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Thread: Talk to me about sanding sealer

  1. #1
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    Default Talk to me about sanding sealer

    Iíve done a lot of painting in my life but Iíve never paid much attention to sanding sealer, maybe because most of my painting is usually over existing. Now Iíve built this new hatch for the boat from new wood, mostly Alaskan Yellow Cedar, a little mohogany. It will all be painted with oil base primer and enamel. Would a sanding sealer on the bare wood first be advantageous? What would it do that the primer wouldnít?

    C155D7DF-C693-40DD-8092-AD313D792ECF.jpg

  2. #2
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    Default Re: Talk to me about sanding sealer

    No. Sanding sealer is a product for interior woodwork. Just use the primer specified by the manufacturer of your topcoat. Barring that - a good shellac-based opaque primer.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  3. #3
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    Default Re: Talk to me about sanding sealer

    I use sanding sealer, clear automotive lacquer, in order to produce uniform absorbtion if I am going to use filler stain wood prior to applying varnish. Otherwise there is no advantage to using it as the varnish or paint will adhere to the wood better by soaking into the grain and forming a chemical bond with every added coat. If you are seeking rapid grain fill, then use primer under the paint. However not using primer will insure a better grip to paint. I just takes more coats to fill the grain.
    Jay

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    Default Re: Talk to me about sanding sealer

    A point to consider is if you think that, sometime in the future, someone will want to varnish that hatch.
    Getting tinted primer will be a bear to get out of the pores, so a clear sealer to fill and seal those pores would save hours or aggravation.

  5. #5
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    Default Re: Talk to me about sanding sealer

    You mean, like...CPES? Not gonna touch that one here.

    Nope.

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    Default Re: Talk to me about sanding sealer

    ^Me too!

  7. #7
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    Default Re: Talk to me about sanding sealer

    For exterior boat woodwork there are only two bright finishes I would consider.Deks-Olje is very durable but the two parts need a fair amount of time for a complete application.The alternative choice would be traditional varnish with a very thin first coat.

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    Default Re: Talk to me about sanding sealer

    Geeze Ron , That is a fancy hatch, lotta potential for the joinery to crack. I see this as one of the best uses of CPES . Stabilize the trim bits and corners .There is never a last coat, but there is a first.

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    Default Re: Talk to me about sanding sealer

    All that joinery is already epoxied together with adhesive filler. Think I’ll just primer and paint, or according to Jay, maybe just paint. The AYC has a pretty tight grain that doesn’t need filling. The mahogany top however is a little more grainy.

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    Default Re: Talk to me about sanding sealer

    There certainly is something to be said for allowing some future finisher to switch to varnish. In which case a couple of coats of varnish first (with or without CPES to start) is in order.

    Some opaque topcoats (paints) are designed to 'self-prime' - either by adding thinner... or not.

    Others are not formulated so as to make that a good option.

    So... what are you using?
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  11. #11
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    Default Re: Talk to me about sanding sealer

    Miller Paint custom color oil base enamel, same as the gray on the rest of the boat. This ain’t gonna be varnished while I own it, and doubtfully will be by the next owner as that would require rebuilding the matching hatch and just plain look stupid as the only varnish on the boat.

  12. #12
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    Default Re: Talk to me about sanding sealer

    The sanding sealer I buy is shellac based (others are available). Therefore it dries very quickly and means that you can get a coat of your finish on without the wait. But I only use it with clear finishes; thereís little point with paint unless youíre trying to seal in resin or knots.

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    Default Re: Talk to me about sanding sealer

    i usually paint with one or two coats of thinned varnish, a quick block sand then a coat of unthinned varnish. After that I paint with good old enamel, block sanding between coats. Wet sanding even, just like it was a Corvette! If anyone in the future wants to go back to varnish it's easier, and if the paint gets nicked or abraided it seems to afford a little extra protection.


    Nice hatch!

    Edit; For painted exterior work anything compatible with the top coats will raise the grain and cure hard enough to sand, works for me. Cheap thinned varnish is my go-to stuff for raising the grain for sanding.
    (I avoid dissimilar products and with traditional oil based finishes even thinned paint will work. It just takes time)
    Last edited by Canoeyawl; 04-08-2018 at 11:12 AM.

