EK Gazette Iris and Sap Green

Arts & Sciences Research Paper #9: Making green paint medievally with spring irises and fall buckthorn berries

02 Monday May 2016
Posted by mollyeskridge in A&S Research Papers, Arts and Sciences
#9: Making green paint medievally with spring irises and fall buckthorn berries
Tags
a&s, Arts and Sciences
Our ninth A&S Research Paper comes to us from Lady Adrienne d’Evreus, of the Province of Malagentia. She turns to the flora of her woodlands to learn ways that medieval painters made green pigments. (Prospective future contributors, please check out our original Call for Papers.)

Making green paint medievally with spring irises and fall buckthorn berries

Iris flower and buckthorn berries. Photo by Adrienne d’Evreus.

 

Many medieval manuscripts explain how to make green for illumination with seasonably available resources. Excited to make green from my local plants, I used iris in May and buckthorn in September to make some beautiful green paint using instructions from an anonymous medieval treatise, De Arte Illuminandi. Even with some incorrect assumptions about materials, by using translated fourteenth century instructions as a guide with iris blossoms and buckthorn berries, beautiful green pigment was produced.
Contents
Iris blossoms and iris green
Buckthorn berries and sap green
References
According to Daniel V. Thompson in The Materials and Techniques of Medieval Painting, the primary medieval substitutes for verdigris in book illumination were iris and sap green (Thompson 169-171). I was inspired by his book and excited to make green paint using some medieval methods.
Iris blossoms and green
My love of iris began as a child in my father’s gardens as I learned how to grow with him. His observation that they tolerated and seemed to enjoy wet soil was driven home years later as a college student when I accidentally chose a tidal riverbed for a late night nap after dark and woke up with the break of dawn a few hours later getting increasingly damp in rising tidewater amongst these beautiful blue lilies! The place I chose for my iris at home is a garden spot that floods in the spring and stays moist but not sopping in the summer. They seem to be very happy and produce many blossoms every year.
Looking to medieval manuscripts to make recipes for iris or lily green (Thompson and Hamilton 2), instructions were found in Mappae Clavicula (Smith and Hawthorne 51), De Arte Illuminandi (Thompson and Hamilton 6-7) and a number of Mary P. Merrifield’s Original Treatises (Merrifield ccxix, 422, 504 and 678, 684), often as clothlets. On Merrifield’s page 678 and 684 she translates recipes from a seventeenth century manuscript. Those recipes inspired me to try fermented iris juice experiments too.
Clothlets are a means of storing pigments. The impregnated cloth could later be placed into a dish (Thompson 144) or clam shell (Thompson and Hamilton 17) and wetted with a bit of glair (egg white) or gum water, and it would release its stored pigment into the vessel, creating a transparent stain. The glossary of the British Library describes “clothlet” as “A piece of cloth impregnated with pigment (generally a vegetable dye)” and in The Materials and Techniques of Medieval Painting Thompson says:
“iris green… was made from the juice of iris flowers, sometimes mixed with alum and thickened… but more often prepared as a clothlet. Bits of cloth were dipped into the juice of iris flowers and dried, again and again, until they contained a sufficient quantity of the color.” (Thompson 171)
De Arte Illuminandi indicates that you should pound iris blossoms in a mortar and pestle then squeeze them through a cloth to extract the juice. Linen cloths pre-treated with rock alum should then be dipped in the juice and dried in the shade multiple times. These clothlets are then stored in books. (Thompson and Hamilton 7). Merrifield’s “Bolognese Manuscript” from the fifteenth century calls for dipping the cloths in rock alum first then iris juice and keeping these cloths in a closed box (Merrifield 422).
The recipes often consist of adding alum to the iris juice. I didn’t get the Dover edition of Merrifield’s Original Treatises until Christmas of 2015 so for the 2015 experiments I used alum acquired from a modern and traditional dye supplier—aluminum sulfate, Al₂(SO₄)₃. What was actually indicated and used by the medieval craftsman was rock alum, defined in the Dover edition of Merrifield’s glossary as potassium aluminum sulfate, KAl₃(SO₄)₂(OH)₆ (Alexander xii, xxviii).
Taking the advice of Wendy Feldberg, I collected iris blossoms as they bloomed daily at the end of May and beginning of June in 2015 and froze them to try with the recipes when they were done blooming. Though there were not freezers in medieval Europe, this seemed like a reasonable compromise since spring inspires so many other activities and obligations. After freezing and thawing the iris blossoms, without the added work of ‘pounding’, they gave me 78.91g of gorgeous transparent blue liquid that I poured into a clean glass jar. I separated the juice into four portions, adding additional variables.
I wondered what would happen when you didn’t modify the juice at all or exposed it to alkaline materials (like clam or eggshell) rather than an acid like the alum suggested by the medieval sources so I tried it all: plain iris juice for a control, and iris juice with clam shells and eggshells for alkaline as well as iris juice with aluminum sulfate, an acid.

