Category Archives: Art

Topazes, Emeralds, and Crystal Rubies. The Faking and Making of Precious Stones

Marjolijn Bol

Today the making and illegal selling of factitious stones has reached an unseen level of sophistication. Advanced technologies allow man to produce synthetic versions of the most precious of stones – diamonds, emeralds, sapphires and rubies (fig. 1). So convincing are these synthetic gems they can only be distinguished from natural precious stones in laboratories with advanced spectroscopic devices.

Fig. 1 Synthetic gemstones
Fig. 1 Synthetic gemstones

The making of imitations of precious stones is not just typical of our modern age. In fact it dates back to at least Egyptian times, as graves from this period show that glass was used to substitute for jewels. Seneca (AD 1 – AD 65) and Pliny the Elder (AD 23- AD 79) were the first authors to write about the practice. Whereas Seneca only mentions that ‘sometimes stones are boiled to resemble emerald (smaragdus)’, Pliny provides us with a rather lengthy account in which he explains the various ways in which gems were imitated. He mentions that glass pastes were used for the imitation of seals and that in some cases stones were cemented together to imitate sardonyx. By a third method, ‘Indian crystals’ were colored with certain dyes to make them look like more expensive minerals. These ‘gems’ were apparently so convincing that ‘(…) there is considerable difficulty in distinguishing genuine stones from false; the more so, as there has been discovered a method of transforming genuine stones of one kind into false stones of another.’ While some physical evidence still survives of the first two practices, the factitious gems made by the third manner, has barely, if at all, come down to us. The many recipes that explain how to make such imitation stones (surviving from the fourth well into the sixteenth century) nevertheless suggest that this last method must have also been practiced, and perhaps even on a large scale. I therefore hoped that a physical reconstruction of the imitation gems might give some further insight into the appearance of these imitation gems. Would it be possible, as the recipes suggest, to make a convincing imitation of a precious stone? Could such a ‘fake’ potentially fool the innocent eye into thinking it was real?

The earliest examples of recipes for imitating stones can be found in the so-called Stockholm Papyrus, a recipe collection written in Greek at about 200-300 AD. The Papyrus includes no less than 71 how-to’s for the imitation of precious stones with lesser materials, including ruby, beryl, amethyst, sunstone and emerald. In subsequent centuries, numerous other recipe books include similar instructions for making counterfeit stones. While the recipes are various, they are almost all based upon two basic operations that I have attempted to reconstruct (fig. 2).

Fig. 2 Opening up of stones
Fig. 2 The opening up of stones

First, a transparent mineral, such as rock crystal, selenite, or topaz, is roughened or ‘opened up’. Following the recipes instructions, I investigated this by cooking the minerals in potash alum (potassium aluminium sulphate) dissolved in vinegar. As soon as I removed the heat from this mixture, it rapidly crystalized into a hard crust around the stones. In accordance with the recipes I left the stones overnight.  Nevertheless, when I inspected them the next day (after having chiseled them out) I could not see any changes. Regardless of whether the stones were successfully ‘opened up’, the coloring of the minerals did produce some surprising results.

The recipes instruct that the ‘opened up’ mineral should be colored using a mixture of a colorant ground with oil or resin to make it assume the appearance of a specific gemstone. The dyes and pigments used varied according to the type of gemstone that was to be imitated. A red dye made from alkanet root (used by ancient cloth dyers) was advised for the imitation of rubies and the green copper pigment verdigris was used to transform transparent minerals into emeralds. For my first reconstructions I choose to make a ‘fake’ emerald. It was one of the precious stones imitated the most frequently and the instructions for making it remained almost the same through (post-) classical and pre-modern times (fig. 3).

Fig. 3 Coloring of stones
Fig. 3 The coloring of stones

I first ground the pigment verdigris with linseed oil and used this substance to cover the base of a rock crystal, topaz and piece of selenite. This resulted in a beautiful, translucent green stone that, due to the instability of the pigment verdigris, in time assumed the saturated forest green color of a real emerald. Whereas more reconstructions are certainly required to investigate the nature of this method of gemstone imitation, these first experiments show that, when ancient sources insist how visually convincing the imitations of precious stones could be, they are probably not exaggerating.

