ABSTRACT—Information on artists' oil paint driers was gathered from sources published in Britain from 1758 to 1900. The sources included oil painting instruction books, varnish or pigment manuals, compendiums of the arts, and encyclopedias and dictionaries on arts and manufactures. A number of American texts from the 19th century were included as well. In addition, a study was made of a series of ledgers from the British artists' colormen firm Roberson, which recorded the purchase of its supplies between 1828 and 1900. Included in the Roberson Archive was a limited selection of recipe books that also yielded useful information. Catalogs from the colormen firms of Winsor & Newton, Reeves, Rowney, and Roberson were studied to establish a correlation between oil painting instruction books and the materials available commercially throughout the 19th century. This article summarizes the information on artists' driers from these sources and explores the routes by which driers entered artists' materials, from commercially prepared products to those added on the palette at the time of painting. Paint film defects are frequently seen on paintings from this period. Thus it is hoped that this historical information will be useful when the role of paint driers is examined in relation to these film-formation defects.

TITRE—Les Siccatifs Mentionn�s dans les Manuels Britanniques du XIXe Si�cle sur la Peinture � L'huile. R�SUM�—� partir de documents publi�s en Grande-Bretagne entre 1758 et 1900, des renseignements ont �t� recueillis sur les produits siccatifs utilis�s par les artistes pour la peinture � l'huile. Ces documents comprennent des livrets d'instruction sur la peinture � l'huile, des manuels sur les vernis et pigments, des abr�g�s sur les arts, ainsi que des dictionnaires et encyclop�dies sur les arts et les manufactures. Un certain nombre de textes de source am�ricaine furent aussi �tudi�s, ainsi que les registres de l'entreprise Roberson, une firme britannique de marchands de couleurs, qui contiennent une liste d'achat des diff�rent mat�riaux entre 1828 et 1900. Cette derni�re source comprend entre autres certains livres de recettes qui contiennent des d�tails tr�s int�ressants. Les catalogues de la firme de marchands de couleurs Winsor & Newton, Reeves, Rowney et Roberson furent aussi �tudi�s afin d'�tablir un rapport entre les livrets d'instruction sur la peinture � l'huile et les mat�riaux disponibles sur le march� au XIXe si�cle. Cet article offre un r�sum� des renseignements recueillis sur les siccatifs utilis�s par les artistes, ainsi que sur les fa�ons dont ces produits vinrent � faire partie de l'�ventail des mat�riaux disponibles, soit directement incorpor�s dans les peintures et mat�riaux ou ajout�s par les artistes eux-m�mes lors de la production de l'oeuvre. De nombreuses oeuvres de cette �poque contiennent en effet des d�fauts dans la couche picturale et il est � souhaiter que les renseignements contenus dans cet article seront utiles pour �tablir un lien entre ces d�fauts et l'utilisation des siccatifs.

TITULO—Los secantes de pintura mencionados en los manuales brit�nicos de pintura al �leo del siglo XIX. RESUMEN—Se recopil� informaci�n sobre los secantes de pintura al �leo utilizados por artistas partiendo de fuentes publicadas en Gran Breta�a desde 1758 hasta 1900. Las fuentes incluyeron libros de instrucci�n sobre pintura al �leo, manuales sobre barnices o pigmentos, compendios de las artes y enciclopedias y diccionarios sobre las artes y manufacturas. Se incluyeron tambi�n algunos textos americanos del siglo XIX. Ademas, se hizo un estudio de una serie de registros de la firma brit�nica Roberson distribuidores de colores para artistas, que daba cuenta de la compra de sus productos entre 1828 y 1900. Incluida en el archivo Roberson hab�a tambi�n una limitada selecci�n de libros de recetas que tambi�n proporcionaron informaci�n �til. Se estudiaron cat�logos de las firmas productoras de colores para artistas de Winsor & Newton, Reeves, Rowney y Roberson, para establecer una correlaci�n entre los libros de instrucci�n sobre pintura al �leo y los materiales disponibles comercialmente durante el siglo XIX. Este articulo resume la informaci�n sobre los secantes para artistas que surge de esas fuentes y explora rutas por las cuales los secantes fueron incorporados a los materiales para artistas incluyendo los productos comercialmente preparados y aquellos agregados a la paleta en el momento de pintar. En los cuadros de este periodo se ven frecuentemente defectos en la capa de pintura. Se espera que esta informaci�n hist�rica sea �til cuando se examin� el rol de los secantes de pintura en relaci�n con la formaci�n de esos defectos en la capa de pintura.

