Update on Oil Painting Mediums

old oil paints

(Published in The Classical Realism Journal, Volume VIII, Issue 1.)

One of the most frequently discussed topics among oil painters is oil painting mediums. There exists a wide diversity of opinion and preferences on the subject, both in books and from artist to artist, with certain mediums enjoying almost cult-like advocacy. Much information has been published on the subject, some written by persuasive authors, many of whom disagree with one another on many points, resulting in a great deal of confusion over which ingredients are best for a given painting style. As in most things, the issue is not as simple as it might seem. It must go beyond focusing on the mediums alone, and begin with the reasons painters feel they need them in the first place.

Some commercially available oil paints, as they come from the tube, are of a stiff consistency that does not facilitate the utmost in control, and thus require the addition of something to improve their brushing qualities. Enter painting mediums. It is important to note that in the days of the Old Masters, the paints were ground in the artists' studios, by the artists and/or their apprentices, in all likelihood to the desired consistency for optimum control under the brush. In such an instance, there would be little or no need to add any medium at all. This hypothesis seems to be borne out by scientific testing conducted by the National Gallery,in London, on many of the paintings in their possession. The preponderance of the 16th and 17th century paintings tested showed no detectable resin content in the paint layers, to the surprise and disbelief of so many who had read 19th and 20th century accounts alleging that specific artists of the earlier times used mediums containing natural resins like mastic, copal or amber. What was found, in most cases, was pigment bound in linseed oil, and in some cases, walnut oil. The indication is that the addition of resin varnishes to oil paints as a common practice dates back to perhaps the mid-1700s, and no farther, with certain individual exceptions. Of course there are many unanswered questions, and the possibility remains,at least theoretically, that the testing methods used were simply unable to detect the resins that might actually have been there. Thus it is not necessarily a closed issue, at least in the minds of those mistrustful of science. But if the current prevailing opinion in the conservation science community is correct, as the best evidence strongly suggests,there may well be a correlation between the widespread use of resinous mediums and the introduction of pre-prepared oil paints on the scene.

To artists making their own paint, the only concern would have been the quality of the paint, but to those in business to make a profit selling paint, the temptation to add less expensive ingredients to keep production costs down was very strong. It is known that many adulterants and fillers were added to paints sold ready-made by artists' color men, and this undoubtedly affected the brushing qualities of the paints in question. The need for mediums to improve the consistency of the paints seems to have grown from this. In modern times, manufacturers add aluminum stearate, a soap, to mitigate the tendency for oil and pigment to separate in the tubes as the paints sit on store shelves or in artists' paint boxes. Aluminum stearate changes the oil from a fluid to a more colloidal consistency, and changes the way the paint handles. However, some manufacturers exercise greater restraint in the use of such substances than others, and artists have choices. With this in mind, the painter of today can get by with less medium simply by choosing less stiff paints to begin with, or by grinding his or her own, as was done in the days of Rembrandt and earlier. There are a number of quality paints currently on the market that exhibit a fluid consistency as they come from the tube, and require little or nothing to be added to them in order to be controllable. Should they require a bit more softening, a drop of linseed or walnut oil may be all that is needed.

From a structural standpoint, the strongest paint layer is one with the optimum ratio of binder to pigment. The best commercially available oil paints are already very close to this ratio. Adding too much of any medium is likely to produce weak spots in the resulting paint film for lack of sufficient solid matter, just as a wall made with poorly fitting stones and too much mortar will be weaker than one in which the stones fit more closely together and a minimum of mortar is used.

Natural resins were long thought to impart desirable properties to oil paint films, but this belief may well be in error, at least as far as permanence is concerned, as each introduces its defects into the paints to which it is added. Discoloring and embrittlement over time are chief among these defects, which are well documented in art conservation circles.The prevailing opinion there, based on the best information to date, is that the paintings composed of simple combinations of linseed oil and pigment are more durable and less problematic over the centuries than those containing significant amounts of any of the natural resins. The works of Rembrandt and others seem to bear this out. Of course, in the world of science, there is always the possibility that new information will come to light that will warrant the revising of opinions. Research is ongoing.

