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Open or download the text below as a printer-friendly pdf file, no images, here.
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| the real secrets |
The search for answers with regard to older painting practice began officially when Reynolds set out to emulate Rembrandt. He kept notes, some of which are reproduced in Eastlake, and these notes detail a great many common errors that have been made with mediums ever since. But the fundamental conceptual problem has always been the same: a search for a lost material, rather than a lost technique. This shell game still goes on at the commercial level, especially with small companies offering unusual or hard to get materials with historical backgrounds. The problem here is that there is no working manual of older painting practice written by an actual oil painter: while Pacheco's Arte de la Pintura has some interesting information attached to its somewhat stilted high culture posture, much of it is technically obscure, and some of the fundamentals are obviously unsound, as the condition of his paintings suggests. This lack of reliable written explanation makes sense since the training was hard won, often paid for, and made one's living in a fiercely competitive environment. What does exist is a great literary jumble sale of odds and ends across centuries of technique. Reading it all is difficult enough, exploring it adequately would take a large research team a lifetime. However, thirty years of research into older paintings at the molecular level, documented in the National Gallery Technical Bulletins, suggests strongly that the materials themselves tended to be simple: oil, pigment, perhaps ground stone, perhaps a small amount of egg or pine resin. This is logical because the last thing a working craftsperson could afford was technical failure. When Leonardo's great gamble, the Battle of the Anghiari wax-fresco, failed, he left Florence.
The way to avoid the complexity of the boutique shell game on the one hand, and the grand literary snipe hunt on the other, is to work with the materials at a fundamental level until you understand them well. This takes time, and patience, but is not rocket science. It is a matter of learning to pay attention at a different level. In America we turn out "Masters of Fine Art" in two years, but Chardin said it takes thirty years to make a painter. Which assessment of this situation is more accurate? The underlying problem is that our way of educating the brain relies on the left brain and linear thought. Not only is painting image or right-brain oriented, it is also multi-dimensional: all modern color models are three dimensional without the added dimensions of relative opacity -- transparent, translucent, opaque -- and the effects of layering the colors over time. Without a willingness to undertake this equal and opposite form of education, it is simply not possible to access the more subtle ways color was used and paint was applied in older practice. Thus we often end up with painting which uses an increasingly superficial version of color, and an exaggerated version of style, in order to be heard above the din of all the other painting doing exactly the same thing. In his wonderful Oil Painting Techniques and Materials, Harold Speed says that a culture gets the art it deserves. Having abandoned all classical or ethical -- to say nothing of spiritual -- precepts about the purpose or meaning of creativity, it is no wonder that a kind of arbitrary commercial chaos has ensued.
If, on the other hand, you are interested in pursuing painting for its own sake, or, as the Taoists say, as a method of cultivation, you will find the real secrets where they have always been: hidden in plain sight. Ongoing experiential commitment to a working dialogue with the craft will easily allow access to aspects of it that are overlooked by those in a hurry, those too intellectual or aesthetic to bother, or those with fame and fortune as a primary goal. It is that simple, but also that complex.
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| process |
A quality oil painting process is developed using sound, archival practice. This involves creating a complex, multilayer structure - the painting - which somehow manages to hold up very well over time. Because of the nature of oil painting, there are many variables involved in how this structure can be made. The nature of oil painting also makes it more of a gamble technically than its predecessor, egg tempera. Because the structure of an oil painting is inherently complex, it's always best to attempt keep both it and its various components as simple as possible. However, this element of simplicity should not necessarily extend to purchasing ready-made materials if the hope or expectation is to create higher quality work: generic materials have a strong tendency to produce generic work. While the new small manufacturers make materials that are usually higher quality, this is not necessarily the case with the most important component, the oil. And these materials still don't impart the vital information about the nuts and bolts of the craft: at the end of the day, there is no real process, just a set of purchases, a pseudo-craft The time and effort invested in developing one's own relationship with the materials can quickly create a much greater understanding of their working characteristics than any amount of work that begins and ends with branded bottles, tubs, and tubes, no matter what their supposed pedigree. Anyone who denies this is trying to sell you something. Just because an "authority" happens to be cynical, thinks it doesn't matter, or isn't aware enough to tell the difference, doesn't mean the painter should settle for less. Quality art begins with quality time, quality time begins with a quality process.
