Dye crystals up close

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Allura Red AC food dye, imaged using differential interference contrast (DIC) microscopy – Linden Gledhill

Biochemist-artist Linden Gledhill was staining yeast cells with food dyes when he accidentally used too much dye on one specimen, and a tiny drop of dye crystallised on the edge of the microscope slide.

Gledhill was so struck by the shapes the dye crystals formed, he immediately began to explore. Abandoning the yeast cells, he placed a droplet of dye on a slide, covered it with a cover slip and let it dry, systematically examining different dyes and other food additives for their unique crystal patterns.

“What’s quite surprising, considering how common these chemicals are in our diet, is there’s nothing out there in terms of imagery of these crystals – very few people have even looked at them,” Gledhill says.

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A mixture of food dyes, imaged using DIC microscopy – Linden Gledhill

By using different food dyes – sometimes alone, sometimes in combination – and controlling how quickly each dye droplet dried, Gledhill could coax many different crystal shapes to emerge, from piercingly sharp spikes to soft, fern-like forms.

 Using a technique called differential interference contrast microscopy, he was able to adjust the background colour with polarised light to make the stunning crystals stand out. 

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Allura Red AC food dye, imaged using dark field microscopy – Linden Gledhill

“Within a few minutes, crystals begin to appear at the edge of the cover slip, but it takes a day or so for the whole slide to crystallise,” Gledhill says. “I often go back to old slides many days later because you never know what may appear.”

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Salicylic acid, a food preservative, imaged using DIC microscopy – Linden Gledhill

One trick Gledhill used to influence crystal formation was to paint nail varnish on to the join between microscope slide and cover slip, slowing the rate the dye dried. Fast crystallisation typically gives multiple small crystals; slowing the process down favours larger ones. The images shown here were captured at around 100 times magnification. 

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Allura Red AC food dye, imaged using DIC microscopy – Linden Gledhill

“Everywhere I look there’s beauty, and that includes all scales from the microscopic up to the Universe,” Gledhill says. “To me it’s all one continuum of art.”

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