The utilisation of wood resins in connection with the construction of wooden sailing ships led to the adoption of the general term naval stores for the rosin and turpentine collected from pine trees. The use of resin from pines for this purpose has a very ancient history, with Genesis 6:14 stating that Noah was to ‘pitch the ark within and without’. Theophrastus in about 300 BC described the technique for producing oleoresin from pines in his ‘Enquiry Into Plants’. The term naval stores first appeared in an act of the General Court of the Province of Massachusetts in 1694 in which a committee was appointed to ‘Consider and Report what quantities of Pitch, Tar, Rezin, Planke, Knee Timber and other Naval Stores for the use of his Majtys Royal Navy &c the Government here may undertake to send yearly to England’. Naval stores are produced by tapping living pine trees. The tree responds to this wounding by producing gum (oleoresin), from which is derived rosin and turpentine. Species used for oleoresin harvesting include slash pine (Pinus elliottii) and longleaf pine (Pinus palustris) in the USA, Austrian pine (Pinus nigra) and maritime pine (Pinus pinaster) in Europe, Asiatic longleaf pine (Pinus longifolia) in India, and mercus pine (Pinus merkusii) in Indonesia and the Phillipines. In 1909, a process was established in the USA to extract resinous products from the stumps left after the felling of pines. This used solvent extraction, and the product is referred to as wood naval stores. This industry has now disappeared, since only virgin stumps yielded resinous products, with second growth plantations not yielding sufficient to make the industry viable. Naval stores production by tapping has also gone in those countries where labour costs make the process very expensive; this production has been replaced by the sulphate naval stores industry (tall oil). The harvesting involves wounding of trees by removal of bark (called a streak), only the bark and phloem are removed, and a chemical agent is applied to promote flow of resin. Each new streak is applied just above the previous one to produce what is termed the naval stores face. The resin production season starts when the growth begins in spring and continues for approximately 32 weeks. A streak is applied every week, or every fortnight if sulphuric acid is used. The streak is generally applied over no more than one third of the circumference of the tree. The resin flows into a gutter and thence into a cup where it is collected. Some oleoresin crystallises on the naval stores face, where the volatile components evaporate. This material (scrape) is collected, because it has value, although it is worth less than the material in the cup. Cups are generally emptied every four weeks. It is the labour-intensive nature of these operations that has caused the industry to collapse in many countries. The turpentine and resin components from pine trees are now usually collected as a by-product of the Kraft pulping process (sulphate naval stores).
Contributor: Dr Callum Hill FIMMM