Air Drying Wood
with Endgrain Sealers

Air Drying Wood Overview: There are numerous methods available to dry green (wet or fresh cut) timber, including Kiln drying, Air Drying, Solar Drying and others. Drying green wood in the open air has been used extensively by woodturners who prefer the many benefits offered by this method, vs. wood dried by other methods, like Kiln drying.

In a modern woodturning environment air drying wood can be an effective and low cost method to dry large amounts of blanks or roughed out bowls, platters and similar projects with a minimum of effort and expense. When I opened my studio several years ago, I frequently used air drying techniques to dry my green wood. To this day, nearly all of my roughouts and turning squares are dried using various air drying protocols.

American Elm crotch blank air drying after being sealed with Anchorseal.

As woodturners, we prize high figure and color in wood and thus many of us prefer air drying wood to retain the highest amount of natural color possible. This article will concentrate on some effective ways for air drying wood blanks, turning squares and bowl and platter roughouts, with a focus on the particular needs of the modern woodturner.

Air Drying Wood with Cold Wax Emulsions

Few defects in green logs, solid wood blanks and roughouts are as universally troublesome to woodturners as checking. Fortunately, surface checking (cracks) and fissures that can develop during air drying wood can be significantly reduced with proper cutting and drying practices and the timely application of cold wax emulsions to the freshly cut surfaces.

Wax emulsion sealers are formulated to control the rapid loss of moisture in green timber. Wax emulsions form a durable, yet flexible and vapor permeable membrane between the exposed treated surfaces and the surrounding ambient atmosphere. The goal is to retard or slow the rate of moisture evaporation to a predictable and acceptable level, not to eliminate it when air drying wood, thereby reducing air drying defects like checking.

Applying Anchorseal to bowl blank to slow down moisture loss when air drying wood.

Wax emulsions do not prevent moisture movement through the wax coating, but instead slow down the rate of moisture loss in the wood. This helps to prevent the formation of steep moisture gradients and differential drying stresses that could otherwise lead to surface checking. The dried wax membrane remains flexible when dried and allows moisture vapor to pass through it, albeit at a much slower rate than an untreated surface. Our goal is not to prevent moisture loss, but to reduce it to a level that allows the wood to dry with as few defects as possible.

If we eliminated the moisture movement altogether, the wood would never dry. We want to moisture to come out of the blank quickly, but not too fast. It is a delicate, but necessary, balancing act. The most critical moisture loss period for the wood is the first one-third. After that, the chance of surface checking is substantially reduced when air drying.

Air Drying Wood with Commercial Wax Emulsions

Two readily available commercial wax emulsion sealers frequently used by woodturners for air drying wood are Anchorseal, by UC Coatings Corporation, and Mobil-Cer M, by ExxonMobil. Anchorseal is a paraffin based colloidal solution, which contains paraffin, water and a surfactant. It is milky-white in appearance when wet, but dries to a clear film. Mobil-Cer M is microcrystalline wax based and contains microcrystalline wax, water and a surfactant. It is also milky-white in appearance when wet, but dries to a clear film. Wax emulsions are very thin and easily applied to cut surfaces by various methods and are excellent products to use when air drying wood. Note: Winter formulations of these products may also contain anti-freeze agents. If you live in an area where temperatures drop below freezing in the winter, you should purchase the winterised formulations to prevent the unused coating from freezing during storage.

Five gallon winterized Anchorseal used for air drying wood.

Air Drying Wood - Protocol for Solid Wood Blanks
and Turning Squares

The key to success when air drying wood blanks and roughouts, is timely application of the wax emulsion sealer to cut surfaces. If you process your own bowl and platter blanks on the bandsaw, you need to apply the wax emulsion to the cut surface immediately after cutting the blank for best results.

If this is impractical, you need to store the cut blanks under a plastic tarp, in a plastic bag, or in a closed plastic trash can until you can apply the wax emulsion to the desired surfaces of each blank. The goal here is to prevent micro cracks from forming on the endgrain surfaces of blanks awaiting application of the wax emulsion. Wax emulsions will not prevent the continued progression of existing cracks when air drying wood.

If for example, you needed to process two-dozen bowl blanks on the bandsaw and you simply cut each one in turn without waxing them as they are cut, the exposed surfaces of the previously cut blanks may check in the open air, whilst you are cutting other blanks. By the time you complete the 24th blank, the first blanks have been sitting in the open air for quite a long time and micro checks may have already begun to form on the endgrain surfaces.

These micro checks may not be readily apparent to the eye, but may in fact be present. To prevent micro checks from forming on the end grain surfaces of cut blanks, simply store the cut blanks temporarily under a plastic bag, tarp, or in a plastic trash can until you can wax the blanks. The plastic tarp or trash can will prevent drafts from rapidly drying the cut surfaces and will effectively “hold” the blanks for a limited amount of time until you can complete the cutting and apply the wax emulsion.

