On one occasion when I was troublesome to my master Rembrandt, by asking him too many questions respecting the causes of things, he replied very judiciously: "Try to put well in practice what you already know; in so doing you will, in good time, discover the hidden things which you now inquire about."

      -- Van Hoogstraten, Inleyding, translated by Eastlake.

As in all things human, there's no free lunch with oil painting materials. The process is about making the most appropriate choices and compromises for a goal which is often receding as fast as we are moving towards it. As in life, the truth with regard to oil painting technique is often complex: attempts to reduce it to the yes/no framework of Aristotelian logic result in a false simplicity from the false strength of the "logic" itself. Sometimes this situation is well-meaning, but more often it is misleading for a commercial purpose. True simplicity is the result of true understanding, but, paradoxically, true understanding is the result of a thorough exploration of complexity. To accept someone else's results in this field can abrogate one's own native possibilities for creative development. Whether, as a painter, one's field even includes the craft and to what extent is of course a personal decision.

       Older paintings were usually made with materials manufactured by the painter and/or the painter's workshop. Modern paintings -- nineteenth and twentieth century work -- are more typically made with materials purchased at the art supply store. It is still possible, of course, to choose to make one's own materials as part of the process of making a painting. This path is in the interesting position of being culturally sanctioned for dead painters, but often held to be equivocal for living ones. But if you are intrigued by the how and why of older painting techniques, if the process shares the stage with the product, the information that follows may be interesting.

Starting in 2002 I became involved in exploring the materials used in older painting. This unusual combination of research and snipe hunt ultimately developed a life of its own which was fun if a bit obsessive at times. At the end of 2006 I realized that, just a suddenly as it had begun, the more active part of this search was over. This was due to the realization that no Holy Grail existed: I had reconstructed many older ways of working and the next step was to explore one in depth. This decision quickly proved effective in terms of the work. Although most of the emphasis in this department is usually on resins and mediums, I found that I made the most progress ultimately by addressing the oil itself. This brings up the subject of balance, and the way older methods and materials existed as a gestalt or family. I found that by eliminating raw oil from the process, and always using oil which had been, in the words of the National Gallery Bulletins, slightly heat-bodied, I was able to work with much less hard resin (amber, copal, or sandarac) involved because the reaction of the resin was dramatically enhanced by the heat bodied oil. This oil is not thickened significantly, and using modern methods can be made without darkening, but it creates paint with a different rheology than modern tube paint. This also helped to create paint which dries quickly with a minimum addition of resin or drying oil. So, the family of materials that came together, using the Strassburg Method (see Formulas) as a point of departure, is:

• Panels covered with linen and glue gesso made with titanium white, quartz, and marble dust.
• Paint made with various heat bodied oils.
• Small amount of hard resin added to the paint on the palette. Usually amber, homemade from light-colored Latvian jewelry waste.
• Paint on the palette may be further enriched in finishing layers with small addition of walnut sun oil, usually dark colors.
• Initial layers thinned with turpentine, subsequent layers thinned with painting oil (see Formulas for recipe).
• Very thin couch used in final layers using Fir Medium (see Formulas).
• Intermediate layers sanded lightly using 400-600 paper (see Formulas).
• White made with heat bodied oils and various combinations of lead carbonate, marble dust, and ground leaded glass. No hard resin varnish is added to the white until possibly in the final impasto stage.
• Various impasto mediums based on exposure-thickened Eminent Oil and/or walnut sun oil with inert additions of calcite, marble dust, and/or ground leaded glass used in the final layers.

In the winter of 2006-2007, after getting a copy of the Rembrandt book from the National Gallery "Art in the Making" series, I began more actively working on a system involving just oil, no resin, following the technical findings of the book with regard to Rembrandt's paint. This system has progressed in the year of 2007 to encompass materials that were beyond anything I could have imagined. But then, I was prejudiced in favor of resins, and had a limited imagination with regard to oil. In 2008 I'm continuing to refine what can be done with a simple mixture of stone dust and oil, it continues to boggle my mind. Commercial putties are beginning to appear, a commercial silica gel has appeared. The important thing to understand here is that these are easy materials to make, and make to exactly your own way of working. The crucial factor is the quality of the oil.

It turns out that a great many different rheologies can be created by variations on refining, heating, aging, sun-thickening, and adding traditional driers to the oil.

