NATURAL GUMS & RESINS

Natural gums and resins have a long history in art, extending from the dawn of humanity to the present day. The Paint Box is very proud of its extensive collection, much of which is for direct sale and some of which is available exclusively to museum conservators. The PaintBox is currently supporting research at The Flinders University of South Australia in collaboration with Indigenous Communities into the history and use of acacia gums in indigenous practices.

True gums are formed from the disintegration of internal plant tissues, mostly from the decomposition of cellulose in a process called gummosis. Gums contain high amounts of sugar and are closely allied to the pectins. They are colloidal and soluble in water, either dissolving entirely or swelling, but they are insoluble in alcohol and ether. They exude naturally from the stems or in response to wounding of the plant. Commercial gums arrive in the market in the form of dried exudations. Gums are especially common in plants of dry regions. They are used primarily as adhesives, and are also used in printing and finishing textiles, as a sizing for paper, in the paint and candy industries and as drugs. Three important commercial plant gums are gum arabic, gum tragacanth and karaya gum.

Resins are formed as oxidation products of various essential oils and are very complex and varied in chemical composition. The resin is usually secreted in definite cavities or passages. It frequently oozes out through the bark and hardens on exposure to air. Tapping is usually necessary in order to obtain a sufficient amount to be of commercial value. Commercial resins are also frequently collected from fossil material. Resinous substances may occur alone or in combination with essential oils or gums. Resins, unlike gums, are insoluble in water, but they dissolve in ether, alcohol and other solvents. Resin production is widespread in nature, but only a few families are of commercial importance. These include the Anacardiaceae, Burseraceae, Dipterocarpaceae, Guttiferae, Hammamelidaceae, Leguminosae, Liliaceae, Pinaceae, Styracaceae and Umbelliferae. The exact botanical origin of a resin is often hard to trace, especially in the case of fossil and semi fossil types. Resins probably serve the plant by preventing decay, which is due to their high antiseptic qualities. They may also lower the amount of water lost from the plant tissues.

Resins have certain characteristics that render them important to art. Their ability to harden gradually, as the oil that they contain evaporates, makes possible commercial varnishes. The resins are dissolved in solvents and surfaces are painted with the mixture. As the solvents and oils evaporate, a thin waterproof layer of resin remains. Resinous substances have been utilized for waterproof coatings, and also for decorative coatings for millennia. Ancient Egyptians varnished their mummy cases and the utilization of lacquer in the arts has been practiced in China and Japan for centuries. The Greeks and Romans were familiar with many of the same resinous materials that are used today (e.g., mastic, amber, sandarac). Another property of resins that is of industrial importance is their ability to dissolve in alkalis to form soap. Resins are also used in medicine; for sizing paper; as a stiffening material for mats; in the preparation of sealing wax, incense and perfumes; and for many other purposes as well.

It is difficult to classify resins because the same term is often used for very diverse materials. In commerce, resins are often referred to as gums, while such terms as varnish resins, hard resins, spirit varnishes, balsams, gum resins, damar resins, soft resins, and many others are used quite indiscriminately. The chemical differences between the various groups are much more definite. In terms of art materials there are three main types which are Hard Resins, Oleoresins and Gum Resins.

You will information on these natural wonders on our website pages and staff are happy to assist you instore.

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