English bog aok: rare bog oak is buried treasure.

Why some woods are different colors and what causes figures and grain patterns remains somewhat of a mystery. Yet, some answers are found in one case involving English oaks.

English or European white oaks have a heartwood that is usually a light tan, but under unusual conditions, the oaks undergo a dramatic color change. The wood--sometimes buried for thousands of years in peat bogs--becomes a deep chocolate color, a transformation due to a chemical change in the wood after being buried for so long.

Fritz Kohl Veneer Mill in Germany says the logs come from "oaks which grew 600 to 8,500 years ago, were felled by natural events and started petrification in gravel beds under water. The dark color is caused by tannin reactions with water containing iron. Bog or moor oaks are generally found when excavating lakes or digging gravel pits in the plains of large rivers."

Such events give bog oaks "a wonderful, rich history," says Charles Stem, president of The Wood Gallery Inc., Floyds Knob, IN. "Bog oaks offer us a great connection with our history and teach us lessons from the past. Most bog oak was found in the peat bogs of England or Ireland, as well as the Rhine River Valley. Some of the logs have been carbon dated to authenticate the tree's age and some are as old as 5,000 or 6,000 or more years."

Stem's library includes a wealth of information about bog oaks, as his late father's veneer company Chester B. Stem Inc. of New Albany, IN, routinely carried bog oak. Stem even has a letter showing the carbon dating results of a log they procured near a Rhine affluent called White Main. The test, known as C-14 dating, was completed in 1969 in a Tokyo lab and proved the log to be 5,570 years old.

Colorful Past

Bog oak, known commercially as black oak, is an extremely rare, expensive wood available in veneer or sometimes lumber. Cam Gantz, sales manager for Fritz Kohl subsidiary Interwood Forest Products Inc. of Shelbyville, KY, says his company carries bog oak veneer. "We sold some recently for the interior of an upscale residence. The veneer is a striking mix of light and dark--sometimes two-toned. It is attractive, but more than that, I think people just fall in love with the mystique of it. History sells the wood. It makes quite a conversation piece to be able to say your paneling comes from a log that was 3,000 years old."

In an early-'70s issue of Country Life magazine, G. Bernard Hughes explains why the trees, after centuries underground, would be petrified rather than rotted. "A report on the bogs of Ireland published in 1840 stated that they were caused by clay spreading over the gravel of ancient forests, producing a kind of puddle and preventing the escape of waters of floods or springs." The resulting muddy pools sustained aquatic plants, which accumulated over time and formed turf or peat as deep as 40 feet.

"It is really coal in its first stage of development, its composition including peat pitch or tar, ammonia, acetic acid and other preservatives," Hughes continues. "Their action has caused the trunks of fallen forest trees such as oak and yew to remain undecayed and intact to be found by men cutting the turf for their fires." Hughes says great supplies of the wood emerged from bogs, "much of it hard, even of grain and black as ebony. When found near lakes tainted with salt sea, water bog wood displays an almost imperceptible bluish tinge." Depending on the time buried, the color varies from a blue-black to a brownish black.

Uses: Past and Present

Bog oak veneers are used as faces for furniture, paneling and parquet flooring. Some material is also used for jewelry, specialty items and in carvings.

Gantz says a popular look in veneer is the material that has the original tan heartwood with the dark black near the outside of the log. "This translates into a beautifully colored wood when the log is sliced."

Early uses for bog oak included furniture and ornamental pieces, then known in London as Turnbridge ware, writes Hughes. "By the 1830s bogwoods were used for articles such as chimney-piece what-nots, inkstands, letter racks, nests of boxes, card cases, chessboards and chessmen, handles for table knives and tools as well as 'denoters' of time exhibiting the day, month and date."

Chester B. Stem has supplied bog oak for many clients over the years, including the Atlanta headquarters of IBM, where a plaque was placed in the lobby, designating the unique heritage of the material.

Editor's note: 112 Wood of the Month articles are now online, with more coming soon. Visit the Wood of the Month archive at www.iswonline.com.

FAMILY NAME

Quercus petraea and Quercus robur of the Family Fagaceae.

COMMON NAMES

Bog oak, black oak, English bog oak, moor oaks, ancient bog oak.

HEIGHT/WEIGHT

English white oaks typically grow from 60 to 100 feet. Average weight of English white oak is 45-47 pounds per cubic foot. Average heights and weights of bog material are not available.

PROPERTIES

Experts recommend air drying only. Wood has a strong tendency to check. Working the material is difficult due to extreme hardness of the wood. Experts recommend using carbide-tipped tools when cutting. Gluing can be difficult. Pre-drilling recommended for screws.