Ask the Experts: Issue 4

Get It Straight on Curly Wood

Q: We all love curly wood grain. One of the most interesting features of this grain is the light-to-dark shift of color when the direction of lighting changes. I usually associate this effect with grain that is distorted, like the grain around knots. I recently discovered that the lighter shades of Lyptus will do this when finished, even though the grain is straight and undistorted. What causes this effect, and is there an official name for it?

Udo Schmidt responds:

Curly figured grain is a rare abnormal growth pattern of a tree. This growth occurs in a wavy or corrugated rather than a straight pattern. It can happen with any species, but maple, ash, birch and walnut are more prone to this irregular growth. The curly grained wood is not visible on the outside of a living tree – there are no bulges, flutes, or other bark irregularities. 

The changes from dark to light wood result from differential light reflections. The darker bands have higher light absorption from the wood fiber ends, and the lighter bands are the reflections from the cell walls. Because cell walls are curved, either concave or convex, the light reflection shifts from different view angles. Even though the surface of curly wood is flat and smooth, the different light reflections of the wood cells give it a three-dimensional appearance.

Now, to answer the part of your question specific to Lyptus: Lyptus is a trademarked hybrid species of Eucalyptus grandis and Eucalyptus urophylla developed by Aracruz Wood Products in Bahia, Brazil and distributed in North America by Weyerhaeuser. These trees reach heights of 140' and a diameter of 2'-3' in 15 to 18 years. Lyptus lumber has the density of hickory and the surface appearance of mahogany. 

Curly grain can occur in Lyptus in two ways. First, it can occur like maple with a corrugated growth pattern, in which the waves or curls run perpendicular to the grain. Second, it can occur parallel to the grain. Tropical woods do not have annual growth rings like native woods, but some species produce a clear growth ring due to seasonal changes in climate, such as rainy or drought seasons. This causes  the growing tree to produce a band of fast-growing early wood and then a slower, denser band of late wood. Any log cut into lumber produces a small number of quartersawn boards, meaning the growth rings on the endgrain surface range from 60-90 degrees. Because Lyptus is a very fast-growing wood, these bands are unusually wide, and the lighter early wood reflects the light differently from each angle. Wavy or curly appearance in this instance runs parallel to the grain.

Udo Schmidt spent 12 years in the lumber export industry kiln drying wood before starting his own cabinet shop. He is the author of “Building Kitchen Cabinets.”

The Straight Story On Tapered Boards

Q: I’m getting a slight taper on every board I run through my 6" jointer. I’ve been flipping the board end-for-end to correct the taper on subsequent passes, but would prefer a permanent fix.

A.J. Hamler responds:

Unintentional tapering of a workpiece is one of two problems that occur when the height of the outfeed table of a jointer needs adjustment. Here’s what’s happening in your case: As you run the edge of the board across the cutterhead, there comes a point when the majority of the board is resting on the outfeed table. At this point, the trailing edge of the board begins to lift from the infeed side, actually raising the board above the cutting arc of the knives in the cutterhead. (You may have noticed that as you joint the edge of a board, the cutterhead makes more noise on the front portion of the board than the rear portion.) The end result is that by the time you’ve passed the whole board over the cutterhead, it may not be cutting the rear portion of the board at all. 

The other cutting error is snipe at the end of the board, which occurs when the outfeed table is too low. When the end of the board is no longer supported by the infeed table and the outfeed side is lower than the cutting arc of the knives in the cutterhead, your board suddenly drops into the cutterhead, creating a gouge called snipe.

Fortunately, one fix cures both problems – simply adjust the outfeed table so it is level with the top of the cutting arc of the cutterhead knives. Unplug the jointer, rotate the cutterhead by hand (use a piece of scrap wood – the knives are very sharp), and stop it with one of the knives at the top of its cutting arc. Lay a reliable straightedge on the outfeed table and adjust the outfeed table height until the straightedge just kisses the edge of the knife. Lock down the table and you should be good to go.

A.J. Hamler is Editor-in-Chief of Woodcraft Magazine. 

Straight Up on Matching Stains

Q: We stripped the paint from the balusters of our staircase with the intention of staining them to match the light mahogany color of the handrail. To our dismay, the thin balusters are pine and the thicker ones are redwood. We can’t find a way to get an approximate match between the various woods.

Mac Simmons responds:

One way of doing this is to seal the woods before staining. For a sealer, you can use clear shellac or the same coating that you will eventually use over the stain. (Be sure the sealer is thoroughly dry before you apply the stain.) A sealer will prevent the stain from completely penetrating the wood, and give you more control of the final color. 

Then buy a stain that’s as close as possible to the color you’re trying to match. You’ll need to do some testing by reducing the color strength with the proper solvent to get the closest match you can. You can ask the salesperson or look at the label on the can to find out what solvent the manufacturer suggests you use for cleanup. Use that same solvent to dilute the color.

It’s best to do your testing on scrap material of the same species – in your case pine and redwood – but if that’s not possible then test in an out-of-the-way spot on one of the balusters. Once you’ve achieved the mix that matches best, resand the balusters you used for testing (don’t forget to reseal them if necessary), and then do all your staining at once.

Mac Simmons is a 45-year veteran of the furniture finishing, refinishing and restoration trades, and writes for several woodworking magazines. His book “Fearless Finishing” is scheduled for publication by F&W Publishing.

Back to blog Back to issue