Rubber gutta
| Gummigutt | |
|---|---|
| Components | |
| RGB ( r , g , b ) | (228, 155, 15) |
| Hexadecimal triplet | E49B0F |
| CMYK ( c , m , y , k ) | (0%, 35%, 94%, 6%) |
| HSL ( h , s , l ) | (38 °, 94%, 94%) |
Gum gutti (also Gamboge , cambogia , Gummigutti , Gutti , lat. Gummiresina guttae , trivial Kaiser yellow ) indicates a rubber resin , and the obtained therefrom dark mustard yellow vegetable dye .
origin
The goods traded in Europe historically came from Siam and Cambodia , from where they were shipped to Europe via Singapore or Canton in China . The name Gamboge (Engl. Gambodge ), and from Gummigut , perhaps comes from Camboja , Cambodia or malay getah "latex".
Extraction
The dye is obtained from the milky sap of the tree species of the genus Garcinia ( Garcinia hanburyi , Garcinia gummi-gutta , Garcinia morella, etc.) native to Cambodia , Mysore , Ceylon and Borneo .
For this purpose, spiral cuts are made in the bark of trees that are at least 10 years old, or leaves and saplings are broken off. The leaking yellow milky sap is caught in bamboo tubes . After breaking the pipes, the solidified juice is obtained in the form of brown sticks ("stick gutta"); Darker, less valuable goods came on the market in the form of lumps ("Kuchengutta").
properties
The raw resin consists of approx. 70–80% yellowish colored resin and 20–30% rubber.
Gummy gutta is partially soluble in alcohol , oil and water, with only the gum portion or only the dye portion dissolving. The pure dye can be obtained by dissolving the resin in plenty of water and then drying it. It has a dark mustard yellow, transparent color. The soluble part consists mainly of β-guttilactone (β-guttic acid) and α-gambogic acid, which belongs to the group of xanthones . The solution turns red when alkalis are added.
β-guttilactone
α-Gambogic acid
use
In the Middle Ages it was used in book illumination , as an anchor for gilding and as a dye to replace gold ( gold varnish ). Today it is rarely used. One area of application is as a dye in the manufacture of violin varnishes.
To a lesser extent, gummy gutta was also used as a powerful laxative . However, if overdosed, it is poisonous, so it is only used in veterinary medicine .
literature
- Lisa Takler: Volatile compounds and antimicrobial effects of selected resins and balms from A – J. Diploma thesis, Univers. Vienna, 2015, pp. 127–133, online . (PDF; 3.18 MB), from ubdata.univie.ac.at, accessed on November 1, 2016.
Individual evidence
- ↑ Entry Gamboge. In: Emrath: Some old pigments and dyes, their origin u. Period of use in panel, book and miniature painting before approx. 1780. Retrieved on January 16, 2009 .
- ↑ a b c Entry on Gummigutt (i). In: Römpp Online . Georg Thieme Verlag, accessed on July 27, 2018.
