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Selection of Wood Veneer and Wood Varnish

To build on our last article on smooth finishes, here we talk about veneer and types of varnish.  2 articles in 1!  Sent in by one of our readers. Thank you Jack T., and we hope you enjoy your store discount! As always, if you write a plan or article for us, we'll get you a store discount.


Discussion on selecting Veneer and Varnish

Selecting Veneer (101)

Types Of Commercially Available Veneer

Today, there are many different types of veneer available to both hobbyists and professional. In general, veneers can be broken down into two categories, Flexible and Standard. Both are used extensively by pro and amateur, however there are significant differences in cost and ease of application. I will briefly describe these two types of natural wood veneer.

Just as every tree has its own character, so does every individual sheet of veneer. When veneer is cut from a log, the manufactures are very careful to stack each sheet in the same order as it comes off the log. If this care was not taken, and the sheets were stacked randomly, you would be unable to select and purchase two or more sheets almost identical. This is especially important if you need to joint two or more sheets together to create a wide matched panel. However, even matching sheets have some variation in grain and color. Whatever your source of supply, make sure the supplier offers consecutively sliced sheets of veneer.

Standard Veneer

Standard veneer is what our fathers and grandfathers were used to working with. The sheets are cut from a log, stacked in consecutive order, then sent to a drier and once again stacked consecutively. Years ago, most standard veneers were cut to approx. 1/16" to 1/20" thick. With advances in cutting machinery and technology along with the need to get more material out of one log, today most standard veneers are cut to a thickness of about 1/28" to 1/40". However, certain species of veneers like oak, walnut, maple, cherry, mahogany and some others can still be found in thicker sheets.

Standard veneer is usually available in random widths ranging from about 3" to 12". Some species like oak and mahogany which grow in larger diameters are available in wider sheets. Veneer distributors usually sell the sheets in 3 to 10 foot lengths. However, many species are only available in short 3 foot lengths. If you are purchasing standard veneer by the square foot and plan to apply it to a door or kitchen table, make sure you specify if you need long sheets or you will probably end up with 3 foot lengths.

Standard veneer should not only be purchased in consecutively sliced sheets, but it also should be of good quality: relatively flat, with little or no knots or sapwood, generally uniform in color, with very few or no checks or splits. There are some exceptions to this. Certain highly figured veneers like burls and crotches are almost impossible to find in perfectly flat sheets, free of splits or some knotholes. This is because highly figured woods are not as stable as flat or quartered cut veneer and tend to warp and buckle much more. Therefore, do not be surprised if you purchase some burl veneer and it is wavy and includes some checks and knotholes. This is a normal condition for these types of veneer. Much more preparation has to go into flattening, filling knotholes, and taping these types of standard veneers before gluing them down. I will cover this in detail in a future document. Also, see the document on flattening veneers.

Standard veneer is usually sold by the square foot. The price varies depending upon species. Some species like poplar can be purchased for about 40 cents per sq. ft. while others like ebony can run $3.50 to $4.00 per sq. ft. No matter what species you are planning to work with, when working with standard veneer, make sure you purchase at least 20 to 30 percent more than what you actually need. This figure factors in waste and excess for trimming and jointing.

Flexible Veneer

Over the past 20 years, this new type of manufactured natural wood veneer product has been gaining popularity with both professional and amateur alike. Flexible veneer is manufactured by slicing very thin sheets of veneer (approx. 1/64" thick) and then treating the veneer to make it more pliable. Once the cutting and treating is done, the sheets of veneer are then jointed together to produce a wide sheet. Finally, a paper type of backing is permanently mounted to the back to bond it and give more flexibility.

The two main advantages are: Ease Of Application Because of its flexibility, it can be cut easily using a craft knife or razor type blade. It can also be cut to rough size with a pair of shears. Unlike some standard veneer, flex veneer can also be easily bent around forms and contours without the need to wet or steam the veneer. Available In Large Sheets The manufacture joints narrow slices together to produce a wide sheet. Most flex veneers are available in 18". 24". 36" or 48" widths and in lengths of 8, 10 or 12 feet. This saves the buyer a lot of time, especially if they would have to joint a number of narrow of pieces prior to gluing down the sheet.

