Paint Pigments: Phthalo Blue (PB 15)

A profile of phthalo blue paint pigment, including its characteristics.

Paint Pigment Phthalo Blue PB15
Paint Pigment: Phthalo Blue PB16. Image: ©2007 Marion Boddy-Evans. Licensed to About.com, Inc
by Marion Boddy-Evans
Marion Boddy-Evans is an artist living on the Isle of Skye, Scotland. She has written for art magazines blogs, edited how-to art titles, and co-authored travel books.
Updated May 24, 2019

Characteristics: Phthalo blue is a bright, intense blue that's very dark when used thickly. Used as a thin glaze it's very transparent. Mixed with white it's an opaque, beautiful sky blue. Phthalo blue is available in green and red shades.

Common Names: Thalo blue, monestial blue, Winsor blue, monastral blue, phthalocyanine blue, heliogen blue, intense blue, Old Holland blue, Rembrandt blue.

Color Index Name: PB 15. PB15.6 (green shade). PB 16 (metal-free).
(Color Index Explained)

Color Index Number: 74100. 74160.

Pigment Origin: Copper phthalocyanine, a synthetic organic pigment.

Used for Painting Since: 1930s. (Invented in 1928.)

Opacity/Transparency: Transparent.
(Opacity Explained)

Tinting Ability: Strong.
(Tinting explained)

Lightfastness Rating: ASTM I.
(Lightfastness explained)

Oil Paint Drying Speed: Slowish.

Specific Notes:

  • Sometimes used as a cheaper alternative for cerulean blue.

Quotes About This Pigment:
"Prized for its mixing abilities, it [phthalo blue] has also become the basis of many student-range blues as it can be reduced considerably and still offer a strong color." -- Simon Jennings, Artist's Color Manual, p14.

"As a blue pigment, [phthalo blue] shares none of the luxuriant hue of ultramarine; but its importance lies more in the fact that it absorbs red and yellow almost totally, while transmitting or reflecting blue and green." -- Philip Ball, Bright Earth, p279.