Caulk

Caulk or, less frequently, caulking is a material used to seal joints or seams against leakage in various structures and piping. The oldest form of caulk consisted of fibrous materials driven into the wedge-shaped seams between boards on wooden boats or ships. Cast iron sewerage pipe were formerly caulked in a similar way. Riveted seams in ships and boilers were formerly sealed by hammering the metal. Modern caulking compounds are flexible sealing compounds used to close up gaps in buildings and other structures against water, air, dust, insects, or as a component in firestopping. In the tunnelling industry, caulking is the sealing of joints in segmental precast concrete tunnels, commonly by using concrete. Traditional caulking (also spelled calking) on wooden vessels uses fibers of cotton and oakum (hemp) soaked in pine tar. These fibers are driven into the wedge-shaped seam between planks, with a caulking mallet and a broad chisel-like tool called a caulking iron. The caulking is then covered over with a putty, in the case of hull seams, or else in deck seams with melted pine pitch, in a process referred to as paying, or "calefaction". Those who carried out this work were known as caulkers. In the Hebrew Bible, the prophet Ezekiel refers to the caulking of ships as a specialist skill. File:Caulked hull timbers, Spry, Blists Hill.jpg|Dried-out caulking on the [[Severn trow]] [[Severn trow, Spry|''Spry'']], now displayed on shore File:Caulking tools.jpg|The tools of traditional wooden ship caulking: caulking mallet, caulker's seat, caulking irons, [[cotton]] and [[oakum]] File:MaryRose-caulking tools2.JPG|A caulking mallet, tar pot and a piece of petrified tar found on board the 16th century [[carrack]] ''[[Mary Rose]]'' In riveted steel or iron ship construction, caulking was a process of rendering seams watertight by driving a thick, blunt chisel-like tool into the plating adjacent to the seam. This had the effect of displacing the metal into a close fit with the adjoining piece.