The fallacy of conventional wisdom

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Forum topic by Clint Searl posted 06-13-2013 01:16 AM 1156 views 0 times favorited 4 replies Add to Favorites Watch
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Clint Searl

1533 posts in 2389 days

06-13-2013 01:16 AM

Topic tags/keywords: finishing

Conventional finishing wisdom has it that thinning a finish will increase penetration. Wrong!! The reducer may soak into the wood, but the molecules of the drying oil or resin that make up the body of the finish will only penetrate a few wood cells deep, where they will cure and present a barrier to any further penetration. Subsequent applications, thinned or not, will simply add to the film already started.

-- Clint Searl....Ya can no more do what ya don't know how than ya can git back from where ya ain't been

4 replies so far

View redSLED's profile


790 posts in 1920 days

#1 posted 06-13-2013 02:19 AM

Makes sense, I would agree with you – although I’ve never read about thinning increasing penetration. I’ve always thinned primarily to get a coat to dry faster or to have it “level” faster.

-- Perfection is the difference between too much and not enough.

View bluekingfisher's profile


1250 posts in 3007 days

#2 posted 06-13-2013 08:34 AM

Is there a need for a finish to penetrate in most circumstances??

-- No one plans to fail, they just, just fail to plan

View bold1's profile


293 posts in 1875 days

#3 posted 06-13-2013 09:46 AM

Unless you’re talking an impregnated finish(oil can be one), the others only seal the surface. They only adhere to the surface fibers. Most of us don’t have the equipment to pressure treat any finish.

View Wildwood's profile


2322 posts in 2162 days

#4 posted 06-13-2013 10:41 AM

Wisdom or advertizing hype you decide!

We use solvents to thin film & penetrating finishes to speed up drying times. Yes, we often use super thinned film finish as, spit, or wash, or sealer before applying topcoats. Film finishes give you a buildup of finish on wood surface even lacquer and shellac melt back into previous coat give a depth.

Penetrating finishes like Tung, Linseed, and Walnut Oils, do not penetrate deep into wood layers. Pure drying oils take several days, weeks, or months to dry. Tung oil provides most protection of these oil finishes. Stand (linseed) & polymerized (Tung) versions of these oils do dry faster. I do not use or include Boiled Linseed Oil as a finishing product. If want a green finish do not use solvents with these oils.

Manufacturer’s advertiser their wipe on wipe off oil blends and wiping varnish/poly as deep penetrating protection of wood. Amount of oil in these products often debatable many contain nothing more than resins, dryers & solvent. Wiping poly/varnish not created equally can have as much as 75% solvent.

-- Bill

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