Four jars of iris juice and different variables. Photo by Adrienne d’Evreus.

The aluminum sulfate and iris juice combination started turning a dark turquoise color. It was swirled to combine and allowed to sit undisturbed for approximately four hours. I decanted the aluminum sulfate saturated juice into a clean jar and used that solution to saturate three clean 8x10cm squares of linen. Then they were dried on a piece of parchment paper under a gentle fan protected from the cat and other disturbances. After waiting for each saturation to completely dry, this procedure was repeated five more times over several days.

Iris juice with aluminum sulfate on linen, wet and dry. Photo by Adrienne d’Evreus.

After the first experiment with fresh iris blossoms, the bag of partially exhausted blossoms was returned to the refrigerator. Several weeks later the blossoms had fermented. Intrigued by the slightly post-1600 recipe ideas that used fermented iris (Merrifield 678, 684), I used the blue liquid squeezed from them too. After letting the white slimy precipitate settle I poured the cleanest juice off for new trials. These used clam shells and eggshells with and without aluminum sulfate, as well as three linen clothlets soaked in a 10:1 aluminum sulfate solution first, which follows the original medieval recipe procedure in De Arte Illuminandi (Thompson and Hamilton 6-7). These second clothlets were only soaked three to four times because I ran out of juice. As they were soaked they had a beautiful blue-green hue. They were dried, as before, between each soaking.

Finished iris clothlets; the clothlets on the right were made with fermented iris juice. Photo by Adrienne d’Evreus.

All clothlets and jars with variables were reserved on the refrigerator away from the cat and as cleanly as possible while drying under a fan.
The trials of iris juice with the addition of aluminum sulfate, from both ‘fresh’ and fermented iris juice, in an alkaline substrate like clam shells or not, all produced green results. A small brush was used to combine distilled water, Winsor and Newton gum Arabic, and prepared pigment from iris to paint out resulting materials onto Strathmore 100lb vellum surface Bristol board.

From left to right: iris juice with aluminum sulfate from a glass jar, iris juice with aluminum sulfate from a clam shell, more-concentrated iris juice and aluminum sulfate from a glass jar, all on Bristol board. Photo by Adrienne d’Evreus.

The plain iris juice, plain iris juice in a clam shell or eggshell without aluminum sulfate resulted only in browns whether fermented or not. I was a little surprised that the juice didn’t stay blue at all by itself after drying.

Plain iris juice in a clam shell on the right; iris juice with a pinch of alum in a clam shell on the left. Photo by Adrienne d’Avreus.

There were no iris clothlets prepared without aluminum sulfate. Both fermented and non-fermented clothlets made with aluminum sulfate produced pretty green linen yielding delicate green ‘paint’ when combined with some distilled water and gum Arabic. The fermented iris juice clothlet produced a slightly more brown-green than the non-fermented. The bacteria and fungus in the fermentation process may have caused the iris green to deteriorate slightly resulting in a more brown-green than pure light green produced from the clothlet prepared with non-fermented juice.

Pigment from fresh iris juice and aluminum sulfate clothlet on the left; pigment from fermented iris juice and aluminum sulfate clothlet on the right. Photo by Adrienne d’Evreus.