There are other advantages to using flex veneer. Some species of burls are also available in flex. Not only are the smaller pieces pre-jointed to give you a large sheet, but the burl is perfectly flat, and any defects such as knotholes and or cracks have been filled and repaired. Flex veneer is sanded smooth at the factory and needs little or no sanding prior to finishing. Because the actual veneer face is so thin, you can not do much sanding or you will cut through the face. Once the flex is glued to its surface and the glue has cured, it can be finished like any other veneer: (stained, filled, sealed, varnished, lacquered, oiled waxed, etc.). By this time you may be asking "Then why should I use standard veneer?". The only consideration is price. Flex veneer is much more expensive than standard. You are not only paying for the product, but also all the work the manufacture is saving you. For the pro, I feel it is still worth the extra cost, but for the amateur, it's a toss-up. If you have not worked with veneer, flex will be much easier to handle and apply, but on the other hand, if you have the time to prep and joint standard veneer, the price may be too high.

Now, lets talk about Varnish for your wood

For many amateur woodworkers or hobbyists who either cannot afford spray equipment or do not have enough space in their shop to set up a spray booth to safely spray finishes like lacquers, brushing on an oil based varnish is one of the best choices for a topcoat finish. Oil based varnish does not dry very quickly, therefore it will take longer to complete a finishing project using varnish as opposed to lacquer, water based or other faster drying finishes. However, if you are an amateur or home woodworker, not a pro who has to worry about meeting a deadline, time should not be top priority, quality should. Varnish has very good resistance against abrasion, wear, heat, solvents and water vapor. Other than its slow drying time, which can also cause problems with dust getting trapped in the finish before it dries, the only other disadvantage to oil based varnish is that it tends to yellow over time. The dust problem can be taken care of by setting up a dust free finishing area in your shop and sealing it off with heavy plastic to reduce the amount of dust and sawdust in that area. The problem of yellowing cannot be handled as easily. First, most oil based varnishes are amber (yellowish) in color to begin with. This is because the oils used to make the varnish are amber. Therefore, oil based varnishes tend to somewhat change the color of the raw or stained wood when they are applied. It is not a considerable change, and unless applied over a very light colored or white stain, it is satisfactory. In fact, amber varnishes actually give darker woods like walnut and mahogany a warmer appearance. Non-amber or what are called water white finishes like some lacquers and water based finishes can leave a cold look on darker colored woods. However, if needed, there are a few water white varnishes available. One is called water white restoration varnish manufactured by H. Behlen & Bro. Nothing can really be done about yellowing of varnish over time and if you think about it, all film finishes break down in one way or another over time and have to be removed and replaced with a new finish. Tung oil yellows less over time than other oils, therefore a varnish that contains tung oil will have a tendency to yellow less over time.

Oil based varnish is manufactured by cooking certain oils that can cure with resins. Once this blend of cooked oil and resin is complete, solvents are added to make it thin enough to apply and metallic dryers are added to help speed up the curing time. Initially, linseed and tung oil were used by manufactures for the curing oils and natural resins like pine and gum resins were used along with solvents like gum turpentine and mineral spirits (to thin it out) and lead used for the drier. These ingredients were not only used to make varnish, but also paint. With the exception of lead, you can sometimes still find some of these ingredients in today's oil based varnishes, but modern varnishes usually use synthetic resins which are superior in strength and longevity and curing oils that are less expensive to use in the manufacturing process along with a blend of solvents and metallic dryers like cobalt and zinc that do not cause health problems such as lead does.

Types Of Oil Based Varnishes

Phenolic Resin

This varnish is made with phenol (a plastic) and formaldehyde. The phenol is a solid and is made into liquid by heating it with oil and then adding in the other ingredients. When the finish is applied in a thin film and exposed to to the air, the solvent will evaporate and it will turn back to its solid form.

Alkyd Resin

Less expensive, this is a type of polyester resin that is combined with alcohol and acid. It is also cooked with oil to create a varnish. This is the most commonly used resin in commercial varnishes today.


Yes, that's right. Polyurethane is classified as an oil based varnish, although some purists will disagree. Initially developed to be used as a substitute for other plastics, polyurethane has become on of the most commonly used resins in the manufacturing of many wood finishes. Polyurethane is a very tough, abrasion resistant resin. There are many types and forms of polyurethane, but the kind of polyurethane finish you are used to seeing in paint and wood finishing supply stores is not pure polyurethane, but rather an alkyd varnish that has been modified by adding some polyurethane into it. That is why polyurethane should be classified as a varnish. Perhaps a better description would be modified varnish, but nevertheless, still varnish. It is applied and it cures in the same manner as other oil based varnishes. Contrary to what many people say about polyurethane, most modern high quality polyurethanes do not dry leaving a plastic appearance. They are available in various sheens from satin to semi-gloss to gloss and can also be rubbed to a beautiful smooth luster. Polyurethane's abrasion resistance makes it on of the most commonly used finishes today.

