Cocobolo

Post date: 15-Nov-2012 01:33:55

This is one of my all time favourite timbers, although rarely seen in Western Australia.

There are a number of different timbers that are known collectively as the rosewoods, of which Cocobolo is one. Due to the high desirability of Cocobolo, there are a number of countries and organisations laying claim to the timber.

The general consensus is that Dalbergia retusa is the true Cocobolo, and it comes from Costa Rica and Nicaragua. Note that the Mexican form is most likely Dalbergia granadillo. This is a very similar timber in appearance.

Dalbergia retusa is a small to medium tree 15 to 20 m high, and approximately 40 cm in diameter. However the bole is typically quite twisted, and branches from a low height. This means that the wood recovered from a tree is not of great length or size.

The wood colour varies greatly from light to deep red, within the same tree. The grain is fairly straight, but can be interwoven.

When freshly cut, the timber is an array of colours from lemon orange to deep red. These mature to darker reds and browns. The sapwood is almost white. Grain is usually fine and even. The strong marking can be either relatively straight, as shown below, or when backsawn, has a distinct circle to it.

The texture is fine, the wood oily without distinctive taste, and slightly pungent when worked.

Cocobolo has a beautiful grain

As seen from the photo the wood is rich and strongly marked, making it a highly desirable timber. It is also very hard, strong, durable and easily worked. Almost the perfect wood. However, the strength characteristics are hardly required, as the timber is typically used in small pieces, and in decorative rather than structural functions.

Cocobolo was heavily logged, and is now only available from private forests that were planted between 80 and 100 years ago. These trees are now ready for harvesting. The Costa Rican government issues permits for the cutting of every tree, and the world supply is small and strictly limited.

The wood is highly durable, but unsuitable for gluing. If the smooth surface is rubbed with a cloth, it acquires a waxy finish without the need for oil or other finish.

The wood dries very slowly, with no tendency to check or split. It is also very stable in service. It is not unduly difficult to work, but has a moderate blunting effect on tools. It releases a mild fragrance from its oils when being machined.

It is a very tough timber that has good mechanical strength in all categories, although it is rare that this property is exploited. It is difficult to glue owing to its natural oils. Cocobolo comes to an excellent finish which feels cold, almost marble like.

Some tool manufacturers, such as Lie Nielsen, do use cocbolo in tools. The wedge of this shoulder plane is cocobolo, and is beautifully shaped, coming to a needle like point where it holds the blade.

Lie Nielsen Shoulder Plane

The fine dust generated during working is quite poisonous, similar to poison ivy, and can become very painful. The effect can be permanent, (allergenic), preventing any further contact with the dust. The dust is a mild irritant, causing dermatitis and stains the skin orange.

Cocobolo is almost impervious to soapy water, which has led to its use in cutlery handles, coat buttons, and boat fittings such as wheels.

In addition to the waterproof nature, it also exudes a natural oil finish, which again leads to uses in areas where raw timber is most suited. This is particularly true for cutlery. The high density of the wood, as well as its durability has led to its use in bowling balls and truncheons. However, the strong grain and striking markings together with its easy workability and ability to hold fine edges have led to its use in all manner of fine work such as scientific instruments, canes, chessmen, tool handles, gun stocks, musical instruments, and turnery.