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| the most important component |
...is the oil. If you want to explore the foundation of the older process, refine a bottle of organic, cold-pressed linseed oil -- flax oil -- from a health food store. Especially if you are an experienced painter, working with this oil leads to a logical explanation of how older painting evolved the way it did. Brands I've had experience with in America are Flora and Jarrow, there are others as well, all much less expensive in quarts online. The Allback cold-pressed organic linseed oil from Sweden is also very good. The availability of oil of this quality is unprecedented in the history of oil painting, however, it must be refined to remove the yellowing potential of the linoleic acid. The oil you create will dry quickly and have working qualities that are far better than any commercially processed oil, regardless of reputation, and at an affordable price. Photo above is of the Jarrow oil after a wash of one day, note the large amount of break removed.
A complete pdf file about the process of refining linseed oil is here. This is all text, no photos, for printing out. The process is a faster adaptation of the water-sand-salt method in the De Mayerne Manuscript (early 17th Century) which Eastlake recommended in the first volume of his Methods and Materials (early 19th Century).
If you make this oil, then make paint with it, you will be in a position to understand the most fundamental "lost secret" of older painting practice: the rheological qualities inherent in the oil itself. Much can be built on this foundation that cannot be built on commercial paint; this is especially true when using the putty medium, see also briefer explanation below. Commercial paint is not bad, but it contains a system of additives and will not lead logically to the old craft, especially in terms of bravura or broken surface painting techniques. It is, in a fundamental sense, incomplete. This is why, since the decline of painter-made paint, so much emphasis has always been placed on the medium.
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Various finished versions of this oil aging in the light. The cold and the addition of a small amount of chalk or lime tend to precipitate out further small particles of break. One would think that the lightest oil would be "the best" but this is not necessarily so.
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| new vs. old |
I'm often asked how it's possible to reconcile older painting practice, such as the material in the De Mayerne Manuscript, or the findings in the National Gallery Technical Bulletins, with the general run of modern, usually academic, recommendations.
It's not, the two systems are irreconcilably different.
Modern writing on the craft has tended to be an uncomfortable mix of the glib, the lily-livered, and the officious. This is especially true in relation to older practice, which is usually deprecated out of hand even while worshiping Rembrandt, etc. This is possibly due to the academic origin of the modern approach: the system must work for college students. As a result, the modern approach has gone off on a tangent which worships the commercial idol of convenience and uses "science" as a justification. The conclusions of this "science", however, are radically oversimplified in terms of an actual painter's experience of the craft. This is because the craft is so much more diverse in its combination and manipulation of materials than the laboratory can readily comprehend. "Science" has not gotten to the point of testing materials in context, this would be incredibly complicated. But of what value are isolated conclusions when the materials are never used in isolation? "Science" tests linseed oil, but where was the flax grown, at what point was it harvested, how was the seed pressed, and, most importantly, how has the oil been subsequently processed? From the older point of view, there is really no such thing as linseed oil, this concept is both too abstract and too vague. There is only the behavior of the specific oils one knows through years of experience. This is a profound difference. Painters, as a result of their naturally deeper awareness of the materials, often end up questioning "science", which "science" finds absurd: painters have proven themselves once again to be irresponsible, end of discussion.
But this commercial-academic "science" is not real science. Genuine empiricism is aware that it's definition of truth is relative and conditional, it is simply what we know up to now. The occasional dogmatism one encounters from a "scientific" source should be viewed in this light. It is a malignant mutation of the great tool of observational and experiential research, refusing to acknowledge that diverse conclusions may well arise from diverse experience. As an unfortunate but inevitable result, the modern academic approach has no functional idea of the depth and potential of the older method. An insistence on a rote approach to the process and materials results in a false certainty: the physical or visceral aspects of the craft are subjugated to a static intellectual theory. Suffice it to say, this is not how the greatness of 17th Century painting came to pass.
