Phthalo Blue is like liquid sapphire that could be administered through a medicine dropper. This is the essence of blue in a bottle, and there is something about it that also lends itself to a chemical age. It is one of the essential colors for a modern high chroma palette— a saturated transparent cyan or middle blue. When high chroma is wished for, it is a Godsend, and it is one of the only routes to a true bright cyan. However for lower chroma blues, it can be a challenge to use. We call this entry "Phthalo Blue Unspecified" because often there is an additional number to the pigment code which tells a person which sub-variety of Phthalo Blue is being used. Sometimes the paint companies leave off this extra piece of information and just write PB15. While there are a handful of sub-types, Phthalo Blues comes in two main varieties, Phthalo Blue Green Shade and Phthalo Blue Red Shade. The Red Shade is a tiny bit more likely to mix toward a middle blue that leans toward indigo where the Green Shade leans more toward cyan. We have an in-depth article as well as a comparison of several different Phthalo Blues in oil.
Phthalo Blue can be tricky to handle in painting because a little bit goes a very long way. It also has a way of making its presence known in a mixture, so some painters prefer Cerulean PB35 or Cobalt PB28 for naturalistic subjects. However, Phthalo Blue makes some of the highest chroma middle blues and cyans, and there is no replacement for this incredibly bright blue.
In terms of health and safety, phthalo blue contains copper. Please see the Artist's Guide to Health and Safety for information about the hazards associated with copper pigments. The author's most recent updated writing can be found through her site. Phthalo Blue sometimes contains impurities depending on the way it is manufactured and may contain dioxins and PCBs.
Phthalo Blue requires a moderate amount of oil. Opinion is divided on its drying time with some saying medium to slow and others listing it as fast. It seems to frequently contain additives, stabilizers, and extenders. While phthalos are thought to be less toxic than other some paints, avoid tubes made before 1982 (or even we have heard as late as 1986) as they may be contaminated with impurities such as PCBs. Handle all artist colors with care.