National Gallery Technical Bulletin, Volumes 15 and 17, National Gallery, London Rembrandt: The Painter at Work, by Ernst van de Wetering, published by Amsterdam University Press Art in the Making: Rembrandt, by David Bomford, Christopher Brown, and Ashok Roy, with contributions from Jo Kirby and Raymond White, published by the National Gallery, London On Picture Varnishes and Their Solvents, by Robert L. Feller, Nathan Stolow, and Elizabeth H. Jones, published by the National Gallery of Art,Washington, D.C.

©Virgil Elliott, 2002

Technical Innovations of Rembrandt

Rembrandt self portrait

Rembrandt Harmenszoon Van Rijn, who many consider the greatest artist of all time, learned all that was then known about oil painting while still a very young man, surpassing his teachers very early in his career, and then proceeded to add his own discoveries to the technical knowledge of his time. To this day Rembrandt’s best works remain unsurpassed, and serve as inspiration to those of us who paint. This being the case, any book on advanced techniques must address Rembrandt separately and at such length as the author's knowledge allows.
What technical information Rembrandt was taught may be discerned by studying the works of his instructors, Jacob Isaacxszoon Van Swanenburch and Pieter Lastmann. Such study also immediately shows the genius of Rembrandt by the extent to which he so obviously surpassed them both, and by how early in his career he did so.  Nonetheless, his training under them was an important factor in his artistic development, and should not be minimized, as both teachers seem to have possessed a working knowledge of the painting methods in use at that time. Various examples of Rembrandt’s work show that he was not limited to any one technique, but employed them all, the choice depending on which approach best suited the subject in question, and for what purpose the painting was intended. His facility with all three of the aforementioned methods of painting soon led him to combine aspects of one with another, and to add innovations of his own.

Some of his paintings are on wood, executed in what appears to be essentially the Flemish Technique; some small studies on wood panels were done in a variation of the direct painting technique, and some on canvas in methods similar to the Venetian and direct techniques. The first layer of primer for the panels is one or another type of glue -chalk gesso, sanded to smooth out the irregularities of the panel’s surface. Subsequent layers might consist of finer-textured chalk bound with hide glue, or white lead oil paint. The final layer was usually covered with a transparent brown imprimatura, which creates the golden glow characteristic of his work. The majority of Rembrandt’s canvases are primed with a double ground, the first layer of which is a red-orange ochre bound in oil, perhaps to fill the texture of the canvas, then overlaid with a gray made from lootwit (lead white with chalk, ground in linseed oil) and one or more other pigments . Clues as to his choice of primer may be seen in areas where he has used a sharpened brush handle to scratch through wet paint in order to indicate bits of hair. This is evident in a very early self portrait, now in the Rijksmuseum, and in many other portraits as well. The primers and/or imprimaturas thus revealed show that he followed no one single procedure, but varied the choices, based on the effect he was after.  The scratching with a sharpened brush handle into wet paint was one of his earlier innovations.

Rembrandt was an extremely versatile artist, who did not follow the same procedure every time. It’s fairly obvious, to the educated eye, that he thought his way through each painting, from the genesis of the idea to the last brushstroke, never lapsing into a routine approach.  From unfinished pictures, we know that, at least sometimes, he began in transparent browns, working in monochrome to establish the design of the picture, attending to the masses of dark and light. He often used opaque white for the strongest lights in this stage, in his version of an imprimatura. This stage was apparently left to dry before further work was done, though there may well have been exceptions. Over the dried brown underpainting, Rembrandt began adding color, working from the background forward rather than working over the whole picture at once.  He exploited to the fullest the qualities of transparence and opacity, relying on the underglow of light coming through transparent color for many special effects, building up opaque lights more heavily for the brightly lit areas, sometimes modifying colors by means of subtle glazes, semiglazes or scumbles, and arranging transparent darks and opaque lights to play against one another for maximum visual impact and depth.

