Nineteenth-century academic-style paintings in Britain, Europe, and North America have gained notoriety for the technical problems they present not only aesthetically but also in terms of their conservation analysis and treatment. Other than the knowledge that bitumen was a popular pigment and that these paintings often appear to have a high resin content in the oil medium, until recently there has been little specific information available on the materials and techniques in use during this period.

Recognizing the dearth of technical information and the usefulness of developing an expertise in this area, in 1986 the then Director General of CCI, Wally Kozar, supported a research proposal to carry out a comprehensive investigation into documentary sources covering 19th-century artists' oil painting materials and techniques. At CCI, and elsewhere in Canada and North America, a large percentage of the 19th-century paintings being treated had been made or influenced by artists trained in Britain. Therefore, this investigation led naturally back to the United Kingdom. The work was carried out as PhD.-level research in the Technology and Conservation Department of the Courtauld Institute of Art, University of London.

Approval for educational leave with allowance was granted in the fall of 1986, and the research began in January 1987. The thesis, entitled "A Critical Analysis of Artists' Handbooks, Manuals and Treatises on Oil Painting Published in Britain Between 1800 and 1900: with reference to selected eighteenth-century sources," was submitted in April of 1991, and was passed on September 25, 1991.

The books that were published in the 19th century on oil painting generally fall into three categories: instruction books on how to paint in oils; handbooks or reference manuals on materials, such as varnishes and pigments; and general compendiums on the arts. These books not only provided information to the amateur, but were also important sources for well-known artists and even for members of the Royal Academy. In addition, selected sources from the 18th century were studied, and further information was collected from general recipe books and from dictionaries of arts and manufacturers.

Two other important sources of information were the colourmen's retail catalogues, which listed the materials available throughout the century, and a series of bought ledgers from the colourman Roberson. The bought ledgers, which dated from 1828 through to 1900, recorded company purchases of materials such as oils, varnishes, pigments, and canvas. A high correlation was found between the introduction of new materials and their appearance in the colourmen's catalogues, the bought ledgers, and the oil painting manuals.

Most of the sources were rare books not available for lending; therefore, the research was carried out with a portable computer equipped with a flat-file database software package. All technical information relating to oil painting was entered in the appropriate categories: oils, varnishes, painting mediums, grounds, painting methods, pigments, etc. Each entry included the direct quote from the book. Summary fields allowed quick access to the materials listed or described. In some cases, the authors provided recipes as well as instructions for the application of various materials; these were also included in the database. Once data entry was completed, chronological and subject sorts were performed. It was then possible to look at the century as a whole, and to chart the materials in use, their popularity and demise, and the introduction of new materials.

This information can be particularly useful for interpreting paint cross-sections and the results of instrumental analyses, and for preparing representative samples in materials research. As well, this work can give some indication of why artists chose certain materials and why they used them in the manner that they did.

Although for many years conservators have had access to information on the components of a painting from their colleagues who carry out material analyses, why these materials are present has not always been elucidated. Documentary research can provide further insight. For example, in recent years fluorescence microscopy has illuminated the presence of many intermediate layers that were used in building up a painting, and newly available equipment for infra-red microspectrometry has identified materials in discrete layers of a cross-section. As a complement to this, the documentary research on painting manuals has provided information on the purpose of these layers and on the reasons artists selected specific materials for use.¹

The database created during this PhD. research on artists' pigments has contributed further information relating to research reported in a previous CCI Newsletter article, "A Double-Sided Panel Attributed to Tom Thomson." In the article, author and Senior Conservation Scientist Ian N.M. Wainwright noted the presence of a mixture of lead sulfate and zinc white, which he recognized as "probably ... prepared or blended by a paint manufacturer rather than mixed by the artist." He continued, "We had not anticipated finding lead sulfate."² A search through the pigment section of the database revealed that a new form of "Permanent White", which consisted of lead sulfate and zinc oxide, had been introduced in the last decades of the 19th century.

