Sand or not to sand?

I for one plane, scrape then sand, because I’ve been led to believe by the masses, including the finishers, that the timber will not absorb the finish if you don’t roughen up the surface with sandpaper.  Now that I think about it, scrapers alone without sanding to some degree more so than planing, will also roughen up the surface and produce a more vibrant surface than the dull surface effect you get with sandpaper.  I know some surfaces regardless will tear even with scrapers and your only option is to sand, but I’m more interested in the finishing side of this things right now.

Why is that the finish need to penetrate the timber?

When you think about it, we apply a sealer so we can build up coats quicker.  Forget the staining side of things to reduce blotchiness, lets just concentrate on the topic of building subsequent coats.  No product that I know of will penetrate the timber deeply, it will penetrate only about 1/4 deep or less, so again I’m asking myself why do we need to roughen up that surface when we’re going to build up several coats that is going to sit on and above that surface anyway.

Wouldn’t it be just easier to leave the fibres compressed and apply your finish that way?

Wouldn’t that also mean that you wouldn’t need to apply the same amount of coats?

Wouldn’t two coats be equal to three and so forth?

I tried this method once with the stool, I burnished the surface and applied German oil on it.  I only applied two coats as to the normal three and the results were equal as if I applied three coats.  My supplier commented that what I did was wrong, that the finish needs to penetrate the timber to give it deep protection, but what protection or nourishment does the timber need internally?  I think that’s a load of crock.  In my view the finish equalises the distribution of moisture if applied on both sides, it also gives some level of protection and obvious beauty.  But if we look at protection alone, it’s the subsequent levels of buildup and hardening that offers that protection.  The best levels of protection a finish can give is marine paint.  Obviously poly is better than oils with mixed poly in it, but if you build up ridiculous amount of coats of so called “Danish oil” you should get the same level of protection.  Because the poly is the key protector not the oil.  Btw don’t build up 50 coats of danish oil it will look ridiculous, believe me I’ve seen clocks coated with ugly thick films of danish oil but each to their own.  Three coats is the right amount of finish.

What got me in asking this question is when I saw this video on youtube, Planing or Sanding.  It’s made in Japan and it’s a short video in Japanese showing the difference between a planed surface and a sanded one. But, what caught my eye was the drop of water on a planed surface and then on a sanded one.  The droplet on the planed surface did not penetrate the timber while the sanded surface absorbed it.

So I’m genuinely curious why is that we need to allow the finish to penetrate our timber?

Is there anyone out there who is a finisher that can answer this question?

 

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5 thoughts on “Sand or not to sand?

  1. It depends. I typically finish with a BLO/wax blend and it works just fine on a tooled surface. The general thinking is that film finishes, such as shellac or paint, need the “tooth” left by sanding to adhere to. How much of that is science and how much is “tradition”, I don’t know enough to say.

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    1. Ok I get the adhesion part even though I must say I’ve burnished, applied oil, then shellac and it’s still adhered just fine. Fair enough going through all that work was pointless but I changed my mind on the type of finish I was going to apply at the very last minute.

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      1. Yep, I have done the same. Ive really only worked with a limited number of products, oil(BLO), wax, shellac and milk paint. I have yet to have any adhesion issues regardless of surface prep (sand/no sand). Possibly other finishes are much more sensitive. My limited experience tells me that given my finishes of choice, sanding is only required if needed to smooth a trouble area. I don’t sand for just the purpose of applying a finish and have had no issues. Maybe its just dumb luck…but, I don’t think so.

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      2. Yeah I agree it’s not dumb luck since I’ve done the same, so then we might call it a myth then until someone proves otherwise.

        Somehow I’m starting to think I have readers only, not contributors.

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