Between Fig Milk and Fish Stones: Remaking Pearlessence from the Ocean
A hands on exploration pre-modern recipes for imitating pearls in the Utrecht University's Art Lab
By Ruth Bryant
Please cite as: Ruth Bryant. 2025. "Between Fig Milk and Fish Stones: Remaking Pearlessence from the Ocean". ArtLab Visual Blog Post Series, nr. 1 (Utrecht University), last updated 12-06-2025: https://story.durare.eu/between-fig-milk-and-fish-stones.
During the Renaissance and Early Modern Period, naturists turned towards artisanal knowledge and their ability to persuade materials to gain insights into the processes of nature.
This knowledge is recorded and preserved in manuscripts and treatises, where the instructions for crafting these counterfeit materials have outlived the original objects. Through historical reconstruction, this research hopes to gain insight into a set of objects using the only surviving evidence—their recipes.
One way of getting at the material experience of -historical practices is to try to remake/follow the recipes through a historical reconstruction. This approach invites reflections on seasonality, tactility, optical properties, and knowledge embedded within the recipe.
The Recipes for Imitation Pearls
This historical reconstruction focuses on three recipes for imitation pearls, as described in the Bolognese Manuscript in the chapter "To Make Stones for Rings, namely, Artificial Gems, clear and fine of colour". The manuscript is held at the Library of the R.R. Canonici Regolari in the convent of S. Salvatore in Bologna.
The recipes were bought together in the mid-fifteenth century Italy, but were likely written much earlier. Later in the nineteenth century, the manuscript was transcribed into English by Mary Philadelphia Merrified and published as the Original Treatises: Art of Painting.
The three selected recipes, numbers, 244, 245, are a part of a larger category of recipes for counterfeit/artificial gems.
I am interested in the recipes from the Bolognese Manuscript as part of a larger research into the connection between art and science. In particular, this study suggests that the author-artisan’s language expresses a value system across the imitation pearl recipes, and how that system reflects or challenges naturalist ideas about what makes a pearl desirable—such as weight, whiteness, roundness, and shine.
In order to assess what qualities made a pearl believable and valuable, it is essential to consider the prevailing naturalist knowledge and believed attributes of pearls.
Pliny the Elder’s Historia Naturalis (77-79AD) offers insights into the geographical, biological, origins, functions, and perceived value of pearls. In Chapter 56, “The Various Kinds of Pearls,” Pliny describes the ideal visual characteristics: “all their merit consists in their whiteness, large size, roundness, polish, and weight.” Notably, he makes no mention of luster, translucency, or a shiny surface quality. Instead, he equates the value of the pearl with its colour, declaring whiteness to be the “most prized of all.”
Pliny’s texts remained influential into the Renaissance and Early Modern Period in Europe. Pietro Andrea Mattioli’s 16th-century treatise, I discorsi di M. Pietro And. Matthioli Sanese, directly references Pliny when discussing the origins of a pearl and places where a pearl could be found. The engravings you see in the background are from Mattioli’s treatise and show how he understood pearls to occur in their natural environment.
However, while Pliny emphasized the whiteness of the pearl, Mattioli’s description shows a slight shift in the idealized qualities of a pearl, writing “the most prized are the large, shiny, round, and heavy ones.”
The Experiment
The selected recipes, numbers 240, 244, 245, appear in close succession within the manuscript and form a gradient of naturality and believability, as suggested by the author-artisan in their titles and the relative quality of their ingredients.
240, "To Make Pearls" or "Ad fatiendum margaritas"
244, "To make fine pearls, and a good colour to all appearances" or "Ad fatiendum pulcras perlas tamquam et laudabilis coloris in aparentia"
245, "To make pearls, which are like natural pearls, and undoubtedly real and good" or "Ad fatiendum margaritas sive perlas tanquam naturales et optimas et veras sine dubio"
The deliberate hierarchy of recipes, as established by the author-artisan, provides a framework for interpreting which physical or aesthetic properties made some imitations more believable than others.
Common Denominator Experiment
For the purposes of this research the recipes have been refined and condensed into a common denominator framework, in which shared structural steps are identified and variable elements are isolated.
1. Combine a powdery base with a binding agent (a type of glue) to form a paste or dough.
2. Shape and Perforate with "una seta porci" (Pig's Hair)
3. Dry/Bake- depending on the instructions
4. Cool/Dip in a liquid solution
5. Dry again
Recipe 240, "To Make Pearls"
For recipe 240, the white paste was made from powdered crystal glass, egg white, and slime of snail.1
Next, the pearls were shaped and perforated with hog's bristle. Due to its sturdy structure, this type of material is ideally suited.
