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 4mm steel ball is dropped from 4 meters onto the wood.) |
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.1 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. |
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