| Checks |
Surface checks occur naturally in Heart Pine. If the product is properly
air-dried and slowly kiln-dried, checks can be sanded out or filled during installation. |
| Grain pattern |
There are three distinct grain patterns: plain sawn, vertical and curly.
Plain sawn has an arching grain. Vertical has pinstripes with no growth rings over 45
degrees perpendicular to the face. Curly is the rarest. |
| Growth rings |
The pair of light and dark growth rings denotes a growing season. The
highest grades of heart pine require an average of eight growth rings per inch. Other
grades may average six growth rings per inch or less. Dense growth with at least 1/3rd in
the dark ring means stronger wood. Longleaf pine often lived 400 or 500 years or more. |
| Hardness |
The scale used to measure wood hardness is called the Janka (¡°yahn-kah¡±)
scale. The Janka measure for Heart Pine is 1225, compared to red oak at 1290. New Heart
Pine is about one-half as hard and comparable to Southern Yellow Pine at 670. (To measure,
a reading is taken from a hydraulic press after a .433" steel ball is pressed into
the wood to half its depth.) |
| Heart content |
Heartwood is formed when sapwood becomes inactive and is infused with
additional resin compounds. It develops slowly in the center of the tree as the tree
matures. The older the tree, the higher the heart content. According to the Forest Service
a 200-year-old longleaf pine averages only 65% heart content (all the 200-year-old trees
are now protected and cannot be cut). Longleaf heartwood turns a rich red color when
exposed to light and oxygen. As heart content decreases, color tones can vary widely from
pale red to yellow. |
| Kiln drying |
A process by which moisture is removed from wood with heat and
dehumidification. This ensures the wood can easily acclimate to a building interior and
avoid excessive shrinkage when properly installed. |
| Knots |
Clear is the highest grade and has no knots larger than a rare ½¡±
¡®pin knot¡¯. Standard knots occur infrequently in the next best grade, often called
select or select and better, and may be up to 1-1/2¡±. A ¡®pith knot¡¯ can be either a
pin knot or a standard knot that has a small hole through the knot. |
| Longleaf pine |
Longleaf (Pinus palustris) is the legendary ¡®antique heart
pine¡¯ wood. The Longleaf ecosystem was once the largest contiguous forest on the North
American continent. It is the quantity of resin in the heartwood that gives antique heart
pine its uncommon hardness and durability. It takes 90 to 125 years to develop any
significant amount of heartwood. Most of the trees were 200 to 500 years old when
originally cut. |
| Nail staining |
Caused when the metal ¡°bleeds¡± around the nail hole. Nail holes are
¼¡± in the select grades of Heart Pine, but may be larger in other grades. They
can be filled onsite. |
| Natural Color |
Heart Pine is yellow when first cut and turns red when exposed to oxygen
and ultraviolet light. Beginning almost immediately, the heartwood will ripen within weeks
and will continue to grow richer in color over the first several months. The heartwood
portion of building salvaged heart pine is usually already red except for some ¡®yellow
heart¡¯ areas. These areas commonly occur next to a more resinous area that may have
prevented the ¡®yellow heart¡¯ area from oxidizing. Once cut the yellow heart will turn
red also. If you want to retain the initial light color, a finish with UV inhibitor may
slow the change. |
| Pitch pockets |
Small pockets of crystallized resin occur seldom in Heart Pine. In the
best grades, pitch pockets will be no larger than 1/8¡± wide, but can be up to 3/8¡± or
more in other grades. |
| Resin |
Oleoresin, the type of resin from longleaf pines, made the U.S. the world
leader in naval stores production until the middle of the 20th century. Longleaf sapwood
contains from 1 to 3% resin while the heartwood contains from 7 to 24% resins. The resin
build-up is mostly in the latewood or the dark ring of the pair that make up a growth
ring. The percentage of latewood is the factor most closely linked with weight and
strength. Longleaf has the heaviest concentration of resin of any of the pines. |
| Sapwood |
Sapwood (non-heart) is the lighter colored wood on the outer perimeter of
the log. It does not deepen in color and is not as hard as the heartwood. The best grades
do not contain any sapwood. Lesser grades can have up to 50% sapwood and may today still
be called heart pine. |
