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Thread: Satin Spar Varnish vs Fast-Dry Polyurethane????

  1. Satin Spar Varnish vs Fast-Dry Polyurethane????

    OK, I'm finishing on the desk now and am wondering if I should take the advice offered to try using Varnish instead of the Polyurethane that I've used on the nightstands and bed that I refinished. First off - the only varnish I could find is Cabot Spar Varnish in satin. Now I'm confused by the label; ..."ultimate UV protection & marine durability Interior/Exterior formula". Should I even consider using this on a piece of furniture? (a desk) What is the difference between this and Poly? Should I brush it on the same way I've been brushing the poly? Is the varnish going to protect the top of the desk better than Poly? (I've used Poly on our dining room table and it has scratched a lot!) Can I apply the first coat & wait the 6 hours (dry to the touch per label) and apply the 2nd coat without sanding, then dry overnight, sand and apply 3rd coat? Thanks for any advice

  2. #2
    Polyurethane is a varnish but one with different resins in conjunction with the oils and solvents. Poly is a short-chain oil varnish, thus less flexible so may crack if the wood shrinks/swells too much. The resins in Poly are harder so work well where you need a surface finish that is more resistant to wear - good for working surfaces like tables or desks. Perhaps the poly you used contained less of the poly resin and wasn't as hard as some are.

    Spar varnishes are made of what is called long-chain oils which are more flexible after curing which is important for applications that undergo large humidity changes, thus shrinking/swelling are more prevalent as in outdoor pieces. The spar would work OK indoors but would have a softer surface. UV protection is important if the piece is subject to direct sunlight as would outdoor use like boats. But no harm of using it indoors. The only way to really know if it will look OK is to put some of the finish you are considering on a sample piece of the wood you are using.

    Maybe some others will chime in here. There are lots of varying opinions on finishing IMO because of personal experience. I prefer lacquer but I spray and it isn't the finish of choice in all applications. It isn't as hard as poly but much easier to repair such as on a dining room table that gets scratched. Here's some pictures of some speaker cabinets I finished with lacquer.
    Last edited by Bill Davis; 06-09-2011 at 10:03 AM.

  3. #3
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    From what I've learned, mostly from the experts here on SMC, is that poly is tougher, not harder. Poly is meant for floors, period. Marketing and lack of education on these products is what leads many to using poly too often, I am guilty of this before I knew better. Poly is cheap to make, and it sells like crazy in the big box stores.

    If I was doing a table or desk top, I would probably use something like Behlen's Rock Hard...
    Last edited by Dave Gaul; 06-09-2011 at 12:58 PM. Reason: poly tougher vs. harder correction

  4. #4
    Thanks Bill! Great info on the poly vs varnish, now I know the difference. I do live in south Florida ( high humidity summer but lower in the winter) but since the pieces of furniture are for the house and not the porch I think I'll keep using the Poly. I like the way the bed and nightstands have turned out and I am comfortable applying the Poly. BTW - beautiful job on the speakers, nice dovetail detail! thanks

  5. #5
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    Polyurethane varnish is tougher than other non poly varnishes it is also SOFTER not HARDER than the other non poly varnishes. e.g. phenolic resin are the hardest resins also very UV stable, alkyd resins are the clearest and also harder than urethane resins. Many manufcturers add alkyd resin to thier poly formula to increase the hardness.

    The Behlen's Rockhard Tabletop varnish mentioned is a phenolic resin varnish. Much better for a desk top than any run of the mill big box store poly. Desks and tables need a hard varnish floors need a tough finish.

    As far as Spar varnish being made for BOTH interior and exterior... HMMM sounds like the marketing guy got carrier away with the discription. It's either a long oil varnish or a short oil varnish, can't be both.

    FYI NON poly varnishes don't have the "MUST BE sanded" between coats rule. That rule is because poly doesn't stick well to itself or anything else for that matter.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  6. OK Scott - now I'm going to get the Behlen's Rockhard Tabletop varnish, actually found a store 20 minutes away that carries it . Do I have to sand in between the 1st and 2nd coat with this varnish? How long should I wait between the 1st coat application and applying the 2nd coat?

  7. #7
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    "Spar" varnish is a poor choice for most interior furniture applications. It's a varnish formulated to be soft and flexible so it can remain adhered in very variable marine applications. Because it is soft, it is very likely to pick up impressions from writing with ball point pens and pencils. Therefore it's poor choice for a desktop.

    A better choice is an interior rated non-poly varnish (Poly varnish is also soft but not as soft as spar varnish). This would resist writing impressions better than a spar varnsish. Two hard varnishes are Waterlox Original and Behlan Rockhard. Both would be excellent.

    Another choice that would not be bad is a waterborne acrylic clear finish. Something like Minwax Polycrylic or General Finishes PolyAcrylic Water Base Top Coat are very hard finishes. Both are water clear and do not "pop" the grain as much as an oil based finish.

    If you have had success with the Minwax Fast Dry, I'd go ahead and use it. While not as hard as the finishes above, it should do just fine.

    No finish is bullet-proof. If the item is going into an abusive enviroment, you can expect that it will need to be refinished as some point.

    BTW, what is the species of wood in the desk? Softer woods are much more prone to impressions. It's really the hardness of the wood that determines the propensity for write through.
    Howie.........

