Tuesday, November 21, 2017
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Wipe on Varnish
Wipe on Varnish
Created by Steve on 8/29/2010 6:11:41 PM

If you are having problems applying varnish then give this wipe-on technique a try.  Its quick, easy, and best of all no runs, sags or brush marks...

Wipe-On Varnish
as close to Fool-Proof as it gets


The only significant difference between applying varnish using the wipe-on technique vs. applying varnish with a brush is ease of application.  The product is the same and you will get identical protection however you apply the varnish.  Once the finish film is on the wood it makes no difference how it got there.  Therefore, if you have been having problems applying varnish with a brush; if you are getting trapped air bubble, brush marks, sags, runs, and other unsightly 'glitches', then give this technique a try.  I think you will find the wipe-on method as close to 'goof proof' as a finish can get.

Rather than buying a product labeled “Wiping Varnish”, let me encourage you to make your own.  Wiping varnish is very easy to make and your home brew will be functionally equivalent to any commercially prepared product. Wiping varnish is simply full strength varnish that has been thinned sufficiently to allow it to be wiped on. Therefore, why pay a finish manufacturer for a can of diluted varnish when you can do the dilution yourself and save?  The standard home brew recipe for wiping varnish is 'regular' varnish thinned 50/50 with mineral spirits.

This may be a good point at which to pause and talk briefly about the issue of thinning varnish. All varnish (except that already thinned by the manufacturer and labeled "Wiping Varnish" or "Sealer/Finish") should be thinned before use. The question is not whether varnish should be thinned; the question is by how much it should be thinned. That is a function of how the varnish will be applied. In the article on Applying Varnish with a Brush I make the point that varnish directly from the can is simply to thick to flow-out properly. Therefore, for best results, varnish should always be thinned. In this article we take the same product and thin it much more so that it can be wiped on.

As you begin to make and use wiping varnish it may be a good idea to use gloss varnish so as not to create problems with improperly mixed flatting agents.  As you become comfortable with the technique you can then begin to use semi-gloss, satin, and even dull sheen varnish with equal success. Just remember that it is very important to thoroughly stir any varnish to which 'flatting agents' have been added before you thin it; and then, to stir it frequently as you apply it so as to keep the heavy flatting agents in suspension and evenly distributed throughout the finish.  If you don’t, the flatting agents will settle and you will get a streaked and uneven sheen.

The most often cited benefit of wiping varnish is its ease of application—even on vertical surfaces, or on projects with lots of moldings and turnings it is easy to get a drip free, run free application.  As with most improvements, there is also a downside.  In the case of wiping varnish the downside is that you must apply more coats of the thinned varnish in order to get the same build that you would obtain with two or three coats of varnish thinned for brush application. It should be apparent that since you (or the manufacturer) have thinned the product up to 50% you should expect to wipe on no less than two coats for every brush applied coat. However, there is a bit more to it than that. Since varnish thinned for brushing has more solids relative to solvent, it goes on thicker. A properly applied brushed coat will be on the order of 2-mills thick, thus, a three-coat schedule will produce a surface film about 6-mills thick in total. The typical wipe-on coat, because of the additional thinner, will more likely be less than 1-mil, assuming you have wiped it on properly (back to this point in a moment). The bottom line is that, as a rule-of-thumb, it is appropriate to use a 3:1 conversion; that is three coats of wipe-on varnish to approximate a single brushed on coat.

So, with this background, let's make some wipe-on varnish.  In the following illustrations I am going to use semi-gloss varnish—varnish to which flatting agents have been added to reduce the sheen. In the photo you can see why it is so important to thoroughly stir the can before you thin the varnish to wipe-on consistency.

Note the 'glob' of flatting agent on the end of the stir stick. If this heavy mineral is not completely stirred into suspension before thinning two things will happen; both of them bad. First, the varnish you draw off to thin will be largely free of flatting agents which means that this material will become concentrated in the can and "flat" the remaining varnish too much. Second, it means that the wiping varnish you make will have a higher sheen than you expected. Therefore, if you are using other than gloss sheen, stir the contents of the can thoroughly before you begin.

After the varnish is properly stirred, determine the amount of varnish you think you will need for the project you are finishing and decant half of that amount into a smooth sided wide mouth container. Plastic one-quart paint containers available from just about any paint or hardware store are ideal.

Decant varnishNext, thin the varnish 50/50 by filling the container to the desired volume with mineral spirits. This is not a critical measurement, nor is it important to achieve precisely the same dilution in a subsequent batch if you find that you have not made enough. The 50/50 ratio is also subject to adjustment, as is the thinner you use. Naphtha will flash off faster than mineral spirits, and pure gum turpentine will flash off much slower. You can also reduce the amount of thinner used to achieve a 'thicker' mix that will require fewer coats. The 50/50 thinning instruction is simply a good rule-of-thumb that will serve you well as you perfect your technique.

Finally, if the varnish you are using contains flatting agents, it is important to stir the mixture thoroughly to get the flatting agents into suspension. Since the varnish is thinner than it was in the can, the flatting agents will settle out much faster. Therefore, it is also important to stir the mixture frequently during use.

