A Brief Overview of
GUMS, RESINS, RESINOIDS

By Jeanne Rose

1. Gums can be natural or synthetic.  Our discussion only allows for natural gums.

      Strictly speaking, gums are always water-soluble.  As an example:  Gum acacia, Gum Tragacanth.

            Acacia gum (Acacia senegal ) also called gum arabic.  Water soluble and when dissolved in boiling water, clarifies and makes a very good adhesive that is used, among other things, to make scented beads and pomanders.  The gum is edible, nutritive, and acts as a demulcent to soothe irritated mucous membranes.  It is also an ingredient in medicinal compounds for diarrhea, dysentery, coughs and catarrh.  The bark of the acacia plant is very rich in tannin.  (Herbs & Things)

      Resins are sometimes called gums.  However, gums form solutions or "sols" with water, resins do not.  Resins are insoluble in water.

      The word "gum" is truly an herbal term, as gums are used in herbalism to make sticky solutions in cosmetics, or to adhere dry ingredients together.

2.  Gum resin.  Extruded naturally from plants or trees.  Consist of both a gum and a resin, sometimes with a small amount of EO. 

      Example:  Benzoin.

3.  Oleo-gum-resin is a term to describe oleo (oily or fatty in nature or look) gum (partly soluble in water) resin (partly or wholly soluble in alcohol).  Therefore, an oleo-gum-resin has a nature that is partly soluble in water and alcohol and looks oily.  Consists mainly of oil, gum and resin.

      Example:  Myrrh, Frankincense, and Opopanax. 

4.  Oleo-resin.  Prepared or natural material.  Exude from trees - trunks or barks.  Sometimes they are prepared and form as an evaporation residue.  Oleoresin often contains "fixed" oils.  They can be described with color: clear, viscous, and light-colored.

      Example:  Copaiba balsam

5.   Resin.   Are Natural or Prepared.  Exude from trees or plants.  They are formed by nature and some resins are prepared in the laboratory as oleoresins.  Resins are solid to semi-solid, amorphous.  If they contain no water, they are translucent.  They are odorless, not soluble in water.  Can be described generally as products that are used as incense, such as Copal from Mexico and Amber.  These only yield fragrance upon burning.  

      Rosin - Prepared from resins. It is the solid amber residue obtained after the distillation of crude turpentine (gum rosin), or of naphtha extract from Pine stumps (wood rosin) used in adhesives, varnishes, inks, etc. and for treating the bows of stringed instruments.

6.   Resinoid.  Obtained from resins.  Resins are solvent extracted, yielding an alcohol-soluble substance, that is less dense, more sticky and liquid-like, called a Resinoid.  These are viscous liquids and semi-solid.  In a perfectly prepared resinoid, the odiferous material or essential oil is left intact.  Olibanum resinoid is typical.  The Olibanum or natural oleo-gum-resin has been made soluble for perfume use by the removal of the water-soluble gum.

      Example:  Resinoid of Frankincense,

Conclusion.

            Often the terms gum, resin, resinoid, essential oil are used to describe the steps in the processing of natural exudates from plants, such as Myrrh and Frankincense.  These two wild trees, which to this day are still left in their wild state, organically grown, not cultivated, or farm-grown, are harvested by tribes such as the Bedouins in Somali.

            The trees are excised.  The globs of gum exude from the excision.  The globs (or tears) are collected, brought to market, graded according to size and color.  In the case of Frankincense, the smaller, lighter-colored tears are used in ritual and as church incense.  The tears are graded in the marketplace, purchased by large companies and sent to their home countries for processing.

            The tears are processed by heat and extraction to produce the purified resin.  (See above)  The resin is then further processed via the application of alcohol in a vacuum extraction to produce the liquid resinoid.  The resinoid is then further processed with the application of heat, alcohol, vacuum-extraction, and distillation to produce the essential oil.  As each of these steps progress, less and less substance is produced, and the price goes higher and higher.

            A plasticizer has to be added in extremely small amounts (1/10th of 1%) to the essential oil to keep it in liquid form.  Leave an essential oil of Frankincense or Myrrh out in the air, and it will soon solidify as the alcohol and plasticizer evaporate.  Therefore, Frankincense and Myrrh, Labdanum, Galbanum, do not yield true essential oils according to aromatherapy terms.

DESCRIPTION OF OLIBANUM  

            Olibanum, also called Frankincense, is a natural oleo-gum-resin.  It is a physiological, liquid product in the bark of several Boswellia species.  (See the photographs) It contains many interesting chemical compounds including verbenone that is an anti-fungal. Rosemary CT verbenone also contains this compound. A combination of essential oils of Frankincense, Rosemary verbenone, Spikenard, and Tea Tree would make a very potent combination to combat fungus infection.

            Trees are most abundant in Somalia, Southern Arabia and parts of India.

            Bedouins make incisions of the bark at regular intervals.  This increases the production of Olibanum.  The viscous oleo-gum-resin oozes out, but will resinify or solidify when left out in the sun.  This is then broken off its branches or collected from the ground.  It is sorted and graded in the port of Djibouti, Aden, etc.  Grading is strictly by looks.  The bigger the tear, the more complete is the resinification, and therefore, the loss of its essential oils.

            "Experience in selecting the correct material for distillation or for the extraction of resinoids or absolutes, is a rare and valuable skill, and is partly based upon years of experimenting with the distillation and extraction of all grades of Olibanum."  (Arctander)

            In Fantastic Trees, Menninger divides odiferous trees into two categories:  the bouquets and the stinkers.

            In the same book, Botting describes Frankincense as follows:

            The frankincense tree...looks like a decomposing animal.  It has stiff low branches.  The leaves are scant, curly, and indented.  A thick bark and a tiny whitish peel cling closely round the trunk of a peculiarly blotchy color.  The woody fiber of the tree, distended with sap, looks like rotting animal flesh, and the clear, yellowing-white resin comes from incisions with a strong aroma.  The fruit is a berry the size of a marble and the flowers are few, red and germanium-like on the end of short spikes.

            The word Olibanum comes from the Arabic al-luban and means 'the milk'  — the true incense.  The word Frankincense comes from the old French word fraunk-encens and also means the true or real incense.

Resources:

1.  Perfume and Flavor Materials of Natural Origin by Steffen Arctander.
2.  Volume 2, Guenther's The Essential Oils.
3.  Fantastic Trees by Edwin A. Menninger.
4.  Herbs & Things by Jeanne Rose.
5. The New Shorter Oxford Dictionary.