Verdigris (cupric acetate)

"A color know as verdigris is green. It is very green by itself. And it is manufactured by alchemy, from copper and vinegar." -Cennino Cennini, Il Libro dell' Arte.

Verdigris (cupric acetate; “Greek green” ) has been manufactured in Europe for more than 2,000 years as a pigment for painting, a mordant, and dye. Instructions for making verdigris survive from ancient Greek, Roman, and medieval sources; typically, copper stripping or foil is enclosed with vinegar (but not immersed in it) in a wood or pottery container. Acidic vapor causes the growth of verdigris on the surface of the copper. It is a modern error to call the results of weathering on copper ‘verdigris.' Verdigris is mixed (tempered) with vinegar prior to use. As a pigment verdigris is unstable, shifting first from blue to green (a desirable shift) and over the long term from green to brown (very undesirable) [1] This shift to brown does not occur in areas protected from air and light, such as book illuminations.[2] I have not yet found scholarly discussion of verdigris' stability as a dye of wood, bone, feathers, and fabric. [3]

Tudor-era dye recipes use verdigris in conjunction with other items, such as blue vitriol (cupric sulfate) and sal ammoniac (ammonium chloride), to obtain green. Conversations in 2005 on the SCA Natural Dyes listserv, however, showed some members regularly use cupric sulfate instead of cupric acetate on the assumption that the results will be the same, despite the fact that period recipes never call for such a substitution or use blue vitriol alone to dye a green. Because period dyers perceived a difference between the two ingredients I wanted to find out if there is a noticeable difference in the resulting color. As it is expensive to buy but easy to find manufacturing instructions in Tudor era ‘how to' manuals, I decided to make my own. An explanation and photographs of my production follows, as well as various period instructions for manufacturing verdigris and using it as a dye.

My early experiments are suggesting the substitution is a poor one, as I am obtaining better color using less pigment with verdigris compared to copper sulfate.

Using equal amounts of white wine vinegar and either verdigris or copper sulfate, I obtained very different results on these bone beads. The green and dark green beads were done with verdigirs/vinegar but as you can see the copper sulfate/vinegar solution caused the bone to degrade.

 

Follow this link for the bibliography.

 

MY PROCESS

Ancient and medieval instructions for making verdigris vary slightly, but all are fairly easy to follow. I purchased recycled copper, and lightly cleaned it before cutting it to length. I chose to use a glass jar because glass is non-reactive and it lets me monitor the development of verdigris without having to open the container. I used red wine vinegar (2 bottles) because red wine vinegar was preferred in period verdigris manufacture. I could legitimately have used apple cider vinegar instead, as it was often used for this purpose in medieval England.[4] Three small bowls kept the copper from direct contact with the vinegar (readers will note varying strategies for achieving the same thing in the attached period recipes). I sealed the glass jar with wax before placing it in a warm cupboard on 12/25/2005.

Photos

Recycled copper strip	Lightly cleaned, and sealed in jar	Day 4	Day 14	Day 21: a close up of a patch of heavier verdigris growth

After 1 month of slow progress, I moved the jar to a warmer spot. At 7 weeks I used a knife to scrape the verdigris from the copper; it was soft & powdery and came off quickly. Post period, verdigris was sold in chunks rather than a powder like this, but I don't know about earlier. The copper was returned to the jar and the vinegar topped off to encourage additional crystal growth before the end of February.

Day 28: Lid removed only to take photos. The vinegar solution STINKS!	Day 35	Day 42: The verdigris was easy to remove using a blunt knife	By February 28, significant regrowth had occurred.	Another shot on Feb. 28.

Although an article on early modern verdigris manufacture reassured me over possible toxicity from handling and scraping,[5] I wore rubber gloves and a mask for extra safety. However, I did experience minor eye and nose irritation, indicating a need for better precautions in the future; on February 28th I wore safety goggles as well as a face mask and rubber gloves and experienced no problems.