Now, let's move on to applying wipe-on varnish

How you apply your wipe-on varnish will impact the time required to complete your finish. Your application tools and technique will also bare on your success. Over the years that I have been teaching the wipe-on varnish technique I have concluded that there is but one underlying cause for virtually all problems. Woodworkers who have had problems brushing varnish are easily able to grasp the concept of thinning varnish to wipe-on consistency; but, many do not easily leave the "brushing mind set" behind. In other words, they continue to try to apply the thinned wiping varnish as though they were still using a brush. This invariable leads to problems. So, let us now consider the wipe-on varnish applicator and the proper technique for its use. Prepare for this by clearing your mind of what you know (or think you know) about applying varnish with a brush.

There are many ways to make wiping varnish applicators. Some prefer old cotton undershirts while others are partial to gauze or washed cotton rags. These are OK, but in my view they present two problems. First, even "lint free" cotton rags are not totally lint free. Second, unless you are purchasing 'new' rags, this material lacks consistency in both dimension and absorbency. Therefore, every applicator that you make may be different than the one before. Rags are also difficult to properly store until you are ready to use them. I have never seen a shop in which, sooner or later, rags did not become a 'critter condo'—mice and assorted 'bugs' love boxes, bags, and drawers filled with rags.

I much prefer rolls or boxes of blue paper shop towels. A roll of towels is easy to hang in the finish room, and the boxes are their own sheet-at-a-time dispenser. Blue paper towels are also outstanding multitaskers—they can serve well in a number of other shop applications. But, as a wipe-on varnish applicator, not only are they lint free, but they are all precisely the same size and are uniformly absorbent, sheet after sheet—every wipe-on varnish applicator made from them will be exactly the same as the last. Simply fold the towel into a convenient size applicator for the project at hand and you're ready to go.

Dip the applicator into the varnish, squeeze out the excess varnish by pressing the applicator against the side of the container, and wipe it on. As simple as this instruction seems, it is the place where most problems begin. You are not 'brushing' the varnish on with the applicator! You are not brushing at all...you are wiping! Let me borrow the instruction that my friend Jim Kull frequently offered on the WOOD Magazine Finishing & Refinishing forum. The visual image of his instruction is perfect to get you headed in the proper direction.

"Wipe the varnish on using the same technique the kid at Denny's uses to clean your table just before you are seated. Wipe quickly and in a circular motion until the top is more or less uniformly wet. Then, without adding more varnish to the applicator, go over the area again, this time wiping with quick, slightly overlapping passes until the varnish has been spread in a thin, uniform film."

There are three key terms in this instruction that lead to your understanding of applying varnish using the wipe-on technique; "Quickly", "Thin", and "Uniform".
  • Quickly because you want to complete the application of varnish before the thinner begins to flash-off.
  • Thin because your objective is to build the finish film in a series of thin, drip, run, and sag free coats that will not support entrapped air-bubbles.
  • Uniform because one of the primary reasons for wiping the varnish on as opposed to applying it with a brush is to control film thickness and eliminate the 'plastic look' so common when the brushing technique has not been mastered.

The other major misunderstanding in mastering the wipe-on technique for applying varnish is revealed by those who wipe on a coat, allow it to cure, sand, and wipe on another. This hold-over from the brushing mind set is unnecessarily slow, and ultimately will require more coats to achieve the same build. There is nothing sacred in the following schedule (there are many acceptable variations), but I have found it effective.

Wipe on (as described above) the first coat of varnish. Then, go do something for 30-minutes or so before you come back and conduct the "pinkie test". The pinkie test consists of lightly touching the just applied varnish with the tip of your finger. If the finish is 'tack free' you are ready to wipe on another coat. If it is still sticky or tacky to the touch wait another 15-minutes and test again. Depending upon temperature and humidity the time between coats is usually 45-minutes to 1-hour, two-hours at the most. Clearly, since the varnish does not cure in this length of time you do not sand between coats. Wipe on three coats in succession allowing each to become "tack free" before the next coat is applied. Then, allow the varnish to 'cure' for 8 to 12-hours.

When the first set of three coats has cured, lightly sand to remove any dust particles that may have settled in your finish. When sanding finish I prefer an open coat sandpaper such as 3M "Gold". Sand the first 'set' with P240 or P320 grade. If sanding produces a fine, dry, white powder the finish has cured sufficiently for sanding. If sanding causes the finish to 'rice' or ball-up on the paper, stop sanding and allow the varnish to cure longer. Clean away the sanding debris with a vacuum or with a shop towel lightly dampened with mineral spirits.

Apply the second set of three coats following the same procedure used for the first set. After the varnish has cured lightly sand with P320 or P400 and clean the sanding debris as before. Check the finish carefully for any glitches you may have missed and correct any defects before you proceed to the third and final set of three wiped on coats.

If the last three wipe-on coats dry a bit "rough" you can buff the finish.  I will cover buffing varnish in a separate article.  For now, just remember to wait for the varnish to cure before you use any abrasives or rubbing compound. Buffing or rubbing out the finish to soon will render the finish permanently dull.   Two or three weeks at normal room temperature will give plenty of time for the new finish to cure sufficiently to allow you to "finish the finish".

Some closing thoughts

Again, the biggest mistake made when applying wiping varnish is the tendency to "brush" with the applicator. The key to a good finish is to apply multiple thin coats. Avoid the temptation to get in a hurry and pile the finish on. Doing so will virtually guarantee a plastic look, particularly if you are using polyurethane.

When you finish with an applicator spread it to 'dry'. Applicators disposed of improperly can contribute to spontaneous combustion and a tragic shop fire. Do not take proper disposal lightly!

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