Lumber scraps and cross-sections of angle cuts sawed from small logs or large limbs can be made into attractive items, but only if the wood is first treated with polymers and then properly seasoned, or if the wood is initially seasoned following special techniques. These treatments and techniques can result in profitable uses of “low grade” logs and oddly shaped scraps that might otherwise be discarded. This publication describes some techniques of stabilizing and bending wood for hobbyists.
Freshly cut cross-sections normally check badly and develop typical pie-shaped or vshaped cracks during the drying process. This is because wood shrinks twice as much in the tangential direction (parallel to the annual rings) as in the radial direction perpendicular to the annual rings). The internal stresses that result from such differential shrinkage invariably cause serious checks and splits as the wood loses moisture and comes to moisture content (MC) in a heated or air-conditioned wood shop. These are some of the techniques for drying wood cross-sections. These techniques can also be used for lumber scraps.
PEG-1000 Chemical Treatment
One method recommended often in recent years is stabilization of wood with a bulking agent such as polyethylene glycol (PEG). PEG treatment requires soaking the wood for a long time. This tends to darken the sapwood. Also, PEG is hygroscopic and raises the MC of the wood; under humid conditions, the chemical may cause the finished board surface to develop discolored streaks. To avoid these problems, you must dry the disks without chemicals.
Many hobbyists use PEG as a bulking agent that greatly reduces the dimensional changes of green wood. PEG is a white, wax-like chemical that resembles paraffin, is solid at room temperature, has an average molecular weight of 1000 and dissolves readily in warm water. PEG melts at 104 degrees Fahrenheit, is nontoxic, noncorrosive, odorless, colorless and has a very high firing point (580 degrees Fahrenheit). It is chemically related to antifreeze.
The PEG treatment, which physically bulks the wood cell walls (fibers), prevents shrinkage and thus prevents the development of destructive stresses (figure 1.). Green wood heavily treated with PEG retains its “green dimensions” indefinitely, and thus is permanently restrained from shrinking, swelling or warping, regardless of humidity changes.
Todd Shupe is the President of DrToddShupe.com and is a well recognized expert on wood-based housing and building materials, wood decay and degradation, and wood science. Shupe worked as a professor and lab director at LSU for over 20 years. He is active in several ministries including his Christian blog ToddShupe.com. Todd is the President of the Baton Rouge District of United Methodist Men, and Board Member for Gulf South Men and a Team Leader for The Kingdom Group. He is a volunteer for the Walk to Emmaus, Grace Camp, and Iron Sharpens Iron. Todd is a Men’s Ministry Specialist through the General Commission of United Methodist Men and is in training to be a Certified Lay Minister through the Louisiana Conference of the United Methodist Church.