“How to make the green from brass which is called Greek or common green - If you wish to make the copper-green which is called Greek, take a new jar, or any other concave vase, and put into it the strongest or most acid vinegar, so as not to fill it , and put strips of very clean copper or brass over the vinegar, so that they may not touch the vinegar or each other, being suspended to a stick placed across the vase. Then cover the vase and seal it, and put it into a warm place, or in dung, or under ground, and leave it so for six months, and then open the vase and scrape and shake out what you find in it, and on the strips of metal, into a clean vase, and put it in the sun to dry.”
(Merrifield, Mary P. Original Treatises Dating from the XIIth to XVIIIth Centuries on the Arts of Painting, 2 vols [London: John Murray, 184], p. 124)
9/14/16- "Growing" the Verdigris
I began my verdigris first by poking a hole in the copper sheet given to us, passing the thread through the hole, and screwing the lid of the jar over the thread to keep the copper suspended over the vinegar I poured in the bottom (about 3/4 of an inch or so). I used distilled white vinegar with 5% acidity, because 1) the recipe provided didn't specify the type of vinegar to use and 2), it's what I had on hand at my apartment.
I left my jar on a sunny windowsill, since the recipe indicates that it should be left in a warm place. After 1 day of "growing", the copper sheet had already turned mostly turquoise with just traces of the copper color still apparent (see pictures above). Over the next couple weeks, the turquoise color intensified, and by the time came for painting it out, it was much harder to see traces of the copper through the verdigris growth (see picture below).
10/3/16- Painting Out the Verdigris
We used palette knives to scrape off the verdigris from the copper sheets. Then, I combined my scraped off pigment with 2 drops of the walnut seed oil, following the advice given by Professor Smith. It was remarkable how little oil the verdigris needed to be transformed into a liquid capable of being painted: after the first drop, it was still very dry and clumped easily, but after the second it immediately dissolved into a liquid. We were then instructed "mull" the verdigris/walnut-oil mixture on a glass panel using a glass tool. This was done in order to grind out any small verdigris particles and produce a smoother mixture.
I then painted out the mixture onto the white panels prepared by the FA15 Making and Knowing students. My verdigris growing experiment didn't produce as much pigment as those of some of the other students, so my painting on the panel was stretched out rather thin.
I also experimented with preparing some verdigris produced by a student on 1/25/16 (red wine vinegar, 5% acidity). This time I combined/mulled the pigment with linseed oil, and it required 6 drops of oil to turn into a paintable liquid. The greater amount of oil needed compared to the trial with the pigment I produced (white vinegar verdigris/ walnut oil mixture) probably resulted from the fact that the second trial (the red wine vinegar verdigris) simply involved a greater amount of pigment, but I wonder if this is also related to the properties of linseed vs. walnut oil and verdigris produced with white vinegar vs red wine vinegar.
Being painted out, the red wine vinegar verdigris / linseed oil mixture produced a deeper turquoise color than the white vinegar / walnut oil mixture, as you can see in the picture below (Panel 5A = white vinegar / walnut oil, Panel 6A = red wine vinegar / linseed oil). This, again, seems to be the result of the greater amount of pigment in the red-wine / linseed oil trial.
10/10/16
Below you can see the painted out verdigris after being left to sit for a week . You can see that, compared to its appearance immediately after being painted out, it has dulled slightly in color and also looks a bit more green.
