Stockholm tar is an especially high grade of pine tar which is used among mariners, and also to treat outdoor furniture and rope designed for outdoor uses. Hardware stores and maritime suppliers are a good source for Stockholm tar, which may also be labeled archangel tar. Typically, Stockholm tar is mixed with other substances like linseed oil to make a spreadable solution which can be applied with heavy brushes or rags.
The production of tar in Scandinavia dates back to at least the 1400s, and it is probably even older. Tar is produced by burning pine in specially designed kilns which maintain a steady low temperature. As the pine burns down, the dense pitch runs out, and it is collected in a chamber located underneath the kiln. This process is known as “destructive distillation,” because it requires complete destruction of the wood to extract the valuable sap inside.
Originally, pine tar was extracted for use in ship building. A layer of pine tar could be applied both inside and outside a ship to help weatherproof it, ensuring that the wood resisted rot. Pine tar was also used to treat ropes and fixtures on ships so that they could endure long journeys, and furniture makers got the bright idea of applying pine tar to outdoor furnishings, as well.
It is not surprising that the production of pine tar took off in Scandinavia, given the region's heavy pine forests. Within Scandinavia, tar from various regions was considered better than tar from other regions, and eventually a monopoly of Swedish tar producers arose in Stockholm, acquiring the best tar and selling it at a high price. As a result, high quality pine tar came to be known as “Stockholm tar,” referencing the city which dominated tar production from the late 1600s to the late 1800s.
Tar can be produced from a variety of trees and also from petroleum, but some people feel that Stockholm tar is especially good, specifically recommending it for certain tasks. People use Stockholm tar for weatherproofing on a variety of outdoor fixtures, from decks to chairs, and it is also famously used in baseball to coat the handles of bats, creating a better gripping surface.
In the veterinary field, Stockholm tar is sometimes used to treat cracked hooves and to seal wounds. It can also be rendered into a strong, useful soap which can be used on people and animals alike.