1 INTRODUCTION

In its broadest sense, a drier, or siccative, may be defined as any material that will enhance the drying properties of oil paint. In the 19th century it was understood that the painters' oils linseed, poppy seed, and nut oil dried by the uptake of oxygen. Driers were seen to be oxidizing agents that accelerated the oxidation of the oil.

The driers referred to in 19th-century artists' literature were metallic compounds, pigments containing these compounds, or varnishes. Around the turn of the 19th century, and for a few decades afterward, the use of ground leaded-glass and smalt was occasionally mentioned. Until the 1860s, the metals most often cited in association with driers were lead and zinc. Very occasionally copper in the form of verdigris was mentioned. Although referred to as early as the 1830s in lists of driers, manganese compounds did not receive any significant notice until the 1860s and were not introduced by name in the artists' colormen's catalogs until the 1890s. Cobalt-based driers were described in a source from the oil paint trade literature published in Britain in 1874 (Riffault et al.) but did not appear in the colormen's catalogs, nor were they ever mentioned in artists' manuals or handbooks in the period of study.

Driers were used in the preparation of the oil itself and in the preparation of separate medial that were added to the paint. They were also added both in the tube and on the palette to slow-drying colors such as Prussian blue, the lakes, and certain browns and blacks. It was recognized that in damp and cold conditions, paint required driers that would not be necessary when it was sunny and warm, so recommendations for driers varied according to the weather and the season. Driers were also recommended for underlying paint layers to hasten their drying prior to further painting.

2 DRIERS IN COMMERCIALLY PREPARED MATERIALS

Aside from the driers that artists may have added themselves just prior to painting, which will be discussed below, it is important to consider the various means by which driers would already have been present in oil painting materials when they were purchased.

2.1 RAW OIL CLARIFICATION

Driers were sometimes called for in the preparation of raw oil. Although the mucilage or water-soluble component in the oil could be separated simply by standing, several authors described methods that made use of driers to assist in this step. Lead oxide, or litharge, was reported to be most efficient for causing the mucilage to precipitate out of solution. For example, an author from the late 18th century recommended adding 1 part litharge to 2 parts oil and shaking them together over several days. This would cause “a tallow-like grease” to be thrown down with the litharge (Williams 1787, 48–49). One of the leading 19th-century authors, the colormaker George Field, recommended the same method but called for 1 part litharge to 8 parts oil (Field 1835, 205). Another recipe for preparing oil, entitled “Liebig's,” was found in one of Roberson's recipe books and involved combinations of driers such as lead acetate and litharge with water (Roberson Archive, ca. 1850s, HKI MS 788–1993).

The preparation method that used sulfuric acid to remove mucilage and clarify the oil was also said to make it more drying, though most sources referring to this means warned that the resulting oil was inferior. One author reported, “The use of colours ground with acidified oils is one of the principal reasons why pictures crack.” He cautioned, “We should always be careful, before grinding the colours, to assure ourselves by means of litmus paper that the oil is not sour; which often happens after submitting it to operations said to be for purifying it and rendering it siccative” (Vibert 1892, 74).

2.2 DRYING OIL

Painters' oil was treated with driers in order to speed its drying time (see recipes below). Such a “drying oil” was used in painting in a number of ways: by itself, it could be added on the palette to specific slow-drying colors or glazes just prior to painting, or it could be applied as a separate oiling-out layer in preparation for further painting. Drying oil was also present in the painters' ready-prepared materials, as it was added to certain bladder or tube colors. For example, the medium for a vermilion oil paint found in one of Roberson's recipe books included 1 part drying oil to 2 parts linseed oil and 1 part mastic varnish (Roberson Archive ca. 1866 HKI MS 788–1993). Drying oil was also an important ingredient in artists' media such as megilp, which was sold throughout the century (Carlyle 1991, 1:141–48; Townsend et al. 1998).

