thumb|Oakum and tools for caulking
thumb|Hemp
thumb|Prisoners picking oakum at [[Coldbath Fields Prison in London]]
Oakum is a preparation of tarred fibers used to seal gaps. Its traditional application was in shipbuilding for caulking or packing the joints of timbers in wooden vessels and the deck planking of iron and steel ships. Oakum was also used in plumbing for sealing joints in cast iron pipe, and in log cabins for chinking. In shipbuilding it was forced into the seams using a hammer and a caulking iron, then sealed into place with hot pitch.
It is also referenced frequently as a medical supply for medieval surgeons, often used alongside bandages for sealing wounds.
History
The word oakum derives from Middle English ', from Old English ', from ' (separative and perfective prefix) + ' (akin to Old English ', "comb")—literally "off-combings".
Oakum was at one time recycled from old tarry ropes and cordage, which were painstakingly unravelled and reduced to fibre, termed "picking". The task of picking and preparation was a common occupation in prisons and workhouses, Over the age of 16, girls and boys had to pick per day respectively.
In modern times, the fibrous material used in oakum comes from virgin hemp or jute. In plumbing and marine applications, the fibers are impregnated with tar or a tar-like substance, traditionally pine tar (also called "Stockholm tar"), an amber-coloured pitch made from pine sap. Tar-like petroleum by-products can also be used for modern oakum. "White oakum" is made from untarred material,
Cultural references
In Herman Melville's novella Benito Cereno, crew members of a slave ship spend their idle hours picking oakum.
Charles Dickens's novel Oliver Twist mentions the extraction of oakum by orphaned children in the workhouse. The oakum extracted is for use on navy ships, and the instructor says that the children are serving the country.
The Innocents Abroad, a travel book by Mark Twain, also mentions in chapter 37 a "Baker's Boy/Famine Breeder" who eats soap and oakum, but prefers oakum, which makes his breath foul and teeth stuck up with tar.
Jack London, in his book The People of the Abyss (1903), mentions picking oakum in the workhouses of London.
Robert Jordan, in Winter's Heart alludes to picking oakum as a punishment among the Sea Folk.
Joshua Slocum in Sailing Alone Around the World, describes caulking his ship the Spray, with oakum.
Guy de Chauliac in The Major Surgery of Guy de Chauliac, frequently cites oakum as a medical supply in his treatments of wounds.
Bernard Cornwell, in his Sharpe novels, refers to Richard Sharpe's childhood in a workhouse, picking fibres from old rope.