Gum copal

Gum copal, also known as manila copal, is a resin produced by the sap of the forest tree (Daniellia sp.), due to common impurities and differences in regions, gum copal ranges in colors from blacks to yellows to whites. Gum copal, along with ivory and slaves, was a significant export from East Africa in the nineteenth century.^[1] Gum copal exists in a state very similar to that of amber but with some primary differences. It is commonly mistaken for amber and oftentimes sold at gem shows or other areas as amber. Unlike amber, gum copal is usually only 100-1,000 years old and it has not yet fossilized. ^[2] Gum copal usually sells for $750-$1500 USD per metric ton in rock form and $1500-$6500 USD Per metric ton in powder form. ^[3]

Grades of Gum Copal

PWS- This is the highest grade of gum copal. It is white in color and 99-100% purity. Used for making varnish for wood surfaces, it dries to a hard and shiny film. Such varnish is high-luster and resistant to external scratches.

DBB- This grade is pebble sized and whitish yellow in color with about 90-95% purity. This is an economy grade, ideal for production of low-end varnishes. Its solubility is good. It can contain some black copal but it is still easily dissolved in alcohol solvent mixtures. It is also the most common grade for use in incense.

WS- The lowest grade of gum copal, larger chunks, black in color with about 60% purity. The impurities include tree bark and soil.

Powder- The leftovers from the processing of PWS and DBB, usually used for varnish. ^[4]

Structure and Properties

Gum copal is a semi-fossilized, amorphous resin which has a unique set of properties such as resistance to water, solubility in alcohols, and has the ability to give glossy finishing along with possessing superior binding abilities. ^[4]

Chemical Structure: C₂OH₁₇FO₃S

The chemical structure of a gum copal molecule as represented by carbon chains and the other atoms found in the molecule.

Melting Point: 90-130 °C

Hardness (Mohs Scale): 2-3

Refractive Index: 1.539-1.545 ^{[5] [6]}

Saponification Value: 140-170 ^{[4] [7]}

Uses

Gum copal has had a wide variety of uses in both past and present times. Primarily used as an incense by ancient civilizations, it also found use as an early form of glue, and traditional medicine for cases such as dysentery, stomach pains, dizziness and fright. It was often used in religious occasions, too, in the form of sacrifices to deities (typically designating the copal as food for the gods).

Today, gum copal is popularly used as incense. It is also used as a varnish or waterproofing material (when it is heated with certain oils, it becomes nearly transparent). It also can be used as an ingredient in adhesives, perfumes, printing ink, paints and films. ^[2]

Gum copal is sold primarily two ways. The first way is as powder, which is usually mixed with turpentine to make varnish. The other way is as the natural "rocks" which can then be used in many different ways.

Regions

Gum copal is most commonly found in East Africa and Indonesia, but is also found in tropical regions of the globe such as South America, Japan, Malaysia, Manila, and even Australia. ^[8]

Comparison to Amber

Throughout history, amber and gum copal have been mistaken for each other as it is extremely difficult to tell the difference between the two materials. However, a drop test using an alcohol or other solvent will leave amber unaffected, while copal will make the surface sticky to touch. A heat test can also be used as amber will soften and blacken its surface and copal will begin to melt.

Another key difference between the two lies in what specimens are inside the material. As both amber and gum copal are produced from tree sap hardening, insects and other organisms can be trapped inside (an idea which provided the basis to DNA extraction in Jurassic Park). Depending on whether this organism can still be found alive in the present or recent past can give reference to the age and identification of the sample.^[2]

References