Difference between revisions of "Category:Gamboge: Ukiyo-e colorant"

Description

Gamboge (shio): A yellow-orange gum-resin produced by several species of Garcinia tree found in India, Thailand, Cambodia, Vietnam, and Ceylon. Gamboge was used as a yellow pigment as early as the 8th century in Asia and Japan. It was regularly imported to Europe in the 17th century but a few earlier deliveries may have occurred. Gamboge is composed of a yellow resinous component (70-80%; morelloflavone) and a clear water-soluble Gum (20%). Gamboge is marketed in the form of dull, brownish-yellow cakes or lumps. When powdered, it has a rich golden color. Gamboge is used as a transparent colorant in glazes, varnishes, and watercolors. The carbohydrate gum acts as a natural binder. The yellow color fades when exposed to light or Ozone. In some cases it has recovered its color when placed in the dark.

For the analysis, it was known that gamboge does not fluoresce in UV light (see below), Thus is was no surprise that gamboge did not produce a distinct pattern using the excitation emission technique. In fact, because it is the only bright yellow colorant that does not fluoresce (of those we have currently analyzed) and because it even absorbs the normal fluorescence given off from the paper, we sometimes used this negative indication to assign the presence of gamboge.

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  Gamboge pieces

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  Gamboge, powdered

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  Gamboge: Vis (left) UV (right)

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  Gamboge, transmitted light

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  Gamboge dyed paper

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  3D EEM plot of gamboge

Examples