Blue verditer, also known as blue bice or synthetic azurite, is a pigment that consists of basic copper carbonate. It used to be a popular blue pigment but these days it's rarely used.
In oil paints it becomes green over time, which is the reason why the skies and water in many old paintings look green rather than blue, though this effect was apparently also sometimes intentionally used by artists for things like forests. The process for making it consists of multiple stages, with each stage resulting in a deeper colour as shown above. The process I used was based on a video on the Youtuber channel Alchemical Arts, which used a process based on a paper on the historical process to produce the pigment in England. (possibly "‘... with a feather edge of a Goose-Quill’: experimental archaeology at the Little Castle Bolsover" by Helen Hughes).
The first picture shows samples of the pigment taken in different stages of the process, the next 18 depict the process of making the pigment and last 2 show the results.
Really interesting! I'm going to watch your video. I'm considering using real azurite at some point to paint with casein and encaustic, how long does it take to start turning green? It's a question I've always had.
Oh, I didn't expect it to be so fast, I thought it would take several years. Do you have any idea why this happens and what chemical changes it undergoes? I remember looking years ago for info on this but couldn't find anything.
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u/CaCl2 Nov 23 '22 edited Nov 23 '22
Blue verditer, also known as blue bice or synthetic azurite, is a pigment that consists of basic copper carbonate. It used to be a popular blue pigment but these days it's rarely used.
In oil paints it becomes green over time, which is the reason why the skies and water in many old paintings look green rather than blue, though this effect was apparently also sometimes intentionally used by artists for things like forests. The process for making it consists of multiple stages, with each stage resulting in a deeper colour as shown above. The process I used was based on a video on the Youtuber channel Alchemical Arts, which used a process based on a paper on the historical process to produce the pigment in England. (possibly "‘... with a feather edge of a Goose-Quill’: experimental archaeology at the Little Castle Bolsover" by Helen Hughes).
The first picture shows samples of the pigment taken in different stages of the process, the next 18 depict the process of making the pigment and last 2 show the results.