2.2.1 Drying Oil Recipes

A source from 1758 describes the preparation of drying oil (mainly intended for “coarser work”) as involving boiling or simmering the oil in conjunction with a variety of driers used at once, including litharge, white lead, red lead, lead acetate, and sulfate of zinc (Dossie 1758, 148–49). Reports on the color of these early drying oils indicate that they could be very dark: “a good drying oil is not to be had of them [the colormen], what they furnish us with being so highly colored as to be improper for the purposes of fine painting, and only can be admitted in the darkest shades or back grounds” (Williams 1787, 25). By contrast, recipes provided in the artists' oil painting instruction books were largely directed toward the preparation of a drying oil that would be as colorless as possible; these tended to include only one type of drier.

One of the preferred methods was to use metallic lead, either by agitating the oil with lead shot or by “grinding” the oil with a leaden pestle in a lead-lined mortar. Prolonged storage in a leaden vessel was also recommended. Litharge (and very occasionally white lead) was sometimes substituted for metallic lead and used in a similar manner. For example, Rembrandt Peale's method was to add 2 tablespoons of litharge to and 8-ounce phial which was then filled with linseed oil. It was to be kept exposed to the sun or near a fire for a few days and shanken frequently (Sully 1873, 33).

Litharge was available in two varieties: silver and gold. Silver, or yellow litharge, was heated higher and was reported to be a harder material than the gold, or red litharge. Field (1841, 108) recommended the silver over the gold because it was more highly oxidized and would therefore make a more effective drier. Sources warned that litharge was often contaminated with iron or copper oxides and noted that it contained significant amounts of silica as an impurity. Although it appeared frequently in drying oil recipes, litharge was not recommended to artists for use by itself (to be added directly to the colors on the palette), and it was not listed as a separate article in the colormen's catalogs.

The earliest recipes for drying oils in the sources consulted contained the highest proportion of driers to oil. In later publications, the ratio of 1 part drier to 8 parts oil or 1 part drier to 16 parts oil became more common. The preparation of drying oil was dangerous because of the risk of fire and required skilled workmen to achieve a consistently high-quality product. Judging from orders for both oil and driers, it appears that Roberson's prepared its own drying oil between 1830 to 1853. Sometime after, the firm consistently purchased drying oils ready-made.

2.2.2 Japanner's Gold Size

The strongest drying oils also tended to be the most highly colored since they were prepared by extended boiling with driers. The strongest and darkest of them all was Japanner's gold size, which was sold by the colormen throughout the century. Because of its color, Japanner's gold size was usually recommended for mixing with dark colors. It was also used in the preparation of some media. For example, it was a component in a brown megilp (a variation of the popular gelled medium). However, despite its dark color, at least one source mentioned using it to assist the drying of lake colors that were used in glazing (Burnet 1861, 27).

Japanner's gold size was made by boiling oil with a number of driers in combination such as litharge, red lead, umber, zinc sulfate, and manganese. Field (1835, 206) noted that its preparation often involved the use of needless “if not pernicious” ingredients, and by the end of the century Winsor & Newton stated in its catalog that it contained “large quantities of turpentine and dryers” and “is not recommended where permanence is required” (Winsor & Newton 1900, 104).

2.3 LEAD HYDROXIDE AS A DRIER

In the later part of the 19th century, white-lead pigment was described as consisting of lead carbonate (PbCO3) and lead hydroxide (Pb H2O2). Depending on its manufacture, various ratios were reported. For example, analysis of a Krems white made by precipitation revealed 91.21 parts PbCO3 to 8.21 parts Pb H2O2, while an English Dutch-process white lead was reported to consist of 63.35 parts PbCO3 to 36.14 parts Pb H2O2 (Hurst 1892, 39).