Of course, not all conservators or academics operate like the Spanish Inquisition. There are many with more responsible and flexible attitudes who are aware of the complexity of the materials situation and are working in partnership with painters. Because both parties are involved in teaching and learning, this offers a better model for the future. The "Art in the Making" series by London's National Gallery provides a great example of this, as does "Seeing Through Paintings", by Kirsch and Levenson, and Leslie Carlyle's excellent "The Artist's Assistant".
In relation to the old way of painting the new system can be compared to what happens when a great novel is made into a Hollywood movie: much is lost in terms of subtlety, depth, and dimension. The fascinating thing about the older way is that it is not particularly complex, it simply springs from a completely different set of root assumptions about the craft. These are much more logical than "alchemical" -- the use of that word in this context is usually well-meant but thoroughly inaccurate -- derived from the cumulative day-to-day experience of the craftsperson and the traditions that were handed down within the master-apprentice system. This hands-on experience is, of course, unavailable to the modern method. It is therefore logical, if a little embarrassing, that the modern method tries so hard to make the older method go away. The older method will never go away. It makes better paintings.
In the older method, the painter starts from scratch and develops a relationship with the materials: the process creates the product. In the modern method the painter purchases commodities and manipulates them: the products determine the process. The justification is that the products are "right": science -- that is, the dogmatic, rigid version of science -- has blessed them. However, commodity based painting tends to devolve because the painter must execute the static formula that works. The process becomes uninteresting to the painter and this ultimately affects the work itself.
The craft requires but also recompenses constant attention. For this reason, craft based painting tends to evolve because the painter is with the materials in the moment. The importance of this ongoing dialogue cannot be overemphasized.
If painting is simply a means to a socio-economic end, -- what invitations are on the mantelpiece, how much one is worth per square inch -- then the craft is useless. If painting is a means of evolving towards ever greater and truer versions of oneself, then the craft is a foundation allowing endless subsequent development. As always, the question of what endeavor defines the quality of life is up to the individual.
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| structure |
A painting is made up of layers, beginning with the canvas or panel, proceeding to the final varnish. The ultimate strength of the painting technically depends on the strength of the structure as a whole, not on the cumulative strength of the ingredients themselves. This is important to consider in using any given material: is it appropriate for its place in the structure? A material which is too strong - commercial acrylic gesso - for it's position may create resulting structural weakness: the applied oil paint flakes off. The use of a strong material like sun oil or copal varnish too soon or in too great a concentration may result in the beading of the paint in subsequent layers: the painting will need to be oiled and sanded down to accept further paint. It is important to think in terms of designing the structure of the layers of a painting so that the ultimate strength of the whole is maximized. This means using the right material in the right place.
Three great aids to structural flexibility from the history of oil painting are the use of panels, the use of chalk or other calcium carbonate as a buffer to the acidity of the oil, and the greater film strength over time of lead carbonate as a white pigment.
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| supports |
The manufacture of canvas on stretchers has become a large industry, with many different levels of quality available. There are also many levels of quality of stretchers themselves. While work on panels predates work on stretchers by centuries, stretched canvas has come to be an expected meme. This is unfortunate, because unsupported canvas will always be less permanent, more subject to various forms of potential damage, than that same canvas mounted archivally to a panel. It is always best to stretch the fabric oneself, and to use linen if at all possible on stretchers. If using commercial canvas, beware of fabric which has been given a shiny surface by the ground, either an oil ground made flexible by the addition of Stand Oil or an acrylic emulsion ground. Also beware of hardboard panels, these are not necessarily archival or acid-free. It is simple to make highly archival panels oneself using cabinet grade plywood covered with cotton or linen canvas. A more recent addition to this family of products is Medite, a particleboard bound with a synthetic resin. This is receiving high conservation marks at this point but anyone familiar with the subsequent history of "wonderful exciting and permanent" new painting materials knows that it may well be wise to be a late adopter.
