Organic yellows are usually derived from plant sources. Very prone to fading following exposure to light, they cannot be securely distinguished using non-invasive analytical methods.
Weld, also known as 'fuller's weed' or 'dyer's weed', was derived from Reseda luteola plants and widely used in textile production, but also mentioned in historic treatises for use in manuscript illumination. Saffron, the golden yellow dye extracted from the stamens at the centre of the Crocus sativus flower, was labour intensive to harvest and very expensive.