Along with its reported qualities of adding body and helping to keep the pigment in suspension in the oil, the lead hydroxide was believed to increase the drying power of white-lead paint, as it “facilitates the absorption of oxygen by the oil, so that the paint dries up with the utmost rapidity” (Scott Taylor 1890, 39–40). In support of his view that lead hydroxide (hydrated oxide of lead or hydrate of lead) contributed to drying, Scott Taylor (1890, 40) noted, “We are often surprised to discover that White Lead was not esteemed for its drying power by the older painters; and we also find that the Venetians had a custom of grinding it repeatedly in Vinegar. Both of these facts seem to lead to the conclusion that there was little free hydrate of lead in the older varieties.”

Painters were warned that white-lead formulas containing as much as 30% lead hydroxide would have detrimental effects on their paint as the lead hydroxide would leave the white pigment in a “chemically active condition” and that “a chemically active white is not only bad for the oil, but bad for every color with which it is mixed” (Scott Taylor 1890, 40).

It was also believed that lead hydroxide would form lead soap more readily than lead carbonate, and the resulting soaps would, in turn, be more reactive to hydrogen sulfide from the air. It was felt that ultimately this white would darken in “foul air” more easily since “a larger proportion of the lead is seized upon by the sulfur and converted into black sulfide of lead” (Standage 1892, 25–27).

2.3.1 Lead Soaps

One modern account of the formation of lead soaps in an oil paint (Dunn 1973, 66) notes that they enhance the characteristics of the dried film:

White leads are chemically active pigments. They react with both the free acidic portions of vehicles and with the breakdown acids that develop from paint vehicles as paint films age. These reaction products … which are called lead soaps, reinforce the paint film. Fortunately these white lead reaction products are formed at a favorable (slow) rate that imparts the right type of plasticity to the paint film for good stabilization.

Elsewhere the same author observes that “all basic lead pigments form lead soaps” and tests determined that “red lead appeared to form the most soap, white lead a smaller amount, and chromated red lead the least amount” (Dunn 1975, 403–4). Unfortunately, the amount of lead soap formed by lead acetate (the most popular drier, see section 3.1) in relation to other lead compounds was not discussed.

Whether some of the problems associated with the use of excess drier (see below) had resulted because of the formation of excessively high proportions of lead soaps and whether one lead compound was more culpable than another remains to be seen. However, perhaps Scott Taylor (1890), then scientific director at Winsor & Newton, was justified in his concern that lead soaps were present in excess and were responsible for problems.

2.4 ZINC SULFATE

Zinc sulfate was a popular ingredient in drying oil recipes and in combinations of driers such as “Patent dryer,” but it was not offered as a separate product in the artists' colormen's catalogs. There were only two references in the literature to the use of zinc sulfate alone. One author noted that coach painters and painters of ornaments added it directly to their paint but warned that in this application it would cause the paint to crack and affect its texture (Tingry 1804, 100). Much later in the century, zinc sulfate was mentioned in passing as a drier for zinc-white paint (Martel 1859, 77). A varnish maker (Neil 1833, 55–56) valued dried zinc sulfate for its ability to remove “aqueous particles” from his varnish ingredients—oil, resin, and turpentine.

In 1835, Field recommended zinc sulfate over lead acetate but noted it was a less effective drier. He cautioned against the then apparently common practice of mixing the two, as he explained that the compounds zinc acetate and lead sulfate would result: zinc acetate was a poor drier, and lead sulfate was “insoluble and opaque” (1835, 56).

Regarding the drying power of zinc sulfate, Laurie (1895, 68) reported in 1895 that on its own it was quite ineffective and suggested that it was used in the past because of the presence of manganese (as an impurity), which did promote drying. However Laurie's position that zinc alone is “ineffective” is not true, for it does contribute significantly as an auxiliary drier:

Zinc driers are auxiliaries and are true driers almost in name only. Their effects are nevertheless highly advantageous. Zinc, in combination with cobalt, is used to prevent film wrinkling. This is accomplished by the ability of sinc to hold the film surface open longer and thus bring about a more uniform drying rate throughout the entire film cross section (Martens 1974, 398).