Fig. 4 Emerald imitation
Fig. 4 Emerald imitation

Recommended reading:

Marjolijn Bol, ‘Coloring Topazes, Crystals and Moonstones: The making and meaning of factitious gems, 300-1500’, in Marco Beretta and Maria Conforti (eds.), F for Fakes: Hoaxes, Counterfeits and Deception in Early Modern Science, 2nd Watson Seminar in the History of Material and Visual Science, Museo Galileo, Florence, June 7, 2013, Science History Publications (Brill Publishers: 2014), pp. 108-129.

Earle R. Caley, “The Stockholm Papyrus: An English Translation with Brief Notes”, Journal of Chemical Education 4 (1927), pp. 979-1002.

Pliny, The Natural History, books 33-37 (book 36 includes Pliny’s natural history of stones):

Prescribing and Describing Art Technology

By Marjolijn Bol

“To Produce a Gold Color by Cold Dyeing.

Take saflower blossom end oreye, crush them together and lay them in water. Put the wool in and sprinkle with water. Lift the wool out, expose it to the air, and use it.”

Stockholm Papyrus (Old-Greek, 4th Century AD)

This recipe describing how to dye wool a golden color is just one example of the many sources on art technology that have come down to us as from as early as 2000 BCE. The recipes range from the making and working of parchment, stone, glass, textiles, paper, pigments and colorants – to the production of embroidery, miniatures in books, metalwork, enamels, ceramics, woodworking, panel painting, glass painting and much more. Here on The Recipes Project, readers have already encountered several posts dealing with topics on art technological sources (see hereherehere and hereand more are planned for the future. For this reason the idea came about to develop a series of posts highlighting the current scholarly initiatives and interest into artists’ recipes.

An art technological source can be understood as any material surviving from the past that provides us with information about the history of the materials, tools and techniques used to make works of art – ranging from realia, to the work of art itself, images, texts and audio-visual sources. In the present series of posts, however, we will focus mainly on art technological sources in the form of recipes – or written records of artistic production. Interestingly, research into art technological sources has also triggered the field of historical reconstructions. On the basis of artists’ recipes, scholars attempt to reconstruct certain painting techniques, metalworking methods, lost objects from material culture such as parchment windows or factitious gemstones and much more. These historical reconstructions help scholars better understand the recipe, re-materialize long-lost objects that we now only know through textual sources and provide insight into the ‘original’ appearance of objects that survived in poor or changed condition. As a result, historical reconstructions can offer us a glimpse into the complex processes through which a certain artwork was made.

In recent years, the study of these so-called art technological sources has gained much momentum within the fields of Art History, Conservation & Restoration and the History of Science. In 2002, the Art Technological Source Research Group (ATSR) was established within the International Counsel of Museums (ICOM-CC) providing research into art technological sources with an international scholarly platform. Whereas many more recent initiatives could be sketched out here, I will only mention two more in the context of the present blog series. In attempt to organize and systematize the vast amount of historical artists’ recipes, the Max Planck Institute for the History of Science in Berlin is making a vast database on historical recipes on art technology (‘Colour ConText‘). Furthermore, the importance of research into art technological sources is attested by the fact that, since 2012, the University of Amsterdam has offered  a masters course on the topic. This course in Art Technological Source Research is not only unique because it brings together students from the Conservation & Restoration and Art History courses, but, additionally, the students have the opportunity to study original recipe books collected by and kept in the library of the Rijksmuseum. All students study a particular recipe from a treatise in the Rijksmuseum collection and make a historical reconstruction of the said recipe as part of their studies. We had groups of students attempting to grind and process petuntse stone according to an 18th century recipe for making Chinese Porcelain, while another group attempted to find out the role of spike oil in an 18th century varnish recipe. The students from textile conservation reconstructed the color “violet” from Runge’s Farbenchemie (1842) and, finally, the fourth group of students made a reconstruction of a painted silver vessel according to a recipe from Wilhelmus Beurs’s The Big World Painted Small (De groote waereld in t kleen geschildert, 1692).


