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Art & Artifacts

Chemistry In Pictures

Chemistry in Pictures: Kinds of blue

by Manny I. Fox Morone
November 25, 2024

Three swatches of silk dyed in different shades of blue, getting darker from left to right, using aniline blue.
Credit: Gracile Roxas

To color these pieces of silk with aniline blue dye, Gracile Roxas had to do her homework. Roxas, a textile conservator who was then a master’s student at the University of Glasgow, wanted to accurately recreate the dying process used on century-old textiles, so she studied 19th-century dye manuals, old academic publications, and color chemistry textbooks to devise her method. She settled on a dyeing process involving two baths: the first one with a colorless form of the aniline blue molecule and sodium carbonate in which the dye molecules were fixed to the fabric, and a second bath of dilute sulfuric acid, which removes a hydroxyl group from the dye molecules and completes the molecules’ conjugated system of electrons and revealing the blue color.

Roxas’s research then looked at how the dyes fade in various lighting conditions. Using this knowledge, conservators will be able to more safely and better preserve dyed samples in their collection.

Submitted by Gracile Roxas

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