Blue verditer is the name given to artificial basic copper carbonate with approximately the same chemical composition as azurite. Refiner's dark blue verditer was widely used in watercolors and distemper during the 17th and 18th centuries.
Origin and History Blue verditer is the name given to artificial basic copper carbonate with approximately the same chemical composition as azurite. It is believed that blue verditer was a byproduct of silver refining. Numerous early recipes for its preparation are known; the best types appear to have been prepared at relatively low temperatures with a copper salt. "Refiner’s verditer" was considered the best type of copper carbonate and was widely used as house paint during the 17th and 18th centuries with continuing use up to the 19th century.
Source Our Refiner's dark blue verditer is made according to an English recipe of the 18th century that requires relatively low temperatures for its manufacture. This deep blue, slightly more greenish than natural azurite, lends itself well to consistent applications of color. Microscopically, blue verditer appears as tiny, rounded, fibrous aggregates, even in size and blue by transmitted light. It is similar in color to finely ground azurite.
Permanence and Compatibility Blue verditer is stable in lime and is well suited for tempera and watercolor, but is liable to darken or become greenish in oil. However, it can be used with some success if it is mixed with lead white ground in oil. The white pigment lightens the blue and keeps it from appearing too dark. Painted swatches of our Refiner's dark blue verditer ground in oil show little change in color after five years.
Oil Absorption and Grinding Verditer absorbs a medium amount of oil (23 g oil per 100 g of pigment).
Toxicity Blue verditer contains copper, which can be toxic if inhaled or ingested. Care should be used in handling the dry powder pigment to avoid inhaling the dust.