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| linen, cotton, paper |
Linen is the stronger fiber and should be chosen for unsupported canvas if possible. If cotton is chosen, the reverse surface should be protected from possible damp by sizing it with PVA or by the older method of a double canvas, the second layer of which had the priming facing the back. Cotton on panels is fine as it is protected both front and back. Small paintings on prepared paper - usually outdoor sketches - have fared surprisingly well over the last few centuries, but should always be mounted to panels or framed behind glass in the long run.
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| size |
The traditional size was some form of hide glue, rabbit skin glue is often said to be the most flexible. When combined with glue gesso on panels, this system has survived in some cases for over five hundred years. On unsupported canvas it is less permanent because of the movement of the canvas and the hygroscopic nature of the size. However, it is important to note here that all 17th Century paintings on canvas were made with this combination of materials and a very thin imprimatura. There are alternatives available now in acrylic emulsion size and PVA size, both of which are more flexible and resist moisture better. Both of these are also stronger, so the questions become: how strong to make the size, and what to put on top of it.
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| the ground |
A commercial oil ground presents potential issues with both adhesion and yellowing. This is because these grounds are made to be rolled and typically contain stand oil. Although the stand oil creates more flexibility for some time, it will darken over time and creates a ground whose surface is less porous, with the potential for the paint not to adhere well.
The danger of a commercial acrylic ground is the typical level of gloss making it difficult for the paint to penetrate the surface enough to safely adhere. Some acrylic grounds now are being made moderately absorbent, these will have no shine and a drier feel.
Because they are rigid, it is possible to put a quality ground on a panel commercially. Still, this is an area where the painter will be able to create a much more personalized and interesting painting surface with ease.
On panel, the logical solution remains hide glue and glue gesso, this gesso can be enhanced with titanium white. It is also possible to make a more flexible oil emulsion gesso, as discussed by Kurt Wehlte in "The Materials and Techniques of Painting", for use on canvas. For more information on this, go here.
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| the oil |
Claims for the quality of modern commercial oil tend to fall not far from commerce itself. While commercial oils are getting better -- they no longer yellow as you watch -- using them always starts the painter in a hole in terms of the deeper aspects of the craft. The oil used for painting should be tested for yellowing: this takes several months. If the oil is cold-pressed, this is often a key to higher quality. At another level comes unrefined cold-pressed oil, usually organic as well in the case of linseed oil: however, this must be refined. The various low-tech processes available to the painter all take time, but are not time-consuming or difficult, and open up a range of possibilities not possible when starting with commercial oil. This is especially true with linseed oil: because of the time factor involved, and the original high price of the oil, no approximation of the linseed oil of older painting exists commercially. While commerce offers refined linseed oil which yellows minimally, this oil has also lost all verve or snap to the refining process, it is essentially generic, remaining linseed oil in name only.
Artist refined cold-pressed organic linseed oil is a totally different product, with many rheological personalities based on various older recipes. How much this matters depends on how of much of a role the craft plays in a given painter's conception of their work. But if someone tells you categorically that it doesn't matter, or is not worth the effort, take a moment to stop and consider the source. It is ironic that, while highly processed oils with high price tags are sold in the art supply store, the interest in the nutritional qualities of unrefined linseed oil have made oils of incredible quality and potential available at the health food store. These can often be found more cheaply online. However, these oils must be refined to dry quickly and remain safely non-yellowing over long periods of time. Adding bread crumbs to clear the oil, then placing it in the sun for two weeks, is not enough. For more details on this process, go here.
The oil used in a painting medium should also not be raw. This is especially true if raw oil commercial tube paint is used. Pre-heated oil offers a very simple method for decreasing yellowing, and increasing the overall strength and potential longevity of the paint film. This is more true for linseed oil, although artist processed linseed oil is significantly less volatile than commercial linseed oil.
More information about working directly with the oil can be found here.
An extensive pdf file about the process of refining linseed oil is here. This is all text, no photos, for printing out.
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| thickened oil |
The simplest way in which oil thickens is by being left open on the palette, or closed in half full containers. This is especially true of painter refined organic linseed oil, which becomes tackier and more glutinous in a matter of a few days in a thin layer in the open air.
