Terms Commonly Used to Grade Antique Heart Pine

 

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.