2.5 MANGANESE DRIERS

After the 1860s in Britain, widespread concern about the effect of lead compounds in oil painting materials was voiced by leading authorities who repeatedly warned artists that all materials containing lead were liable to darken and discolor as the lead reacted with hydrogen sulfide in the air. It was not simply white-lead pigment that was considered susceptible to sulfide-induced darkening: drying oils, media, or oil varnishes where lead driers were used were also cited (Carlyle and Townsend 1990). As a result of this view, lead driers were no longer recommended. The most popular alternatives were manganese-based driers.

Manganese as a drier for oils had been available for some time; it was first mentioned (in the texts consulted) in 1830 (Merim�e 1830, 58). In the 1850s it was recognized that earth pigments such as umbers and Cappagh brown owed their drying qualities to the presence of this material (Field 1850). The trade literature for color manufacturing indicates that there was a strong interest in manganese driers as early as 1874 (Riffault et al. 1874, 578–79), but it was not until the 1890s that the artists' colormen featured “manganesed oils” while warning artists in their catalogs against the use of drying oils made with lead-based driers. Apparently manganese driers were not generally recommended until there was a strong incentive to stop using lead compounds. Early references were to manganese oxide, but by the 1890s it appears that manganese borate was preferred (Church 1890).

3 ARTISTS' USE OF DRIERS

Thus far, the presence of driers in the commercial preparation of painters' oil and in drying oil has been detailed. In addition, a separate product was sold in bladders and tubes to be used by artists as they prepared their palettes. One early account (Fielding 1839, 71) of this prepared drier indicates that it was a mixture of lead acetate and oil:

Acetate, or sugar of lead, ground with boiled oil, poppy, nut, or linseed, can scarcely be called a vehicle, being merely used to force the slow-drying colors, such as Vandyke brown, Blacks, & c. to dry when frosty or cold weather prevents this very necessary operation from proceeding at the same rate with colors of better qualities. This mixture should be ground exceedingly fine, by which its desiccating properties are greatly increased. It is kept in bladders [and “metallic tubes” was added in the 1846 edition of this book] at all the color shops, and known by the name of “drier.”

Artists' colormens' catalogs regularly included sugar of lead or sacrum (synonyms for lead acetate) among their lists of oil tube colors; it is likely the “drier” referred to in the above quotation.

3.1 LEAD ACETATE

Aside from being available from the colormen presumably mixed with oil, lead acetate powder was sometimes used by itself, either being ground with oil and pigments or added to the painting medium. For example, one artist-author, Julius Caesar Ibbetson, recommended adding anywhere from one-sixth part up to equal amounts of lead acetate according to the pigment used (table 1).

TABLE 1. THE ADDITION OF SUGAR OF LEAD TO PIGMENTS

Field (1835, 57) remarked that artists “strew their pictures while wet with the acetate of lead,” and although he decried this practice, later in the same work he suggested that a weak solution of lead acetate in water might be brushed over the ground prior to painting to enhance drying in damp weather.

Of all the metallic compounds available as driers, lead acetate received the most attention in the sources. Like most detailed information on materials, this was confined mainly to books published before 1850.

Lead acetate had apparently been widely available in Britain since the 18th century. In 1758, Robert Dossie (1:152) provided instructions for making lead acetate from vinegar and metallic lead but noted, “It is to be had so constantly, and at so much less expence [sic] at the shops of chemists and druggists, than it can be made in small quantities, that is is needless to give any more particular recipe.”

Nevertheless, authors did caution artists on the quality of lead acetate to use: they noted that if it was to be used in the preparation of an oil varnish, it should be prepared from white lead rather than from litharge, since the latter contained impurities that could hamper the purity and transparency of the varnish (Neil 1833, 55). Artists were also warned that they should ensure the lead acetate had been dried before use and was afterward stored in an air-tight container because it was apt to pick up moisture from the air (Neil 1833; Cawse 1840). Others recommended that the basic lead acetate should be used rather than the more acidic variety, which was generally more pure and crystalline. To make the purest and most acidic variety more alkaline, one author advised adding litharge; this way it would be more effective and safer to use in oil (Field 1850).