The earliest known recipes for painting oil all direct that the oil be heated for a reasonable length of time. Heating an oil to just below the smoke point with constant stirring for as little as fifteen minutes, as long as half an hour, results in a significant increase in density with little increase in color. This oil dries faster and is more leveling than raw oil, and is still thin enough for undiluted use.
The other traditional method of producing a thicker oil is to allow it to thicken in the sun. If you are in a climate where this is easy in the summer, sun oil is an excellent and simply made material. It can be made for undiluted use in a few weeks, or allowed to thicken to the point of being a taffy. True commercial sun oil is always relatively expensive, and smells quite sharp. If you have found a surprisingly cheap "sun oil" that has a denser, cooked smell, this is burnt plate oil, see below. When making sun oil from linseed oil, this oil should be refined, either commercially or by the painter. While an unrefined organic linseed oil placved in the sun for several weeks will dry somewhat faster, it will not dry as fast as that same oil, previously refined, and still contains a full complement of water-soluble fatty acids which can yellow significantly as the paint film oxidizes over time.
Stand oil is a more modern thickened oil, usually linseed oil which has been heated in a vacuum. Stand oil is produced by many manufacturers, and from many different grades of oil. It can be, but is not always, a reliable material. If the working qualities of stand oil fit with your style, please make sure to test several different brands for yellowing, these tests take about three months.
Another modern commercial thickened oil is the burnt plate oil of the graphic trade, used to alter the viscosity of printing ink. The original burnt plate oil was literally oil that had been heated until it caught fire. Modern burnt plate oil is an evolution of stand oil which involved heating the oil in a kettle which sparks off the rising volatile elements. The result is a thicker oil which has a more mobile or slippery quality, and which has less of a tendency to yellow. Burnt plate oil is also very slow drying, and imparts a great depth of saturation to the color. It should be used in very small amounts in a medium or putty, 5 percent is enough. If working with the product from Graphic Chemical, the most versatile grade is 5, about the consistency of stand oil but lighter. Photo is of grade 7, somewhat thicker but still on the light side.
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| the medium |
Mediums became increasingly important once paint began to be engineered to be put into and kept for long periods in a tube: this paint has the advantage of convenience but does not typically suspend the pigment adequately or resist atmospheric oxygen effectively. Modern conservation research has made it clear that, while many materials were additionally used in older painting in decided moderation, the oil itself was by far the most prevalent ingredient in any medium. It's very important to keep any resin to a minimum. A small amount of hard (cooked oil) resin varnish such as amber or copal has more to offer protectively for the paint film than a soft (spirit) resin varnish. However, the research in the National Gallery Technical Bulletins suggests that older painters may well have used a small amount of soft resin fused into the oil as a simple, readily-made solution. Mediums are a place where creeping complexity needs to be scrupulously avoided. This is especially true in terms of maintaining paint film consistency from layer to layer by using the same medium throughout the course of a painting. The medium should always be leaner or used more sparingly in the beginning layers. It can be used more richly at the end, or in an alla prima painting which will dry in a single layer, but the spot use of different additions or underlayer treatments for specific effects should always be avoided; these have proven to cause significant difficulties with paint film integrity in the long run. The Tate book on the Pre-Raphaelites illustrates several examples of what happens when painters overthink the process without understanding the materials in the first place.
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| putty mediums |
Although simple, this medium has no historical reference in any older text. It's origin is the result of modern conservation research, which has found additions of chalk or other forms of calcium carbonate in the paint of painters such as Rembrandt, Chardin, or Velásquez, and ground silica in the paintings of various older Venetian painters. The various types of ground calcium carbonate and silica can be coupled with the stability of pre-heated oil and the quick drying nature of sun or unsun oil to produce a family of mediums with many different working characteristics. The strength of the medium lies in it's technical stability, solvent-free ease of use, and protean versatility. This last quality also means that using the medium effectively can involve a bit of a learning curve as the painter becomes acquainted with it's endless possibilities and adapts them to personal taste. While older painting practice contains many lost secrets , next to the craft of the oil the use of inert stone dust as an extender, brightener, stabilizer, and impasto creator is at once both the most prosaic and the most profound.
