A wipe-on varnish is an ideal finish for the woodturner. It is easy to apply, very forgiving, easy to repair, and gives the wood a durable protective film that is not easily damaged by water, food acids, body oils, or solvents. The only negative to using varnish as a wipe-on finish is the time that is required to build a high gloss surface film, and the “blotchy” discoloration that is often associated oil finishes. Discoloration, darkening and yellowing with age are the result of the resins and oils that are used, and this can be corrected to a large degree with selection of the varnish resins and oils.
In their simplest form, the wipe-on varnish is an oil, either Tung Oil, Linseed, or some other "drying oil", to which varnish resins have been added. These resins are harder than the polymerized oil, and impart a harder more durable surface film on the wood. Most of these finishes use Polyurethane resins, and the popular "poly finish" is nothing more than an oil finish to which polyurethane resins have been added. Other resins such as alkyd, phenolic, and any number of natural resins and gums, may also be used. These other resins are more expensive than the polyurethane, however, they may have some properties that we will like better.
Reading the resin content of a finish from the label can be confusing. The confusion comes from the tendency for the manufacturers to list the solidified oil that remains after it has polymerized is listed as a resin. For this discussion, I am using the term "resin" to define those that are ADDED TO the oil in the product and not the oil itself.
As a straight oil finish, Tung Oil develops a hard surface that is waterproof, doesn’t darken or turn yellow with age, and doesn’t discolor the wood. But, it doesn’t penetrate the surface very well, it takes forever to dry, and is more expensive than other oils. Partially polymerized Tung Oils solve the drying problem, and thinners can improve its penetration. However, these products are expensive and can cost upwards of $30.00 for a quart. Linseed, soybean, and other vegetable oils offer faster drying and better penetration, but they also turn very dark with age, many become rancid, they are not as durable, and they must be periodically renewed. They are also are far less expensive than Tung Oil.
The Varnishes (a very brief summary)
There are four types of varnish – alkyd, polyurethane, spar, and quick-drying. Any of these varnishes can be substituted whenever we mention “varnish” in this discussion.
Alkyds are the traditional varnishes extracted from Tung and Linseed Oils. These varnishes are durable, flexible, resistant to abrasion, have good adhesion qualities, resistant to discoloration from UV and light, and are relatively less expensive than the other varnishes. Their only negative is that they are very slow drying and will take 24-hours or longer to dry sufficiently for recoating. For this reason alone, the alkyd varnishes are becoming difficult to find as a furniture finish, but their superior qualities make them the choice for floor finishing varnishes.
Polyurethane resins have replaced the alkyds for only two reasons – they dry and cure faster, and they are less expensive. They are also more water resistant. But, several of the benefits of the alkyds have been sacrificed. Polyurethane varnishes are not light and UV resistant, and therefore will turn “yellow” rather quickly. They can become very hard and brittle with age and exposure to sunlight. Refinishing is difficult at best. They can also have adhesion problems with themselves and other finishes.
Spar varnish is a formulation of phenolic and alkyd resins in Tung Oil. Another crude comparison would liken phenolic resin to Bakelite®, waterproof, and very hard. Spar varnish is a relatively hard finish with superior water resistance and flexibility. It has a good resistance to damage from either acid or alkali substances or deterioration from light and UV. Unfortunately, it is very slow drying and it has a naturally deep yellow color.
Fast-drying, or VT, varnishes have been modified with styrene resins to produce a very fast drying time that is similar to that of a nitrocellulose lacquer. This speed comes with the sacrifice of the protective properties found in the other varnishes.
Which Varnish?
It should be obvious from a comparison of the properties of the various varnishes that we should be using either alkyd or spar for our woodturnings. Either will offer the flexibility to move with the wood as it changes with seasonal moisture changes, and provide the durable surface protection required for an item that will see frequent handling over a period of many years. Although I have preferred the alkyd varnishes for many years, it has become difficult to find as a furniture finishing product. However, it is readily available as a floor finish, but usually in nothing less than a 1-gallon container. I started using spar several years ago because it was easier to find. I have not found it to be superior to the alkyd as a finish for turned wood.
Many woodturners prefer the higher gloss from fewer coats and faster drying of the polyurethane varnishes. I don’t use them because I don’t like their plastic appearance. They may be faster drying, but there are the other problems as described above. The manufacturers have added a variety of ingredients in an attempt to solve these problems, but they have only succeeded in reducing them while increasing their cost.