Information from the 19th-century texts can in part be related to modern descriptions of lead acetate. Its molecular weight, melting point, crystallinity, and solubility vary considerably according to its method of manufacture. The basic salts formed are neutral lead acetate, basic lead acetate, lead acetate trihydrate, and lead tetraacetate. Lead acetate made from lead carbonate, or white lead, which Neil (1833) had recommended using, would likely have resulted in neutral lead acetate. Judging from the descriptions in the 19th-century sources overall, the lead acetate used was neutral, basic, or lead acetate trihydrate (Kirk-Othmer 1981).

Nineteenth-century authors noted that the more finely ground in oil, the better lead acetate's drying properties, and many recipes recommend dissolving it first in water. A number of sources warned that lead acetate should not be used in its crystalline or granular form, since as one early 19th-century author remarked, it will “ultimately effloresce on the surface of the work, and throw off the colour in sandy spots” (Field 1835, 56). This same phenomenon was described in a late 19th-century source:

I have seen one of the results of this commingling of sugar of lead with the medium or the paint in the production of an immense number of small spots in the picture, sometimes appearing through the surface varnish in the form of a white efflorescence (Church 1890, 94).

A modern description of neutral lead acetate confirms that it slowly effloresces but notes that it becomes “incompletely soluble” as it takes up carbon dioxide from the air, which implies that its propensity to effloresce may change in time (Budavari et al. 1989, 851).

Other authors warned, in more vague terms, that lead acetate may “injure the colours.” However, leading authorities such as Sir Charles Eastlake and George Field agreed that problems with this material were related to its use in excess. Eastlake (1847, 1:350) wrote, “The extreme case of its [lead acetate] visible efflorescence can only occur when it is used in unnecessary abundance,” although he did note, “The use of acetate or sugar of lead is further dangerous, on account of its tendency to recrystallise, thereby rendering the transparent colours dull.” In his copy of Eastlake's first edition (now in the Canadian Conservation Institute Library), Field added a handwritten comment to this section, “The objections against it arise chiefly from using it in excess.”

It is important to note that lead acetate may also have been present as an intentional addition during the manufacture of artists' materials. For example, one 19th-century source complained that up to 3% lead acetate was being added to artists' white-lead paint. The reason, oddly enough, was to keep the white “from growing hard in the tubes” (Scott Taylor 1890, 40). This author was writing in 1890; whether that practice had begun much earlier is not known.

This curious reversal in the use of lead acetate to retard drying had been recommended by Ibbetson (1828) for vermilion. He advised that nearly an equal quantity of lead acetate should be added to vermilion because “the sugar of lead prevents the vermilion from becoming hard.” The only possible explanation for this was alluded to by Field (1835), who noted that an excess of drier would inhibit drying.

3.2 LEAD DRIERS AND GELLED MEDIA

Lead compounds were popular as driers because they were cheap, available, and the most effective. However, there was another very important reason why lead driers were favored: lead-treated oils, in the presence of certain resins, will gelatinize. This property was exploited to form gelled painting media that would influence the handling properties of the paint. These buttery transparent gels were used to enhance the paint's brushability and to achieve transparency (Carlyle 1991, 1).

Megilp, the best known of the gelled media, was made by mixing drying oil (prepared with lead) and fairly concentrated mastic varnish. The ratio was usually either 2 parts oil to 1 part varnish or an equal mixture of both (Townsend et al. 1998). A variation of megilp that was initially known as “gumption” was sometimes called white megilp. In its original form it was made by grinding lead acetate powder and mastic resin in linseed oil. Although subsequent recipes varied, this medium was usually distinguished by the use of lead acetate (instead of other lead compounds) with otherwise untreated oil. According to the 19th-century authors, the advantage of lead acetate was that it could be added to the oil without heating and would therefore result in a less-colored product.

