Blackjack pine (Ponderosa pine)

Date: 2010-06-11

Gene Wengert, wooddoc@uwalumni.com

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Ponderosa pine (Pinus ponderosa) has many names including western yellow pine, blackjack pine (my favorite), and pino blanco. Growing throughout the western mountains of the U.S., Mexico, and Canada, it was believed at one time to be critical to the survival of the spotted owl, so harvesting in the 1990s was severely curtailed. With less harvesting, it has been, in recent years, burning in forest fires at an accelerated rate. Forest fires in many areas destroy in a cataclysmic event more wood than was ever harvested. Only now are the politicians and land managers appreciating the beneficial role of harvesting for the overall health of this species. Supplies should be increasing again somewhat if this message reaches more of the people.

The wood has been historically the best wood for millwork, especially for windows and doors. This top rating is because this wood has the ability to withstand scuffs, shocks and jars without splitting, is straight grained, has good paint holding, and has moderately low shrinkage properties; all this means excellent performance in use. The knots are also fairly small and resulting in a pleasing appearance for knotty pine paneling

The wood resists splitting when nailed which allows for the use of larger nails and increases nail holding power. Most ponderosa is free from pitch and resin pockets, has an even grain and is dimensionally stable. All in all, furniture and cabinet makers find that ponderosa pine is an excellent species.

Due to staining risks prior to and during drying, the lumber would normally be purchased KD, S4S (kiln-dried, surfaced 4 sides). Unfortunately, the lumber price for KD clear stock is fairly high. Purchasing milled-to-size parts (or maybe over-sized blanks) may be a more economical decision.

Processing Suggestions and Characteristics

Density.

The wood is fairly light weight, especially compared to its close relatives, the Southern yellow pines. The density is approximately 27 pounds per cubic foot. Kiln-dried and surfaced lumber weighs about 1-2/3 pounds per board foot.

Drying.

The wood has a high risk of blue (fungal) and brown (chemical) staining in warm weather if the logs are not sawn promptly or if lumber is not dried promptly. It is mandatory, in order to achieve good color, to dry the lumber on site as soon as it is sawn, rather than shipping it green to a distant location for drying. Kiln schedules to achieve fast drying rates are widely published. Heating to 180F at the end of the schedule is suggested to set the pitch, so sap will not ooze out later. Equalizing and conditioning are also suggested to provide a uniform MC, stress-free product.

The wood dries quickly with little risk of downfall due to splits or warp. Occasional compression wood may increase warping, however. Very old trees can develop wetwood, which is difficult to dry without defect or high final MCs.

Final MCs should be 10 to 11 percent MC to avoid brittleness when machining.

Shrinkage of flatsawn lumber in drying is roughly 5 percent, which is typical for most conifers.

Gluing and Machining.

Ponderosa pine glues quite well, except in knotty areas.

Machining is fairly easy, except that the high contrast between the low density light-colored wood (earlywood) within an annual ring and the dense dark-colored wood (latewood) will result in corrugated surfaces if tools are dull, feeds are too fast, pressures are high, or stock removal rates are high.

Stability.

Once dried, the wood is fairly stable when the moisture changes. The straight grain results in little warp, unless there is compression wood or knotty areas present.

Strength.

Ponderosa pine is a moderately strong conifer. The strength (MOR) is 9400 psi. The stiffness is 1.3 million psi. Hardness, due to the low density wood within the ring (that is, earlywood), is only 460 pounds.

Color and Grain.

The color of the sapwood is yellowish white. The heartwood has more reddish tinge. Most clear lumber would be sapwood if sawn from younger, second-growth trees.

The grain is rather striking due to the color contrast within a annual ring; that is, earlywood and latewood color contrast is high). Nevertheless, the grain is straight with little tendency to twist or cup.

Ponderosa Pine takes most finishes beautifully, including paint, stain, lacquer and varnish. Unlike some of the heavier pines, paints and stains do not raise the grain; however, as mentioned, kiln drying temperatures should exceed 160 degrees F for at least one day to prevent sap or resin from bleeding through the finish.

Blackjack pine (Ponderosa pine)

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