Thursday Terms: Aniline Dyes

Goat skin dyed with aniline dyes for book casings

Welcome to Thursday terms! Today we'll be discussing aniline dyes, a type of water (or alcohol) soluble dye that is used for coloring untreated leather. Leather can be dyed for many reasons, including to hide natural imperfections in the animal skin, but book artists tend to dye their leather for aesthetic reasons.

A selection of aniline dyes

Aniline was first used to dye fabrics in 1834, when Friedlieb Runge isolated the substance from coal tar and noticed it produced a beautiful blue color. This blue dye became the precursor to indigo, and was used to dye blue jeans. In 1856 aniline dyes began to grow more popular as new colors was discovered, such as dyeing something purple. Further exploration of aniline (and the colors it made possible in fabrics) in the 1850s and 60s helped make the synthetic dye industry grow, and many natural dyes became replaced with aniline-based ones.

Today, aniline dyes are still used to color leather—including certain pieces of leather clothing—and are important terms for book artists. Unlike pigmented leather, aniline-dyed leather is semi-transparent, allowing the natural grain, texture, and blemishes of the animal skin to show through. Aniline dyes also allow for a mixture of colors: the skin can be dyed in shades, fades, and blended mixtures of color as opposed to having the uniform and glossy look of treated leather.

Flower pressed into leather & painted with aniline

Aniline dyes come in a powdered form, as seen in the jars above. They are mixed into boiling (or very hot) water, producing a vibrant-colored liquid. While aniline dyes are fairly safe to use, one should be careful not to inhale the vapors from the mixture (or the powder itself) as some studies have shown it to be toxic. Once the dyes are mixed, the liquid is allowed to cool before it is used on leather.

One of the best aspects of aniline dyes is their versatility. Like watercolor paints, these dyes can be mixed or layered on top of each other to produce different effects. The artist can use a ball of cotton batting soaked in the dye to cover the whole piece quickly, creating different textures based on the hand motion one uses to put on the dye. Aniline dyes can also be applied with a thin brush, which is especially useful for painting in details. In fact, a leather book cover can be entirely painted with aniline dyes, producing an amazing and original piece of work! Aniline dyes can also be used in lieu of water when pressing a linoleum plate into the damp leather, giving the same impression but coloring it at the same time.

-Christina Squitieri

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