Satin Vs.Gloss Or Semi-Gloss

Throughout the years, many pieces of furniture have been finished with varnishes and other topcoat finishes. Years ago, and on much custom furniture still today, the varnish was applied and then rubbed down with steel wool or sandpaper to cut down the shine and give it a more pleasing look. Today, wood finishing manufactures make varnishes in different levels of shine so the furniture does not have to be rubbed down after the finish has been applied thus saving many hours of hand or machine rubbing. These varnishes are sold in different sheens. Some will give the user a high gloss finish, others like a satin will have a slight gloss. All topcoat finishes start out as high gloss and if the manufacture wants to make a satin or semi-gloss finish, they take the gloss finish and add a flattening paste into the finish along with the oils resins and other ingredients we now know are used to make varnishes. This paste is usually some kind of zinc oxide and it settles to the bottom of the can. This is why you do not have to stir a gloss varnish before it is applied, but you must stir satin or semi gloss varnishes to get the paste off the bottom of the can and mix it into the finish. The flattening paste makes the finish a little duller and prevents the light from reflecting off the surface as much as a gloss finish. The flattening paste also makes the finish less transparent, thus creating a cloudy look. If you apply too many coats of satin or semi-gloss varnish, you could actually start to obscure the grain of the wood. Whenever I elect to use a satin or semi-gloss varnish, I will use gloss varnish and then only on the last one or two coats use the satin or semi-gloss, this way I can keep the clarity and still achieve the desired sheen. Satin and semi-gloss varnishes are also softer than gloss varnishes because the flattening paste or agent used will soften the film finish. If you need a really hard abrasion resistant finish, but want a satin or semi-gloss sheen, it's best to use a gloss and after it has cured, rub it down with steel wool or other fine abrasives. This will also give you a smoother surface, removing any dust nibs and leveling the surface.

What Varnish Should I Use For My Job?

To determine what type of varnish you should use for a particular job, you must look at what type of oils and resins are contained within a varnish and what the ratio of oil to resin is. Varnishes that contain a larger amount of oil to resin are called long oil varnishes. Varnishes that contain a lower amount of oil are called medium oil varnishes. Long oil varnishes are more flexible than medium oil, but also softer. Medium oil varnishes are harder, but are more brittle. For exterior use, a long oil varnish is best. Because it is more flexible, the varnish will expand and contract with the wood as changes in temperature and humidity take place. A medium oil varnish will not move as much and therefore as the wood moves and the varnish does not, the varnish will soon start to crack and peel. Medium oil varnishes are best used indoors where a lot of wood movement does not occur and a harder finish is desired. The resin contained in a varnish is also important in determining what type to use for your project. Some resins are more elastic than others, making them best suited for exterior uses. Phenolic resin is more elastic than other resins, therefore it will be able to withstand the extreme wood movement of exterior projects without quickly breaking down and cracking. Alkyd and polyurethanes are better suited for interior use. Not as important, but still a factor is what type of oil is used. Tung oil is more water resistant than linseed or other oils, therefore it would be a better oil for exterior use, but much more expensive.

Putting this all together, we basically come down to two categories, interior and exterior use. For exterior use, a modern spar varnish which is long oil and is made up of tung oil, Phenolic resins, solvents, dryers an Ultra Violet blockers (to protect the color of the wood from fading) is probably your best choice if you elect to use an oil varnish outside. Although Spar varnishes have a tendency of initially being more amber (yellow) in color because of the color of the Phenolic resin. For interior use, my favorite is polyurethane modified varnish. The best I used is a product called Wood Glo, it is a satin poly that flows out beautifully and lasts decades. It is sold by Constantine's in New York (See Sources) back on my homepage. They also have a gloss version called Super Shield.

Brushing On Varnish

While not very easy to apply by spray application, oil based varnish is one of the easiest finishes to apply by brush. Because varnish sets-up slowly it gives the user plenty of time to brush and spread it out evenly on to the surface. It's hard to spray because it has a tendency to run if applied too heavy. I firmly believe that any film finish can be sprayed successfully if thinned out enough, but varnish is one of the last finishes I would want to spray. Over many years of testing, I have come to realize that brushing is the best way to apply oil based varnish.

Before applying varnish by brush, you should know a little more about how long it takes for each coat to set-up and how long before you can apply the next coat along with how it reacts to temperature and humidity and some other facts. Oil based varnish is much higher in solids than some other film finishes like lacquer. Therefore, it should only take a few coats of varnish to build a film significant enough to protect the surface of what you are finishing. After the surface has been sealed, it usually only takes about three coats to give you enough protection.

