Verdigris


Name: Cleo Nisse
Date and Time: Monday 25th January 2016
Location:My apartment
Subject: Making verdigris
I began to make verdigris pigment. I used the equipment and ingredients given to me in the laboratory.
Ingredients - 20% acetic acid, thin copper plate.

The method used was based on instructions in Merrifield 1967 edition, p.418,
This is from what Merrifield calls the 'Bolognese Manuscript', an MS from the fifteenth century preserved (according to Merrifield) in the Library of the R.R. Canonici Regolari in the convent of S. Salvatore in Bologna. Merrifield describes it as 'a book of recipes rather than a treatise, and it affords interesting notices of all the decorative arts practised at that period in Bologna.' Merrifield, ed.1967, p326

‘Here Begins the Fourth Chapter - On Making Greens from Copper and From the Juice of Herbs in Various Manners and First-…
…84. To make verdigris - Take platers of copper, and suspend them over the vapour of strong vinegar in a jar covered with clay and well closed, so as to be air-tight; then put the jar into dung or the refuse of grapes, in the time of the vintage, for the space of fifteen days, when you must open the jar, and you will find the verdigris adhering to those plates. Scrape it away, and return it as before.’
I took a single copper plate and used thin rope to suspend it in a glass jar with a metal, screw-top lid. In the bottom of this jar was put acetic acid 20%. The acetic acid took the role of vinegar in the Merrifield recipe. The copper plate hung over the acetic acid without touching it, to allow the ‘vapour’ to act upon the copper. I interpreted the instruction to place the jar in dung as identifying a need for warmth, therefore I placed the jar near to a warm radiator.

I am curious as to how close my process is to the one described in Merrifield. In particular, my decision to place the jar by a radiator for added warmth. While this had been prompted by the instruction about ‘dung’, is it truly necessary in a modern home that is warmer than a typical building from fifteenth century Italy, at least for most of the year? Of course, in fifteenth century Italy the temperature depended on the time of year, as the summer could have been quite warm, but I did not find any indications in this particular recipe as to time of year that this would have been carried out. Could I be over-heating the copper by doing this?
There are plenty of other issues of 'authenticity' here - rather than vinegar I was using 20% acetic acid. The copper plate was thin and regular, I wonder what kind of copper plates would have been used in the fifteenth century?


<a data-flickr-embed="true" href="https://www.flickr.com/photos/128418753@N06/24783044292/" title="2016_Spring_labsem_Nisse_Verdigris_20161202"><img src="https://farm2.staticflickr.com/1683/24783044292_6cd967c9da_m.jpg" width="240" height="180" alt="2016_Spring_labsem_Nisse_Verdigris_20161202"></a><script async src="embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>2016_Spring_labsem_Nisse_Verdigris_20161202


Name: Cleo Nisse
Date and Time: Tuesday 26th January 2016
Location:My apartment
Subject:Making Verdigris

As I was concerned about the jar being knocked by others in the apartment, I moved the jar to a more protected spot, but still by the radiator for warmth. Whilst the jar was being moved, a small amount of 20% acetic acid splashed directly onto the bottom corner of the copper plate. I wonder how this will affect the process.



Name:Cleo Nisse
Date and Time:Wednesday 27th January 2016
Location:My apartment
Subject:Making Verdigris
Parts of the copper plate have already begun to turn blue. The colour is distinctly turquoise blue.
I am interested in considering which factors cause a verdigris to tend blue or to tend towards green.


Name:Cleo Nisse
Date and Time:Sunday 31st January 2016
Location:My apartment
Subject:Making Verdigris
Much of the copper plate is now covered in turquoise blue. From what can be seen through the glass jar this seems to be a fine powder adhering to the plate.