Gel Finishes
These finishes have been promoted as “the answer” to our wood finishing problems. Gel finishes are the polyurethane varnish resins without the liquid solvents. These are the solids that will settle to the bottom of a can of poly-varnish. These finishes will give a more uniform surface coloring because they do not penetrate as deeply into the end grain as the liquid varnishes. Other than that, they have all of the same characteristics associated with any other polyurethane varnish. Bartley’s and General Finishes are the most recognized brand names.
Our preference should be a varnish based finish that can be applied with either a rag or a paper towel, rather than by a brushing or spray application. Any varnish can be used as a wipe-on finish with the addition of 50% thinner. The addition of more oil will help it flow out into a thin uniform coat. The amount of oil will influence the flexibility of the final surface finish and the drying time of the finish, more oil is more flexible and takes longer to dry. If too much oil is used the finish will be soft.
The quantity of oil in the finish is often referred to as being a long, short, or medium oil finish. Commercial varnishes as they come from the can are a “medium oil” varnish with about 50% oil. A typical wiping varnish is a “very long oil” varnish with 75% oil.
We will begin this discussion with the commercial products because they are where most woodturners go for this type finish.
Regardless of their advertising claims, all of these commercial finishes are the same – a mixture of varnish resins, some type of oil, and thinner. A true Danish oil doesn’t have the varnish resins. Most manufacturers have sacrificed finish quality for a product that is easy to use and fast drying. Most of them have added metallic drying agents to decrease their cure time. Some of them are adding varnish resins so that a surface film is produced. All of them contain a very large amount of thinner and a relatively small quantity of varnish and oil.
Although the manufacturers recognize the superior qualities of Tung Oil in a finish, many do not contain any Tung Oil at all. Regardless of their labeling, “Tung Oil Finish” has become a generic term for any oil finish. I have heard claims from other woodworkers that some of these do contain Tung Oil, but absent any list of ingredients on the label, I can only assume that they do not. Tung Oil has a unique odor that I can recognize, even in small quantities. Waterlox is the only commercial finish with that odor. There is nothing wrong with these products if they will produce an acceptable finish for you. I just object to the false advertising and labeling, and prefer to not use anything with “secret” ingredients.
I can recommend the following commercial products on the basis of personal experience. There may be others in the marketplace that just as good, but I have yet to find them.
Daly’s Sea-Fin Teak Oil
This is a Tung Oil finish that is widely available in the Northwest. In recent years their distribution has increased, so it may now be available in other areas. In my opinion, it is the best of the commercial wipe-on products. It is easy to get a good finish when the directions printed on the label are followed. It is a marine finish with good UV protection properties.
Waterlox
A nationally available Tung Oil product that is similar to Sea-Fin. It is generally available only through the mail-order catalogs. It is available as either the “Original” or as a “Marine” finish. Other than the “Marine” costing $10 more per gallon, I have never found any difference between them. Buy the “Original” because it is cheaper. It is now available in several degrees of gloss. I recommend the "High Gloss" and cutting it back with 0000-steel wool if you want a softer gloss.
Gillespie’s Tung Oil Finish
An excellent Tung Oil finish that is not quite as good (personal opinion) as Sea-Fin or Waterlox, but it is usually available at most paint specialty stores, and sometimes at Home Depot, Lowe’s, and similar retailers. It is available in both "gloss" and "satin". I have always preferred the satin gloss in this one.
Hope’s Tung Oil Finish
Another good product, but one that I have not used for several years because it is difficult to find, and when I have, the stock was very old. If you can locate fresh stock, try it. You will be pleased with the results.
Watco Teak Oil Finish
This is the one in the can with the blue label. While it is a Linseed Oil finish with UV inhibitors added, its finishing properties are considerably different from the more familiar Watco Danish Oil in the can with the brown label.
One of the good things about Watco products is that they have changed ownership so many times over the years that we can tell how long the can has been on the shelf by looking to see who made it. The latest manufacturer is RPM, and it is better than it has been in years. If you have sworn-off on Watco products because of things you have heard, or have had bad experiences with them, then try this one. I think that you will like it. Even the Danish Oil has improved since ownership by RPM.
.Watco Danish Oil
This is the one in the familiar brown can. There have been several different manufacturers in the past 20 years, and each has made their own adjustments to the formula. If you haven't used Watco Danish Oil for several years, try the latest made by RPM-Rustoleum. It is a good finish with more soliods for faster and more surable coating than any of its predicessors. It is a far different finish than the inferior product that was made by Min-Wax.
