Another organic yellow pigment was called gamboge.

The hard, mineral-like raw material is the solidi ed resin of trees native to South-East Asia.

The gamboge farmer collects the sap using a similar method to rubber extraction. A deep incision is made in the the bark of the tree and a hollowed-out bamboo tube is carefully placed beneath the cut. The resin lls the bamboo mould and takes a year to harden after which it is removed.

Once hardened it can be ground to a bright yellow powder. Unfortunately, like many organic colourants it fades rapidly in bright light and now has very limited use in painting. It is an ingredient of the 18th C. water-colour called Hooker’s green, where it was mixed with Prussian blue or indigo. Modern recipes replace gamboge with a lightfast synthetic yellow.

The resin takes its name from Camboja, the old form of Cambodia which was the pricipal country of supply. It was used from the 8th century in Japan and China, and then in the early 17th C. the British East India Company started importing the colour into Europe.

In more recent times the supply of the resin has had a darker side due to the bloody con icts in the region. The resin farmers collect the gamboge in old battle- elds where unspent bullets are still found mixed into the resin and unmarked landmines can be stepped on and kill.