The story starts as a dirty yellow made from sediment and soil. Dug up and mixed with water and oils, it was used to decorate bodies, mark walls and communicate meaning. This early pigment was a natural iron oxide – found in the ground at specific spots around the globe. In the 18th Century, a yellow iron oxide pigment was synthesized in the lab alongside a range of other iron oxides. Made by precipitating ferric oxide hydroxide, it was then washed, dried and milled to give a pure result. This new pigment could be manufactured anywhere, to a consistent quality and color. It was free of the regular impurities found in the natural variant. The natural earth oxide pigment was still used (and still is today), but the new synthetic variant quickly became widely available and popular with artists.

How do you tell the difference between the two yellow iron oxide pigments? You can check their chemical name – the natural variant is PY43, the synthetic is PY42. It’s not easy to visually spot the differences. The particles of PY42 are generally more uniform in size, giving a more vibrant, ‘cleaner’ color than PY43.