Stabilizing and Bending of WOOD for the Hobbyist

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.

To read more please visit our publication: Stabilizing and Bending of WOOD for the Hobbyist

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.

Wood – Its Nature and Properties for Woodworking

For most cabinetmakers and furniture makers, wood is the raw material of choice. Wood has thousands of uses. Although wood may appear to be a relatively simple substance, closer examination shows that wood is one of the most complicated and unusual natural materials. The more you know about wood and its properties, the more valuable wood can become to you.

Wood is made up of many tiny tubular cells which are held together by the wood’s own cement, lignin. These tubular cells are similar to a bundle of drinking straws (see Figure 1). These cells carry the supply of necessary nutrients and water which nourish the life processes of the tree. The walls of these cells also provide support and strength to the tree. These cells run up and down the tree, and produce grain that is visible on the cut surfaces and edges of lumber.

Each of the cells is very narrow and rather long. These cells consist of a cell wall and a cell cavity (lumen) inside the cell wall (see Figure 2). Most of the cells in a tree are dead. The only living cells in a tree are the recent growth produced by the cambium (how the tree grows in width) and some cells in the sapwood.

When the wood is sawn, the openings in the cells are exposed, forming openings on all the wood surfaces. These openings are small pores, and the quantity of pores is called porosity. This porosity is quite extensive. This structure of open space and cell walls gives wood its strength and its properties.

Hardwoods and Softwoods

The terms hardwood and softwood are botanical terms and do not indicate the actual hardness or softness of the wood. Some hardwoods are softer than some softwoods, and vice versa. Hardwoods are actually broadleaf trees. Some examples of hardwoods include walnut, oak, ash, maple, cherry and mahogany. Softwoods come from conifers, which are actually trees that bear cones or have needle-like leaves. Some examples of softwoods are the southern yellow pines, white pines, fir, cedar and redwood. Figure 3 compares the softwoods and hardwoods.

Hardwoods and Softwoods

The growth ring is often used in reference to the annual growth of a tree. The rings are not always as easy to see as the ones shown in Figure 4. Some woods do not show any visible indications of annual growth. Some species have quite distinct growth rings; others are not easily visible.

The growth rings of wood are made of springwood and summerwood. The portion of the growth ring formed early in the growing season is called the springwood or early wood. That which forms later in the season is called the summerwood or late wood. Generally, the springwood has larger cell cavities and thinner walls, and is less dense than the late wood (see Figure 2).

Hardwoods are classified into three groups, based on the pattern of growth of the annual rings:

Ring-porous species have springwood cells that are wide and distinct, usually several cells wide. The summerwood cells are small, indistinct and thick walled, making the rings very distinct. Some examples are oak and ash. Figure 5 illustrates a ring porous wood, red oak.

Semi-ring porous (semi-diffuse porous) species have fairly distinct springwood cells but are not as wide and obvious as the ring-porous wood. The summerwood, which comprises most of the annual growth ring, has distinct, thick cell walls. Some examples are black walnut and pecan. Figure 6 shows a semi-ring porous wood, black walnut.

Diffuse porous species have no distinct difference between the springwood and summerwood and no distinct ring or annual grain patterns. Some examples of diffuse porous woods are birch, poplar, basswood, maple and cherry. Figure 7 shows a diffuse porous wood, maple. Structural arrangement of wood.

To read more please visit our publication: Wood – Its Nature and Properties for Woodworking

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.