So much about painting works against system: it's at least good to have one in mind. There are two I use, and they are opposites. The first is an alla prima system which starts from a warm, dark, transparent, medium-rich underpainting and moves towards cool, light, opaque paint through translucent midtones. Because the paint is going on in one continuous wet-in-wet layer, this system can use a rich, thixotropic medium with as much abandon as I can effectively handle. I use this technique for studies from life in the studio and for landscapes outside.

      The second system uses layers and works from cool towards warm. The underpainting is done in black and white with a small amount of red earth for the shadows. The values in the underpainting are kept very high, with no true darks. As the painting progresses, the values drop slowly: the medium becomes richer, and the darks become darker while still maintaining transparence. In the final layers, impasto can be built up in the lights.

The search for lost secrets began in earnest in the first half of the nineteenth century, both Eastlake and Merimee conclude that older paintings had fared better over time due to their hard resin content, the use of amber or copal varnish in the paint. Eastlake traced the addition of a resin varnish back to the fifteenth century Strassburg Manuscript, and in England in the nineteenth century a hard resin revival took place, amber and copal mediums being popular as well as various varieties of mastic gel medium. Modern research done by the National Gallery in London on older paintings has turned up very little in the way of hard resin used in the paint: some pine resin in Van Dyck but no mastic even, a few soft resin glazes in Rembrandt but almost all paint samples simply reading as linseed oil. Velásquez has long been known to have used simply calcite and sun oil. There has been an undercurrent among painters and scholars that the research wasn't "finding everything". Given the nineteenth century involvement with resin and old master effects, this may seem logical. But the research has found sandarac varnish layers that are approximately five centuries old, one a spirit varnish and one an oil varnish. In this context its important to note that the nineteenth century was also involved in commercially prepared paint made with raw oil and further modified to prevent it from drying in the tube. Experience has shown that it's possible, using various combinations of modified oil, to produce the sculptural and thixotropic effects associated with hard resin varnishes: see below. The key to this is that the paint itself -- and/or the putty medium -- must be made with what the National Gallery Bulletins call a "slightly heat-bodied oil". This paint has inherently more body and saturation than raw oil paint. The use of raw oil paint can lead to the perceived need for resin.

      De Mayerne recorded that Gentileschi used amber varnish, and De Mayerne himself was an amber enthusiast. But the Gentileschi painting analyzed by the Getty proved to be made with copal varnish. For me the summary effect of all this information has been to question how much these secrets have been lost, and how much many of them have simply been found. There are many ingenious combinations of materials possible, especially in the realm of resins and gels, it goes on and on. But it seems to get art tangled up in the idea that a specific form of arcane knowledge is necessary for the success of an endeavor. But real art and real painting exist beyond the realm of ideas, in the realm of commitment. The search for secret ingredients and formulas is not a substitute for the genuine practice of the craft. This is the essence of Rembrandt's advice to Van Hoogstraten: the authentic craft develops naturally from one's own experience. So, it seems reasonable to suggest that the search is not for various "lost secrets", but for one's own practice. It is in fact easy to simply start making materials. At first they may not be great, but a realer process has begun.

In the winter of 2007, I took the Allback Organic Cold Pressed Swedish Linseed Oil and refined it according to the instructions in De Mayerne, Eastlake, Merrifield, et al, using water, sand, and salt. It took six weeks for it to stop expelling, the final wash was with water. The final oil was lighter, but slightly cloudy. I then put various inert substances of the literature into it, including barytes, marble dust, and bread crumbs, but clarification happened quickly, along with an element of lightening, when I added a small amount of lead carbonate, again one of the historical additions recommended in De Mayerne. Comparison photo of the oil as it arrives and the lighter oil after processing. The processed oil is thinner, having been essentially de-fatted. It also seems to dry differently, not forming a skin but thickening throughout. It also dries much faster than the raw oil, which I'd point out in the context of the current interest in unrefined oil. Beyond this I haven't gone yet, as of July 2007, but there are still several avenues to explore even at this stage. In a situation where someone actually knew what they were doing, this process would still take at least two months. Somehow I don't see this as the starting point of any modern manufacturing process.

