Lignum Vitae

Lignum vitae () is a wood, also called guayacan or guaiacum, and in parts of Europe known as Pockholz or pokhout, from trees of the genus ''Guaiacum, toughness. It is also the national tree of the Bahamas, and the Jamaican national flower.

The wood is obtained chiefly from ''Guaiacum officinale'' and ''Guaiacum sanctum'', both small, slow-growing trees. All species of the genus ''Guaiacum'' are now listed in Appendix II of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) as potentially endangered species. ''G. sanctum'' is listed as Near Threatened by the IUCN Red List. Demand for the wood has been reduced by modern materials science, which has led to polymer, alloys and composite materials that can take lignum vitae's place.

Name

''Lignum vitae'' is Latin for "wood of life". The plant derives its name from its medicinal uses; lignum vitae resin has been used to treat a variety of medical conditions from coughs to arthritis, and chips of the wood can also be used to brew a tea.

Other names for lignum vitae include palo santo (Spanish for "holy wood"), Aura palo santo and "bastard greenheart" (not to be confused with true greenheart ''Chlorocardium rodiei'', a popular wood in shipbuilding, cabinetry, and woodturning but a completely different timber). Lignum vitae is also one of the numerous hard, dense woods loosely referred to as "ironwood".

Description

Wood products

Lignum vitae is hard and durable, and is also the densest wood traded (average dried density: ~79 lbs/ft³ or ~1,260 kg/m³); it will easily sink in water. On the Janka scale of hardness, which measures hardness of woods, lignum vitae ranks highest of the trade woods, with a Janka hardness of 4,500 lbf (compared with Olneya at 3,260 lbf, African blackwood at 2,940 lbf, hickory at 1,820 lbf, red oak at 1,290 lbf, yellow pine at 690 lbf, and Balsa at 100 lbf). The densest of all woods is ''Allocasuarina luehmannii''. Krugiodendron typically has a higher density, among many other woods that vary by sample.

Various other hardwoods may also be called lignum vitae and should not be confused with it. The best-known come from ''Bulnesia arborea'' and ''Bulnesia sarmientoi'' (in the same subfamily as ''Guaiacum'') and are known as verawood or Argentine lignum vitae; they are somewhat similar in appearance and working qualities as genuine lignum vitae. Some hardwoods from Australasia (e.g., ''Vitex lignum-vitae'' and some species of ''Acacia'' and ''Eucalyptus'') are also referred to as lignum vitae.

Description

The tree is slow-growing and relatively small in stature, even when mature and old. It bears small, purplish-blue flowers which result in paired orange dehiscent fruits. The bark is mottled.

Uses

Due to the density of the wood, cricket bails, in particular "heavy bails" used in windy conditions, are sometimes made of lignum vitae. It is also sometimes used to make lawn bowls, croquet mallets, and skittles balls. The wood also has seen widespread historical usage in mortars and pestles and for wood carvers' mallets.

It was the traditional wood used for the British police truncheon until recently, due to its density (and strength), combined with the relative softness of wood compared to metal, thereby tending to bruise or stun rather than simply cut the skin.

The belaying pins and deadeyes aboard USS ''Constitution'' and many other sailing ships were made from lignum vitae. Due to its density and natural oils, they rarely require replacement, despite the severity of typical marine weathering conditions, and also resisted jamming in their mortise holes. The sheaves of blocks on sailing vessels were made of lignum vitae until the introduction of modern synthetics.

Due to lignum vitae's toughness, it can also be used as a lap in the process of cutting gems. The wood is covered with powdered industrial diamond, attached to a spindle, and used to smooth rough surfaces of gems.

Master clockmaker John Harrison used lignum vitae in the bearings and gears of his pendulum clocks and his first three marine chronometers (all of which were large clocks rather than watches), since the wood is self-lubricating. The use of lignum vitae eliminates the need for horological lubricating oil; 18th-century horological oil would become viscous and reduce the accuracy of a timepiece under unfavourable conditions (including those that prevail at sea).

For the same reason it was widely used in water-lubricated shaft bearings for ships and hydro-electric power plants, and in the stern-tube bearings of ship propeller shafts until the 1960s saw the introduction of sealed white metal bearings. According to the San Francisco Maritime National Park Association website, the shaft bearings on the WWII submarine were made of this wood. The aft main shaft strut bearings for , the world's first nuclear-powered submarine, were composed of this wood. Also, the bearings in the original 1920s turbines of the Conowingo hydroelectric plant on the lower Susquehanna River were made from lignum vitae. The shaft bearings on the horizontal turbines at the Pointe du Bois generating station in Manitoba are made from lignum vitae. Other hydroelectric plant turbine bearings, many of them still in service, were fabricated with lignum vitae and are too numerous to list here.

The United Railroads of San Francisco (an ancestor of the San Francisco Municipal Railway) began installing insulators made of composite materials to support the heavy 600-volt DC feeder wires for their trolley system in 1904. These lines were damaged, along with most everything else, during the 1906 earthquake and the fires that followed. Rebuilding the trolley system and expanding it to replace cable car routes destroyed in the quake created a huge demand for insulators, a demand manufacturers further east were unable to meet. The properties of lignum vitae, namely its ability to withstand high stress (from heavy cables on long spans and the strain of lines rounding corners) and high temperature (due to the feeder cables becoming very hot during peak operating hours), and its ready availability from the holds of the ships in the harbor (used as dunnage and ballast) made it an ideal 'temporary' solution. Many remained into service well into the 1970s, with the last few pieces replaced in the 2000s in favor of an underground feeder system.

It was also used extensively in the manufacture of British Railways Mark 1 Rolling Stock, as a "bump stop" in the bogies (the frame that carries the wheels).

Lore

Pioneering calypsonian/vaudevillian Sam Manning recorded a song titled "Lignum Vitae" in the 1920s. His reference was doubly salacious, referring to both the bark tea's contraceptive qualities and the phallic symbolism of the hard wood.

Benvenuto Cellini recounts using lignum vitae (presumably in tea form) to cure himself of a venereal disease (the so-called "French Pox", presumably Syphilis).

According to T. H. White's version of the King Arthur story ''The Once and Future King'', lignum vitae, from which the wand of Merlin is made, has magical powers.

Gabriel García Márquez's novel ''Love in the Time of Cholera'' includes a bathtub made of this wood in one of the main characters' homes. His novel ''Chronicle of a Death Foretold'' also refers to the use of this wood in making a cane for the blind Poncio Vicario.

American folksinger Pete Seeger fashioned the neck of his trademark banjo from lignum vitae.

In Charles Dickens' novel ''Bleak House'', one of the characters, Matthew Bagnet is referred to as lignum vitae, "... in compliment to the extreme hardness and toughness of his physiognomy."

In Philip Pullman's novel, The Secret Commonwealth, the heroine Lyra Belacqua carries a truncheon made from lignum vitae as a weapon.

Image:LignumVitaePlane.jpg, A hand plane with a lignum vitae sole, likely ''Bulnesia'', and a pearwood body
Image:PanamaRR Rail Spike Tie.jpg, Example of the original construction 53 lb/yd (26 kg/m) inverted "U" rail aka "Bridge" rail, "screw" spike, and lignum vitae tie used to build the Panama Railroad from 1851 to 1855.

See also

*Lignum nephriticum

References

{{DEFAULTSORT:Lignum Vitae
Wood
Guaiacum