Tar burning required a variety of professional skills, with tar-rich wood acquisition taking the most time. It could take as long as five years before the de-barked trees filled with resin and were fit for tar production. After spring sowing, the pines were scraped with an iron barking-tool as high as a man could reach from the ground. A palm-width strip of bark (a ‘spine’ or ‘lifeline’) was left on the north side of the tree. Good tar wood also included twisted, shrunken trunks and resinous tree stumps. The stripped pines increased in resin over a period of three years and were then stripped from higher up, using a high sawhorse to stand on. The trees were then allowed to stand another two years.