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

  1. #31
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    Howie,

    Pratt & Lambert #38 is an alkyd resin/soya oil varnish. Not Alkyd/linseed. SW Classic oil varnish is indeed an alkyd resin/linseed oil varnish. I use both; P&L #38 is one of my favorite varnishes.
    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.

  2. #32
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    Quote Originally Posted by Scott Holmes View Post
    Howie,

    Pratt & Lambert #38 is an alkyd resin/soya oil varnish. Not Alkyd/linseed. SW Classic oil varnish is indeed an alkyd resin/linseed oil varnish. I use both; P&L #38 is one of my favorite varnishes.
    This is strange, when I did a google search on varnishes, none of these paint store varnishes showed up.

    Why is it your favorite and what do you use it for? Have you ever polished it?

    I see they have a data sheet:

    Dry Time: @ 77°F (25°C) 50% RH:
    To Touch: 2.0 Hours
    Recoat: 6.0 Hours
    Use: 24.0 Hours
    Rec. Film
    Thickness: Dry: 0.9 Mils
    Wet: 2.9 Mils

    With a dry film of 0.9 mils and only 33% solids, this looks good for a finish coat, but It'd be an arduous task filling grain. But recoat in 3 hours, wow! But then I see their spar varnish has the same specs with 51% solids. This doesn't seem right as the spar should leave a thicker dry film.
    Last edited by Harvey Pascoe; 06-29-2011 at 4:41 AM.

  3. #33
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    This doesn't seem right as the spar should leave a thicker dry film.
    You're overlooking a critical piece of information..

    The #38 has a dry film thickness of .9 Mils at a spreading rate of 550 sq ft per gallon.
    The #61 has a dry film thickness of .9 Mils at a spreading rate of 800 sq ft per gallon.

    You're also mixing solids by weight & solids by volume.
    The #61 Spar has 44% solids by volume - that's the figure you use to compare it to the #38, not the soilds by weight number (51%)

    For calculating spread rates and dry film thickness, you always use the soilds by volume figure.
    Solids by weight are used to detemine if the product is up to spec.


    BTW & FWIW - you're only fooling yourself that clear coats will "fill" surface imperfections.
    Anything that flows - even drywall mud - will conform to the surface it's applied to.
    If you want to fill grain - use some form of mastic (filler) & save the clear coat for what it's intended use is - a clear protective coat.

  4. #34
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    Okay, Rick, so you're saying that the millage rate given is only for comparative purposes at the spread rate given? Makes sense if the spread rate is unusually low. Apply a thicker coat and the dry millage is also thicker. Got that.

    But as for filling grain pores, I've tried many water base "clear" fillers and find two serious weaknesses: (1) they cause a color shit in many dark woods and (2) they are not very effective so I gave up on them as not worth the effort. Don't know why you think I'm fooling myself. I work at leveling grain porous wood with just varnish every day, leveling by sanding between coats. Usually takes 5-6 coats to produce a mirror finish, even on burls. On imperfections, such as bit of tear out, I daub varnish in the depression with an artists brush to fill it, then continue the finishing after it cures. Tedious but effective.

  5. #35
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    Harvey,
    Clear coats aren't meant to go on heavy. Too much of a good thing type of deal. Also, any coating, clear or otherwise, depends on the integrity of the film to form an effective barrier. When you apply a coating, then remove the high spots, you break that continuous film. You can't "bandaide" it by putting on another coat.
    Another thing "heavy" application does is lead to solvent entrapment.

    Scott is spot on above about thinner and solvent being two different things. If you thin varnish with MS and it skins over w/out fully curing and traps the MS, there's no harm/no foul ( Howie is also spot on in that respect). Thinners extend materials by getting in between the molecules and spreading them out. Generally, the molecules of a thinner are smaller than the moleules of the materials they thin. They can pass through even a film that's dry to the touch.

    Solvents, OTOH, dissolve - or rip apart the molecules - literally at an atomic level.
    If you trap solvents underneath a film, it will destroy the film as those solvents escape.

    You may or may not see the effects right away. It may takes months for the effects to show up.

