The paintings of Vincent van Gogh are instantly recognizable from both their strong brush strokes and their vibrant color. The pigment industry had given new exciting colors by the time his canvases were created. His strong blues and yellows are colors that stand out when we think of his work.
Cornfields and sunflowers were dependent on chrome yellow for their sparkle. Louis Vauquelin first produced this in 1809, from a mineral source. It was a real killer color and was used until late in the nineteenth century to make some candy yellow. It is easily synthesized from solutions of lead nitrate and potassium dichromate, and its high toxicity is due to its Chromium 6 and Lead 2 content.
Chrome Yellow is the US School Bus color, and when mixed with lead sulfate as a white pigment, yields a lemony tint. Unfortunately the pigment combination is a strong oxidizer, and UV light is encouraging the reaction at the pigment varnish interface of the van Goghs. The high energy X-ray beam from Grenoble’s great synchrotron has seen the reaction product Chromium 3 in the thin interfacial layer in experiments carried out by a team from Delft Technological U. Chromium 3 is just dull, dirty brown so soon the sunflowers will look wilted and ready to be tossed – if we keep looking at them that is. Kept in the dark, they would last longer.
On a completely different topic, I see that best way of persuading large crocodiles not to munch you for lunch, is to poke them in the eye. They really don’t like that. They don’t think your playing fair and won’t play with you anymore. A Queenslander, Mr. Eddie Sigai, put this to the test when a 10-foot beastie grabbed his hand for an underwater game. The UK Daily Mail last Saturday reported that he had deep cuts on his hand and scratches on his back after the dust up.
It is hard to imagine those vibrant van Goghs fading. But then there is something wrong with the thought of storing them in a vault to keep them fresh.