The first of the authors to describe this pigment mixture was Henry Seward in 1889: "Permanent flake white is a recent addition to the list of white pigments, and is manufactured under a patent granted to Messrs. Freeman & Co. It is composed of precipitated lead sulphate, mixed with zinc oxide, and submitted to great pressure, by which the bulk is considerably reduced and opacity obtained. The white is slightly different in tone to flake white, similar in body, and unalterable."³

More insight into the reasons for combining these two materials can be gained from A.P. Laurie, who provides an account of this pigment mixture: "These zinc oxide and lead sulphate paints are now being brought before house-painters and artists under various names such as, 'White Lead, Caledonia Park Works, Glasgow, ' 'Freeman's White, ' 'the New Flake White or Cambridge White, ' 'Marble White,' etc. They have the advantage of keeping their colour better in the impure air of large towns and gas-lighted. rooms .... Zinc White prepared the old way was believed by artists to flake off, but these new whites have shown no such tendency. They are also practically non-poisonous, and free from the disagreeable smell of white lead."⁴

Tom Thomson may have specifically chosen this white as a non-toxic and more durable alternative to lead white, or he may have been unaware of the ingredients in Permanent White and may simply have found that it served his purpose, was economical, and was easily available.

As Ian Wainwright suggested, "Further research and analysis are necessary to determine the extent to which Thomson and his contemporaries may have used lead sulfate, lead white, zinc white, or mixtures of them."⁵ It is to be hoped that such further research, coupled with what we know about Permanent White, will also inform us of Tom Thomson's and his contemporaries' intent in adopting this new white.

The information gained from this research into artists' materials and techniques also reveals the reasoning behind the use of resins in 19th-century academic-style paintings: painters felt it necessary to mix resins with their oil paint to achieve the translucency of the old masters, whose techniques they emulated. The difficulty that many conservators have experienced in cleaning such resinous paintings is further explained by 19th-century sources. Throughout the century, artists were advised to employ the same resin throughout their painting — if they used mastic resin as an addition to their medium, they should also use mastic resin in the final varnish. The same applied to copal resin — if it was used in the medium, then the painting should be varnished with it. Homogeneity in the use of resins was seen to be important, since the presence of different resins was believed to lead to cracking. There were some counter arguments, but generally the homogeneity theory appears to have been the most popular. This idea worked in reverse as well. In the 1890s, the then President of the Royal Academy, Sir Fredrick Leighton, wrote to author Arthur Church, "Is it not always better to have some resin in a picture throughout since it has to be varnished at the end?"⁶

The research on the instruction books, manuals, and treatises identified a number of themes that were important to 19th-century artists and their colourmen. Amongst the most prominent were the quality, authenticity, and durability of their materials. The concern with durability is most ironic for an age that produced some of the most unstable paintings of all time.

With this new information available on 19th-century oil painting materials and techniques, research does not have to be restricted to the identification of materials alone. Our understanding can also encompass aspects of the design and intended application of materials.

References

1. L. Carlyle, "British Nineteenth-Century Oil Painting Instruction Books: A Survey of Their Recommendations for Vehicles, Varnishes and Methods of Paint Application." Cleaning, Retouching, and Coatings, Preprints of the Contributions to the IIC Brussels Congress, 3-7 September 1990, pp. 76-80.
   
   
2. Ian N.M. Wainwright, "A Double-Sided Panel Attributed to Tom Thomson." CCI Newsletter, no. 7 (Mardi 1991): 12.
   
   
3. Henry Seward, Manual of Colours, Showing the Composition and Properties of Artists' Colours, with Experiments on Their Permanence. London: George Rowney & Company, [18891, p. 42.
   
   
4. A.P. Laurie, Facts About Processes, Pigments and Vehicles: A Manual for Art Students. London: Macmillan and Co., Ltd., 1895, p. 49.
   
   
5. Wainwright, p. 12.
   
   
6. Correspondence from Lord Leighton (President of the Royal Academy) to Arthur Church (Professor of Chemistry at the Royal Academy from 1879 to 1911). Royal Academy Library, London, England.