      There are many paints which are still made with linseed oil. Sometimes the manufacturers point to recent research which shows, for example, that Rembrandt's medium was principally linseed oil. However, Rembrandt's medium was not the alkali refined oil expressed by heat of modern commerce. So, just from the point of view of that battered immensely inconvenient old problem, the truth, it's important to realize that commercial tube paint, whatever the claims of the manufacturer and well-known modern artists who use it, is still commercial tube paint, with a specific set of pros and cons by its very nature. While it may be made with linseed oil, that oil is very different than the linseed oil used by older painters.

The first linseed oil I refined by washing it with salt, sand, and water, is almost a year old. I've been keeping it in the window. The recent samples taken a month ago appear to be yellowing less, this is about at the yellowing rate now of refined walnut oil. A test I made using the acid activated bentonite bleaching clay of commerce has finally cleared after months and lost all color. It is very slow to dry, though, logical. But might prove a good starting point for another procedure. The experiments with an oil treated with litharge have proven to give the oil which dries the fastest of all linseed oils made in the tests, about 48 hours in winter, low heat but also low humidity. This also appears to yellow less as it ages: even two to three months aging produces an oil which yellows at the low rate of refined walnut oil, perhaps less. The cold leaded oil also dries differently, has very little tendency to form a skin in the usual manner.

      At this point it seems like the most crucial factor is the cold-pressed organic oil and aging in sunlight after processing. While neither of these processes yields, for example, something which dries as truly clear as the long-to-dry sunflower oil, they both yield oils which are pale straw color on drying and dry quickly: the washed in three days, the cold-leaded oil in two.

I placed all the oil I originally washed in the windowsill. some was closed, some was open to the air through a lid of folded cheesecloth. This oil has become a pale straw color, just noticeably lighter than the remaining oil, which has also lightened over the year. I've been using this oil in various putty formulas for the last few months, it dries quickly and hard. Yellowing tests show it to yellow at about the rate of walnut oil.

"Heat pre-polymerization has several effects on the oil. Drying properties are improved and are further enhanced by the addition of metal salts (usually those of lead) during the process. The refractive index of the oil is increased, thus reducing light scattering at the pigment-medium interface and thereby increasing the saturation of the pigment colour; the paint film may also have a glossier appearance. The pigment is less liable to sink in the oil film, which itself decreases less in volume than a conventional oil film, reducing the amount of wrinkling that may occur. White paints appear less discoloured because, as the polyunsaturated fatty acids initially present in the paint film are destroyed by the formation of carbon-carbon single bonds, there is less scope for the formation of chromophoric and auxochemic groups, the presence of which give the yellow appearance to the film." From Rembrandt and his Circle: Seventeenth-Century Dutch Paint Media Re-Examined by Raymond White and Jo Kirby. National Gallery Technical Bulletin volume 15.

An example of paint made with "slightly heat-bodied oil". Also an example of something that is a genuine aspect of older painting. I make it relatively soft for a longer life in the tube but the body given the paint by the heated oil is still quite apparent: no other ingredients, just pigment and oil. This is old Mount Amiata Raw Sienna, a great color.

This is made with finely ground calcite or marble dust mixed with a mix of semi-heat bodied and sun walnut oil. It can be made in any degree of thickness and acts as an immobilizing medium in various degrees. It can also be thinned with solvent or a small amount of thinner oil. This should be tubed for long term storage or made fresh on the palette. There are many different varieties of calcium carbonate: natural and precipitated chalk, marble dust, the whiting sold to potters. They all have slightly different characteristics in putty: marble dust being more gluey or slumpy, natural chalk absorbing almost twice as much oil and having more mobility and natural thixotropy. The ratio of thin to thick oil also comes to bear here. Putty can be made to work with the finest method, or the most expressive.

Chalk comes in many different varieties. Because chalk is absorbent, it creates a mobile but also thixotropic or "boingy" putty. Pictured, the very fine Ruegen Chalk from Kremer Pigments, mixed with walnut oil. Capable of great detail and fine impasto-relief.

The coarser "French Chalk" available from Graphic Chemical, still not gritty but firmer in working.

Like marble dust, the putty made from calcite is relatively white but more gluey and slumping than putty made with chalk.

Made with a combination of calcium carbonate, cristobalite, and a small proportion of bentonite. Whiter without the bentonite, but this gives it an extra ability to make detail as seen in this close-up.

Small amounts of egg -- whole, yolk, white -- can be added to a putty to create different qualities of seizure. Photo here of two tests of a chalk-linseed oil putty with a small addition of egg white.

