Tar

Tar, the most useful stuff I've ever worked with. Just don't get it on your hands, it sticks and burns.

— a master shipwright, to an apprentice

Tar has long been a critical material in shipbuilding, but traditional refining methods consume a great deal of pine and other woods that are high in pitch. The Naphtha refining process used by the Guild of Nightsoil Collectors has provided a much more plentiful alternative, producing more tar than ever before while preserving wood for use as ship timbers or in other construction.

Caelestran Shipbuilding

The large and seemingly limitless supply of tar in Caelester is one of the major underlying causes for the numerous advances in shipbuilding made in the city over the last 130 years. Having a plentiful supply of tar allows for waterproofing of not only the keel and other parts of the ship that are exposed to the open ocean, but also components that would never normally have been considered worth the effort.

Structural Uses

Most timbers used in Caelestran shipyards are soaked in tar for years before they are ever put to use. This allows the tar to seep into the wood, preventing water from doing the same and thus slowing the rate it rots to a fraction of its normal duration. This is done both for ships and for dock construction, enabling Caelester to build up much more elaborate dockyards than many other cities. In shipbuilding, tar is also slathered between the planks of a ship, allowing an edge-to-edge style to be just as watertight as traditional overlapping planks. This in turn allows for lighter, faster ships, or much larger ships than could otherwise be supported. Done properly, this also has the benefit of closing any minor gaps between planks caused by wood warping or mistakes in sawing the timbers, which replaces the need for cutting custom pieces to fit or hammering in shims or scraps of rope, though both of these practices remain useful for making repairs at sea where heating tar to a liquid state is ill-advised due to the risk of fire.

Blackened Sails

Sails made in Caelester are usually also treated with tar. This makes them heavier than ordinary canvas sails, but they catch the wind better, while also shedding rainwater rather than soaking it up. This reduces strain on the spars in wet weather, allowing Caelestran ships to sail through weather that many sailors would consider alarming. This process also gives Caelestran sails a distinctive black colour, though as the technique has spread, this has ceased to be an identifying feature of the Caelestran fleet.

Construction Uses

Since the Caelester Earthquake, ship construction has slowed to a fraction of its normal rate, which has allowed construction workers to start experimenting with the material. They have discovered that it greatly enhances the speed of construction, allowing workers to easily patch gaps in window frames and doorways, removing the need for refining the fit of every structural fitting while also preventing the drafts that would quickly become intolerable in a building that left such openings. Roofers have similarly started using tar between shingles or roofing tiles, which they hope will allow a roof to last many more years before leaks need to be patched.