Pigments through the Ages - Overview

A painted swatch of Cobalt yellow:

Brief description of Cobalt yellow:

An expensive yellow that was briefly in vogue. It is of very pure yellow color and is lightfast but has only fair hiding power. Introduced as a pigment in 1852, it replaced an earlier pigment called Gamboge, an Asian yellow gum used until the 19th century. Cobalt yellow remained popular until the late 19th century, when less expensive, cleaner and more lightfast pigments like the Cadmiums were introduced.

Names for Cobalt yellow:

Pronounciation:

ko • bawlt yel • low

Alternative names:

Aureolin

Word origin:

The name "Cobalt yellow" comes from Middle High German kobolt = an underground goblin (cobalt was thought to be detrimental to silver ores).

Non-English names:

German	French	Italian
Kobaltgelb (Aureolin)	jaune de cobalt (aureolin)	giallo di cobalto

Color Index (C.I.)

PY 40

Chemical name:

potassium cobaltinitrite

Source of Cobalt yellow:

Example of use by artists:

Unique tiny leaf like particles

One common way of identifying a pigment is to look at it under an optical microscope. Here are micrographs showing (A) the leaf- like crystals of cobalt yellow, a pigment used primarily in the 19th century for watercolors, and (B) orpiment (arsenic sulfide), a poisonous mineral used since classical times. Micrographs also show that crystals found in modern pigments, such as the chromium oxide green shown in (C), are far more uniform in size than the ground-up particles found in ancient mineral pigments such as malachite green, a basic copper carbonate (D). Micrograph (E) shows how malachite green looks under polarized light.