How to Apply an Oil-Varnish Finish
Traditional oil-varnish finishes are easy apply, versatile, durable, and highly resistant to water and stains. And with minor modifications they work well on both large (e.g., furniture) and small (e.g., candleholders) pieces. That's why they have been in use for literally hundreds of years. And while there are varying opinions on the subject, as a chemist I'm convinced that, after adequate curing (I prefer 2 months), oil-varnish finishes are perfectly safe for contact with foods.
Before you apply the finish, you should completely sand the piece, proceding through the grit grades (100, 150, 220, 400). If you happen to plan on staining (why would you want to do that?) then you should stop at the 150 stage, stain, and then resume the sequence.
After you finish sanding, make sure to remove all sanding dust
by wiping with a clean rag. Then, you’re ready to apply the finish.
My preference is Minwax Tung Oil Varnish*. It’s much easier (for me)
to work with in all situations.
Caution: Spread out all towels wet with varnish and allow to dry (24 – 48 hrs) before compacting and discarding. Varnish drying produces heat and the towels can actually catch fire if you ball them up while wet.
1. Wipe off all sawdust with a clean rag.
2. Using a bristle brush (chip brushes, available in a variety of sizes at home supply and crafts stores, are inexpensive and work well), apply an even, flooding coat of finish to all surfaces. Apply from one end of the piece to the other, and then go back and repeat immediately. [If the piece is large, as in the case of furniture, coat no larger area than you can cover in 5 min. and then immediately go back and start wiping off from where you started. Lap the next adjacent area and feather your wiping back into the previously coated area.]
3. Allow the piece to stand undisturbed for 5 min (so the finish will soak in), then with a good quality paper towel (Bounty is best), wipe the piece dry. Pay particular attention to crevices where liquid might have accumulated.
4. Set the object on a piece of unfinished, clean scrap wood (that will soak up liquid from the bottom and avoid sticking) and allow it to stand in a dust free environment for from 12 – 24 hrs. It will be “dry” to the touch within 3 hrs, but resist the urge to touch it.
5. Using 0000 grade steel wool, rub all of the surfaces to remove any dust or wood fibers that are present on the surface.
6. Use a small magnet, passed over all surfaces, to remove steel wool fines. Be careful not to scar the surface with the magnet. Pay special attention to any holes where particles might have accumulated. Then wipe with a clean cloth to remove fine particles.
7. Repeat steps 2 – 4 from Coat 1. If during step 2 this time around you see wet and dry areas, apply a little extra varnish to the dry areas.
8. Same as Coat 2, except that, if you don’t feel any roughness, there is no need for using steel wool.
Coat 4 – The Final Coat
For a matte finish -
9. Apply a thin coat of finish with a brush. Let stand for 5 min. Wipe completely dry with a clean paper towel. Let dry in dust free space for 24 - 48 hrs. before handling.
For a gloss finish
10. Dilute the varnish to 90% with mineral spirits, i.e., 1 part mineral spirits to 9 parts varnish.
11. Saturate two half sheets of paper towel with diluted varnish. Towel should be saturated, but you should not be able to squeeze out liquid. Wipe the entire surface with the towel, being sure to coat crevices. This application should take no more than 2 min max. – longer will create a tacky surface that will not shine.
12. Set the piece on an unfinished board and allow to stand in a dust free area for 24 – 48 hours before touching.
Change your mind?
Oil-varnish finishes are very forgiving and adaptable. Gloss can go to matte simply by rubbing well with 0000 steel wool and repeating step 9.
Matte can go to gloss simply by repeating steps 10 – 12.
Yet another variation to get matte is to perform steps 10 and 11, but after applying the finish let the piece and the towel dry for 10 – 15 min and then rub again. By that point, both the piece and the rag will have become tacky and the result of the second rubbing will be a matte finish.
The Final Polish – for both matte and gloss finished pieces.
13. After your finish has cured for at least 2 full weeks, polish off any incidental dust particles by rubbing vigorously with a rough paper towel. One of the well dried (4 weeks) towels from step 11 works fine.
14. Apply a thin coat of high quality, neutral color paste wax (Butcher’s, Briwax, or Minwax brands) with a paper towel or rag. Allow the wax to dry 30 min. Then buff with a clean soft rag or paper towel.
* I prefer Minwax Tung Oil Varnish (available at Home Depot but not Lowe’s) to Formby’s Tung Oil Varnish (available at Lowe’s but not Home Depot). Formby’s dries too quickly (i.e. gets tacky) and it is more difficult to treat large objects with it. Others, like Norm Sartorius, swear by Waterlox. In my hands Waterlox took too long to dry and thus was more prone to accumulate dust.
Varnish Storage hint: Each time you use the can of finish, before capping, be sure to flush out the airspace in the can with Kensington Duster II, Dust-Off, or some similar product. Just make sure that the product contains no air (actually oxygen is the culprit). Most computer, office supply, and home supply stores carry aerosol cans of several different brands of compressed air duster. Make sure your can has the 5" tube for directing the gas into your can or bottle. To use, insert the tube in the valve, then insert the other end of the tube into the can (but not below the surface of the liquid), lean the lid on top and release a gentle stream of gas into the can to displace all of the air (a couple seconds generally does the trick). Slide the tube out of the can and immediately tighten the cap.
By the way, don’t be surprised if the can tends to collapse on storage. The duster gas slowly dissolves in the varnish, creating a vacuum. But if no oxygen is present, the varnish will stay fluid for literally years. You might want to transfer the varnish to a glass bottle with a tightly fitting lid and flush well with duster for long term storage (glass obviously won't collapse under the vacuum).
When I open a new, large can of finish, I routinely pour most of it immediately into a glass bottle, flush, cap, and put away for storage. The rest of the can, just the amount I expect to use within a week or two, goes into a smaller glass bottle, which I flush and cap after each use.
Brush cleanup: Clean your brushes in mineral spirits or kerosene very soon after use. Brushes will last for years if cleaned immediately after use. To remove the buildup that inevitable occurs at the base of the bristles after long use, soak the brush in methylene chloride (dichloromethane, the key ingredient in many paint strippers) for a few minutes, dry with a paper towel, and use a stiff brush to clean out the hardened flecks of varnish.