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Sanding sealer

Discussion in 'Woodturning Discussion Forum' started by Vic Sinai, Aug 11, 2020.

  1. Vic Sinai

    Vic Sinai

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    Why use sanding sealer? I’ve read several articles about its use and many say it’s not necessary if you are going to apply a finish which also seals the wood. So I was hoping someone could tell me why & how they use it and what they think it accomplishes that most other finishes don’t. Thank you.
     
  2. Perry Hilbert

    Perry Hilbert

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    I make a lot of small items to be painted. Unless there is a sealant, particularly on bass wood or poplar, the paint job looks like crap. Seal first and then paint & looks good. I don't use it for things that will not be painted. WOP works well too. The items are sealed on the lathe, set aside to dry for a day and then painted.
     
  3. Mark Jundanian

    Mark Jundanian

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    I think the name "sanding sealer" is a misnomer. The purpose of this surface coating is to level out the microscopic gullies in the woods surface with a material that itself can be sanded to remove the microscopic peaks. It provides for a smoother surface than was achieved by sanding bare wood alone. Further coatings, such as varnish or paint can then be applied over this initial surface coating. In the paint example this can help prevent the grain pattern from telegraphing through, with varnish it will leave the surface smoother to the touch.

    Sanding sealers do not really seal any more than any other surface coating. All coatings provide some barrier, some more than others, but nothing short of molten plastic is impermeable to water vapor. The only place where sanding sealer may in fact provide for some sealing is when dye stain is applied after the sealer. I believe that some of the dye will penetrate, but sealer may modulate how much and where. I think there may be an effect with pigment stains, as well, but I'm not sure.

    Sanding sealer is most commonly a dilute (1 pound cut) of shellac, which has the advantage that shellac adheres to all other coatings. I believe there are sanding sealer products based on lacquer, as well. A good resource on finishes (surface coatings) is Flexner's book, Understanding Finishes.
     
    Last edited: Aug 11, 2020
  4. Vic Sinai

    Vic Sinai

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    Thank you. Would it help to apply when there are very light tool marks or tear out and then send.
     
  5. Larry Copas

    Larry Copas

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    No, I use a vinyl lacquer sanding sealer. The reason is it drys in seconds, easy to wipe on with the turning in the lathe, and improves water resistance of lacquer top coats. It also enhances defects such as tool marks, tear out, and scratches so I can see/correct them before finishing. I use it no matter what final finish I use.
     
    Ed Davidson likes this.
  6. Vic Sinai

    Vic Sinai

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    Appreciate the responses. Not as interested in making imperfections easy to see, but more so, easier to get rid of. Thanks again.
     
  7. Mark Jundanian

    Mark Jundanian

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    Vic, another trick is to wipe with mineral spiriits before applying coatings. This mimics what the finish will look like and brings out blemishes before you're committed to coatings. It also removes any remaining sawdust.
     
    Last edited: Aug 16, 2020
  8. Vic Sinai

    Vic Sinai

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    Thank you, so I guess by the answers so far it doesn't really make minor tool marks and tear out easier to deal with. Just helps to provide a microscopicly, (if there is such a word), smoother finish and feel once it is smooth to the naked eye. Correct maybe?
     
  9. Ed Davidson

    Ed Davidson

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    I've had good results using sanding sealer before painting. Never been able to get a finish like this without the sealer:
    [​IMG]
    [​IMG]
     
  10. Vic Sinai

    Vic Sinai

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    Amazing. You guys say you use it, but how. Apply a coat before every grit of sanding, only before the last grit or after all sanding is done? I guess in other words how do you use it.
     
  11. Ed Davidson

    Ed Davidson

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    I normally sand to 400 grit, apply sealer, and then a final sanding with #600
     
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  12. Vic Sinai

    Vic Sinai

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    Thank you, very helpful.
     
  13. Ed Weingarden

    Ed Weingarden

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    Another "non-finishing" use for sanding sealer is the following:
    If you need to do a repair on a piece, for example filling a crack (with sawdust, metal powder, coffee grounds, etc.) and applying CA glue, the CA will stain the wood and be very difficult to sand out. If you use sanding sealer before doing the repair, any stains from the CA will readily sand out.
     
  14. Perry Hilbert

    Perry Hilbert

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    Sanding sealer generally uses unwaxed shellac, because the shellac with the wax does prevent some finishes from adhering well. It may not seal the wood, but when I follow it with latex paint, the paint goes on smoothly, doesn't cake flake or raise more whiskers.
     
