Rublev Colours Pigment Phthalo Blue - 4 oz

Non-toxic and easy to work with, Phthalo Blue is a versatile and reliable choice for artists seeking a durable and brilliant blue hue.

Phthalo Blue, a vibrant and enduring synthetic pigment, has become a cornerstone of artists’ palettes worldwide. Known for its intense chromatic strength and exceptional lightfastness, this pigment offers unparalleled versatility and reliability. Its synthetic origin ensures consistent quality and availability. At the same time, its compatibility with various media—ranging from oils to acrylics and watercolors—enables artists to explore a broad spectrum of creative possibilities. Non-toxic and easy to work with, Phthalo Blue provides a brilliant hue and maintains its integrity over time, making it an indispensable choice for both professional and amateur artists seeking to create lasting works of art.

Permanence and Compatibility

Phthalocyanine blue is renowned for its exceptional permanence and lightfastness, making it a highly stable pigment under a wide range of conditions. It resists fading and degradation over time, even when exposed to strong sunlight or adverse environmental factors. This stability makes it compatible with various media, including oil, acrylic, watercolor, and tempera. It also mixes well with other pigments, allowing artists to achieve a broad spectrum of colors without compromising the integrity of the final product.

PB 15:3 is rated ASTM Lightfastness I in all artist media and is exceptionally resistant to acids, alkalis, solvents, and over-painting. Its crystal structure remains stable up to 180 °C and withstands 3,500 h of xenon testing, allowing it to be safely combined with fugitive organic reds without risk of colour shift.

Oil Absorption and Grinding

The oil absorption rate of phthalocyanine blue is moderate to high, requiring 52 grams of linseed oil for every 100 grams of pigment—about twice that of ultramarine—so stiffer binders or stand oil additions help maintain brushability. Its very high specific surface area (≈54 m² g⁻¹) yields smooth transparent glazes when mulled with bodied oil or walnut alkyd. A balanced amount of oil is required to achieve the desired consistency without becoming too runny or too thick. The pigment’s fine particle size ensures smooth grinding and dispersion in the chosen medium, resulting in a uniform, homogenous paint. Artists appreciate its ability to maintain a high chromatic strength even when used in small quantities.

Unlike mineral pigments,  phthalocyanine (phthalo) blue does not have formal Mohs hardness values. Both are synthetic coordination/organic pigments, so hardness—defined for crystalline minerals—doesn’t strictly apply. That said, their effective or functional hardness in artists’ materials can be described accurately. phthalo blue forms a coordination polymer with relatively weak lattice cohesion compared with oxides. Pigment particles are soft, friable, and readily fractured. The practical implications for paint making are very low abrasiveness, negligible tool wear, minimal wear on glass, granite, or agate mulling surfaces, and exceptional chemical and light stability despite low mechanical hardness.

Toxicity

Phthalocyanine blue is considered non-toxic and safe for use in artistic and industrial applications. Under normal usage conditions, it does not pose significant health risks through skin contact, inhalation, or ingestion. However, as with all pigments, it is advisable to handle phthalocyanine blue with care, using appropriate protective equipment, such as gloves and a mask, especially during processes that generate dust or fumes. 

Copper-phthalocyanine is considered non-toxic and is approved under U.S. FDA 21 CFR § 178.3297 for indirect food-contact plastics. Regular studio hygiene practices (avoiding dry-spraying and dust inhalation) are sufficient. Dispose of paint waste responsibly—copper traces can accumulate in waterways.