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Buckthorn berries and Sap Green
In the fall it took me what felt like forever to find Rhamnus spp. berries for the sap green. I searched the fields and ditches near my house, and even went to “Buckthorn Lane” in my local neighborhood. I found other trees with other fruits but no buckthorn! Even though my dad had taught me about many plants and how to garden, he never taught me about buckthorn. Non-native invasive species were to be eradicated in his experience, not fostered or encouraged.
Finally someone said “look for tall trees, usually somewhere wet” so I went back to my stomping grounds as a teenager in Westbrook, Maine and found spindly trees with small berries in what used to be a wetland for protected turtles. “This?! Is this it?!” I begged my friends to confirm cell phone pictures of my find. The leaves looked right from the National Agricultural Library’s invasive plant website (NAL 2015) and Mistress Isabel Chamberlain’s blog (Siconolfi); the berries were dark and the bush was spindly and taller than I might have guessed, growing somewhere wet. “Yes!”, they chorused, “that looks right, try it!”
Sap green from buckthorn berries (Merrifield ccxviii) is defined by Pigment Compendium as a flavonoid dye coming from buckthorn, Rhamnus spp (Eastaugh et al. 338). De Arte Illuminandi and Original Treatises have recipes to produce it, just like the iris green. The identification of the berries and when to gather them is described in De Arte Illuminandi (Thompson and Hamilton 43) which points to Cennino Cennini for their identification (Thompson 32n). Once identified, the buckthorn berries should be combined with lye and rock alum dissolved under heat to make green (Thompson and Hamilton 7). Recipes to make the green were also found in Merrifield’s Original Treatises (420-428, 662, 706, 708-710, 786, 808). The recipes after page 640 in Merrifield’s books are from manuscripts written after the sixteenth century. They were not as interesting to me but I feel that these other sap green recipes are relevant to researchers of the earlier sources due to their material and procedural similarities.
According to De Arte Illuminandi the green from buckthorn could have been prepared and stored as clothlets, like iris, or sealed in a glass bottle (Thompson and Hamilton 7). I decided to experiment with the second method.
On September 4, 2015, 100.00g of buckthorn berries were added to a 12oz glass jelly jar and crushed with a plastic fork. They were sticky and smelled slightly winy. They ranged from almost black and squishy through reddish to green and firm.

Buckthorn berries. Photo by Adrienne d’Evreus

The recipe in De Arte Illuminandi contains lye as I previously mentioned. Lye or ley is defined in the new Dover edition as an alkaline solution made from mixing wood ashes with water (Alexander xxiii). In an online conversation with Geffrei Maudeleyne, he explained where in De Arte Illuminandi to look (Thompson and Hamilton 36-37) and Asplund confirmed that potassium carbonate, K₂CO₃, is what the medieval craftsmen would have made and used. Since I didn’t have the Dover edition with its glossary until Christmas 2015, I relied on the sage advice and resources of these online friends and fellow pigment makers.
In a Corning Ware sauce pan (to emulate the “glazed porriger” of De Arte Illuminandi‘s instruction) 11.60g of lye, K₂CO₃, was mixed with 100g of distilled water. Adding 5.05g of aluminum sulfate, Al₂(SO₄)₃, resulted in immediate bubbling. The reactions at this point had increased the temperature a little to 80 degrees F. Warming the mixture on a simmer burner on low, I hoped to dissolve more of the alum. After about ten minutes the bubbling had mostly stopped. The temperature had risen to 120 degrees F and the solution had a pH of 6 and a milky appearance. Heating it up to encourage the aluminum sulfate to dissolve, a little mass and volume was lost by evaporation and in the sink when it was transferred into the jar with crushed berries. A little residue remained in the pan, and the total weight of the solution decreased to 87.07g. Pouring the liquid into the berries caused an immediate color change like I saw in the spring with the iris! Turquoise again!

Crushed buckthorn berries mixed with aluminum sulfate and lye. Photo by Adrienne d’Evreus.