  8. #8
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    Suzanne - some stuff Scott has 'splained to me in the past couple months on this very topic. Scott will be happy to identify exactly where I screw up in the translation:
    1] If you are brushing on the Behlens [or others similar] wait 12 hours before 2d coat, but less than 24 hrs. Then, no sanding needed.
    2] For brushing, reduce 10%. Official Behlen's reducer preferred over mineral spirits for reducing the Behlen's.
    3] From my personal experience, plowing though > 2 qts in the past few weeks: as a former failed brush-on guy, it turns out that it has been easier for me to do a really good job with about 15% reduction. It also turns out that a really good brush also made a huge difference for me, versus the best brush I could get at the BORG or hardware store.
    4] Once the can is opened, and also with the reduced varnish overnight, it will quickly skin over. Scoop off the skin, and if it looks like you left bits behind, strain through cheesecloth before using. However, I use my copper plumbing propane torch - without lighting it, of course - to fill the can/mixing cup with propane - other stuff works too, but propane seems to be fine, its cheap, I already had some, and it is about 50% heavier than air.
    5] You might consider wiping it on instead. 3 wipe on coats is approximately 1 brush on coat. Reduce 50/50. "Wipe it on like the kid cleanign the counter at Denny's" is what Scott said. Wait about an hour. No sanding then next coat. Wait an hour, then next coat. Wait overnight - up to 24 hours, then start again. Use the Famous Scott Blue Paper Shop Towels from the hardware store - no texture, and lint free. If [when] you get dust nibs, I just waited an extra day after last set of 3 wipe-on coats, then lightly sand it back with 320, then one final wipe-on coat.

    The table tops with the 4 brush-on coats - I will be "rubbing them out" - personal preference to get a dead-smooth surface. So - I sanded back the dust nibs between coats 2 and 3, and after coat 4 - and then one final wipe-on coat. Annnndddd....as explained carefully and clearly, I will be waiting a month before rubbing out.
    Once more unto the breach, dear friends, once more;
    Or close the wall up with our English dead!

  9. #9
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    You only "need" to sand between coats if you let it dry and cure for more than a few days. Since you are brushing it on i have a some more advice for you. Buy the Behlen's Reducer so you can thin it about 10-20% before you brush it. I have found it works better than regular mineral spirits. Make sure you use a natural bristle brush and soak it in the thinner BEFORE you start to use the brush. This will make the varnish flow better from the brush; will also make the brush much easier to clean up later.

    The can will tell you time to recoat, it should be very dry to the touch... not tacky at all. One coat per day brushing is a good rule of thumb. If you thin the finish 50% with the thinner and wipe it on you can do 3 coats per day waiting until it is dry to the touch before the next coat. Wipe-it on as the kid wipes the table just before you sit down at the fast food joint. A desk top should not take more than a few minutes to wipe-on the varnish. You want a very thin, damp coat as a wipe-on coat. typically 3 or 4 wipe on coats equals one brush on coat. I usually brush on the first two or three coats, then sand it flat and wipe-on the last 4-6 coats. Behlen's dries slowly so don'yt rush it.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  10. thanks guys, I'm so glad I found this site, it's been quite the education and I have greatly benefited from all of your awesome advice and wealth of knowledge
    I bought the Behlens Rockhard Tabletop Varnish, Behlens Reducer and the most expensive brush that I've ever purchased! (Badger?!! At first I felt sorry for the Badger but then I remembered from my childhood how a nasty Badger went after our family dog!!) I thinned the varnish for the first coat with about 10 - 15% of the Reducer. It went on so easy, much easier than the MinnWax Fast Dry Poly that I was using. So far so good and I'm so glad that I went out of my way to purchase the right varnish.
    Thanks to all of you again

  11. #11
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    We need photos.
    Once more unto the breach, dear friends, once more;
    Or close the wall up with our English dead!

  12. will take photos when it's completed and back in our newly remodeled bedroom

  13. #13
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    >>>> Badger?!! At first I felt sorry for the Badger but then I remembered from my childhood how a nasty Badger went after our family dog!!

    Don't feel bad for the badger. You may have bought a brush that claimed to be badger but if you spent less than $100+ dollars, it was a faux badger brush. No badger was killed or shaved.
    Howie.........

  14. #14
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    I used to do boat work and badger brushes were considered imperative. Then foam brushes came along and nobody ever bought another badger as foam does a vastly superior job. I can lay varnish on with foam brush that is as good or better than spray and the real joy is that when done, I throw it away.

    On another point all varnishes continue to cure for years and become very hard and shrink. Even spar. Just ask anyone who's had a wooden sail boat whether spar doesn't become brittle after about 5 years. One of the main differences between akyds and polys is the solids content which in poly is very low with high solvents so that most of what you pay for evaporates away. Poly is lousy for built up finishes as it takes so many more coatings. I usually build up with alkyd and finish with poly because it flows out so much better. My rule is that poly is fine for closed grain woods, but open grains you need the softer, more flexible alkyd or spar, otherwise in time you get checking with wood movement, no matter how thick your finish.
    Last edited by Harvey Pascoe; 06-23-2011 at 12:11 PM.

  15. #15
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    Polyurethane varnishes don't have more thinner than traditional resin varnishes, at least not generally. (By the way most single part poly varnishes have a substantial amount of alkyd resin along with the polyurethane resin.) Polyurethane resin is generally more flexible, not less, than interior alkyd varnishes. Spar varnish is even more flexible than most poly varnishes since that is a requirement on the marine applications where spar is called for. Spar varnishes are traditional made with phenolic resin (with tung oil) though there are marine spar varnishes that do include alkyd resin. Whether a varnish is brittle or flexible depends mostly on the proportions of oil to resin in the ingredients. Long oil (lots of oil) varnishes, such as spar varnish, are flexible, while short oil varnish is harder, more brittle which makes them rub out more easily.

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