In the image above, you can get a closer look at the resulting hole. While in the background image you see my attempts at piercing the pearls.
Then the pearls are heated over the fire until “white hot.”
Immediately afterwards, the pearls are quenched in cold water.
While the purpose of this step is not explicitly stated in the recipe, it may have been intended to mimic smithing techniques used to strengthen and harden materials. However, in this context, it did not appear to have that effect on the remade pearl.
The process of firing and immersing in cold water proved finicky—requiring lots of trial and error. In the background, you can see burnt, cracked, or squished pearls.
This image shows a couple pearls from the final results of recipe 240.
Recipe 244, "To make fine pearls, and a good colour to all appearances”
For recipe 244, the white paste was made from "stones of fish heads" and egg white.
“Stones from heads of fishes,”or otoliths, like pearls, are primarily composed of calcium carbonate and are formed through organic processes inside of animals. Each fish contains three pairs of otoliths embedded within the cartilage structure of a fish head. The chemical makeup of the otolith is a direct reflection of the quality and temperature of water in which the fish lived and migrated. For the purposes of this reconstruction, the otoliths were sourced from sheepshead fish, native to Lake Erie. Given the sensitivity of an otolith’s chemical composition, any contemporary otolith would inevitably be different to one obtained in the fifteenth-century.
The physical and material similarities between otoliths and pearls suggest a deliberate connection between the ingredients used in the recipe and the substance being imitated.
Next shaped...
The pearls were then boiled in "new milk" and dried.
While remaking a historical recipe, I encountered challenges in sourcing materials and maintaing historical accuracy. Instead of using "new milk", as the recipe called for, I opted for fresh whole milk. The substitution may have effected the optical or physical properties of the final pearl. That said, the intention is not to produce a perfect replica but about thinking through the materials and processes— understanding how such substitutions and limitations shape our engagement with historical practices.
This image shows a couple pearls from the final results of recipe 244.
The pearl on the left is made with white gum arabic as a binder instead of egg white.
Recipe 245, "To make pearls, which are like natural pearls, and undoubtedly real and good”
For the final recipe, the author-artisan instructs to use "mother of pearl, or very fine pearls, or that shinny matter which is in pearl's shells."
The powdery pearl is then combined with "white gum arabic," specifically denoting the color and quality intended for this recipe.
I sorted a variety of gum arabic by color, organizing from light to dark, and both the white and red varieties to test how the color would affect the appearance of the imitation pearls.
This image shows the paste of the shaped pearls, with the ones made from white gum arabic on the left and red gum arabic on the right.
You can see the lighter shade of gray pearls is made using the white gum arabic, whereas the darker, more purple-toned pearls are made with the red gum arabic.
After the pearls are shaped and dried, they are polished.
The image shows a comparison between a polished on the left and an unpolished pearl on the right. Note the differences in texture, surface finish, and overall roundness.
For the milky-coating, the recipe calls for "milk of a fig tree," or the plant's latex.
In order to obtain the fig-latex, I went to the Utrecht's University's Botanical Gardens. This process underscored the author-artisan’s embodied knowledge of natural materials.
This image shows the total amount of fig latex harvested from approximately two dozen figs, yielding only 2–3 drops per fruit. To gather this much fig milk, I was harvesting for two hours highlighting seasonality, locality, and the expertise required for this labor.
Moreover, the difficulties I faced in collecting the fig milk underline the seasonality and geographic specificity embedded in the recipe’s execution. The challenges to getting a proper yield underline the significance of season and environment for the Italian recipes. In the region of origin, fig trees were likely much more abundant, making the collection fig latex more accessible and routine.
Historically, the latex of a fig tree was believed to have medicinal properties, namely as an anticoagulant, meaning it works as a thinning and dissolving agent.
In this context, the fig milk solution likely acted as another binding agent to keep the pearls intact.
The fig milk was then mixed with a powdery white cheese. For the purposes of this reconstruction, casein was used, given that it is the main type of protein found in milk and a primary component of cheese.
Additionally, I experimented with variations of the coating solution—creating one set of pearls with a casein-and-water mixture (left) and another using a casein-based tempera binder (right).
Next, the pearls are heated before the fire as the recipe instructs.
and dipped in the various "milky-coating" solutions, that I had prepared beforehand.
