How To Find Pearls In Burls
Start with the harvest
Burls — those odd, bulbous growths on trees that result from an injury or disease — hold hidden treasures of exotic figure beneath their haunting exteriors. For a woodworker, this figure makes for eye-catching turnings; accents such as inlays, box lids, and handles; and veneers. To get the most from burls, you need to know how to properly cut and preserve them. Bruce Hoover, right, an award-winning professional wood turner from Virginia's Eastern Shore, knows burls inside and out. He shares his tips below on preparing these prized beauties.
When you're lucky enough to come across a downed tree with burls (and you have permission to take them), cut oversize sections that include a minimum of 6" of trunk material above and below the burls. The extra wood, Bruce notes, will protect the burls from drying too quickly and checking. To save as much of a burl's figure as possible, avoid slicing the burl from the trunk. However, if a trunk section is too large to handle, you can cut through the pith to remove the back half of the trunk, reducing its size and weight.
For extremely large burls, you may be better off cutting them into more manageable sections or slabs for transport, again allowing extra material, where possible, for drying and mounting on a lathe or later slabbing into box material or some other project.
For faster drying, trim and size the burls
To speed up drying, cut the burls that you plan to use in the near term into rounds and blocks for turning or boards and veneers for other woodworking purposes. If you're not in a hurry to use the burls, leave them whole for storage. Allowing them to dry slowly can produce spalting and color change that adds additional character, as you can see right.
When cutting burls into boards, cut the boards 25 percent thicker than you'll need to allow for distortion during drying. Also, be aware that your cutting direction can make a difference in the figure's appearance, depending on the burl's grain pattern. Burls typically have either an eye figure or random, swirling grain. If you're cutting a burl with eye figure, the board will exhibit either eyes or radiant lines depending on the way you slice it, as shown on the drawing below.
How can you tell if the burl has eye figure? You can't be sure without taking a thin slice off the burl's top. But, you generally can expect to find eye figure in maple, cherry, ash, and walnut burls. If a burl has swirling grain (typical in mulberry, gum, and birch), you needn't be concerned about the cutting direction. Just cut it to get the best yield.
In order to slow the release of moisture, seal the exposed end-grain surfaces on your cut pieces. (It's not necessary to seal any oversize sections or rounds that you plan to turn wet within 8 to 10 weeks.) Use a sealer, such as End Grain Wood Sealer, available from Packard Woodworks Inc. (call 800/683-8876, or go to www.packardwoodworks.com).
Now, store oversize sections outside, off the ground, and sheltered from direct sun and rain. Keep the cut pieces inside. How long will it take the cut pieces to dry? This varies with temperature and humidity conditions. As a general guide, Bruce has found that small rounds and blocks less than 11/2 thick or boards less than 3/4" thick dry in about 12 weeks in warm air. Thicker pieces can take up to 6 months.
3 easy steps to prepare a round
In order for the weight of your burl to be evenly distributed when turning it on the lathe, you'll need to flatten its back and round its outside, as shown in these photos. Waiting about four weeks before turning the burl will allow initial moisture release to help stabilize the wood so there's less chance of distortion.
Step 1: Chainsaw through the pith of the oversize section to remove the back half of the log while also flattening the back of the burl.
Step 2: Trim the excess trunk ends, then chainsaw along the sides of the burl to square it, as shown here.
Step 3: Nail a cardboard disc of suitable size for a cutting guide to the burl's top. Band saw the burl round, following the disc.