Anchorseal wax emulsion
End Grain Sealers Overview: If you're working with green wood, you're probably already using some type of sealer to help prevent checking. The most popular sealers are wax based and offer excellent protection from rapid moisture loss when applied correctly. Recently, while visiting a friend's woodturning studio, I noticed some bowl blanks that had been treated with Anchorseal, a popular wax emulsion sealer.
Several of the freshly cut blanks had checks showing on the cut end grain surfaces and I noticed several areas on each blank that had little, if any end grain sealer on the surface. The blanks had been check free before the wax had been applied, and the timber was one of the species that dries well in most situations. This begs the question, why did my friend's blanks check only a few days after being treated with the end grain sealer?
The most probable answer is that the untreated areas on the rough sawn blanks continued to dry at a rapid pace vs. the sealed areas, causing a steep moisture gradient to form on the exposed and untreated end grain surfaces. The cut surfaces were very rough (chainsawn) and my friend used a small paintbrush to rapidly cover the cut areas, but it was late and he was tired, so he ended up rushing to complete the job.
Brushing on a wax sealer to the
end grain section of a fresh cut pecan log
As I closely inspected the checked blanks, I noticed that lots of the deeper chainsaw cuts were totally untreated, leaving freshly cut end grain surfaces exposed to the open air on the rough cut surface. This is a recipe for disaster with most species and one that will usually result in checked blanks. Fortunately, this problem is relatively easy to prevent… The key is to insure that the cut surfaces are thoroughly coated with the end grain sealer, leaving no areas unsealed. On rough cut logs, or bowl blanks this may mean using something other than a paintbrush, to insure a more uniform coating on the irregular surfaces.
If you use and apply end grain sealers properly, they can be a tremendous asset in your studio by controlling the rapid loss of moisture through freshly cut surfaces on logs, blanks and roughed out projects. Two widely available end grain sealers are Anchorseal and Mobil-Cer M. Anchorseal is paraffin based colloidal solution for logs and lumber. It contains paraffin, water and a surfactant and is milky-white in appearance. Mobil-Cer M is a microcrystalline wax based coating. It contains microcrystalline wax, water and a surfactant and is also milky-white in appearance.
How Wax Emulsion Sealers Work
Wax emulsions (also known as end grain sealers) form a flexible and vapor permeable membrane between treated surfaces and the surrounding atmosphere. As woodturners, our goal is not to prevent moisture from moving through the log or the wax coating, but instead to retard the rate of moisture evaporation. When this is achieved, drying defects are reduced and the maximum amount of timber can be utilized in every log.
Application Methods For End Grain Sealers
Brushes, rollers and spray equipment can all be used to apply end grain sealers
grain sealers can be applied by various methods including brush-on, dip
tank, roll-on, spray-on and vacuum assisted. The decision on which
method to choose should be based on the quantity, size and location of
the logs or blanks to be processed. Correct application procedures are
essential to obtain maximum protection from the wax coating.
Brush-On: Wax sealers can be easily brushed onto the exposed end grain, or side grain surfaces of logs, turning squares and bowl blanks. For an optimum surface coating, the cut surfaces should be as smooth as possible. Excess sawdust or debris should be brushed off before applying the sealer. In addition, if any checking is evident on the exposed end grain, it should be cut back until solid wood is present. When brushing the sealer on the end grain portion of re-sawn turning squares or bowl blanks, also coat 1" of the adjacent side grain. This insures a better coating on the area where the end grain and side grain areas meet.
The sealer should be applied onto the end grain until it nearly runs off. Applying too thin a coating will reduce the protection level and may compromise the successful seasoning of the timber.
If any bubbles are present on the surface, brush across the area again until the bubbles are completely removed.
Bubbles that are left in the wet film may cause differential moisture gradients to form in the surface coating.
These differential moisture gradients cause uneven drying zones across the face of the treated surface, which may result in surface checking.
Brushing on end grain sealer to pecan crotch blank
Brushing on end grain sealer to the sides of a freshly cut pecan bowl blank
Roll-On: Standard 9" paint rollers make excellent applicators for medium to large sized logs and blanks. My favorite roller is the type sold for painting in tight areas. It is approximately 4" long and works exceptionally well for any but the largest of logs. Rollers can apply the coating much faster and more uniformly than hand brushing. In addition, because the nap on the roller is available in different sizes, rough or uneven cut log surfaces can be more easily and uniformly covered.
Small dip tanks can be used to apply end grain sealer to pen blanks
Dip Tanks: When processing large amounts of smaller blanks or turning squares, dip tanks are simple and efficient. Almost any shallow container can be used for making a dip tank. Old pie pans work well, as do small plastic bowls.
Simply decant a small amount of the sealer into the tank and dip each end of the blank into the sealer. The level of the sealer inside the dip tank should be adequate enough to coat the end grain and the small amount of adjacent side grain, in one step.
Spray-On: If you will be processing a large amount of squares or logs, or you are working with very large diameter (2’ to 6’ diameter or more) logs, consider spraying the sealer. Many types of sprayers are available including electrical, gas and manually powered with sizes and prices to fit any budget. Manual sprayers are excellent for spraying in remote locations without electrical service.
Trombone type slide sprayers are also available that draw directly from five gallon buckets. I have found that simple pump-up garden sprayers available in most home centers, work very well and are much easier to use than trombone, or backpack style sprayers. Spraying is a fast and easy application method, especially if you are short of time, or the weather is rapidly turning inclement.
Vacuum Assisted Application
When sealing high figured wood, unstable burrs or crotch figured blanks, vacuum assisted impregnation of the surface can be utilized. This method applies sealer to the side grain and end grain simultaneously, producing a well sealed outer surface. My use of this method is typically limited to pen blanks, but it can be adapted to larger turning squares quite easily with proper equipment.
My friend learned an expensive lesson, just like I did many years ago when I first opened my studio. Wax emuslion sealers can be a valuable product to help prevent checking in green wood logs and blanks, but only if you take care to insure a thorough application of the emulsion to the cut surfaces of the wood. Anything less and you may end up with an opportunity to practice your inlay techniques.
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 the current and founding President of the Lone Star Woodturners Association, Inc; an AAW member chapter. The LSWA is a 501(c)3 non-profit educational organization dedicated to teaching and demonstrating the art and craft of woodturning.
Steve is also a 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 articles covering technical topics, or project based articles in an upcoming issue.