A little bit about spalted wood: This naturally distressed wood gives a unique look to any project.


The photo above shows spalted European beech boards that have been milled.

Recently, I was talking with a woodworker who mentioned that he was going to buy some wood for a job that he was going to have to highly distress. He mentioned a few species he was considering and why he thought they would be right for this job. I thought for a moment and then asked, “How about using spalted wood?” He responded, “What is spalted wood?” and I explained to him what this unique wood is.

That conversation made me think that the subject of spalted wood would make an interesting article. So, here is a little information about spalted wood, which is highly decorative in appearance, thanks to its unique markings, colors, lines and streaking. No two pieces of spalted wood are ever the same.

How and Why It Happens

What causes the unusual characteristics in spalted wood is a fungus called “white rot fungi.” This fungus causes rotting decay from a microorganism that spreads erratically throughout the wood and causes unsymmetrical markings and coloring. This unusual event occurs in downed timber or in wood that is specifically selected to be spalted by timber men or woodworkers. The spalting may be in different shades of black, pink, gray or even multicolor streaks, making the wood attractive to many woodworkers.

The spalting process can take weeks, months and even years to mature. It is an ongoing phenomenon. The two big dynamics that are needed to produce spalting are: the right amount of moisture, which is about 30%, and a temperature of 60 to 90F. Once the spalting process has begun, the wood must be watched carefully so it does not rot for too long. Otherwise, it will get to the point where it can no longer be of use.

There are certain precautions that should be taken whenever you handle or work with spalted woods that has been air dried, however. You must always wear personal protective gear, since there is a possibility that air-dried spalted woods may still contain dormant but live spores of the fungus inside or outside the wood. These latent fungi may be reactivated if the right conditions are present and can be harmful to your health, possibly causing asthma or other respiratory problems.

To be on the safe side, always wear OHSA-approved protective gear whenever you work with air-dried spalted wood. Kiln-dried wood should not pose the same problem since the kiln heat, in most cases, kills spores in wood.

These seven vases were turned out of spalted beech and are a good example of the unique streaks and colors spalted wood provides.

Spalting Your Own Wood

If you want to learn how wood is spalted, you can experiment on your own. To do this, start by using a piece of air-dried spalted wood on a project and save all the sawdust and wood chips that come off the wood. These can be used as an activator to start the spalting process in other wood.

Take a few pieces of the wood you want to spalt. (I suggest maple, birch or beech, because they are good for spalting, although many other species also will spalt under the right conditions.) Place the sawdust, wood chips and pieces of wood in a black plastic trash bag with some holes in it, which will be used for an air exchange. You will have to keep the sawdust, chips and wood moist inside the bag; you can bury it under some leaves and soil or place it where you can monitor its progress. When you want to stop the spalting process, take the wood out of the bag and allow it to air dry.

Temperature change will stop the spalting. To restart the process, place the materials back into the same environment. Remember, spalting needs the moisture and high temperature in order for dormant spores to begin to cultivate and to reactivate other spores to start the process. In due time, if you are attentive and patient, you will end up with your own spalted pieces of wood that you can work and transform into one-of-a-kind classic projects.

Working Spalted Wood

Whether you purchase air-died spalted wood or make your own, you should always check for soft areas, which result from the wood being overly spalted. In some cases, these spongy areas can be hardened with cyanoacrylate glue, which sometimes will stabilize the wood so that it can be repaired and used. If you are buying spalted wood from a lumberyard or other supplier, they are usually kiln-dried. So they are ready to work and be finished.

Finishing Spalted Wood

Once the wood has been worked and it is ready for finishing, I suggest that you first make up complete start-to-finish samples. (This step is not needed if you are only using clear coats to protect the woods.)

If you plan to stain spalted wood, you may find that blotching occurs. This is why you should make up samples, so you can see how the final finish will appear. The samples will also allow you to make any necessary corrections and give you an opportunity to learn any new finish that you may have never tried before.

If your first sample does show blotching from the stain, here is one way to prevent it:

Apply a few thin wash coats of de-waxed shellac, a water clear coating like acrylic or a water-based coating to the sample. Once the coating is dry, a light scuff sanding will smooth out the coating. Remove the sanding dust, apply your stain and allow it to dry thoroughly. Once it is dry, you can apply clear coats to protect the finish. If you are satisfied with the results, you can begin to work on your actual project.

A look at the vases featured in the photos on the right are a good example of how using spalted woods can help a custom woodworker achieve a unique look for his projects. Spalting creates a natural aging and distressing in wood, and each project can never be replicated.

Mac Simmons is a freelance writer and 50-year veteran of the furniture finishing, refinishing and restoration trades. Mac has written articles for woodworking magazines in the U.S. and in the UK, Austria and Canada. Questions may be directed to him in writing c/o CWB, 400 Knightsbridge Pkwy., Lincolnshire, IL 60069 or via e-mail c/o [email protected]

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