No one knows for absolute sure why some trees secrete resin. However, with the aid of some marvelous macrophotography, although the mystery surrounding this subject cannot be solved for certain, its beauty – at times deadly – becomes evident.
Resin is a chemical that oozes out of various trees. It is known as a secretion rather than an excretion. Excretions are purely waste products whereas, although the reasons behind resin are still a little obscure, most scientists believe that it has some sort of purpose or function. It is probably not simply to trap insects, although there is something almost morbidly satisfying about the sight of an insect being ‘consumed’ by resin. Perhaps it is the fact we have watched Jurassic Park too many times and take some satisfaction in imagining a scientist in the year ten thousand working out the DNA of an amber trapped insect. Most probably it is the wonder of seeing something trapped in time as perfectly preserved as it was on the day it died.
Resin is a hydrocarbon – that is it is made up of two elements and two elements only – hydrogen and carbon. So, it also qualifies as a compound, which is when something is made up of two or more elements. What is more it can also be called an organic compound – which is when one of the elements has to be carbon. Some hydrocarbons are impure as they contain traces or have bonded with other substance, and the same can be said of resin, so in this sense it is impure. So, all in all resin is an impure organic compound hydrocarbon – which is quite a mouthful to say the least.
Resin has a multitude of uses and is highly valued the world over. It is used in varnishes, which is a hard and transparent finish and it is pretty obvious why that idea first occurred to someone centuries ago. It can also be used as an adhesive – perhaps the insects trapped inside it gave one of our ancestors that idea – and is one of the ingredients that can be used to glue or stick one thing to another. More surprisingly, perhaps, it is also used in the manufacture of perfume and incense. You may remember frankincense from a story about someone born round about two thousand years ago and given to him on his birthday – that started its life out as a resin although its manufacture does render it synthetic.
Resin is something of a puzzle and why plants secrete it has been the subject of heated debate for many years. Resins consist of compounds that do not seem to play any part in the main physiology (how something functions as a living organism) of the plants from which it comes. So some scientists do see it as a waste product – an excretion rather than a secretion. Others argue, however, that it is a secretion as it has many benefits to the plant. The compounds inside resins seem to have an effect on a wide range of insects and herbivores – a deadly one at that. Plus resin can also attract birds and insects that can stand its toxicity while at the same time snacking on the predators of the plant.
Resin is usually a viscous liquid – in every day terms viscosity is thickness so, for example, water is thin and honey is thick. You have already figured out which resin is. This liquid is made up of a large and very varied class of hydrocarbons known as terpenes. Strangely enough, plants are not the only living things that produce them – some termites and butterflies do as well. The bits that makes the resin sticky are dissolved solids. The constituents of resins can be separated by a lengthy process known as fractional distillation. The different compounds in resin have different boiling points and so they can be separated at the temperature at which they become gaseous and they can then be collected on their own.
Some plants produce explosive resin. The Jeffrey Pine of California produces resin which is highly volatile – that mean it has, under the right circumstances – a tendency to vaporize. When people tried to distil it in nineteenth century America, they thought it was Ponderosa Pine resin. A number of distilleries exploded as a result of this mis-classification and the mistake was put right in something of a hurry. The reason behind the explosion was that the Jeffrey Pine resin is made up largely of pure heptanes – highly flammable. Distillation of Jeffrey Pine resin continues to be very dangerous to this day but the denizens of California have managed to get it right since the great pine explosions of 1852.
There are some resins which, when they are soft, are called oleo-resins. When they contain either cinnamic or benzoic acid they are known as balsams – and these have traditionally been used in optics. They are also used in oil painting to produce a warm glow effect and have made their way in to at least one cough mixture as well. Most people have heard of amber – which is resin in its fossilized form. However, you can also get African Copal and again, as with amber there are often insects trapped inside, frozen in time. Copal is distinct from amber as – comparatively – it is very young, under a million years old.
Resin is first visible on the bark of a tree as a tiny bubble, much like when your skin is pricked and blood forms a perfect but minute sphere. Many people have uncomfortable first contact with resin. They will lean against a tree or sit upon one and when they remove themselves they will find that they have resin sticking all over their clothes. As is the case with chewing gum – rather than wash the clothing in order to remove the substance it is a much better idea to put them in a freezer and then chip off the pieces after a few hours.
There are some places in the world where fossilized resin – amber – can be found in great quantities. Kämpinge in Sweden is one such place. Located by the sea, when storms begin at the end of the summer the locals make a beeline for the beach as amber is washed up in large quantities, so much so that it is referred to as the ‘gold of the north’ (though some amber can be blue!). Sometimes pieces weighing over one kilo can be found, although they are rare. The reason that it washes up is because it is a little heavier than water and so floats like soap near the sea bed. Eventually it comes up on the shore – helped by the storms – and so the later months of the year are always the best to go amber hunting.
In ancient times up to the present it was believed that amber had healing properties and as such was often worn as a charm or a necklace or even carried in a small pouch. It was believed that the presence of amber would help to relieve such maladies as rheumatism and sore throats. Ironic then that it is in fact resin that has the medicinal properties and has long been used in herbal medicine. This insect is not quite getting those benefits, however.
So, there you have it – a short tour of the mystery of resin. Although its actual purpose is for now shrouded in some mystery there is no denying its innate – if sometimes dangerous or even deadly – beauty.