Recipes for megilps were provided in the sources throughout the century, and these products were also available ready-made from the colormen. One of the most popular was a formulation sold by the artists' colormen Roberson and known as Roberson's Medium. To ensure that the more intractable resin, copal, would form a gel, this recipe specified a copal oil varnish that had been boiled a second time with extra red lead and litharge, and mastic varnish was included in the recipe (Roberson recipe, transcribed in Carlyle 1991, 2:338).

3.3 GLASS AND SMALT

The author of a 17th-century oil painting manual noted that “the whitest glass” ground to an impalpable powder would “dry all Colours without drying Oyle, and not in the least Tinge the purest Colours, as White, Ultramarine, &c. and is much us'd in Italy” (Smith 1693, 73). Two sources close to the turn of the 19th century mentioned that powdered crystal (leaded-glass) was an effective drier (Practical Treatise 1795; Compendium 1808). In 1835, Field (81) noted that yellow orpiment was believed to be affected by the use of oil treated with lead driers and that “levigated glass” had been used instead as a drier. Smalt, too, was held to be a strong drier, and on that basis one author recommended that 1/20 part of smalt was to be added to ultramarine in the winter to assist its drying (An American Artist 1845). References to the use of powdered glass or smalt as driers were not found after 1845.

3.4 SICCATIFS

There is one other category of driers that became available commercially to British artists in the last half of the 19th century. These were the “siccatifs” such as Siccatif de Courtrai and Siccatif de Harlem.

Siccatif de Courtrai was described as a powerful drier: one source warned artists away from its use since it was “a very dangerous mixture, heavily loaded with compounds of lead” (Church 1901, 111). Vibert (1892, 83) considered it “dangerous” because Siccatif de Courtrai contained turpentine and therefore tended to be used like a diluent, encouraging artists to use excessive amounts. Siccatif de Harlem, was based on copal resin and, according to Vibert (1892), contained only oil of spike with the copal. It apparently produced a hard, brilliant, and tough film and could be used either as a medium or a varnish. From the description of its applications given in a Lechertier, Barbe & Co. catalog from 1879, it sounds similar in use to a medium. Although intended to function as a drier, descriptions of Siccatif de Harlem indicate that it was simply a resin. Vibert (1892) explained that it only appeared to help the paint dry through its own evaporation and, unlike a true siccative, did not provide oxygen for the oil.

3.5 VARNISHES AND THE RESINATES

There are a few occasional references to the use of varnishes to assist the drying of paint. One author had described a mixture that was predominantly mastic resin with a small proportion of nut oil and alum meant to act as a drier for ultramarine and the lakes (Merim�e 1839). In addition, there was another class of driers presumably initially used by house painters—the resinates or rosinates. These contained a metallic compound such as lead or manganese mixed with rosin (colophony). References to these driers did not appear in artists' manuals until after the turn of the 20th century (e.g., Church 1915, 113). According to a modern account (Elm 1934, 387):

When in 1885 the so-called soluble driers (the fused and precipitated linoleates and resinates of lead and manganese) made their appearance, the industry was very slow in accepting them. … This may have been caused partly by the difficulty of manufacturing entirely satisfactory soluble driers of this type.

3.6 PROBLEMS WITH DRIERS AND PIGMENTS AS DRIERS

Throughout the literature consulted, authors warned of problems associated with the use of driers. The darkening of pigments and media associated with lead driers and the formation of lead sulfide have been discussed above. Other problems were attributed to excess amounts of driers. As Field (1835, 56) explained, the use of too much drier “renders oil saponaceous, is inimical to drying, and injurious to the permanent texture of the work.”