A painting putty can be made with a somewhat dizzying variety of inert ingredients and oils. There are several varieties of calcium carbonate available. A chalk putty is soft, natural chalks tend to have a warm or cool tone, chalk is the most widely used ingredient found in older paintings. A marble dust or calcite putty is more adhesive, the widely available Fredericks marble dust works well for this, very white, relatively transparent in oil. There are also many commercial marble dust mixtures available in bulk from pottery suppliers, the minimum mesh for a gritless putty is #400. Gypsum, calcium sulphate, can be used. Blanc fixe, barium sulphate, can also be used and is virtually transparent in oil. The fine silicas available to potters can be used as well, these add an unusual dryness to the putty, use all possible caution and wear a serious respiratory mask when dealing with fine silica. Another interesting and very fine silica is the cristobalite available from Kremer, alas no longer in this country. Another completely transparent silica would be one of the many very fine fumed silicas available. I've used Cabosil, serious respiratory warning here, very light and flocculant material. Bentonite adds a characteristic bounce, or boing, but makes for a more colored putty even in small amounts. Leaded glass and fine glass "beads" can also be used, but both of these will impart a bit of grit to the mixture.

      With the oils used to make a putty, I've stayed away from any raw oil when using the putty with commercial paint. The foundation oil is a walnut oil heated to a little over 100C for three or four days. A small amount of sun oil or other thicker oil can be added for a putty which dries with a gloss. Even in very small amounts, a burnt plate oil contributes significantly to the saturation of the putty, see Formulas for more on these interesting oils. Sun oil is also possible and is a traditional ingredient in the calcite putty of Velásquez, although probably not made as thickly as the usual sun oil of commerce. The thinner Kremer sun oils might be more appropriate here, although sun oil of this viscosity is easy to make oneself.

      A commercial putty is available from Sennelier, but it has everything but the kitchen sink in it, unnecessary.

Above, an assortment of putties showing different rheologies. Number one above is made with Graphic Chemical calcium carbonate, finer and less gluey than marble dust, good for fine work but still pretty adhesive. Number two is a natural chalk putty with a small addition of egg white which increases the spring or boing, can be used with soft brushes in spite of apparent viscosity. More mobile than Number one. Number three is natural chalk with a small addition of Cabosil. Very different as a result, a bit gelatinous, even more slide. Number four is a marble dust putty, needs to be on the thinner side for finer work. Number five is a more dense marble dust putty using small additions of Burnt Plate Oil as well. For use with bristle brushes, soft brushes could not budge this.

Below, detail of a rose in progress made with a mixed putty system, putty does not need to be thick. Four times life size, two working sessions on successive days. Detail of a rose in progress made with a mixed putty system, putty does not need to be thick. Four times life size, two working sessions on successive days.

The putty medium offers a type and subtlety of color manipulation not possible otherwise. Set up shows Venetian Red about to be cut progressively with chalk putty, lead white, and titanium white.

The chalk putty creates warmer values by far as dilution increases. Note the pronounced color-obliteration and blueness of uncut titanium in comparison. This effect can be ameliorated to some extent by pre-cutting titanium white with putty before use.

Older paintings by painters who used a chalk medium often exhibit a technique for maximizing the chromatic shift available from a palette of relatively low chroma earth colors, black, and white. This technique involves using the warm colors -- yellow ochre, raw sienna, venetian red, burnt sienna, and including black -- without white, the lighter values of these colors being made by the chalk putty medium. A layer of these goes down first, followed by a cool, opaque layer using only black and white. By controlling the amount in which these distinct warm and cool layers remain separate or blend together via the putty medium, a great deal can be accomplished in one layer while keeping the color, value, and temperature clean. The eye perceives more chroma because of the exclusion of white from the warmer values. As with any technique, more is possible through experience and practice. Landscape, 1640, by Rembrandt below. The warm colors are beneath, anything with white, mostly greys, on top.

One of the things it took time to figure out was that the inherent adhesiveness of the putty would overcome a looser or thinner consistency, that it didn't need to sit up in order to alter the paint appropriately. So, over time, I've found myself making putties that are thinner but also maintaining a small amount of thicker oil for saturation, see recipe below.

A good example of how much trial and error it takes to make something simple, this recipe took over a year to develop. 1 cup chalk, 2T 72 hour walnut oil, 4T 48 hour walnut oil, 2T slightly thicker linseed oil, 1t sun oil. Nice balance of movement and body, will break if tubed or stored but that's not an issue in practice. A small amount of Cabosil keeps it from breaking but produces a very different feel, much more slide. A small amount of egg white produces a slight increase in thixotropy and set.