    Seriously - you're going to a lot of work to end up with an inferior finish. One "classic" symtom of too heavy a coat is premature failure.
    If the mfg says 3 coats, they mean 3 coats. Anything more is going to detract from the final finish - not add to it.

    I can't help you much with the selection of a specific filler, other than to say there's a lot of them on the market.
    You'll probably just have to look around for one you like.

  6. #36
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    Rick,
    You are saying that by final wet sanding and polishing varnish, I am producing an inferior finish?

    I produce a commerial product, many of which are years old and I see no deleterious effects.

  7. #37
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    Harvey,

    You may want to try de-waxed blonde shellac as a filler. I would NOT use it on red oak or ash (pores are too large); on walnut, maple, alder, cherry and mahogany is works better than any varnish as a filler. I usually apply a couple of coats of 3# shellac, then sand it back so the shellac is only in the pores. Fresh shellac mixed from flakes is completely dry in a day or less. Give it time to co,pletely dry so you don't get shinkage later. Shellac is hard, optically clear, color fast and fast drying. Varnish can be used as a filler; it is very slow drying compared to shellac.

    As for P&L #38 varnish I use it when I don't want the dark amber color of the phenolic resin varnishes. As for poly (single part) I only use it on floors. Never outside, UV damage is guarenteed in Houston.
    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.

  8. #38
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    At what ratio would you mix it? Never even occurred to me to use as a filler since the standard ratio produces an extremely fine film. I"m thinking you must be getting close to 1:3 or thereabouts? Kinda syrupy?

    I usually sun dry my work so its dry to handle within and hour or so; we are very dust free here, but I have to be careful to not let it get to hot or it will gassify and make nice little bubbles. Winter is a different matter, so I switch to fast drying despite its low viscosity.

    I never said filling grain with varnish was easy, but that is the way it was always done in the boat building biz, except for interior work where they used filler stains. Varnished teak no less, a very grain porous wood.

    So, I guess we've covered all the reasons why creating mirror finishes is not popular and wipe-on products are. LOL.

  9. #39
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    If you apply numerous coats in order to fill pores, then you will have sanded off most of the surface material, leaving total film thickness quite appropriate. There just isn't a problem applying 6 coats of varnish in that context. And, I suspect with oil based varnish, there is enough more flexibiltiy even in interior varnishes to tolerate more film thickness that there is in certain newer finishes, such as conversion varnish, where the thickness limitations are really important to observe.

    Spar varnish, while too soft and flexible for interior furniture, is also an example where you don't have problems with building a finish. It needs thickness to work, and 6 or 8 brushed on coats are quite appropriate.

  10. #40
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    As I stated, I use a 3# cut (3 pound cut) e.g. 3 oz of dewaxed shellac flakes in 1 cup of alcohol.
    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.

  11. #41
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    I'm about to tackle some India rosewood, which needs a shellac sealer anyway because of the wood resin, so I'll take a shot at thickening up the mix a bit and see how that goes with multiple coats for grain filling. I work small and mix batches of about 3 oz so the pound/cut rations are greek to me. I don't measure, just guess.

    Sure does sand quick, so maybe that is a solution.

  12. #42
    Here's a shortcut that works for me:

    "1# cut" = 1lb of shellac in 1 gallon of DNA.
    1 gallon of DNA = approx 8 lbs ethanol.

    So, for a 1# cut, however much DNA you have, just add 1/8 as much shellac.

    It's easiest for me in 8oz batches:

    1# = 1oz flakes + 8oz DNA.

    For 4oz, it'll be about:

    1# = 1/2oz flakes + 4oz DNA
    2# = 1oz flakes + 4oz DNA
    3# = 1.5oz flakes + 4oz DNA

    Truth be told, these days I just do it visually.

  13. #43
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    Remember that you need to sand it back, so it's only in the pores to use it as a filler. Then one light coat of 1# or 2# to seal the rosewood.
    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.

  14. #44
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    >>>>Truth be told, these days I just do it visually.<<<<

    Truth be told, probably every one does, but won't admit it. I have a micro scale so I could go the hard way, but I see no need for exactitude. I do enough mixing of glues with the scale to discourage me.

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