2.18 Contemporary Documentary Technical Evidence as the Basis for Scientific Examination of Art Objects

The Getty Conservation Institute

Arie Wallert
Period of Activity: Current Research

Project Abstract
Many art historians give a lot of attention to problems of attribution, changes of style, and artistic innovation. But often enough they are not equipped to gain more than a superficial knowledge about the very materials and techniques that were used to give these innovations their physical form. The changes in style and particularly the relations this has with aspects of material nature can often be no more than estimated with scholarly conjecture. Yet, knowledge of these aspects can have important significance for the conservation of works of art and should be one of the primary bases for curatorial decisions. Technical analyses can then be very helpful. Modern methods of chemical analysis are able to reveal many details about the techniques used by artists and craftsmen in the creation of works of art. It may be rewarding, however, to take a closer look at what craftsmen themselves have said about their own profession and to study the workshop records they used.

Art-technical treatises can be extremely useful tools in the examination of art objects. The importance of the study of technical historical documentation seems obvious. Sources like these show us what pigments and colorants were available in certain periods. They give insight to the geographical distribution of certain materials or specific working procedures. They show us where or when innovations came in use and what the advantages or drawbacks were. They help us to understand the material being of the objects.

Several hitherto unpublished technical treatises are at the moment being studied. The project shows some similarities with the project on computerized data management and retrieval Tincl of (mainly Dutch) technical historical sources. That project is under way at the Amsterdam Central Laboratory under the direction of Prof. Dr. E. van de Wetering.

1. Instructions for Oil Painting in the Eikelenberg Manuscript

In the last quarter of the seventeenth century the Alkmaar painter Simon Eikelenberg began preparation for the ultimate painter's handbook. To facilitate this, from 1686 to 1732 he gathered an enormous amount of notes that are now being kept in four volumes in the Alkmaar Municipal Archives. Many of these notes are the bases for current literature, like the books of Symon Andriessen, Carel Batin, and Dodoneus. More information came from colleague-painters or paint traders, and from his own laboratory notes based on personal experience and experiments. Among his assembled notes is a small treatise, written in a different hand than Eikelenberg's, on the technique of oil painting. Unlike most of Eikelenberg's other notes, this manuscript is coherent and well organized. It describes in a systematic manner the making of an oil painting from the preparation of the panel to the final application of the varnish. This manuscript is one of only a very few surviving contemporary primary texts describing the techniques as practiced by masters like Rembrandt, Frans Hals, and Vermeer. We have begun by making a transcript of the original manuscript. Comparison is made with other texts on the arts and in the next stage, related matter available to painters in the Netherlands in the seventeenth century. Work on the manuscript is to conclude with a translation of the text into English and the preparation of an annotated bilingual publication.

2. "aquae conficiendae ad temperandos omnes colores"

The Leiden University Library keeps an interesting German fifteenth century art-technical manuscript. It has the shelf mark Cod. Voss. Chym. Oct 6, and has on the first page a description of its contents: Methodus aquae conficiendae ad temperandos omnes colores, & sic procedidt ad quaecunque alia sive remedia, sive oblectamenta tinctuarum, privato labore collecta. Germanice & Latine. The contents make it clear that we are dealing with a collection of recipes devoted to the practice of manuscript illumination. It describes the making of inks, the preparation of parchment, the application of gold leaf, and the preparation of various transparent organic colorants.

What makes this manuscript so important is the fact that it appeared to be related to the famous Strasbourg manuscript. The Strasbourg manuscript, which was lost as a result of bombardments of the city during the German-French war in 1870, has been considered the oldest treatise on painting technique in the German area. For a long time it was thought that it had no precedent nor any later copies.

Finding this manuscript allows us to reexamine the contents of the "Strasbourg-texts." It also makes it possible to reevaluate the interpretation of E. Ploss ("Das Amberger Malerbuechlein: Zur Verwandtschaft der spaetmittelhochdeutsche Farbrezepte," Festschrift fuer Hermann Heimpel, Max Planck Institut, Goettingen 1971, 693-703) on the application of organic colorants of anthocyanin type on paper or parchment.