There are several other products sold under the name “Danish Oil”. These are an oil finish that is made from linseed, soybean, and other oils, and a thinner. Some of them now contain varnish resins, and they will build a surface film and gloss. Those that contain no varnish resins will not form a surface film, and are truely an in the wood no gloss finish.
While true Danish Oils are fast and easy to apply and have many other uses for our finishing, they are not a good final finish for our turned wood. The finish is soft, not very durable, and will require rejuvenation every couple years when exposed to even indirect sunlight.
It is interesting to note that there is nothing “Danish” in these finishes. They were first marketed in the late '50s as a way for the amateur woodworker to duplicate the finish on the “Danish Modern” furniture style that was popular at the time. Danish Oil is an oil finish. Danish Modern furniture was finished with a no-gloss lacquer.
.My Home-Brew Oil/Varnish Finish
I mix my own oil/varnish because I have control of the ingredients, it is always fresh, it contains more solids than the commercial finishes and therefore builds faster, and it is less expensive to use than commercial products. My opinion may be somewhat biased because I learned to mix my own finishes before any of the commercial mixtures were available.
I use a mixture of equal parts 100% pure Tung Oil, Varnish, and Turpentine. The proportions aren’t critical. If there is any error in the proportions, it should be towards a lesser amount of oil, and a greater quantity of thinner. Additional oil will improve its wiping properties, but it will also increase its drying time.
In my opinion, McCloskey’s, “Man’O War”, Gloss Spar Varnish (in the red can) is the best varnish on the market for turned wood. It has all of the benefits of a spar varnish because of its Tung Oil, phenolic, and alkyd resins. Its only disadvantage is that it is more expensive than other varnishes. A similar spar varnish is available as an Ace Harware house-brand in the green can. I have always preferred the traditional alkyd varnishes for furniture and turned wood, but they are getting difficult to find, and I have limited experience with the floor finishes mentioned earlier.
Pure Gum Spirits of Turpentine are used for the thinner because the natural oils become a part of the finish and enhance the qualities of the varnish. . Other thinners do not become a part of the finish. Turpentine substitutes are nothing more than an expensive form of Mineral Spirits (paint thinner) that evaporates more slowly.
Either 1-K kerosene, VM&P Naptha, or Mineral Spirits can be substituted for the turpentine. Naptha dries faster than Turpentine, Kerosene dries slower and mineral spirits dries only slightly faster, but also gives the mixture a shorter shelf life. None of them impart anything to the finish. The new odorless Mineral Spirits is not “odorless” and it is more expensive.
I use whatever good quality 100% Tung Oil is available at the local paint store because I like to inspect the cans for signs of aging before buying. Old Master’s and Hope’s are the brands usually available, and both are good quality. Boiled Linseed Oil can be used, but the resulting finish is softer and it will become darker faster than with Tung Oil. Changing the oil that is used to a 50/50 mixture of Tung Oil and Boiled Linseed Oil seems to better enhance the grain in highly figured wood such as Maple.
Wipe-On Application
The wipe-on, wipe-off, wait, buff with steel-wool, and repeat, application is familiar to nearly all woodturners who have ever used a commercial finishing product such as Watco Danish Oil. A “finishing-ball” is easier to use than a paper towel, and it doesn’t fall apart. Prepare the ball by making a golf ball sized wad of cheesecloth, and then wrapping it in a 6” square of cotton cloth. A sheet of paper towel that has been folded into as small a square as possible can substitute for the cheesecloth inside the ball.
A paper towel works well for small projects. Paper towels are always changing. I used Viva for years because it was softest and most lint free that I had used. Today I prefer Bounty. I fold the towel twice in the long direction, and then roll it as tight as possible to make an applicator that will keep my fingers out of the finish.
The directions for application are simple-
Wet Sanding Application
An alternative application is sanding with wet/dry paper while the piece is spinning on the lathe, using the finish as the lubricant. I dry-sand through about 150-grit, and then wet-sand starting at 180-grit and continue through 600-grit. Wipe the slurry from the wood surface before going on to the next finer grade. When you are done sanding you are done finishing. Let it dry overnight and buff with steel wool.
