oakum n : loose hemp or jute fiber obtained by unravelling old ropes; when impregnated with tar it was used to caulk seams and pack joints in wooden ships

English

Noun

oakum

1. the material, consisting of tarred fibres from old rope, used for caulking or packing joints in a wooden ship

Translations

• Finnish: rive

Oakum is a preparation of tarred fibre used in shipbuilding, for caulking or packing the joints of timbers in wooden vessels and the deck planking of iron and steel ships, as well as cast iron plumbing applications. Oakum was at one time made from old tarry ropes and cordage of vessels, and its picking and preparation has been a common penal occupation in prisons and workhouses. In modern times it is made from virgin hemp fibers. White oakum is made from untarred materials. The fibrous material used in oakum is most commonly a hemp or jute fiber impregnated with tar or a tarlike substance. This "tar" is not the tar used on streets and roofs, which is really asphalt, but rather pine tar, also called Stockholm tar, an amber-colored pitch made from the sap of certain pine trees.

The term oakum is also used to describe the use of the thumb in the application of intercostal pressure. The word oakum is derived from Middle English okum, from Old English Acumba tow, from A- (separative & perfective prefix) + -cumba (akin to Old English camb comb) - literally "off-combings".

When the first session of the Supreme Court convened in 1789, the tradition of wearing wigs still lingered. Justice William Cushing was the only one to show up wearing a wig and was chided by the boys. Thomas Jefferson advised him: "For heaven's sake, discard the monstrous wig which makes the English judges look like rats peeping through bunches of oakum."

Use in plumbing applications

Until plastic (ABS, PVC or CPVC) drain pipes were used, oakum was one of two materials used to seal cast iron drain piping. After setting the pipes together, oakum was packed into the joints, then molten lead was poured into the joint, creating a permanent seal. The oakum swells and seals the joint, the "tar" in the oakum prevents rot and the lead keeps the joint physically tight.

References

In victorian times in prison for labour they made prisoners pick oakum.