3. Instruction and Standards for Textile Dyeing from the Gobelin and Savonnerie Workshops (Proposed study along with Anne Kraatz and Brian Considine, J. Paul Getty Museum)

At the beginning of the fifteenth century, dyers had settled on the banks of the Bievre, a little river in one of the suburbs of Paris. It was there that the name Gobelin first occurred, a family which originated in Flanders or Northern France. Jehan Gobelin, a dyer, owned a house and garden on the banks of the river in 1443. His wealth and reputation grew rapidly and eleven years later he was made alderman and magistrate of the community, Saint Marcel. It was scarlet dyeing that founded the great fortunes of the family. Jehan Goblin spent enormous sums, and his splendid house on the Bievre was mentioned as Gobelin's Folly by Rabelais.

Nearly all the members of this large family followed the profession of the founder. Documents show that by the sixteenth century, the Gobelin family, partially through marriages with another wealthy family of dyers, the Canayes, had grown to such an extent that they owned a large part of Saint Marcel. It was in the course of the sixteenth century that some of the Gobelins found preferment at Court. In 1604, Bathasar Gobelin, after having been raised to the ranks of the nobility, even took charge of royal finances. Receipts have been preserved for sums borrowed from him by Henry IV, "en ses urgens affaires." The family continued to ply its trade after the tapestry weavers Coomans Canayes, had grown to such an extent that they owned a large part of Saint Marcel. It was in the course of the sixteenth century that some of the Gobelins found preferment at Court. In 1604, Bathasar Gobelin, after having been raised to the ranks of t;and Francois de la Planche had settled in the workshops of the Gobelins. A marriage at the beginning of the seventeenth century between Marie Gobelin and Antoine de la Planche set the foundation of the great tapestry workshops in the house of Gobelin. The products of these workshops acquired such fame that the name Gobelin, from a family name, has become a generic name for tapestries. The Gobelin workshops exist till the present day.

In the Paris Bibliotheque National a peculiar seventeenth-century manuscript is being kept. This manuscript contains an extensive number of descriptions and recipes. These recipes for dyeing yarns for embroideries and tapestry weavings were in use from the seventeenth century onward in the Gobelin factory. Quantitative prescriptions of the dyestuff components and mordants for each of the colors that were in use, are accompanied by actual contemporary silk and wool samples. The recipes and the samples have been kept over the ages in the manuscript, protected from UV light, humidity, and temperature fluctuations. The people of the Gobelin workshop, who seem to be quite willing to cooperate, have let us know that in their own archive, even more of such standards (of later date) exist. Also, wool color samples of the other famous workshop, the Savonnerie, are known to exist. These, too, "have always been kept in boxes, and their range and strength of color is very startling."

The samples in both the Gobelin and Savonnerie collections provide us with an unequaled opportunity to characterize the dyestuffs of the period: "You can proceed to the most advanced and complex chemical and physical-chemical analytical techniques. But if you don't have known samples of authentic material for comparison, your conclusions cannot be reliable. Your results will be no better than the quality of the known material that you use for comparison." The dyes that are on these Gobelin and Savonnerie samples are as authentic and documented as we could ever hope to get. They may provide a sound and-probably the best-basis for everyone who is involved in the analysis and conservation of dyestuffs on historical textiles.

Making transcripts of the original manuscripts, and comparison with other texts on the arts and related technical matter, would be the first thing to do. Translation of the text into English in order to prepare the text for bilingual publication would be the next step. Samples must be taken from each color and prepared for analysis. Analytical data will be gathered from microchemical tests, UV-vis spectrophotometry, thin-layer chromatography, fluorescence spectrophotometry, HPLC, and FTIR.