Field's reference to the texture of the work being affected by an excess of drier may relate to a condition described in a modern source (Martens 1974, 404) as “seeding”:

The occurrence of an unexpected and undesirable rough-textured appearance of the coating surface after drying [seeding], is caused by an incompatibility of ordinarily soluble formulation components. This condition, although occasionally caused by a reaction of lead driers with acidulous vehicles, is more often brought about by other sources such as the presence of highly polymerized particles of vehicle or moisture contamination.2

In recognition of the dangers associated with the use of driers, Field attempted to tailor the use of drying agents more specifically to the requirements of individual pigments (table 2). There were also occasional attempts to avoid their use altogether. For example, one author recommended that artists add small amounts of fast-drying pigments to pigments that were slow drying (table 3). Artists also were advised to paint their first layer of paint (called the dead coloring) with fast-drying pigments exclusively, choosing from lists of the appropriate pigments (table 4).

TABLE 2. SPECIFIC DRIERS FOR SPECIFIC COLORS

TABLE 3. ADDING FAST-DRYING PIGMENTS TO SLOW-DRYING PIGMENTS

TABLE 4. QUICK-DRYING AND SLOW-DRYING COLORS

4 DRIERS: SUMMARY

The only lead compound, and indeed the only metallic drier, that was offered in 19th-century artists' colormen's catalogs as a separate product, until the last decades of the 19th century, was lead acetate. It was also the most frequently mentioned drier in the artists' instruction books and handbooks. It is only through descriptions of the preparation of drying oils that we learn of the use of litharge, white lead, and red lead. Except in a passing reference to decorative painting, litharge was not suggested as an addition to paint, and other lead compounds, such as red lead and white lead, were not generally recommended as driers per se but did receive occasional mention as additions to slow-drying pigments to enhance their drying properties (see table 3).

Other materials, such as zinc and manganese, would have been added during the commercial preparation of drying oils. Zinc was used throughout the period under study as a drier in its own right, and manganese, apart from its presence in certain pigments used as driers, was introduced into artists' materials as a specific compound only late in the century, primarily as a replacement for lead.

Considering the number of avenues by which driers may have entered an artists' paint or medium, during the processing of the raw materials, in the commercial preparation of the paint and media, and by the artists themselves, it would be expected that at least some of the paint film defects in paintings from this period are associated with the excessive use of driers.

5 CONCLUSIONS

It will no doubt be some time before we as conservators and researchers are able to positively relate the use of specific driers with specific paint defects in the works we study and treat. However, by knowing what materials were available, and when, we can at least begin an exploration of these questions.

NOTES

1. The term media is being used here to conform to JAIC style. However, the author prefers the term mediums.

2. Some years ago two 19th-century oil paintings exhibiting disrupted surface textures that could correspond to this description of “seeding” were studied at the Canadian Conservation Institute (CCI). In both, many tiny inclusions in the paint could be seen, which were responsible for the texture effects. These particles were identified as consisting primarily of lead soaps (CCI 1992). Since the mechanism for their formation was not established, it was not clear whether lead based driers were responsible for this defect. Recently, similar inclusions in Rembrandt's Anatomy Lesson of Dr. Nicholas Tulp (1632, Mauritshuis, The Hague) have been investigated where lead soaps, fatty acids, diacids and a large quantity of lead chloride hydroxide were found in the inclusions. Researchers (Noble and Wadum 1998) hypothesize that treatments on linseed oil to render it more drying could be responsible. Further research is needed to establish whether the 19th-century inclusions which are morphologically very similar to those found in the Rembrandt result from the same mechanism. See also Campbell 1997.

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AUTHOR INFORMATION

LESLIE CARLYLE has a B.A. in art history and theater arts from Queen's University, Kingston Ontario, 1973; a bachelor of fine arts (studio art), Concordia University, Montreal, Quebec, 1975; and a master of art conservation, Queen's University, Kingston, Ontario, 1979. She was assistant paintings conservator at the National Historic Parks and Sites from 1979 to 1980. She joined the Canadian Conservation Institute (CCI) as a paintings conservator in 1980. In 1987, she was granted educational leave to pursue a Ph.D. in the Technology and Conservation Department of the Courtauld Institute of Art in London. She resumed her position as paintings conservator with CCI in May 1991. She received her doctorate from the University of London in September 1991. In 1995, she transferred to the Conservation Processes and Materials Research Division at CCI in order to carry out research as a materials historian.

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