Name:Cleo Nisse
Date and Time: Tuesday 2nd February 2016
Location:My apartment
Subject:Making Verdigris
The copper plate is now almost entirely turquoise blue. The bottom tip of the plate has not turned blue. Is this because this area was splashed directly with acetic acid? The instructions do insist on the vapour and not the direct application of the ‘vinegar’ in this particular recipe. On the other hand, different recipes in the same manuscript describe direct applications of vinegar to copper plates suggesting that this should not prevent verdigris from forming. For example
’82. To make verdigris - Take very thin slips of copper, and put them into a vase, and then place the vase three palms deep in horsedung, underground, in a damp place, and let it remain thirty or forty days; then take it out, and rub the slip well with very strong vinegar; then put them back under the dung in the vase, and let them remain well covered or the space of one month, when the verdigris will be formed.’//



Name:Cleo Nisse
Date and Time: Monday 8th February 2016
Location:Laboratory Chandler hall
Subject:Making Verdigris pigment

Before opening the jar I checked the MSDS sheets for health and safety information on Verdigris. MSDS data sheets describe that copper acetate is harmful if swallowed, causes skin irritation, causes serious eye irritation, may cause respiratory irritation, is very toxic to aquatic life with long lasting effects. These can be avoided by wearing appropriate protective equipment (gloves, lab coat and protective glasses) and proper disposal of materials.

I then opened the jar and removed the copper plate. I used a spatula to scrape the verdigris off the copper plate onto a glass working plate. The painter’s spatula is an ideal working tool for this task because it combines a sufficiently sharp edge with some flexibility. Therefore it is possible to push downwards and slide the powder off the plate in a slightly curved motion. The same motion would not be possible with other, stiffer, metal tools. As I scraped the pigment onto the glass plate, I periodically gathered the powder up towards the centre to avoid loosing too much during the process and to keep the amount of workspace I took up contained, since I was working alongside colleagues who had produced verdigris with 15% acetic acid. I wanted to avoid contaminating my pigment with pigment made with 15% acetic acid to help us ascertain the differences cause by changes in acid concentrations.

I put a few drops of pressed linseed oil on to the glass plate and mixed it together with the powder using the spatula. I then began to grind together the powder and oil. There were not enough glass mullers to go around in the laboratory and so our group had to use a mortar instead. This was somewhat successful but not the ideal tool for the task. The glass muller is heavy, with a large flat underside. This allows one to put considerable weight into the grinding process and to move in smooth circular motions, which results in small particle size in the resulting pigment. By contrast the mortar had a round base, was smaller, and was made of ceramic. The ceramic absorbed some of the oil and pigment during the grinding. It was not possible to put the same force into the grinding of the pigment. As a result, fort the same period of time spent grinding, the particle size of the pigment in the pigment-oil mixture remained larger and this was visible in the final paint as gritty, visible dots. Had it been possible to grind the pigment and oil together for longer, smoother results could have been achieved even with the mortar. Better grinding of the pigment and oil mixture may also have resulted in a stronger colour in the final result.

After approximately ten minutes of grinding the verdigris and linseed oil together a paint had been formed. I took a brush (what kind of hair were these?) and painted it out onto the pre-prepared board. The board had been prepared with multiple coats of gesso (check) and sized with glue to prevent the oil paint soaking into the support. The paint was quite liquid, although not so much that is ran when the board was put upright. It held the brushstrokes to a certain extent, although it would not be possible to achieve (for example) a thick impasto with such a consistency. The final paint is somewhat translucent, although it does not have the rich, glossy quality of a true glaze.


Name:Cleo Nisse
Date and Time: Friday 12th February 2016
Location:Laboratory Chandler hall
Subject:Making Verdigris pigment
I returned to the lab to try making the verdigris with all of the equipment available and to try a different type of oil.

I made verdigris using glass muller, glacial acid and harvested verdigris and walnute stand oil. One square with one layer, one with two layers.
I used the stand oil present in the laboratory, it seems that this has been made by standing the jar of pressed walnut oil by the window in the sun for long periods of time. I ought to check with the team for more details on this.
I found that using the glass muller made considerable difference to how finely one could grind the particles of the pigment. Stand oil seemed to result in a more bodied paint in the end.
The results of this second attempt were more satisfactory as the verdigris resembled an oil paint, one that could even be used for glazing, to a greater degree. However, due to limitations of time I still did not grind the pigment for as long as I ought to have, and therefore there are still granules in the final paint.


ASPECTS TO KEEP IN MIND WHEN MAKING FIELD NOTES