 

ENDNOTES
[1] Illustrated in Hermann Kuhn, “ Verdigris and copper resinate.” Studies in Conservation , 15, 1970:12-36
[2] Tracey D. Chaplin, et al. “The Gutenberg bibles: Analysis of the illuminations and inks using Raman spectroscopy.” Analytical Chemistry , 77, 2005:3611-3622.
[3] I have so far been unable to check the early volumes (vols. 1-9) of the journal Dyes in History and Archaeology.
[4] Daniel Thompson, The Materials and Techniques of Medieval Painting , page 164.
[5] Benhamou relates that no sign of copper poisoning was found among women working in basements, or among their infant children who were present in the same damp, enclosed space.

 

 

 

PERIOD INSTRUCTIONS FOR MANUFACTURE

Pliny the Elder, Natural History, Chapter 26(Roman, 1st C). Verdigris is also applied to many purposes, and is prepared in numerous ways. Sometimes it is detached already formed, from the mineral from which copper is smelted: and sometimes it is made by piercing holes in white copper, and suspending it over strong vinegar in casks, which are closed with covers; it being much superior if scales of copper are used for the purpose. Some persons plunge vessels themselves, made of white copper, into earthen pots filled with vinegar, and scrape them at the end of ten days. Others, again, cover the vessels with husks of grapes, and scrape them in the same way, at the end of ten days. Others sprinkle vinegar upon copper filings, and stir them frequently with a spatula in the course of the day, until they are completely dissolved. Others prefer triturating these filings with vinegar in a brazen mortar: but the most expeditious method of all is to add to the vinegar shavings of coronet copper. Rhodian verdigris, more particularly, is adulterated with pounded marble; some persons use pumice-stone or gum.

Theophilus, On Divers Arts, Chapter 36 (12 th C). Now if you want to make Spanish green, take thinned-out copper plates, scrape them carefully on both sides, moisten them with pure hot vinegar without honey or salt, and lay them together in a smaller wooden chest in the same way [as you make salt green, which requires sealing treated copper in wooden cask partially filled with vinegar or urine]. After two weeks inspect and scrape them, and continue doing this until you have enough pigment.

Mappae Clavicula (ca. 850-900) Green. If you wish to make Byzantine green, take a new pot and put sheet of the purest copper in it; then fill the pot with very strong vinegar, cover it, and seal it. Put the pot in some warm place, or in the earth, and leave it there for six months. Then uncover the pot and put what you find in it on a wooden board and leave it to dry in the sun.

The recipe for verdigris. Take very clean copper leaf and hang it over very sharp vinegar. Leave it undisturbed in the sun for 14 days. Open it up, take away the leaf and collect the efflorescence; and you will make the cleanest verdigris. {This second recipe is repeated in shortened format in chapter 221-D}

Liber Coloribus (French, late 14/early 15 C). On making verdigris. If you wish to make verdgris, take a new pot, or any other hollow vessel, and put into the vessel some very strong vinegar, and arrange sheet of the purest copper over the vinegar, in such a way that they may not come into contact with the vinegar. And so cover it up, and seal it, and put it in a warm place, or underground, and set it aside for six months. And then you must open the vessel, and scrape off into a very clean dish the material which you find in it, and set it in the sun to dry.

The Secretes of Master Alexis of Piemont (English translation, 1580). Take a great earthen pot leaded within, and put some strong vinegar into it, or else it would profit nothing, and have in a readiness a great many of scales or shearings of copper or latten, that be strong and small, that there may be a great number of them, and make a triangle of earth in the bottom of the pot that the scales may not touch the vinegar. Then set the cover upon it close and well stopped with Lutum Sapientiae, to the intent it may take no air, and so lay it in a dung hill, or in some hot place of your chamber where the sun shines much, the space of fifteen days, then take the pot and uncover it and you shall see the Verdigris cleave and stick fast to the scales of copper, and therefore you shall scrape it off with a knife and make it to fall into the vinegar. Hen dress it again as men do bricks in a furnace, and uncover it, and make clean the said scales, as before, and do so until they be consumed, then strain them slightly into the vinegar, and you shall take up the verdigris, the which you may put into a bladder or some other commodious thing, and you shall have fine Verdigris.

Booke of secretes (English 1596) …take copper plates, put them in a copper pot, and put stilled vinegar to them, set them in a warm place, til the vinegar become blue, then put it into another leaden pot, pour vinegar into it again, let it stand so til it become blue, this do so many times, til you think you have enough, then let it stand til it be thick.