    Brandon Sloan likes this.
  15. Perry Hilbert

    Perry Hilbert

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    I do something similar. Sand to 400, apply the sealer, but since my items are small, I don't re sand. I make lots of Christmas tree ornaments for charity. Bright colors, a bit of shine, but they are not handled that much, like YoYos and some other items. That is also why I use cheap easy to turn woods like bass and poplar. very easy to sand out blemishes compared to maple or fruit wood.
     
  16. Richard Coers

    Richard Coers

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    Traditionally, shellac is a sealer. Sanding sealer is a base product with zinc stearates added for easy sanding with no clogging of the sandpaper.
     
  17. Don Wattenhofer

    Don Wattenhofer

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    Hey you should not be using derogatory terms for Italians. OK if WOP means wipe on poly that would not be compatible all possible top coats, however shellac is.
    The best thing to use when filling cracks or voids with powered stone or the other inferior (in my opinion) materials listed is a light cut of shellac and the purpose is to prevent the CA from sealing the surrounding wood and thus affecting the appearance of the final finish.
     
  18. Charles Cadenhead

    Charles Cadenhead

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    What brands do people use? Are all brands the same? Thanks!
     
  19. Dean Center

    Dean Center

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    No, sanding sealer will not remove or make your tool marks and tear out easier to manage. I don't paint things and almost never use sanding sealer. If I wanted a glass smooth surface on a project, a 'museum quality finish', I would use sanding sealer.

    Getting rid of tool marks and tear out is a perennial and lengthy topic. The basic answer is to sand a lot until you get better enough not to cause those problems.
     
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  20. Glenn Lefley

    Glenn Lefley

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    2434C1F6-4808-4D72-93B3-ECFBBDDA019F.jpeg
    A very good answer to what is sanding sealer and when to use!
     
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  21. Vic Sinai

    Vic Sinai

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    A great explanation. Thank you
     
  22. Mark Jundanian

    Mark Jundanian

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    @Glenn Lefley , from what publication was Dresdner's article taken?
     
  23. Perry Hilbert

    Perry Hilbert

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    I use Zinsser's Seal Coat. Getting hard to find. There is now a water based sealer, but it raises the grain too much for my use. Zinsser's seal coat is getting hard to find in these parts. Not at Lowes, Home Depot, Ace Hardware, Got mine at a True Value Hardware store that has since closed. I did find a qt of wipe on lacquer at my local Lowes. marked down to $2. It dries almost before it is applied to the item. Really lots of fumes. Found it works better for dipping items in it.
     
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  24. Ed Weingarden

    Ed Weingarden

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    Perry: Zinsser's Seal Coat - if you have a Woodcraft near you, they usually carry it.
     
  25. Dennis J Gooding

    Dennis J Gooding

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    Mark, Michael Dresdner has an excellent book "The New Wood Finishing Book" published by Taunton Press.
     
  26. Damon McLaughlin

    Damon McLaughlin

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    I use Zinsser's Seal Coat as well, our Ace Hardware carries it.
     
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  27. Gerald Lawrence

    Gerald Lawrence

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    Shellac can be used as a sealer but is not sand and sealer. As the article stated sand and sealer has stearates in it and according to Flexner this process was invented by the furniture industry in the late 1800's and the purpose to make sanding easier because it makes a soft finish. Anytime you use sand and sealer you have places a coat of a softer finish under your hard surface finish and it will dent or scratch easier per Flexner.
     
  28. Donovan Bailey

    Donovan Bailey

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    I rarely use a sanding sealer, however, when I do use it I use a lacquer sanding sealer cut 50% by lacquer thinner. Does a fine job and dries lickety-split.
     
  29. Don Wattenhofer

    Don Wattenhofer

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    I have never used sanding sealer on turnings and when I want to achieve a glass smooth finish I spray unthinned lacquer and sand between coats. The open pores will show up as shiny spots after the sanding so when those spots don't show up it is time to polish the finish to restore the gloss.
     
  30. Glenn Lefley

    Glenn Lefley

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    I’ll try and find where I got that. I save things I deem important so I don’t forget. Never thought to write down where 8 saved it from.
     
  31. Glenn Lefley

    Glenn Lefley

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    Found it. 2496E220-3DD5-4C6F-AFF2-26FF1F386BAC.png
     
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  32. Randall Hoch

    Randall Hoch

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    I remember hearing Bert Marsh at the 30 th Anniversary of the Utah symposium in a demo saying that he did the same thing with a 50-50 mixture of nitrocellulose lacquer and thinner. I’ve been doing the same
    And I like most of the time.
     
  33. Perry Hilbert

    Perry Hilbert

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    thats fine for items that won't be painted. I found with lacquer that some of the paints run and bleed terribly. I use oil paint pens for detail and striping. Sort of like magic markers but with oil paint. They work great over Zinsser's Seal Coat, fine over WOP, but bleed something awful when used over lacquer.
     

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