This process was then reversed with cooled pearls being dipped into a heated solution until, as the recipe recommends, "very bright" (luccidissimas). 2
This image shows the fig-milk coated pearl alongside two polished, uncoated pearls. The fig milk coated pearl is signifigantly more yellow, shiny, and sticky to touch.
This image compares the (left) water-casein and white-gum arabic pearl, (middle) the casein-binder and red-gum arabic pearl, and (right) the fig-milk and white-gum arabic pearl.
While none of these appear white, in the way we imagine pearls today, it is striking how the ingredients have significantly altered the pearl's optical appearance.
Results: Accessing Quality and Believability
Given that the three imitation recipes rely on different materials and the author-artisans suggest an hierarchy of value and naturalism among them—this comparison offers an opportunity to examine the alignment between artistic practices and naturalistic conceptions.
The progression from using common crystal glass to mother of pearls implies a hierarchy between materials, one closely tied to a perceived natural relation to real pearls. Variation in ingredients and outcomes across the different recipes suggests an exploration of a pearl's essence through artistic practices and the manipulation of natural substances.
Size:
For all three recipes, the size and shape of the pearls were highly customizable and could fluctuate based on the practitioner’s intentions or preferences.
Roundness:
The degree of roundness varied significantly across the three reconstructions.
In Recipe 240, the paste was highly moldable and remained workable throughout much of the process. For these pearls, roundness is a product of the artisan’s skill rather than the material.
The pearls produced from Recipe 244 were the least round. The crystallized base material was very fragile and difficult to manipulate, making shaping a challenge.
Recipe 245 produced the most round pearls; the strong, dense base material was easiest to shape, and the inclusion of a polishing step helped refine the any inconsistencies on the surface.
Weight:
In Pliny’s and Mattioli’s writings, the weight of a pearl is described as an indicator of authenticity—a heavier pearl being considered a better one.
To test for weight, the pearls from each recipe were measured for diameter (d) and weight(w).
Recipe 240: d=0.9cm, w=0.44g
Recipe 244: d=0.8cm, w=0.32g
Recipe 245: d=0.7cm, w=0.49g
From these findings, we see that Recipe 245 produced the heaviest pearl, despite having the smallest diameter; while the pearls in Recipe 244 were the lightest overall.
Color:
For color, the pearls from Recipes 240 and 244 resemble the white ideal historically associated with pearls. While whiteness is primarily emphasized, the pearls from Recipe 244 exhibit a slight iridescent and milky opacity that add complexity to their surface.
In contrast, the pearls in Recipe 245 are far from the ideal, exhibiting a dark yellow-brown-gray hue.
Even without the discolored fig-milk coating, this recipe produced light-gray pearls— likely caused by the gum arabic.
Supporting this idea are the experimental comparison in Recipe 244, where the pearl made with the gum arabic binder was a slight white-gray color as opposed to the one with the egg white binder.
Shine:
In regards to shine, the pearls from Recipe 240 are entirely matte and produce no reflectivity.
The pearls from Recipe 244 and 245 are much shinier, but neither achieve the smooth white shine associated with real pearls. The uneven surface of 244 and the discoloration of 245 take away from the promising shine.
Based on these findings, the descriptions in the recipes correlate to the physical qualities that naturalists identify as necessary for a pearl. The pearls from Recipe 240 rank in the mid-to-low range compared to the other two. In Recipe 244, the practitioner emphasizes the visual appearance, highlighting the good color and shine— where the pearl ranked highly— giving less attention to weight, shape, and roundness. The final recipe, 254 is described as “undoubtedly real.” While this seems like a bit of an exaggeration due to the color, the pearl had the best overall appearance.
These results of the reconstruction correlate to the perceived degree of realness of the materials used, based on the relationship to a natural pearl.
Ultimately, believability of the counterfeit pearls is determined by the unknown, intended audience. Nevertheless, the results from this historical reconstruction demonstrate a meaningful convergence between artistic and naturalistic knowledge and practices. Both naturalists and artisans looked towards each other for a deeper understanding of the materials and the natural processes that shaped them.
Through the processes of historical reconstruction, I noticed cross-temporal parallels in experimentation—between pre-modern artisans and my own work in the Art lab.
The recipes reflect the pre-modern curiosity of the natural world, as the recipes play with the construction and physical traits that define a pearl. The hierarchy of materials, engagement with naturalist knowledge, and variety of final optical outcomes suggest that those who were engaging with the recipes sought a deeper understanding of pearls through tactile and material exploration.
