Gamboge
Gamboge
Gamboge or gutta gum is a gum resin extracted from some tropical plants of the genus Garcinia and in particular from Garcinia hanburyi, originating in the forests of Southeast Asia.
The extraction from Garcinia plants is carried out by making spiral incisions in the trunk of trees of at least ten years of age; from these incisions a resinous liquid emerges which, dripping, is collected in hollow bamboo canes. Once the liquid has solidified, the bamboo is opened leaving large sticks of raw gutta gum.
The gutta gum looks like a powder with an intense golden yellow color, characterized by a fair stability to light, good transparency (suitable for making glazes).
The gutta gum contains 60-80% of resin, 15-25% of rubber and small quantities of essential oil.
This natural compound is partially soluble in alcohol, ether and other organic solvents and is of an intense golden yellow color and is used to color watercolors or even as a drastic purgative.
The term gutta gum comes from the Latin rubber and the Malay gatah (ghutah) which means resin.
Once upon a time, gomagutta was used in painting, especially as a transparent yellow, to color prints or even for glazes.
It was used by Flemish painters of the sixteenth century until the nineteenth century, but its use has drastically reduced due to the high production costs.
One of the most particular preparations in which gommagutta is used is Florentine mecca, a patinated varnish with which gold leaf decorations are taken on (the appearance of gold).
Furthermore, due to its characteristics, gutta gum is used in violin making and in restoration as a pigment for the preparation of colors (recommended in tempera, oil and watercolor techniques) and as a dye for paints based on natural resins (e.g. shellac, shellac dewaxed, sandracca, copal rubber, benzoe rubber, elemi rubber) and ethyl alcohol specific for the wood finish. In fact, the colored paints with gommagutta give the treated wooden surfaces (e.g. violins, period furniture, etc.) a warm and pleasant golden yellow hue that highlights the grain of the wood without covering them.
For the use of gutta gum, as a coloring agent for alcohol paints, it is recommended to dissolve it first in a colorless alcoholic solution or in bioethanol in the proportion of 50/100 gr. of gommagutta per liter of alcohol.
Obviously, this proportion is purely indicative as it is possible to increase or decrease the quantity of gutta gum, with the same solvent, according to the intensity of the golden yellow color to be obtained.
Once the concentrated coloring solution of gutta gum is prepared, it can be added to any alcohol paint (such as natural shellac, waxed shellac, ruby shellac, sandracca, copale) to obtain the desired color tone.
Warning: The information shown is not medical advice and may not be accurate. The contents are for illustrative purposes only and do not replace medical advice.