film finish or oil like finish

[Dave Fritz]

Would a home made mix of poly/mineral spirits/boil linseed oil equal parts be considered a film finish or a soaked in finish like an oil finish?

[Jim Becker]

It's still a film finish because of the varnish (poly) component...as are most "Danish Oil" products. It does "soak in", but if you were to put on enough applications, the "film" would become obvious. Most oil finishes not intended for things like cutting boards also cure, but they tend not to build like a varnish, at least in a reasonable number of applications.

[Dave Fritz]

Thank you Jim, I wondered if the addition of oil and mineral spirits did enough justify calling it an oil finish. Interesting that Danish Oil and Tung Oil are really not oil finishes. I've used the polymerized tung oil from Lee Valley thinking that was an oil finish but maybe I'm mistaken.

[Mel Fulks]

In 19th century writings there are recommendations to put shellac OVER a coat of rubbed oil. I guess that was over well rubbed in
oil. Did it once as a kid , so I don’t remember how it looked . But at the time , I thought in looked great !

[John TenEyck]

From a Bob Flexner article:

Film finish is any finish that can be built (by repeated applications) to a hard, thick layer, or layers, on top of the wood. The key requirement for a film finish is that it must dry hard. Alkyd and polyurethane varnish, shellac, several types of lacquer, water-based finish and various two-part high-performance finishes are all film finishes. Wax and any finish that contains mixed-in rather than cooked-in oil cannot be a film finish, because wax and oil dry too soft to be functional in any thickness.
Penetrating finish is a somewhat misleading term used to designate linseed and tung oil that don’t dry hard, so they can’t be built up to a functional film. The misleading part is that all finishes penetrate. Nevertheless, “penetrating” is the term most commonly used for oil finishes.

John

[Prashun Patel]

The mineral spirits thins the poly varnish for ease of quick and even coverage, but doesn’t otherwise change it from its film forming nature.

The inclusion of BLO however - depending how much you use - will inhibit the ability of the poly to polymerize into a hard film.

So you may end up with a soft , gummy finish if you try to lay it down like a varnish.

These blends are usually intended to rub on, wipe around and then wipe off so that no visible film remains. You will end up with a hard finish but little appreciable film.

I used to do mixes like this years ago, but realized (for me) that the blo does nothing but increase the flammability of any rags and that you can really achieve the same look and feel with a simple wiping varnish like Waterlox, arm r seal or poly thinned with mineral spirits. Just apply it the same way as you would the “Maloof Mix”. Wipe on, wipe off.

[Stan Calow]

This is the most interesting part of that quote from Bob Flexner:

". . . The misleading part is that all finishes penetrate. Nevertheless, “penetrating” is the term most commonly used for oil finishes."

I like the look of true oil finish too, but I know that it doesn't really penetrate significantly, and I can't see below the surface anyway. I think the benefit is that oil slightly hardens the surface (anyone ever do a mohs test for hardness on this?), but it's mostly for appearance. I like danish oil for the reason it provides the best of both.

[John TenEyck]

This is the most interesting part of that quote from Bob Flexner:

". . . The misleading part is that all finishes penetrate. Nevertheless, “penetrating” is the term most commonly used for oil finishes."

I like the look of true oil finish too, but I know that it doesn't really penetrate significantly, and I can't see below the surface anyway. I think the benefit is that oil slightly hardens the surface (anyone ever do a mohs test for hardness on this?), but it's mostly for appearance. I like danish oil for the reason it provides the best of both.

I doubt there's a mohs scale low enough for wood, though I could be wrong - and often am. But the pencil test often is used to determine finish hardness, after first determining how hard the underlying substrate is. I think the products that increase hardness of the wood itself would be limited to epoxy primer, CA glue, and similar products.

John

[Stan Calow]

John, that being the case, is the only "protection" oil provides is water resistance?

I used to hear that oil was popular because it "penetrated deeper", light scratches would not show, or would be easy to hide with another wipe. But I dont think thats true.

[Jim Becker]

Stan, it's surprising at how far oil does NOT penetrate!

[John TenEyck]

John, that being the case, is the only "protection" oil provides is water resistance?

I used to hear that oil was popular because it "penetrated deeper", light scratches would not show, or would be easy to hide with another wipe. But I dont think thats true.

Didn't Lincoln say something like "Believe nothing you hear, and only half what you read." But I would agree that defects in an oil finish are easier to hide by applying a little more finish to them.

From my experience, Jim is right about oil not penetrating very deeply, same with dyes, and pretty much everything. I once tried measuring how deeply dye penetrates during normal application. Best I could measure it's only a couple of 0.000's inches. Hard to imagine all that "depth" we think we see by highlighting grain with dye or oil is no deeper than that, but so it seems to be. If you have ever tried getting dye to penetrate a piece of veneer all the way through you'll see how hard it is to accomplish.

John

[Stan Calow]

Once, I had done my own experiment with a variety of wood scraps, sanded to a few different grits, and then painted with some oil and some varnishes. After a week, I cut through the pieces, and saw there was no penetration visible to the eye for any oil (tung, BLO, mineral or walnut). But I still wanted to believe that "drying" oils would make the surface tougher.