To make good green. Take copper plates, let them lie six months in vinegar in a warm place, then take them out and dry them in the sun, and the flower you find upon the plates, scrape it off, for that is the colour

 

PERIOD DYE RECIPES USING VERDIGRIS

Innsbruck Manuscript (c 1330) To make a green dye, take verdigris and boil it in urine and mix alum thereto and a portion of gum arabic, and dye therewith; to make the color lighter, take the same color and add orpiment and mix it with alum, cooked in lime water and dye therewith.

Segreti per Colori (15th C) To make a green dye for dyeing cloth, thread or silk . Take roche alum , and dissolve it in a boiler, and let it boil till it is well dissolved; then take it off the fire, and let it cool so that you can bear your hand in it, and then put th e cloth, or silk, or thread, into it, and let it remain for a day and a night, and then take it out and let it dry well. Next take a little verdigris and make it boil in the water, and then remove it, and when the water is become tepid, put the cloth into it, and work it well in your hand, and let it dry, and if you give it another wetting with a little roche alum, it will become of a brighter colour. If you wish it to be darker, add more verdigris.

Allerley Mackell (1532) Take two parts verdigris , one third of sal ammoniac , grind it well together, and lay it in strong vinegar. In this vinegar lay the wood, bone or horn, and cover it tightly, and let it lie therein until it is green enough.

Another green. Lay the wood, bone, or horn in a glass jar, and pour vinegar thereon which has verdigris mixed in it so that it is quite thick and not too thin. Cover it well and let it sit seven days under warm horse manure. If it is not green enough, let it stand longer.

Another green. You can also do it in the same way as described above, verdigris mixed with vinegar. Lay the wood, bone or horn therein, let it stand the same amount of time, take it out and lay it for 18 days under hot horse manure, which is moist.

The Plictho (16th C ) . To make a beautiful green. Measure verdigris and grind [it] fine and filings of copper and mix together. Put this material into a vessel of copper and wet the said materials with very strong vinegar, in which there must be a little sal ammoniac dissolved and a little roche alum and rock salt . Set it in warm manure in its copper vessel and rub every day said things with the vinegar and it will be a beautiful green. The filings should be one pound ad a half and the verdigris 2 pounds, and so much vinegar that lasts 15 days, keeping the above cited order; once every morning with a stick, you will have a good and beautiful green. It will serve you to do what work you want and as long as you want.

To make a color that dyes all things green. Measure red vinegar and place it in a glazed vase and put in much filings of copper or brass, and Roman vitriol and roche alum and verdigris and let all these things stand for several days. Know that you must boil these things before you let them rest. This will be very fine dyeing and when you wish to dye some things make them boil in said dyebath, and it will be very beautiful.

Water to dye feathers, bones, tables of wood and handles of knives, and all other things. Measure red vinegar very strong as much as you want and put it in a glazed vase and into it much filings of copper and of brass, Roman vitrio l, roche alum, verdigris . Put each thing together for several days but first let it boil a little, that is a good boil. You will make a fine tincture of green so strong that never more will it go away.

The Secretes of Master Alexis of Piemont (English translation, 1580) . To dye woodde, bones, and horne, into greene. Take two partes of Spanishe greene , a thirde part of salt Armoniacke , bray them well together, and put them in Vineger. And put into it the thing that you wyll dye, couering it well, and so let it stande untill it be greene inoughe. But before you dye any thing you muste lay it halfe a day in Alome water, and then drye it well agayne.

An other greene. Put your horne, or woodde, or that you wyll die, in a varnished pot, and put to it strong Vineger, mingling with it some Verdegrease that is very thick and not cleare. Couer it well, and set it seuen dayes together in a dunghil, and if then it be not greene ynough, let it stande there longer. A man may do the lyke with Spanish greene or Verdet.

