Gum copal
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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 often times 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 for gum copal, white in color and 99-100% purity, it is used for making varnish specifically for wood surfaces. Its result is very good luster and very good in resisting external scratches. Plus it dries to a hard and shiny film.
DBB- This grade is pebble sized and whitish yellow in color with about 90-95% purity. This is an economy grade and ideal for production of low end varnishes, its solubility is good. It can contain some black copal but it is still perfectly and easily dissolved in alcohol solvent mixtures. It is also the most common use for incense.
WS- The lowest grade for gum copal with larger chunks and black in color with about 60% purity, the impurities include treebark and soil.
Powder- The is 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
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 a very wide variety of uses in both past and present times. Primarily used as an incense by ancient civilizations, it also found usage 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 associating the copal as food for the gods).
Today it still finds popular usage as an incense. In addition, it finds a niche as being a varnish or waterproofing material (as when it is heated with certain oils, it becomes nearly transparent). It also can be used as ingredients for 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
- ^ Galbraith: Mackinnon and east Africa, Cambridge, 1972
- ^ a b c Aber, Susan Ward, Ph.D. "Copal An Immature and Controversial Resin."Copal. Emporia State University, 16 Jan. 2004. Web. 01 Dec. 2015.
- ^ "Gum Copal." Gum Copal, Gum Copal Suppliers and Manufacturers at Alibaba.com. Alibaba, n.d. Web. 07 Dec. 2015.
- ^ a b c "Gum Copal Indonesia." Gum Copal Indonesia. PT Naval Overseas, n.d. Web. 04 Dec. 2015.
- ^ JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1
- ^ JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1 Issue: 9
- ^ Ralph, Jolyon, and Katya Ralph. "Copal." Gemstone Information. N.p., n.d. Web. 04 Dec. 2015.
- ^ Forestry Department. "Non-wood Forest Products for Rural Income and Sustainable Forestry - HARD RESINS 4." Non-wood Forest Products for Rural Income and Sustainable Forestry - HARD RESINS 4. FAO, n.d. Web. 06 Dec. 2015.