One very important factor when applying varnish is how the temperature effects the speed at which it cures. You should not apply varnish in temperatures lower than 65 degrees. If you apply varnish in lower temperatures it may take several days, even weeks for it to cure. Room Temp. (approx. 70 to 75 degrees) is good for applying varnish. Hotter temps. will make the varnish cure quicker, but the solvent in the varnish will evaporate quicker, making the varnish set-up quickly and you may have a problem getting the varnish to flow out properly. This could result in brush marks, bubbles and an uneven film. When working in temperatures higher than 75 degrees, try not to work on large surfaces.

Some Tips For Preparation

Try to set aside a room or part of your work shop to apply your varnish. This room should be as dust free as possible. Do not do any other woodworking, (especially sanding) in this area. If you are going to set aside an area of your shop instead of using a different room, it would be a good idea to also surround this area with heavy plastic sheeting. Before applying the varnish, wet mop the floor, this prevents you from kicking up any dust when you walk around. I always place clean craft (brown) paper under the piece I will be varnishing. Once the surface has been prepared properly you are ready to brush on your varnish.

Choosing A Brush

There are a number of high quality brushes that can be used for brushing on clear topcoats. The best for shellac and lacquers are natural hair (like badger) or china bristle brushes. While any of these brushes will do a great job when applying varnish, there is a much less expensive alternative. A polyfoam brush. That's right, the disposable type. Oil based varnish is classified as a cold finish. This means the solvent use is not as strong as evaporative finishes like shellac and lacquer. Alcohol and lacquer thinner will melt a foam brush but the mineral spirits, solvents or turpentine used in most oil based varnishes will not harm a foam brush. Foam brushes are especially useful for novices who have a hard time getting brush marks out when applying a finish. If used properly, you can get excellent results. I always have a good supply of 1",2" and 3" foam brushes in my shop. They are very inexpensive, so I use one for each coat and then throw it away.

Applying The Varnish

Sealer Coats

You don't need a special sealer to seal the wood. Special sealers like sanding sealers will not do any better of a job of sealing the wood than the finish itself. Sealers only make the first coat easier to sand, thus speeding up production time. Also, if you use the wrong type of sealer, you may have adhesion problems. The best sealer for your first few coats should be the varnish itself. Take some of the same varnish you are planning to use as your finish and thin it down 50 percent ( this is a 1 to 1 ratio) with mineral spirits or gum turpentine. This will be your sealer. It will do a good job of sealing the wood and you won't have to worry about contamination problems. Pour some varnish through a paper paint strainer or stocking into another can or jar, then add the same amount of mineral spirits into the varnish. Stir well and strain a second time into a deep dish or bowl. It's best to work out of an open bowl or dish so you can easily dip your brush into it. Now, dip the foam brush into the mixture until the brush has been loaded slightly past the bevel on the foam brush. Lift the brush up and let the excess drip back into the dish. Next, brush on the first coat with the grain making sure not to leave any puddles or drips. Allow the sealer coat to dry overnight and then sand with 320 grit paper. Remove the dust with a vacuum, or tack cloth. If you are working on very porous woods, apply a second sealer coat following the previous steps.

Varnish Coats

It's a good idea to also thin out your coats of varnish a little. You can reduce your varnish 20 to 25 percent 4 parts varnish to 1 part mineral spirits or gum turpentine or 3 parts varnish to 1 mineral spirits or gum turpentine. This will not effect the strength of the varnish, it will only make it flow better and allow time for air bubbles that form when brushing to pop. The only drawback is that you will have to add a few more coats because less will remain on the surface once the varnish has dried. Prepare the varnish by mixing and straining in the same way you prepared the sealer. Use a foam brush and load it in the same manner as the sealer. Apply the varnish to the surface by brushing either with or against the grain initially. The main idea is to get it on the surface doing as little brushing as possible. Once on the surface take one light pass with the tip of the brush moving with the grain. Overlap each pass slightly, then leave the varnish alone, do not do a lot of brushing, this will make the solvent evaporate quicker and the varnish will set up too quickly and not have enough time to flow out. Let the varnish dry overnight, and then sand with 320 grit sandpaper and remove dust using vacuum or tack cloth. When sanding, if the varnish starts to clog the paper, it has not dried enough. If the varnish turns to powder, it is dry enough to sand and apply the next coat. Continue to apply 2 to 3 more coats of varnish using the same process. If you are going to rub out the finish (by wet sanding) after it has cured, you may want to apply at least a total of 6 coats ( not including sealer coats). This is because if there is not enough varnish left on the surface, you may cut through the finish into the raw wood in some spots. Once you have applied the last coat, let the finish cure for several weeks before you are ready to use it or rub it out. Varnish does not need much maintenance. If you wish, you may apply a coat of paste wax or liquid polish from time to time.