Al-Oxide or Garnet samdpaper can be used with the oil. The difference is that the binders that hold the grit to the paper will soften in the oil and the grit will come off the paper. The resulting slurry will do a good job of sanding the wood, The only problem is that it may have to be discarded after each use.
Apply a heavy coat of finish and keep it wet for several minutes. Sand the first coat with 400-grit wet-dry, and the second with 600-grit, to form a slurry that will act as a grain filler. Add more finish as it starts to dry. Sanding is omitted after the second coat.
Wait a few minutes until it becomes tacky.
Remove all of the finish with a soft cloth or paper towel.
NOTE:
This step is a problem for most users of oil finishes. When the directions say "wipe dry" they mean "DRY". It should be wiped dry enough that there is no smudge left from tiuching it. If you can see a fingerprint, wip it some more with a clean towel.
Wait overnight.
Buff it back with steel wool.
If the finish is not removed as a fine white powder by the steel wool, wait a few more days until it is.
Repeat Steps 1 through 5 as many times as required to achieve the desired gloss. I apply as many coats as needed to leave a glossy finish after waiting overnight, 5 or 6 depending on the wood, and then add one more. The highest gloss we can get with an oil finish is when the gloss of the dried finish is the same as that of the new coat that we are applying, and that will take at least 12 coats on most woods.
Submarine Application
This works very well for small articles - weed-pots, vases, etc. It also works for large pieces but will require larger quantities and containers. It may take several hours to days to complete the finish, but the actual time spent working on the finish is small.
A suitable mixture for this type of finish application can be made from:
1-gallon Boiled Linseed Oil
2-gallons Turpentine or Paint Thinner (Mineral Spirits)
1- quart varnish.
Add ½-cup of Japan Drier if you want it to cure faster when the shop temperatures are below 65˚F at night.
Use equivalent smaller quantities if you don’t want to make it in a five gallon bucket. This is not an ideal finish, but it is inexpensive, and just a good as Watco or the other Danish Oils. It is also an excellent preservative finish that is better than anything commercially available for wood decks and outdoor furniture.
I use this method for finishing large pieces that are turned from Western Red Cedar and Redwood burls. The wood is turned to its final form and thickness and rough sanded while it is still wet. Then it is placed in a tub filled with enough of the home-brew mixture to cover the wood, and left to soak until all of the water in the wood has been replaced with the mixture. This may take several days or several weeks. Then the piece is removed from the tub and set aside until the “finish” in the wood has cured. Again, this can also take several days to weeks. When all of this has dried, the wood is put back in the lathe given a final sanding, and the bottom is finished. A higher gloss can be brought out with a buffing wheel.
This same method that is used for Cedar and Redwood will give a translucence to Ponderosa Pine, Norfolk Island Pine, and Cottonwood, that I know of. There may be other woods that will exhibit the same effect, but these are the ones that I have used.
Water Borne Finishes
I don’t use any of these finishes because I don’t like the results and because they are constantly changing. These finishes could have a lot to offer. They could solve many of the problems that are associated with traditional varnishes and oils because they penetrate well, do not discolor the wood, and have a hard durable surface film that is clear and will not change color with age.
However, water borne finishes have a “bluish” tint and poor reflective qualities that leave the wood with a “muddy” appearance. And, they will not enhance the wood grain like an oil. They will raise the grain, but that is a minor problem. The manufacturers have added soluble oils and other ingredients to reduce the effects of these problems and make them behave more like the traditional finishes. So far, they have not been successful (my opinion). Meanwhile, the products are constantly changing as the manufacturers change their formulations, making it difficult to get consistent results from inconsistent products.
The manufacturers have created another problem for themselves by calling their water borne products by the same names as the traditional finishes. Then they have taken on the task to make them behave the same when they are not and never will be. Some brands have disguised the fact that their product is water borne, and we have to read the fine print on the back of the can to determine that water is actually used for clean-up.
After dry sanding, submerge the piece in a container of the finishing liquid for at least a couple hours, or until it is saturated.
Allow it to drip dry. Set it aside for several days until the finish is completely dry. If necessary, wipe off any excess that refuses to dry.
Buff it with a soft linen wheel that has been charged with a little Tripoli compound, followed with a wax buffing. The buffing wheels that are specifically made for wood finishing are the best. However, any hardware store cotton wheel can be used when nothing else is available. I always recommend using one of these first, then ordering the expensive wheels from Craft Supplies after determining that you want to continue using this finishing method.
