Sky Blue (Phthalo)

PW4—Synthetic mineral - zinc oxide, introduced as a painter’s white c.1780. A late arrival, zinc white was taken up by the Impressionists for clean, non-toxic tints and by 19th-century watercolourists; Turner was among the early adopters. Valued for transparency, slow drying and a lack of yellowing - the white of choice for pale tints and delicate glazes.

PB15.3—Phthalocyanine Blue (green shade). Synthetic organic. A stabilised green-shade phthalo blue; very strong and permanent.