Applying Anchorseal to pecan crotch blank to provide extra protection to crotch figure while air drying.

When I first began processing my own green wood blanks, I would stop and wax each blank after cutting. This is fine if you are only processing a few blanks, but if you have a large amount of blanks to process, it can be very inefficient to stop cutting and wax each blank, resume cutting, stop and wax the blank etc. Therefore, to maintain high efficiency, I simply place each cut blank under a plastic tarp, or in a plastic trash can, whilst I cut all the blanks in one session.

Air Drying Wood - Endgrain and Sidegrain Surfaces

Typically when air drying wood, the entire cut blank is waxed, including all sidegrain and endgrain surfaces. However, in areas of the country that have high humidity, many turners prefer to wax the end grain surfaces only. Where I live just north of Houston, Texas, we have humidity to spare. Therefore when air drying wood, I rarely wax all exposed surfaces and usually only apply the wax to endgrain surfaces and any high figured areas on the blank (like crotch feather, heavy curl, burl formations etc).

However, if I lived in Arizona, Utah, or in similar areas that have very low average humidity levels, I would wax the entire blank, including all exposed surfaces. If I did not, a high percentage of my blanks would develop checks as they dried. You should experiment for yourself to see what works best for the area where you live.

It does not harm the blank to wax all of the exposed surfaces, but in areas of high relative humidity, it increases the time necessary for the blank to reach equilibrium moisture content, or EMC. EMC is the point at which the moisture content in the wood reaches equilibrium with the moisture level present in ambient storage environment. This is what most turners would call dry, or well seasoned wood.

Below are the waxing protocols I use in my production bowl turning studio when air drying wood blanks and turning squares:

Air Drying Wood - Solid Bowl and Platter Blanks: Wax all endgrain surfaces and 1" up on the sidegrain surface. (A small amount of sidegrain is waxed to insure a complete coverage on the knife-edge located at the intersection between the endgrain and sidegrain surfaces). If any high figured areas are present on the blank (crotch feather, heavy curl or fiddleback, burl deposits etc), wax these as well. If in doubt, wax it.

Air Drying Wood - Turning Squares and Pen Blanks: Wax all endgrain surfaces and ½" up on the sidegrain surface. Wax any high figured areas that are present.

Use a dip tank for pen blanks before air drying.

Air Drying Wood - Roughouts – Bowls, Platters and Boxes, etc.: Wax endgrain surfaces on the inside and outside surfaces only, all sidegrain areas are left untreated. Wax any high figured areas that are present. Endgrain surfaces on spigots should also be waxed. On bowls and platters, the upper rim areas adjacent to the endgrain treated surfaces are also waxed.

Air Drying Wood - Dimensional Lumber Planks: Wax all endgrain surfaces and 2” up on the sidegrain surface. Wax any high figured areas that are present.

Air Drying Wood - Exotic Wood Blanks and Turning Squares: Wax all endgrain and sidegrain surfaces before air drying.

Application Methods of Wax Emulsions
for Air Drying Wood

There are numerous methods to apply cold wax emulsions to the surfaces of your blanks and roughouts when air drying wood.

Almost any brush will work for applying wax sealer.

Paintbrush: On smaller logs, bowls and solid blanks, a 2" or 3" paintbrush is a simple and efficient applicator. The paintbrush can be stored in a small container with any unused wax, eliminating the need to clean the brush after each use. If you prefer, you can use the cheap throwaway “chip” style brushes instead.

Paint Rollers: On larger surfaces, or the ends of larger logs, a 4” paint roller is a great way to apply the wax. The roller will hold much more of the emulsion than a paintbrush, allowing fast coverage of larger surfaces. The roller cover can also be stored in a container with the unused wax emulsion. However, the frame should not be stored in the unused wax. Over time, the roller frame will rust and cause the wax to become discoloured.

A 4" paint roller is ideal for applying sealer to small and medium logs.

Dip Tanks: For small turning squares like pen blanks, bottle stoppers and similar sized pieces, a simple dip tank is the most efficient way to apply the wax emulsion. Dip the endgrain surface into the wax and lower it until it reaches approximately ½” up on the sidegrain surface. Periodically replace the emulsion in the dip tank to insure a ½” depth. If the entire surface needs to be treated, simply lay the blank in the tank and roll it around to cover all surfaces.

Pump and Pressure Sprayers in the Studio: As a production turner, I frequently process large numbers of blanks. To speed up the application of the wax, I use a sprayer to apply the wax onto cut surfaces. If you have an air compressor in your studio, you can purchase an air sprayer that uses a suction tube in a bucket to take up the wax and spray it onto the surface. This is a very fast and easy way to spray the wax. These types of air sprayers cost about $15.00 - $20.00. If you have pressure or HVLP type spray equipment in your studio, these can also be used to apply the wax to cut surfaces.

