Natural
It is a hardened exudations from trees. Those that exude or are extracted from living trees are sometimes called "recent resins" to distinguish them from the "fossil resins," which are dug from the earth or recovered from the beds of streams where they have been deposited by vegetation of former times. Some of these fossil resins are identical with or analogous to resins obtained from living trees in the same locality; others are the remains of completely extinct vegetation. A third group, the synthetic resins, comprises a number of man-made compounds which have resinous properties.
Resins are insoluble in water
But will dissolve wholly or partially in such liquids as oils, alcohol, turpentine, etc. In the varnish industry, resins are commonly known as gums—damar gum, kauri gum, gum copal, etc.—but when they are considered for artistic or scientific discussion the precise term "resin" is always used, and the term "gum" is applied only to water-soluble substances. As the varnish industry is little concerned with the true gums, it uses this term without much confusion.
Resins vary greatly in properties
Such as odor, shape, hardness, solubility, color, and color stability, and specimens of the various kinds and varieties are easily distinguished from one another. Many resins bear the names of. localities; these sometimes represent their places of origin, but more often the ports from which they are shipped. The various species come on the market in more or less well-standardized grades or qualities, each with its own system of grading and designation. The terms bold" and "sorts" both indicate that the grade is largely or entirely composed of clean pieces of the largest size. Grades of resins which consist of small fragments or powder always contain large amounts of impurities and usually considerable low-grade resin. Adulteration with cheaper resins is possible only in these grades; adulterants would be detected immediately among the large pieces of the better grades.
Films of pure resins, as formed by simple-solution varnishes, have a considerably higher resistance to permeation by water vapor than oil films have, but they are less durable in other respects.
Frequently Asked Questions
What are natural resins in art materials?
Natural resins are hardened exudations from trees. They may be collected from living trees or recovered as fossil resins that were deposited by ancient vegetation and later preserved in soil or stream beds.
What is the difference between recent resins and fossil resins?
Recent resins come from living trees, while fossil resins originate from ancient vegetation that has hardened over long periods of time. Some fossil resins are chemically similar to modern resins, while others come from extinct plant species.
How do natural resins differ from synthetic resins?
Natural resins occur naturally in trees, whereas synthetic resins are man-made compounds designed to imitate or improve certain resinous properties such as hardness, solubility, or durability.
Are natural resins soluble in water?
No. Natural resins are insoluble in water but will dissolve wholly or partially in substances such as oils, alcohol, and turpentine.
Why are resins sometimes called "gums" in the varnish trade?
In the varnish industry, resins are often referred to as gums, such as damar gum or copal gum. In precise artistic and scientific usage, however, the term resin is reserved for water-insoluble materials, while gum refers only to water-soluble substances.
Do all natural resins have the same properties?
No. Resins vary widely in odor, color, hardness, solubility, shape, and color stability. These differences allow artists and conservators to distinguish one resin from another.
Why are some resins named after places?
Many resins are named after geographic locations, which may refer to their place of origin or the port from which they were historically shipped and traded.
What do resin grades such as "bold" or "sorts" mean?
These terms indicate high-quality grades made up largely of clean, large resin pieces. Smaller fragments or powdered grades usually contain more impurities and lower-quality material.
Can natural resins be adulterated?
Adulteration is most likely in powdered or low-grade resins, where cheaper materials can be mixed in more easily. High-grade resins made of large, clean pieces reveal adulteration quickly.
How do resin films compare to oil films in paintings?
Films formed from pure resins resist water vapor more effectively than oil films, but they are generally less durable and more vulnerable to long-term deterioration.
Why are natural resins important in varnish making?
Natural resins contribute clarity, hardness, and protective qualities to varnishes, making them historically important despite their limitations in durability.