The posts in this series titled Describing and Prescribing Art Technology intend to form a first glance into present-day research into art technological sources. It highlights the special collection of recipe books at the Rijksmuseum of Amsterdam with an interview with the head librarian Geert-Jan Koot. Later in the month, Ad Stijnman, a key member of the Art Technological Source Research Group, will tell us a little about the history and research scope of this group, and, finally, Sylvie Neven will offer us a fascinating example of research into artist’s recipe books.

Medieval Makeup ‘Artists’. Painting Wood and Skin

by Marjolijn Bol

What there is stays the same. That she can never change.                                                                        Jan van Boendale (ca. 1280 – ca. 1351)

For art historians, one of the most important and best-known ‘recipe books’ is  Cennino Cennini’s (c. 1370 – c. 1440) Il Libro dell’arte (The Craftman’s Handbook). The Italian treatise is famous because it offers the reader many detailed recipes that explain how to make a panel painting. These include the preparation of wood so that one can paint on it, how to make paint from egg and pigments, how to make brushes, how to paint draperies, faces and beards, and, finally, how to varnish the finished work with a mixture of oil and resin (the ‘tears’ from trees such as amber) so that it becomes it shiny and is protected from dust and dirt (fig. 1).

Fig. 1. Giovanni Boccaccio, Marcia painting her self-portrait from De Claris Mulieribus (Of famous women, written 1361), early fifteenth century illumination, Biblioteque Nationale, Paris, ms. 13420, f.101v
Fig. 1. Giovanni Boccaccio, Marcia painting her self-portrait from De Claris Mulieribus (Of famous women, written 1361), early fifteenth century illumination, Biblioteque Nationale, Paris, ms. 13420, f.101v

Little known, however, is the fact that Cennini also writes that painters were sometimes asked to be ‘makeup artists’:

In excercise of your profession, you will sometimes have to stain or paint on flesh, chiefly to paint the face of a man or woman.1

Cennini explains that there are three methods for painting faces. You can have the colors or pigments tempered with egg, or, when you want to make the face more brilliant, with linseed oil or varnish (the oil-resin mixture). Cennini writes furthermore that in order to clean the face, one takes egg yolks and, gradually rubbing them on the face with the hands, this removes the face paint. The fact that panel painters were asked to be make-up artists, begins to make more sense when we consider the fact that for painting on wood and the face many similar materials were used (figs. 2 and 3).

Fig. 2. Shared materials panel painter and face painter, left to right: Egg, linseed oil, resin tears, dried resin (mastic) and below: two pigments: white lead and vermillion.
Fig. 2. Shared materials panel painter and face painter, left to right: Egg, linseed oil, resin tears, dried resin (mastic) and below, two pigments: white lead and vermillion.
Fig. 3. Bernardo Daddi, detail Virgin Mary's face, 14th century. Egg-based paint on panel Gemäldegalerie, Berlin (inv. nr. 1064)
Fig. 3. Bernardo Daddi, detail Virgin Mary’s face, 14th century, egg-based paint on panel, Gemäldegalerie, Berlin, inv. nr. 1064.

There are in fact many more painter’s recipe books that include instructions for making face paint. The fifteenth century German Strasburg manuscript for instance, a collection of recipes for painting in books and on panel, also provides us with an instruction for making a face paint from the resin mastic.2

Another interesting  source that reflects the similarities between panel painting practice and face painting practice is the fourteenth century poem Jan Teesteye (ca. 1330-1334) written in Middle Dutch by Jan van Boendale (ca. 1280 – ca. 1351). In the section of his verse that deals with ‘women and their bad habits’ Van Boendale compares the crèmes and ointments used by women to cover up facial irregularities to the painter’s varnish:

They (the women) grease and anoint their faces, to appear beautiful, and admired by many;but as a painter varnishes an image with all its deceiving decoration, shining beautifully as if though it were solid gold, it is, on the inside, still wood; So a woman, has varnished her skin to make it look beautiful and shining, it is, however, still a futile thing; What there is stays the same. That she can never change.3

Thus, for Van Boendale, women who varnish their faces are like the painter who has varnished his work, embellished with fake jewels, glistening beautifully like gold but, ultimately, on the inside still made from wood (fig. 4). This way, Van Boendale uses the practice of make-believe in painting to compare it to another aspect of fourteenth century material culture; how women sometimes fool us with their counterfeit beauty created with face paint. What makes van Boendale’s comparison even more interesting is that he synonymously uses the Middle Dutch word ‘vernis’ for both the cosmetics used by ladies to smooth their faces and the final varnish layer applied by painters to make a painting look smooth and shiny (and protect it).

Cennino Cennini, like Van Boendale, also had some critique on the practice of painting faces. Contrary, however, to Van Boendale’s moral critique on the trickery involved in face painting, Cennini, as a painter, was well aware of the health risks involved in using some of the painter’s materials for painting the skin:

But I will tell you that if you wish to keep your complexion for a long time, you must make a practice of washing in water – spring or well or river: warning you that if you adopt any artificial preparations your countenance soon becomes withered, and your teeth black; and in the end ladies grow old before the course of time; they come out the most hideous old women imaginable.4 

Cennini was certainly right to warn against face paint. At least since antiquity many of the materials used on the face included toxic ingredients, such as the pigment lead white for applying a ‘foundation’, or vermillion for making one’s cheeks look red and blushing. Such pigments poisoned the person using it, and, eventually, could even lead to death. Here the old Dutch proverb – that one has to suffer for beauty – applies a little too well.


1. Daniel Varney Thompson (ed.), The Craftsman’s Handbook: the Italian “Il libro dell’ arte”. Cennino Cennini, New York, 1960, p. 123 and for the Italian see: Fabio Frezzato (ed.), Il libro dell’arte. Cennino Cennini, Vicenza, 2004, p. 203 [nr. CLXXIX].

2. Rosamund Borradaile and Viola Borradaile, The Strasburg manuscript: A medieval painter’s handbook/Das Strassburger Manuskript: Handbuch für Maler des Mittelalters, München, 1976, p. 83.

3. Gerrit Komrij, De Nederlandse poëzie van de twaalfde tot en met de zestiende eeuw in duizend en enige bladzijden, Amsterdam, 1994, p. 103, English translation by author

4. Thompson (ed.), The Craftsman’s Handbook, p. 123.

Now you see it? No you don’t! Images in Alchemical Manuscripts

By Anke Timmermann

The scene seems almost idyllic: a stone basin in a green landscape, a stylised cloud floating above with the heads of three blond, chubby cherubs. But then we realise that the sweet, angelic faces are spitting a greenish-blue liquid into the tub, from whence it flows through a spout into a glass vessel. This means business!

Glasgow University Library, MS Ferguson 6, s. xvii. By permission of University of Glasgow Library, Special Collections.
Glasgow University Library, MS Ferguson 6, s. xvii. By permission of University of Glasgow Library, Special Collections.

The business at hand is the manufacture of the philosophers’ stone as outlined in the Rosarium Philosophorum, a popular alchemical tractate first printed in 1550. It represents one of the increasing number of illustrated alchemica that emerged from the fifteenth century onwards. Manuscript pages came to life with pictures of alchemical metaphors previously confined to descriptions. Colourful animals or humanoid figures (representing substances) were now shown engaged in activities (chemical processes and reactions), from knowing each other in the Biblical sense to mutual ingestion, in fiery or watery environments alike.

But, as exciting as this development was, alchemical practitioners still needed to translate imagery into practical terms to make sense of these ‘visual recipes’. Like the interpretation of recipe texts, and especially in combination with verbal recipes, this proved to be a difficult task. Today it is historians who try to find a recipe for the meaningful description and analysis of alchemical images.[1] Here the little flask above, gathering the angelic fluids so faithfully, demonstrates how complex the business of alchemical history can be.