  14. #14
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    Default Re: Talk to me about sanding sealer

    Different tensions in expanding and contracting wood, metal, almost any base structure mean there is a risk in mixing fillers primers, topcoats.
    I'd never seen it in the UK but here it is typical to use a first coat of celulose grain filler, applied with a fad not a brush, then sanded back and a second coat, with a brush and sanded back. It leaves a surface like silk. then a coat or three, or like chinese lacquer work as many coats as you bother with, of alcohol based trad shellac. then gild, or prime, undercoat, paint, spray , varnish....... but all those different tensions would be a problem on exterior or marine work . Perfect and unbeatable for furniture,, interior woodwork , picture frames....
    For the hatch I would stay with the traditional primer undercoat topcoats in same base paint. Don't use acylic primer and enamel top coat, or other dissimilar media combinations. oil.oil, oil, or celulose celulose etc...
    'C'est la vie' say the old folks it goes to show you never can tell

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    Default Re: Talk to me about sanding sealer

    Pettit 2018 does a nice job. Generally dries in 2 to 4 hours.

  16. #16
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    Default Re: Talk to me about sanding sealer

    Part of the problem in discussing this topic is that the terms are sloppy. By that I mean that it's not at all uncommon for people to call something 'sanding sealer' when it's not actually.

    There are actually several different products that could be relevant to varnishing or painting wood: pore filler; sanding sealer; sealer; primer; topcoat


    'Pore filler' is designed to fill the grain of open-grained woods, like mahogany. Unlike the other products on the list, it's designed not to shrink. If you try to fill pores with anything else, the later shrinkage will show up the pore locations.

    'Sanding sealer' was developed for production use in the woodworking industry... to address two issues faced in a production environment. Back when the overwhelming choice of topcoats was clear (though the same chemistry applies to tinted/opaque) nitrocellulose lacquer. First - wood, esp. some species, can soak up a lot of 'sealer' material before the grain is sealed, pores filled, and it's ready for topcoat. Second - as we all know - end grain soaks up far more material. Which creates a production bottleneck... needing to add all those extra coats on the end grain before IT'S ready for topcoat.

    So sanding sealer was invented. It was based on nitrocellulose lacquer, but with a good bit of filler material added. Zinc stearate. Essentially... fluffy soap that works chemically with n.c. lacquer. The addition of the filler did two things. First - it slowed absorption into the wood, which substantially reduced the issues caused by end grain absorption. Second - it made the sanding sealer much, much easier to sand. The compromise? Sanding sealer is less water-resistant, it's much softer, and loses some adhesion. There are now vinyl versions also, but the compromises are similar. So that's 'sanding sealer'.

    'Sealer' is similar product without the zinc stearate. The differences between 'sealer' and 'primer' are even less well-defined - esp. in common usage. But the general idea is that sealer 'seals'. Examples would be using shellac to isolate a pitchy pocket or knothole... or using an oil-based 'pigmented primer' over plaster to isolate the alkali in the plaster from slowly attacking and breaking down the topcoat. Or any product that will separate and allow use of otherwise incompatible topcoats... like sealing an oil-based finish with shellac or vinyl so that a water-based topcoat can be used over it.

    'Primer' is quite similar to sealer, but with no larger consideration given to sealing. Some topcoats are formulated to work best with a separate primer product. Some are best 'self-primed' with a first coat (thinned, or not... follow the instructions) of the topcoat itself.

    There's another term that fits in here as well. 'Undercoat' is not a specific product, but can be used to describe any of the products described so far. We can argue about 'pore filler', but let's keep it simple and say 'undercoat' is anything under the topcoat except for coloring agents.

    'Topcoat' is simple. Barring any exotic 2/3/4-step finishing schemes... it's the top coat. Shellac, lacquer, varnish, paints (oil-based & water-based). It's what you touch and admire when the job is all done.

    That's a long answer to Ron's question - but I hope it clears up a bit of the muddiness, and gives us some common language.

    So that brings us back to the original question -- Would a sanding sealer on the bare wood first be advantageous? What would it do that the primer wouldnít?

    And my answer remains the same. NO. Sanding sealer was developed for a mass-production environment in order to make things happen faster, with more predictability. Using it in a more demanding marine environment would only highlight it's weaknesses.

