine it would work well on a boat.
I have no idea of the original finish or if it had ever been redone. I suspect some areas had been refinished. In the main cabin I sanded out as many of the small scratches as possible then worked carefully tp reduce in size the larger ones.I started with 150 grit and worked my way up to 320 and then bronze wool. Then wiped it down with alcohol. The first coat was Minwax satin varnish this has enough color to bring a uniform color to the wood. Next applied Minwax Hand rubbed satin bronze wool fine between coats. This was all applied with cheese cloth. When looking at the original finish on the back side of doors ect it is close but not the same.I believe the front side has seen a lot more wear and light so consequently the wood will change. My objective was to make it better not perfect . Including the cabin sole over 2 months work.Had the finish not been as bad as it was I believe a good cleaning a light scuff with bronze wool and a coat of Minwax hand rubbed would have done the job.
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Old 06-08-2013, 13:26   #8
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Re: Varnish over Polyurethane? And PU over Varnish?

I've only redone spot jobs below with varnish, places like the head and the companionway. So far I've gotten reasonable results using the inexpensive Cabot Spar Varnish from Lowes or Home Depot for interior finishing. For exterior I use Petit Z-Spar Flagship varnish. There is just too much wood to try for a factory finish, even if I had the formula and all the stuff that goes in the formula.

Rich
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Old 06-08-2013, 16:31   #9
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Re: Varnish over Polyurethane? And PU over Varnish?

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I've only redone spot jobs below with varnish, places like the head and the companionway. So far I've gotten reasonable results using the inexpensive Cabot Spar Varnish from Lowes or Home Depot for interior finishing. For exterior I use Petit Z-Spar Flagship varnish. There is just too much wood to try for a factory finish, even if I had the formula and all the stuff that goes in the formula.

Rich
Thanks for the info on Cabot.FWIW last year I removed the strike rail teak for painting the hull.Put new teak back up treated with Cetol light a year later still looks good.Now the cap rail. Dave
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