4. Instructions and Models for Manuscript Illumination. (Current study in progress along with James Marrow, Princeton University, and Peter Gumbert, Leiden University)

The way recipes and maxims on techniques in medieval workshop manuals have been laid down can vary from simple recipes, via lists of concordances, to very elaborate modelbooks. A valuable and rare treatise, which is now kept in the "Historisches Archiv" in Cologne, contains recipes to make paint, inks, and pigments; it has lists of concordances containing detailed instructions on the application of the paints; and it has a series of small but beautiful models, images in which is depicted what the various concordances look like. Manuals like these are extremely rare. (The only existing text comparable to it may be the so-called Goettingen Modelbook.) The Cologne modelbook can be linked to the book production of the "Devotio Moderna" as current in the convents around Zwolle and Arnhem linked to the Windesheim congregation.

The first step in the project is the translation into English of the Latin and Middle Netherlandish recipes, descriptions, and comments of the original manuscript. For solving paleographical problems in making reliable transcripts, one of the foremost scholars in this field, Professor P. Gumbert of Leiden University was called in. Some preliminary work on this has already been done. The next step is the valuation of the contents in relation to other comparable treatises from the Southern Netherlands (Flanders) and Northwestern Germany (Westphalia). Work on this is in an advanced stage. In the models there is stylistic evidence to suggest their origin was the Eastern part of the Netherlands, around 1480. To give more light on the rather hybrid style of the models and a more precise estimate of their art historical significance and the transmission of motives, we received the help of Dr. J. Marrow of Princeton University.

The next step consists of analytical work. In the past, samples have been taken from the models. These paint samples from the models will be studied by polarized light microscopy, energy-dispersive X-ray fluorescence, X-ray diffraction, scanning electron microscopy and the microprobe, three dimensional fluorescence spectrometry and HPLC for pigment, organic colorant, and binding media identification. The results of analysis will be related to the contents of the recipes. It is expected that these combined efforts will lead to a publication in which the manuscript is viewed from every possible useful angle. These recipes and models deserve to be more widely known, and their publication will mean a highly valuable contribution to manuscript illumination studies. It is foreseen that the publication of the recipes together with the scientific analysis will set the standard for more examinations of techniques of northern medieval manuscript illumination in the future.

Primary Publications
Wallert, A., R. Westmoreland, and J. Bassett, "Encarnaciones and Estofado on Spanish Polychrome Sculpture," ICOM Triennial Conference, Washington, D.C., Working Group 5, Polychrome Sculpture, August 1993.

ABSTRACT-The polychrome sculpture San Gines de la Jara (now in the J. Paul Getty Museum) was made in 1692 by the little-known artist Jose Caro of Murcia. In its expressive and vivid realism it is a striking example of the emotional religious experience that was predominant during the Counter-Reformation. The life-size sculpture still retains almost all of its original polychromy. The head, hands, and feet are encarnaciones, polychromy in traditional flesh tints. The saint's vestment is executed in estofado, simulating sumptuous gold brocade over the traditional brown Franciscan habit. An examination of the object's structure and original polychromy has been carried out. The construction of the sculpture itself could be understood by studying X-radiographs and by close examination of the pattern of cracks visible through the paint layers. The sequence of the preparation, gesso ground, bole, gilding, and various paint layers was studied in paint cross-sections. The binding medium of the grounds was analyzed by thin layer chromatography. Casts in silicone rubber of the various punchmarks were made to be studied in the environmental scanning electron microscope. The pigments were identified by polarized light microscopy, X-ray fluorescence, and X-ray diffraction. The varnishes were analyzed by thin layer chromatography. The results of analysis were compared with contemporary technical descriptions in Francisco Pacheco's Arte de la Pintura, allowing a better interpretation and understanding of the traditional techniques of encarnacione and estofado of polychromy in the south of Spain.

Wallert, A., "Anthocyanins on Parchment," ICOM Graphic Documents Working Group, Conference, Jerusalem, October 1992.