Garden sprayers make ideal applicators for large surfaces.

Remote Spraying: For spraying in the field, a pump up garden sprayer works well for applying the wax. A side benefit is that you probably already own one of these garden type sprayers. If you do not, they are quite inexpensive. Buy the cheapest one you can find in the 1-gallon size. This will allow you to load it with approximately ½ gallon of the wax, which will cover a large area when sprayed. Pump up trombone style sprayers are also available for spraying wax emulsions in the field. These utilise a pick up tube and a sliding handle that is pumped to create a vacuum, so the wax can be sprayed. These work very well, but they can be expensive and tiresome to use for long periods – unless your forearms look like Popeye’s. The cheap garden style sprayers work as well as the trombone style and are much easier to use.

Application Tips for Emulsions when Air Drying Wood

For best results, follow these simple rules when using wax emulsions:

Apply the wax to the surface as soon as possible after cutting. If the surface is dry, or has been cut some time earlier, make a fresh cut on the endgrain area to expose a moist, unchecked surface. No bubbles should be present in the wet wax after application. If you see bubbles in the finish, brush the surface a few times in alternating directions. This will help to insure a uniformly thick wax film when dried.

Log should be coated as soon as possible after cutting to prevent checking.

• If you want to apply two coats of wax onto the surface, do not let the first coat fully dry, before applying the second. When the first coat starts to dry, it will become clear in appearance. When part of the wax is clear, but part is still milky white, apply your second coat of wax. If you let the first coat fully dry, it will be difficult to apply the second coat. The second coat will most likely bead up on the surface of the first coat, causing an uneven film thickness.
• Do not thin the wax emulsion; use it straight from the container for best results. The only time when thinning may be necessary is when spraying through very small diameter tips on spray guns. Otherwise, use the wax as it is supplied from the manufacture.
• If you wish to dilute the sealer, always add the water to the wax emulsion, never add emulsion to the water. Dilution water generally should not exceed 100 ppm CaC03, or the wax may separate from the emulsion.
• Do not store the unused wax near high heat sources, or allow the product to freeze. High temperatures or freezing may cause the product to separate. Winterised versions of the emulsions are available, if you live in an area that sees freezing temperatures in wintertime.
• To clean-up equipment, use ordinary soap and water. Be careful about spills in your studio, as both the wet and dry wax is very slippery and may cause you to fall. Since the dried wax is clear, it can be difficult to see small spills on the floor. I like to put down an old tarp to catch any spills, or drips when applying the wax. When finished, all I have to do is roll up the tarp and I am done.

In most cases, the facegrain does not need to be coated for air drying unless highly figured.

Cold wax emulsions can be an important tool in your studio. If properly used, they can significantly reduce the amount of drying defects encountered when air drying green wood in your studio. As good as wax emulsions are, they are not perfect and should be considered a temporary measure only when working with logs. Even properly treated whole logs will check if left in the whole log form too long. Very few species of timber in the world can be successfully dried in the whole log form. If you are working with whole logs and applying the wax sealer to the endgrain surfaces, use two coats for best results. In addition, process you log as soon as possible into blanks, turning squares planks etc. to improve your overall chances of getting crack free dried blanks.

Wax emulsions are available in numerous sizes, up to 55-gallon containers. If you have several friends who are woodturners, you may want to investigate purchasing a 55-gallon drum and splitting the wax. When purchased this way, the net cost per gallon is much lower than the cost of individual gallons. Many woodturning clubs purchase wax emulsions this way and divide the wax among club members who are interested.

Note: If you want to learn more about using wax emulsions when air drying wood and turning bowls, check our our 2 hour, 20 minute , two disk DVD video, Bowl Turning: Step by Step

Safety Note: Always follow all manufacturers safety instructions before working with your lathe, or any of the tools or products you may use. If you are unsure about any operation, obtain competent professional instruction before proceeding. Use and wear all necessary safety devices during turning and observe safe woodturning practices to prevent accident or injury.

Steven D. Russell is a professional studio woodturner, teacher and writer. He has written numerous articles for international woodturning magazines, which have been published in more than 78 countries around the world. Steve has demonstrated in numerous cities across the United States. His studio, Eurowood Werks, specializes in bowls, platters and hollow forms with unique visual and tactile treatments.

Steve is also a regular featured writer for the Guild of Master Craftsman's "Woodturning" magazine, published in London England. Woodturning magazine is the world's leading magazine for woodturners. Look for his monthly articles covering technical topics, or project based articles in each issue.

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