The lye/aluminum sulfate solution was mixed into the berries with the plastic fork. The following day the solution had bubbled out of the jar a little. The jar was relocated into a glass bowl in an undisturbed corner for two more days. The third day after the addition of aluminum sulfate and lye, a clean square of cloth was used to strain the juice into another jar. The jar was capped and closed when not accessing this liquid for paint experiments. It produced another pretty green liquid! This is most likely the sap green I was hoping for.
A small brush was used to combine distilled water, Winsor and Newton gum Arabic, and prepared pigment from the buckthorn to paint out resulting materials onto Strathmore 100lb vellum surface Bristol board.

Sap green, concentrated and dilute, applied to Bristol board. Photo by Adrienne d’Evreus.

Both iris and buckthorn berries produced green pigment using the fourteenth century instructions from De Arte Illuminandi, despite using aluminum sulfate rather than potassium aluminum sulfate. Moving forward with the “correct” alum will be interesting next time. I wonder if it will produce the same green or a different one. My father would be satisfied that I made lovely green paint from the plants I grew and found using science. My science teachers would have been happier with better note taking and more pictures so I will attempt that with fresh and correct materials in 2016. There are so many colors achievable from other berries and more invasive and native plants and weeds using historic European recipes from hundreds of years ago. I can’t wait to see what else is achievable! What are you inspired to learn, experiment with, and achieve?
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References
Alexander, S. M. Glossary of Technical Terms in Medieval and Renaissance Treatises on the Arts of Painting. By Merrifield xi-xxxiv. New York: Dover, 1967.
Asplund, Randy. Personal communication on Facebook and in e-mail, 2015.
Broecke, Lara. Cennino Cennini’s Il libro dell’arte, A new English translation and commentary with Italian transcription.  London:  Archetype Publications Ltd., 2015.
Brown, Jamin. Accessed December 2015.
Brown, Michelle P. Understanding Illuminated Manuscripts: A Guide to Technical Terms (J. Paul Getty Museum: Malibu and British Library: London, 1994). 
Clarke, Mark. The Art of All Colours. London: Archetype Publications, Ltd., 2001.
Eastaugh, Nicolas, et al. Pigment Compendium A Dictionary of Historical Pigments. Boston: Elsevier, Ltd, 2008.
Feldberg, Wendy. Personal communication via blog comments and e-mail, 2015.
Maudeleyne, Geffrei. Personal communication, August 2015.
Merrifield, Mary P. Original Treatises: Dating from the XIIth to XVIIIth Centuries on the Arts of Painting, in Oil, Miniature, Mosaic, and on Glass; of Gilding, Dyeing, and the Preparation of Colours and Artificial Gems; Preceded by a General Introduction; with Translations, Prefaces, and Notes, In Two Volumes. London: John Murray, Albemarle Street, 1849. (The new Dover edition with a glossary also suggests some of her dating of the manuscripts is not correct.)
Medieval and Renaissance Treatises on the Arts of Painting, Original Texts with English Translations. New York: Dover Publications, Inc, 1967, 1999.
National Agricultural Library. Accessed September 2015.
Siconolfi, Claire. Accessed September 2015.
Smith, Cyril Stanley and Hawthorne, Daniel G. Transactions of the American Philosophical Society held at Philidelphia for promoting useful knowledge. New series Volume 64, part 4. Mappae Clavicula, a little key to the world of medieval techniques. 1974.
Thompson, Daniel V. The Craftsman’s Handbook. “Il Libro dell’Arte”. New York: Dover Publications, Inc, 1960.
Thompson, Daniel V. The Materials and Techniques of Medieval Painting. New York: Dover Publications, 1956.
Thompson, Daniel Varney and Hamilton, George Hurd. De Arte Illuminandi, the Technique of Manuscript Illumination. New Haven: Yale University Press, 1933.

Acknowledgements: I wish to thank Ian TheGreen for connecting me with some great people and resources including Geffrei Maudeleyne and Randy Asplund, Jamin A. Brown for his support and editing skill, Claire Turner for her inspiration and guidance and Molly Eskridge for her patience and editing prowess.