ABSTRACT-In the scientific study of painted art objects like miniatures, paintings, and polychrome sculptures, a wide and ever-expanding knowledge has been gathered on inorganic colorants. Much less attention is usually given to colorants of organic origin. These colorants, however, are usually the most vulnerable to environmental conditions. Also, more than mineral pigments, they often change color on the slightest changes in pH. In short: From the point of view of conservation of cultural property, organic colorants deserve wider attention than they have had thus far.

Many historically used organic colorants were derived from plants. In plants, organic colorants usually occur in combination with a large number of other vacuolar constituents, such as other colorants, mineral ions, sugars, peptides, and organic acids. Most dyestuffs that were to be applied in art objects in their natural state customarily are linked to sugars. The extraction procedures usually involved the breaking of these sugar bonds, often by enzymatic hydrolysis. The second step was to establish new bonds between the aglycon, i.e., the colorant without its sugars, and the fiber or substrate by metal complexation. Of the mordants mordants ;used for complexing the aglycon colorants, aluminum, potassium, calcium, magnesium, tin, copper, and iron are the most important. For medieval panel paintings or manuscript illuminations, colorants based on quinoid or flavonoid compounds were extracted by warming the plant materials in soft lye solutions. Then the plant material was filtered off. The colorant in the lye (the lye usually being potassium or sodium carbonates) remained. Upon addition of a warm aluminum sulfate solution to this extract, a dense aluminum hydroxide precipitate would be produced that formed highly stable and color enhanced bonds with the colorants. Other colorants were not complexed with metals but linked with sugars. These colorants mostly belong to the anthocyans. These are pigment glycosides that are responsible for most of the red, blue, or violet colors in the flowers of higher plants. The aglycons are called anthocyanidins. The anthocyans do not form a specific group but are part of the larger group of flavonoids. They differ from most other flavonoids through the presence of a single oxygen atom. Unlike most other flavonoids, the anthocyanidins cannot be laked into insoluble pigments by complexing with mineral ions.

Anthocyans possibly occur in vivo as salts from weak organic acids. The differences in color of the anthocyans, usually blue, red, or purple, are caused by substitution at the B-ring. Most aglycons have hydroxyl groups at the 3, 5, and 7 positions. The B-ring can have substitutes on the 3', 4', and 5' positions. The differences in color then are determined by both the structures of the colorant and the position and number of attached hydroxy- and methoxy- groups.

Descriptions of the use of these anthocyans on parchment can be found in a hitherto unpublished fifteenth-century manuscript treatise. This illuminator's workshop handbook, strongly related to the famous Strasbourg manuscript, primarily gives recipes for the use of these anthocyanins in the form of clothlet colors. Anthocyanin colorants in works of art have hardly ever been the object of study. The biogenesis, chemical structure, stability, historical use, and possible methods of analysis of the anthocyans will be examined. This will be done together with a discussion of the position of the recipes on anthocyanin colorants in this particular manuscript in relation to those of the other texts within the "Strasbourg-group."

Wallert, A., "Instructions for Manuscript Illumination in the 15th Century Netherlandish Technical Treatise," Masters and Miniatures, Studies and Facsimiles of the Netherlandish Illuminated Manuscripts, Vol. 3, Doornspijk, Holland, 1992, pp. 447-456.

ABSTRACT-Detailed instructions with models of combinations of color can be found in a fifteenth-century manuscript in the collection of the "Historisches Archiv" in Cologne. The manuscript contains two gatherings of eight leaves each. The first gathering, written in a regular hybrid hand, has recipes and instructions in Northeastern Middle Dutch. The text of the second gathering, in another cursive hand, is written in Latin, but sometimes Dutch words occur in the Latin text. The outer leaves of the second gathering, i.e., fols. 9v-10r and 15v-16r, show in small pictures of high quality, the different mixtures and combinations of colors as they are described in the manuscript. The contents of the recipes are discussed, and the chemical characteristics of the pigments and organic colorants are explained in light of their compatibility, as reflected in the concordances.