Early in his career Rembrandt began building up the opaque passages in his lights more heavily, and texturing them to take on the physical convolutions of the lighted surfaces of his subjects, most notably the skin textures of male subjects, including himself. Exactly how he created this texture is not known with certainty. It can be duplicated or approximated by building up a somewhat thick layer of opaque paint, then passing a soft brush over the surface while it is still wet. At some point Rembrandt began to superimpose glazes of red over these textured passages when they were dry, then wipe them off with a rag, leaving traces remaining in the low spots to create an even more convincing texture of rough flesh. A contemporary once said that a Rembrandt portrait could be picked up by the nose.
As Rembrandt began to expand the effect of glazing over dried impasto to include other textures as well, he devised a method employing two different whites; one for impasto and one for smoother passages. The latter seems to have been composed of a high grade of white lead, ground in unheated linseed oil, or less frequently, walnut oil. The impasto white would have been faster drying, perhaps made so by the addition of chalk, and/or ground glass (probably smalt). It was very lean, and consisted mostly of white lead with a minimum of binder.  He began applying it more and more heavily as the first stage of a two (or more) stage operation, which was finished with transparent glazes and wiping. This technique created fantastic special effects, the most extreme example of which is the man's glowing, golden sleeve in the painting referred to as "The Jewish Bride," in the Rijksmuseum in Amsterdam. The brilliance of this effect cannot be achieved in any other way.  Rembrandt used the same technique on the bride's costume in the same painting, but here the underpainting contains vermilion, which is deepened with a glaze of a red lake, carmine (cochineal), and ground glass (possibly finely ground smalt, used as a transparentizing pigment as well as for its drying effects) bound with linseed oil .  The red carpet on the table in “The Syndics of the Drapers' Guild” (sometimes called "The Dutch Masters"), also in the Rijksmuseum, is done in much the same way, but with an earth red probably used in place of vermilion.  The impasto underpaint appears to have been trowelled on with a knife or some sort of flat stick, then sculpted before it dried.

It appears that Rembrandt worked into the wet underlayer with sharpened brush handles and other tools while the paint was soft, and then allowed it to dry before applying the darker glazes. By wiping the glazes off as soon as they were applied, leaving them only in the nooks and crannies, Rembrandt was able to create a bas-relief effect of remarkable three -dimensionality. By glazing these areas again, this time with transparent yellows and/or browns, he gave the textures a rich, sparkling golden glow. In The Night Watch, Rembrandt used this method, but with less heavy impasto, for the ornate brocade work on Lieutenant Ruytenburch’s yellow tunic.

Scientific analyses have provided some major revelations in recent years regarding Rembrandt’s working methods and materials. A number of reports indicate that he added body and transparence to his glaze-like passages by mixing in a bit of chalk and/or ground glass. The chalk functions as an inert, and essentially transparent, pigment when mixed with oil, and also serves to enhance the drying characteristics of white lead and other paints. The glass most likely would have contained lead and/or cobalt, both drying agents .  The glass, which was perhaps used as a bulking additive, among other functions, may have been ground leaded glass (crystal), or a low grade of smalt. The latter is less blue than the better grades of smalt, which were used as blue pigments in the seventeenth century, and lower in tinting strength, so it could be mixed with any color without altering its appearance noticeably. Rembrandt also appears to have used another blue pigment, azurite, as a drier, added to paints whose pigments normally dried much more slowly in oils, including ivory black and madder lake in particular.
From the eighteenth century up until the last few years, painters and writers could only speculate on what sort of medium Rembrandt used to achieve his startling and unusual optical effects, with nothing more to go on than appearances. On this basis, just about everyone assumed that there had to be resins, and perhaps exotic blends of oils cooked with lead and/or various varnish resins, as media in Rembrandt’s paints. Some suggested wax as another possible ingredient; again, based solely on visual analysis. Modern science has recently made some discoveries that shed more light on this issue, and we now have a much clearer, albeit not totally conclusive, picture. The binder detected, according to the most up-to-date scientific analyses, is linseed oil in the vast majority of the many paint samples analyzed, with few instances of it being heat-bodied. Walnut oil was sometimes found, but in most instances it was linseed oil, with no wax, no resins, no exotic alchemy concoctions. In a few samples, some of the oil is reported to have been “heat-bodied,” as in perhaps boiled or stand oil. It is possible that these were added to the paints in which he wanted a long brushing quality, and perhaps in some of his glazes. Reinforced with chalk for body, and ground glass for body, faster drying and perhaps transparency, these appear to comprise Rembrandt’s glazing media, as nearly as is discernible by the present level of scientific knowledge, which, it must be noted, is subject to change at any time, as new discoveries are made. A resin or balsam, as yet not identified as to specific type, but tentatively suspected to be pine resin, has recently been detected as the vehicle in one sample from the brown glaze on the man’s sleeve in The Jewish Bride. Subsequent tests may well bring new information to light that bears on Rembrandt’s glazing media.
Rembrandt’s palette consisted of a black (perhaps bone black or ivory black, less frequently charcoal), a number of earth colors (ochres, siennas and umbers), Cassel earth, lead-tin yellow, occasionally vermilion, a number of yellow and red lakes, high-grade smalt (used as a blue), azurite, flake white (schulpwit, a higher grade of lead carbonate without chalk), and lootwit (lead carbonate with chalk). His brighter reds are more frequently earth reds, intensified with red lake pigments mixed into them, although he sometimes used vermilion. Rembrandt also often intensified his earth yellows with yellow lakes in the same way, for brighter yellows.  In Rembrandt’s method, the evidence indicates that drying was accomplished by adding fast-drying pigments to his mixtures where they were needed. The principal pigments used for this purpose were smalt, azurite, umbers and white lead.