Blockx Ultramarine Light, cut with approximately one, two, four, eight, and sixteen parts putty.

The mixtures showing the slight opacity of the putty medium allowing an unusual control over value without the use of white.

The one to sixteen blue from above with approximately twice the amount of putty medium.

The above mixed showing various textures possible and the manner in which a putty medium can be used to make a translucent film which operates as neither a glaze nor a scumble.

There are many interesting variations possible based on the idea of fine inert stone dusts and various combinations of oil.

As this gel sits overnight, it clarifies. Shown, a slice of it, about an inch or so high, on the palette. Not as fast to dry as the putties, but virtually transparent. Made with fumed silica, the commercial variety Cabosil.

The leaded oil recipe adapted from the first volume of Eastlake thickens and becomes gelatinous on exposure to air, will ultimately become a viscous taffy, immobilizing paint in the same manner as a thick solution of damar. This can be replenished, lidded, etc. to control the viscosity for a particular method of working. Clouds in transit, dries clear.

One of the features of developing this resinless system has been several different whites on the palette at once with different degrees of adhesiveness or flow. The more calcite in the paint, the more inherent adhesion. Also, the longer the paint oil has been heat-bodied, the tighter the paint in spite of puddling. A very small amount of solvent or unheated oil will introduce flow. This picture illustrates the general chaos that accompanies this procedure, but in the end it seems one white at each end of the stick-flow axis will be enough.

Below is a series of illustrations of different rheologies possible with lead white without the use of resins.

The players. Left: a tube of lead white made with walnut oil that has been heated to about 225 degrees F for 72 hours. Middle: The yolk of an organic egg. Right: Sun walnut oil.

The white as it comes out of the tube is dense but slumpy and adhesive, somewhat stringy but stays put.

A small amount of egg yolk is added.

The white seizes dramatically, essentially becoming an immobile mass.

Dense, crisp white with egg yolk incorporated. Will make highly defined detail and/or stiffen other paints significantly.

Sun walnut oil added.

The paint relaxes and strings readily. This paint moves easily under a soft brush but also stay put.

More egg introduced.

Egg incorporated.

More straight paint introduced.

White which is smooth and bouncy but will maintain and hold significant texture.

Another resinless method of creating a white capable of great texture is illustrated below.

The players. On the left, a tube of white made with lead carbonate, calcium carbonate, and walnut oil that's been heated to about 225-250 F for 72 hours. On the right, a jar of modified oil. All traditional ingredients used in painting since its recorded history began: and, no resins.

While I mix it as tightly as I can by hand, the white as it comes out of the tube is quite loose, stringy, but surprisingly adhesive.

A very small amount of the oil is needed.

The white begins to thicken or gel as the oil is mixed in.

Once the oil has been mixed thoroughly, the white makes impasto which will stay put or move without being sticky. This is quite a stiff mixture, and would stiffen other colors accordingly. More white added now would make a smoother gel. However, the stiffer mix will take color on top without blending. Or can be blended a small amount through pressure of the brush.

Slightly larger than life detail of an alla prima study of onions from life done with paint made with slightly heat-bodied oil extended with calcite putty and the white detailed above. While this isn't exactly great, the fascination of this system is that there's no limiting factor except perhaps experience on the one hand, exhaustion on the other. The paint can be added to, carved, blended, removed, to any degree. There is no resin in this paint.

Another white made with older technology gleaned from the National Gallery Technical Bulletins.

Just the paint and a knife are needed.

The paint responds to friction and becomes a tight mass.

The above photos illustrate the complex rheological possibilities available to the painter using a traditional system of oil alone with no additional resins. This means, in addition, no solvents: brushes are kept in oil, washed in soap and water. The more I work with this system, the more it develops: perhaps more subtly after the first year or so, but it hasn't lost a sense of constant improvement and expansion. The decision to work with this system came as a result of questioning just what motivated my prejudices with regard to resins and their use. With the exception of the clear gel variation, which employs a modern fumed silica, all materials used on this page are documented in earlier literature and were available to oil painters from the time the process was invented. There are many technical tricks available now, but if you are interested in the deeper aspects of the older craft process, I feel the key is to study the oil.