Popular Woodworking 2005-11 № 151, страница 76

As a result, varnish is actually the most difficult of all finishes to apply with near-perfect results. But there is a way around the problem: Thin the varnish so it cures faster (the thinner film combines faster with oxygen in the air), levels better and releases bubbles easier.

The product made by thinning varnish is "wiping varnish."

History of Wiping Varnish

Wiping varnish has been very popular with amateur woodworkers and refinishers for at least 35 years, but few have actually known that it was wiping varnish they were using. The finish was made popular in the late 1960s and early 1970s by Homer Formby. He traveled the country doing demonstrations ofhis new miracle finish, "Tung Oil," at shopping malls and antique clubs, and he made a number of infomercials that were broadcast on TV.

Few people were familiar with tung oil, which has its origins in China, so the exoticness of the name and source made the finish seem special. Formby was a master salesman.

But he wasn't selling tung oil. He was selling thinned varnish that he labeled "Tung Oil Finish." This finish is still available and the oil used to make the varnish isn't even tung oil. It's modified soybean oil.

It's important to note that even if this finish were made with tung oil - that is, tung oil cooked with a resin to make varnish - it still wouldn't be "tung oil." It would simply be varnish made with tung oil instead of some other oil.

Formby made contact with a very large number of people, however, and his mislabeled wiping varnish was a very good finish. So he won a big following and created a market for finishes labeled "tung oil." Soon other manufacturers joined in with their own "tung

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To make your own wiping varnish, add mineral spirits to any varnish. The more thinner you add, the better the finish will level and the less dust it will collect. But the thickness of each coat will be less. Begin by thinning with one part m ineral spirits to two or three parts varnish, and adjust from there to your satisfaction.

oils." Some made their varnish like Formby did - by cooking alkyd resin with modified soybean oil. Others cooked real tung oil with one of the resins.

Some misunderstood what was happening and actually sold real tung oil in its raw state and this really created problems. Incorrectly labeled or not, thinned varnish is an excellent finish because it cures hard. Tung oil doesn't cure hard, so it can't be built up on the wood without being sticky and gummy.

Moreover, unlike boiled linseed oil, which will produce an evenly attractive satin sheen after just two or three coats, tung oil requires five or more coats to produce an equivalent satin sheen. And each coat requires several days to cure and then has to be sanded smooth before the next is applied. Tung oil is a difficult finish to apply effectively, and many people who have tried it have been very dissatisfied.

Despite the difficulties with real tung oil, the market for a thinned varnish finish had been established. So as time passed, other manufacturers marketed their own versions of wiping varnish. Unfortunately, many of the manufacturers further confused the marketplace by labeling their finishes with non-informative names such as Waterlox, Seal-a-Cell, Salad Bowl Finish, Val-Oil, Profin and more.

The result is that no one using one of these brands now knows what finish they are using if they do no more than read the label. But all of these brands, being wiping varnish, are easy to use, and they produce excellent results.

Make Your Own

You don't, of course, have to buy pre-packaged wiping varnish. You can easily make your own. If you do, you can choose which type of varnish to use, polyurethane, spar or alkyd, and you can also choose between gloss and satin.

After choosing a varnish, turn it into a wiping varnish by thinning it with mineral spirits. (You can also use turpentine, but there is no advantage, and turpentine is more expensive and has a more pungent odor.)

To recreate a commercial wiping varnish, thin the varnish 50/50 with mineral spirits. To get a faster build, thin the varnish less. The less you thin the varnish, the

You can see the differences in the build of four coats of varnish thinned with 25 percent mineral spirits (top) and 75 percent mineral spirits (bottom). Each coat was brushed on and not wiped off. The lower the percentage of mineral spirits the greater the build of each coat, but the more likely you are to get brush marks and dust nibs.

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