Glass vessels feature prominently in alchemical images from the late medieval and early modern period. The image above might indicate the use of an actual glass flask in this step of the manufacturing process, or, more likely, simply be intended to conjure up the mental image of gathering liquids with any appropriate vessel. However, in many visual alchemical scenes such as the Splendor Solis series or the Ripley Scrolls, drawn glass containers were clearly not intended to represent actual equipment, but rather to provide a visual frame for a process depicted in figurative form.

The translucence of glass benefited the artist aiming to reveal alchemical processes within a conceptual, as opposed to actual, space. By contrast, in actual laboratory practice, glass vessels were generally only used for distillation “where they may be used without fear of breaking or melting”.[2] What we see, and what contemporary readers saw, in these ‘visual recipes’ is not an object, but a concept.

Glasgow University Library, MS Hunter 110 (T.5.12), s. xiv, f. 28r. By permission of University of Glasgow Library, Special Collections.
Glasgow University Library, MS Hunter 110 (T.5.12), s. xiv, f. 28r. By permission of University of Glasgow Library, Special Collections.

A much more pragmatic depiction of a similar flask may be found alongside Albertus Magnus’s appropriately-named Straight Path in the Art of Alchemy in GUL MS Hunter 110. This manuscript is roughly two hundred years older than the copy of the Rosarium Philosophorum above. Instantly recognisable as a receiver for distilled liquid, drawn complete with the entire apparatus, this flask nevertheless surprises in comparison with the previous image: this illustration does not show any liquid either before or after distillation. Such detail would have been realistic, but perhaps unnecessary for contemporary readers to understand the experimental setup.

Glasgow University Library, MS Ferguson 67, s. xvi, f. 10r. By permission of University of Glasgow Library, Special Collections.
Glasgow University Library, MS Ferguson 67, s. xvi, f. 10r. By permission of University of Glasgow Library, Special Collections.

Our final image could be mistaken for a regular kitchen if it weren’t for the distilling apparatus shown in the foreground[3]. This piece of equipment was familiar to readers who had an alchemical background from practical manuscripts (like the previous one), but also to those employing distillation for medicinal or other purposes. This image reminds us of the intersection of alchemical recipes with those of other recipe literatures, in word and image.

What is particularly wonderful about this image is a detail that might be overlooked when considered in isolation from the other illustrations: the liquid in the receiving vessel is shown to stand at an even, calm level, while the liquid in the heated vessel is boiling, bubbles clearly visible. The present, nervous reader of this manuscript cannot help but worry about the stability of the glass, which could melt or break at any moment. It is only in comparison with other flask depictions that this detail emerges.

Questions about different purposes of illustration as well as local, temporal and individual preferences in visualising different aspects of the alchemical work come to mind. But is this a detail contemporary readers would have picked up on?

Well, now I see it. But maybe I shouldn’t.

My focus on the flask, just for the purposes of this blog post, was inspired by Tillmann Taape’s excellent recent post on distillation.

[1] Two seminal articles in this area are Barbara Obrist, ‘Visualization in Medieval Alchemy’, HYLE-International Journal for Philosophy of Chemistry 9 (2003), 131-70; see also Obrist’s earlier oeuvre on alchemical images. And Christoph Lüthy and Alexis Smets, ‘Words, Lines, Diagrams, Images: Towards a History of Scientific Imagery,’ Early Science and Medicine 14 (2009 ), 398-439.

[2] John French, The Art of Distillation (London, 1651), Book I. See also Tillmann Taape’s posts on this blog.

[3] This manuscript is described and analysed in Paul Engle, “Depicting Alchemy: Illustrations from Antonio Neri’s 1599 Manuscript”, in Dedo von Kerssenbrock-Krosigk, ed., Glass of the Alchemists (New York, NY, 2008), 48-61.