The hands-on process of learning mirrors my own efforts to remake historical recipes of objects now lost to history. Rather than aiming to recreate the perfect pearl, I focused on comparing the recipes, evaluating the role of the various materials, accessing their believability, and the intersections between naturalist and artisanal knowledge.
Just as artisans and naturalists looked to each other to replicate material processes, my art-historically informed laboratory work attempts to reconstruct their experience—bridging artistic practice, observation, and experimentation in study.
Endnotes
1. Snail slime was omitted from the reconstruction due to its difficulty to source and ethical concerns surrounding its industrial production, which are known to involve the mistreatment of snails. Its absence is unlikely to significantly affect the outcome of the recipe.
2. The final produced imitation pearl from this recipe would likely look ‘whiter’ than in this reconstruction due to experimental errors and lack of reproducibility. Since the fig milk was manually obtained at the Botanical gardens, there was only a finite amount that could be used in the recipe. Due to the very small amount, the fig milk and casein solution quickly burned causing the yellow-discoloration on the coating of the pearl. Without this incident, the imitation pearls would most likely have an off-white color to them and be visually closer to the ideals of Pliny and Mattoli.
Resources
Bennett, Catherine. “There’s a Deep Ugliness and Some Slippery Ethics behind the Snail Slime Beauty Boom.” The Guardian, April 20, 2025. https://www.theguardian.com/commentisfree/2025/apr/20/theres-a-deep-ugliness-and-some-slippery-ethics-behind-the-snail-slime-beauty-boom.
Bol, Marjolijn, and E. C. Spary, eds. The Matter of Mimesis: Studies of mimesis and materials in nature, art and science. Leiden, NL: Brill, 2023.
Bol, Marjolijn. “In Search of Splendor: Gems and Their Imitations before 1400.” Essay. In The Varnish and the Glaze: Painting Splendor with Oil, 1100–1500, 120–53. Chicago, IL: University of Chicago Press, 2023.
Dioscorides Pedanius, Of Anazarbos, and Andrés De Laguna, translator., De Materia Medica. Antwerp: Jean Laet, 1555. Pdf. https://www.loc.gov/item/2021666851/.
Matthioli, Pietro Andrea. I discorsi di M. Pietro And. Matthioli Sanese. Venice: Valgrisi, 1563.
Merrifield M.P. (Mary Philadelphia), 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. London: J. Murray, 1849.
Pliny, the Elder, “Chapter 54.—Pearls; How they are Produced, and Where.,” Natural History. John Bostock, M.D., F.R.S. H.T. Riley, Esq., B.A. London. Taylor and Francis, Red Lion Court, Fleet Street. 1855.
Smith, Pamela H, and Isabella Lores-Chaves. “Counterfeiting Materials, Imitating Nature.” Essay. In The Matter of Mimesis: Studies of Mimesis and Materials in Nature, Art and Science, 27–53. Leiden, NL: Koninklijke Brill , 2023.
The Elder, Pliny, “Chapter 56.—The Various Kinds of Pearls,” Natural History. John Bostock, M.D., F.R.S. H.T. Riley, Esq., B.A. London. Taylor and Francis, Red Lion Court, Fleet Street. 1855.
Credits
This blogpost was written in the context of the ERC-project Dynamics of the Durable: A History of Making Things Last in the Visual and Decorative Arts (DURARE), grant no. 852732 and the Research Master in Art History at Utrecht University.
I would like to thank Dr. Anatasia Stefanaki at the University of Utrecht’s Botanical Gardens for facilitating my visit and enabling the collection of the sample. It was an invaluable experience to work directly with the botanical materials.
Additionally, I am grateful to Marjolijn Bol for her generous advice, time, and material contributions to this project. I am deeply appreciative of the opportunity to contribute to and benefit from the DURARE project.
Image Credits:
Cover of Merrifield M.P. (Mary Philadelphia), 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. London: J. Murray, 1849.
Illustration in Matthioli, Pietro Andrea. I discorsi di M. Pietro And. Matthioli Sanese. Venice: Valgrisi, 1563.
Please cite as: Ruth Bryant. 2025. "From Fig milk to Fish Stones: Remaking Pearlessence from the Ocean". Last updated:23-05-2025. https://story.durare.eu/between-fig-milk-and-fish-stones.