Aside from his innovative special effects, Rembrandt’s basic technique was much the same as that of his contemporaries. The lights were painted most opaquely, employing thick impasto highlights from a heavily-loaded, somewhat large hog-bristle brush, while he rendered the deepest darks more transparently, adding dark opaque touches in those areas while the larger, transparent dark masses were still wet. He generally painted the lighter shadow areas with opaque paint, but applied more thinly than the lights. He adjusted edges for their proper degree of softness or sharpness while the colors on both sides of them were wet. The highly refined imagery of his younger days gradually gave way to a rougher, more painterly finish in his middle and later years, perhaps due to changes in his eyesight, but his basic methods of working remained essentially the same throughout his life.

Rembrandt probably had at least one life size jointed mannequin, on which he would pose the clothes of his sitters.  The mannequin, unlike a living person, would remain motionless for as long as was needed to paint the clothing, the folds of which would remain essentially undisturbed for days, or weeks, if necessary.  A live sitter would have to visit the bathroom, eat, sleep, move around, etc., after any of which the folds of the cloth would never be likely to asssume their previous shape.  The use of the mannequin may or may not have been Rembrandt’s innovation, but it was, and is, a good idea regardless.
Technical issues, however, are not the essence of Rembrandt. Of the unique attributes that elevated him above all other painters of his time, if we may analyze these assets of his individually, perhaps among the most significant was his complete mastery of selective focus, or houding, as the Dutch term it. Rembrandt demonstrated mastery of that particular aspect of image-making so completely that it set him apart from everyone who preceded him, and most of those who followed, with the possible exception of Johannes Vermeer of Delft, whose understanding of that principle was shown to be equal to Rembrandt’s. There is a possible connection between them, in that Carel Fabritius, who had studied with Rembrandt, lived in Delft, and undoubtedly knew Vermeer. But beyond selective focus, Rembrandt had the most profound sensitivity and perceptivity into human emotions, an empathy that charged his portraits with the thought-provoking psychological depth that is universally considered as his trademark, his most distinguishing characteristic. That is not something one can get from reading a book about painting. We cannot expect to be able to rival the great genius of Rembrandt merely by following some of his procedures and using the same tools and materials he used. These are only a small part of his brilliance as an artist. At the core was his intelligence and artistic sense, his constant striving to improve upon what he had already done without losing sight of the original concept for the painting, and to devise techniques, on the spot, that would create the effect he was after. We might hope to achieve our own personal best results by adopting this same attitude towards our work, rather than by attempting to reduce the methods of a great genius whose works we admire to a simple formula and then following it, unthinking. This is not meant to disparage technique, but to show it in its proper context. The more we know of technique, the more effects we have at our disposal, to serve our creativity and inspiration in the execution of our finest conceptions. If there is anything remotely approaching a formula for creating Great Art, it might be stated as the combination of knowledge and intuition in a single endeavor, plus a lot of work.


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