Cobalt Aluminate Blue Watercolor Paint – Rublev Colours

Cobalt Aluminate Blue originates from the spinel group of minerals, created by calcining cobalt and aluminum oxides at high temperatures. These spinels crystallize in a cubic lattice and are chemically inert and insoluble, giving the pigment exceptional lightfastness and stability. The pigment family dates back to the 18th century; cobalt aluminate was identified on Egyptian ceramics and later manufactured in Europe by calcining cobalt oxide and alumina. Variations of cobalt blue arise from substituting other metals—zinc or chromium—into the spinel lattice, but the pure cobalt aluminate spinel (Pigment Blue 28) remains prized for its clean hue.

In watercolor, cobalt aluminate blue exhibits semi‑transparent coverage with moderate tinting strength. The pigment’s fine particles naturally flocculate, producing a gentle granulation that lends skies and water areas a soft, luminous texture. This color lifts easily and is low‑staining, so it can be manipulated for glazing, wet‑on‑wet washes, and delicate transitions. Compared with phthalocyanine blues, it is easier to control and less overpowering in mixtures. Rublev Colours crafts this watercolor using only cobalt aluminate pigment, gum arabic, and traditional humectants, without fillers or brighteners, allowing the pigment’s natural handling to shine.

Notes: Rublev Colours watercolors are made with pure pigment, gum arabic, and traditional humectants, without fillers, dispersants, brighteners, or other additives. Some separation of pigment and medium may occur because no stabilizers are added. Color swatches are shown in mass tone and in tints for reference; due to monitor and printer variations, actual colors may differ slightly from what you see online.