    If you want to use a pore filler first, to make for a smoother substrate for whatever primer the mfgr. calls for... that's not a terrible idea. After that - use the specified primer, then paint.
    Last edited by David G; 04-08-2018 at 09:52 AM.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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    Default Re: Talk to me about sanding sealer

    The primer I noted above is clear nitro cellulose automotive lacquer. It takes anywhere from several minutes to an hour to dry, depending on temperature and humidity. Since lacquer is getting hard to obtain, due to EPA restrictions, clear shellac works fine as well. It just takes a bit longer to dry.
    Jay

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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by ron ll View Post
    All that joinery is already epoxied together with adhesive filler. Think I’ll just primer and paint, or according to Jay, maybe just paint. The AYC has a pretty tight grain that doesn’t need filling. The mahogany top however is a little more grainy.
    The joinery is too good for epoxy. Those corners look like they were made by an actual carpenter. Betcha they develop wee cracks!

  19. #19
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    Default Re: Talk to me about sanding sealer

    BIN (brand) primer sealer shellac(based) available at all the big box stores.

    You can put varnish over it or paint,
    They have clear and white.
    I love the smell of fresh cut plywood in the morning.

  20. #20
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    Default Re: Talk to me about sanding sealer

    Maybe I'm dreaming, but it seems like the longer the very first coat takes to cure, the better it will absorb into the wood.

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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by donald branscom View Post
    BIN (brand) primer sealer shellac(based) available at all the big box stores.

    You can put varnish over it or paint,
    They have clear and white.
    I've not used the clear BIN. But I've seen it on the shelf. As I remember, it's not actually shellac, nor even shellac-based. Some other chemistry entirely, if I'm remembering it correctly. No idea how it compares. Though they still manage to get the word 'shellac' on the label. 'Shellac-like' or some such verbiage.

    But the same company, Zinsser, DOES make a clear shellac sealer/primer. It's called 'SealCoat', and I've used it a lot, and like it a lot.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  22. #22
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    Default Re: Talk to me about sanding sealer

    When in doubt, read the instructions on the can. The paint manufacturers want their product to work. Really.

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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by pcford View Post
    When in doubt, read the instructions on the can. The paint manufacturers want their product to work. Really.
    Just so. And they set up those tech support phone lines for the same reason.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  24. #24
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    Default Re: Talk to me about sanding sealer

    My primer of choice is Pettit EZ Prime which is what I’ll probably use on this.

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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by ron ll View Post
    My primer of choice is Pettit EZ Prime which is what I’ll probably use on this.
    The truest answer is Pat's. Just use whatever primer the mfgr. specifies for under the topcoat you've chosen.

    The only question is whether to use the pore-filling goo first.

    The broader answer is that almost any primer designed to use under an oil-based topcoat is liable to work just fine. Maybe not nee-plus-ultra-best... but fine.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  26. #26
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    Default Re: Talk to me about sanding sealer

    The AYC definitely does not need any pore filling goo. It is baby butt smooth. It is the easiest nicest wood I’ve ever worked with, like carving a bar of soap. My friend gets a lot of scrap wood from a company he used to own (Quantum Wood Windows) and he can’t stand the smell of AYC so he gives it all to me.

  27. #27
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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by ron ll View Post
    The AYC definitely does not need any pore filling goo. It is baby butt smooth. It is the easiest nicest wood I’ve ever worked with, like carving a bar of soap. My friend gets a lot of scrap wood from a company he used to own (Quantum Wood Windows) and he can’t stand the smell of AYC so he gives it all to me.
    You're a lucky man. No, AYC is not a species needing pore-filling. Mahogany often can benefit.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  28. #28
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    Default Re: Talk to me about sanding sealer

    Not like the smell of AYC???
    That’s some blasphemy there.

  29. #29
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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by wizbang 13 View Post
    Not like the smell of AYC???
    That’s some blasphemy there.
    He's not alone. From my own small sample of woodworkers, it seems to be either love or hate.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  30. #30
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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by David G View Post
    He's not alone. From my own small sample of woodworkers, it seems to be either love or hate.
    I love the smell of it. My friend, a lifelong woodworker couldn’t get it out of his shop fast enough.

  31. #31
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    Default Re: Talk to me about sanding sealer

    I don't like the smell,
    but Port Orford Cedar is just fine...

  32. #32
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    Default Re: Talk to me about sanding sealer

    Quote Originally Posted by wizbang 13 View Post
    Not like the smell of AYC???
    That’s some blasphemy there.
    You deffinatly won't like the smell of Piss Elm then.
    Jay

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