A Profitable Book (1580). How to make a greene water. Take nye halfe an ounce of Verdigreace , and crush it well in a woodden dish, then put thereto the yolke of an egge and two blades of saffron, then take of the leaues of spurge halfe a handfull, and beate them in a morter, and thereto cast a good glassefull of Vinegar, and strayne it thorow a cloth. Then take of this stuffe, and put thereof in a dish with the Verdigreace, and stirre it well together and make it thinne, that it may be the better to dye, or to worke with a pensill, or as ye shall thinke best

To dye a faire yealowe. If ye will dye yealow with [weld], take off the [weld] leaues, and cut off the rootes, then cut them in peeces, and lay them to soke in lye of comon ashes three houres, then seeth it a quarter of an houre, till ye thinke it be meetely well sodde. Then put therein two quarts of water, and as much stale Urine of sixe dayes old at the least, so let them seeth together a little, then cleanse it thorow a siue, and then put unto the same againe, of lye and Urine as aforesayd. Then straine it thorow a faire cloth and seeth it, and to two pound of wood take two pound of Verdegreace , with the lye that ye have sod, your wood and al, putting them in your sayd colour, which must be medled and well stirred all together. Then shall ye boyle it all a little, and it shall be well.

 

 

BIBLIOGRAPHY

Primary sources

Anon. (14 th C). Innsbrook Manuscript . Translation by Drea Leed. http://costume.dm.net/dyes/innsbruck/

Anon. (15th Century). Segreti per Colori . English translation by Mary Merrifield, originally published in Original Treatises on the Arts of Painting, 1846, and available online at http://costume.dm.net/dyes/segreti.htm.

Anon (1596). A very proper treatise where is briefly set forth the art of Limming. London: Thomas Purfot, 1596.

Cennini, Cennino d'Andrea . The Craftsman's Handbook “Il Libro dell' Arte.” Translated by Daniel V. Thompson Jr. New York: Dover Press.

Edelstein, Sidney M. (1964). “The Allerley Matkel (1532): Facsimile Text, Translation, and Critical Study of the Earliest Printed Book on Spot Removing and Dyeing.” Technology and Culture , 5(3): 297-321.

Philip, William (1596). A Booke of Secrets shewing divers waies to make and prepare all sorts of Inke, and Colours…. London : Adam Islip for Edward White.

Pliny the Elder (1 st C). The Natural History. Translated by John Bostock and H.T. Riley. Available online at http://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Plin.+Nat.+toc .

Rosetti, Gioanventura (1548) The Plictho of Gioanventura Rosetti: Instructions in the Art of the Dyers which Teaches the Dyeing of Woolen Cloths, Linens, Cottons, and Silk by the Great Art as Well as by the Common. Reprint by S. M. Edelstein and HC Borghettym, trans. Cambridge: MIT Press, 1969.

Smith, Cyril S and John G. Hawthorne, eds. (1974) Mappae Clavicula: A Little Key to the World of Medieval Techniques. Philadelphia : Transactions of the American Philosophical Society, New Series, volume 64, part 4.

Theophilus, Trans. by John G. Hawthorne and Cyril S. Smith (1963, 1979). On Divers Arts. New York : Dover Publications.

Thompson, Daniel Varney Jr. (1926). “Liber de Coloribus Illuminatorum Siue Pictorum from Sloane MS. No. 1754.” Speculum, 1(3): 280-307.

Warde, William (1580). The seconde parte of the Secrets of maister Alexis of Piemont… London : Henry Bynneman for Iohn Wyght.

Secondary Sources

Benhamou, Reed (1984). “Verdigris and the entrepreneuse.” Technology and Culture , 25(2): 171-181.

Benhamou, Reed (1990). “The verdigris industry in eighteenth century Languedoc : Women's work, women's art.” French Historical Studies , 6(3): 560-575.

Chaplin, Tracey D., et al (2005). “The Gutenberg bibles: Analysis of the illuminations and inks using Raman spectroscopy.” Analytical Chemistry, 77:3611-3622.

Crews, Patricia Cox (1982). “The influence of mordant on the lightfastness of yellow natural dyes.” Journal of the American Institute for Conservation, 21(2): 43-58.

Kuhn, Hermann (1970). “ Verdigris and copper resinate.” Studies in Conservation, 15:12-36.

Orna, Mary Virginia, M.J.D. Low and Norbert S. Baer (1980). “Synthetic blue pigments: Ninth to sixteenth centuries. I. Literature.” Studies in Conservation, 25(2): 53-63.

Thompson, Daniel V. (1936, 1956). The Materials and Techniques of Medieval Painting. New York : Dover Publications.