Iso Yellow is short for Isoindoline which is itself a shortening of the full chemical name for this pigment. It is a vat pigment. Vat pigments are called so because they are made in vats, but while that sounds fairly ordinary, vat pigments have a reputation for being particularly lightfast colors with all round good qualities. They have high tinting strength and are very clean colors.
Chemical Description: Isoindoline
Pigment Number: PY139
Lightfastness Rating: ASTM I
Pigment Opacity: Semi-Transparent
Paint Opacity: Semi-Transparent