At it's most basic, this medium is simply ground stone dust used in conjunction with oil and the paint on the palette. Oil to make the paint move more, stone to tighten it once again. From the highly irregular surface impasto of some of his later self-portraits, this may well be one way, if not the only way, Rembrandt used this method.
The medium can also be pre-mixed into a putty. This putty can be mixed into the paint before painting in any amount, conservators have found evidence of Rembrandt's use of translucent glazes using chalk.
Other forms of calcium carbonate can also be used and have slightly different rheologies as putty. Chalk is the most absorbent and, unless it is very fine, also has a certain mobility. The finer chalks, such as Champagne Chalk, have a somewhat stickier quality in oil but are also suitable for the finest detail work. The more crystalline forms of calcium carbonate - marble dust, calcite - make a putty which is more adhesive but with less potential for the glutinousness of the finer chalk putties. As Velásquez used ground calcite and Rembrandt used ground chalk, the difference isn't one of quality, but of personal preference, or perhaps simply availability, coupled with the all important element of long experience with a given material. Pure white and finely ground marble dust is readily available and works well. Ground silica presents a different case depending on particle size. Larger particle silica - 200 to 400 mesh - will tend to a make a putty feel drier under the brush. The smaller particle silicas - such as fine cristobalite - tend to produce the lubricating effect, sliding more than the other finer particle stone dusts. While the calcium carbonates tend to accelerate drying slightly, silica tends to retard drying slightly. Any ground silica presents a long-term respiratory hazard and should always be used with a serious particle mask when in the dry state.
The putty medium is especially effective at altering the relative lack of body and tendency of commercial paint to slide due to the common modern addition of aluminum stearate as a gelling agent. By using only high quality, pre-heated oil in the putty, the instability of raw oil commercial paint - its tendency to shrink and crack - can also be significantly diminished. The putty can be engineered to any level of final gloss as an addition to the paint, again overcoming the tendency of raw oil paint to dry matte and sink-in. It is ultimately possible for the painter to create a tube - or several different tubes - of putty which, when added to commercial paint, consistently give it a number of desirable characteristics it does not have on its own. This presents a viable alternative to the longer learning curve of making one's own paint. More on the putty medium can be found here.
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| mastic gel mediums |
Of all the soft resins in use, the mastic gel - meglip, Maroger medium -- is the most controversial: there are many conservators who say outright that it should not be used at all. If a simple answer is needed, this is a wise one. However, as usual, the truth is more complex. This situation provides a good example of how the medium does not exist alone, but in the context of the entire structure of the painting. As a material, mastic is very soft, it can be chewed. In the resulting paint film it is both brittle and fragile. But if the other ingredients in the paint film are strong, it is possible for the mastic to be trumped by them. This is what happens with Roberson's medium, a mastic gel with an addition of copal varnish. Or in a painting where the paint is handmade from oil that has been artist processed, aged or pre-heated. But if the painting is made with raw oil tube paint, which makes a relatively weak film to begin with, and if the mastic gel is then used in large amounts, the results will not last long, especially if the painting is on the usual unsupported canvas.
So if for some reason a mastic gel needed to be used, it should be on panel and made with Eminent Oil (go here),
not the usual Black Oil. The paint used should be handmade from pre-heated oil for a stronger film, and lead white should be used to further increase the strength of the paint film. The medium will be stronger if it is fortified with copal varnish, as in Roberson's medium. The white food grade mastic is obviously lighter but is also much more elastic than the smaller yellow mastic, although much harder to find outside the Mediterranean. Finally, the medium should be used in absolutely the minimum amount: the hardest part since it's working characteristics invite exactly the opposite.
The significant difference between the above recommendations and the usual way a commercial Maroger medium is used with tube paint shows why certain older paintings made with a mastic gel medium have stood reasonably well over time.
A detailed account of the known historic development of the mastic gel medium can be found in Leslie Carlyle's amazing book, The Artist's Assistant. I don't recommend Maroger's book as a source of information, at this remove it is an obviously synthetic system with a forced logic, the recipes themselves largely derived from formulas and ideas in Merimee and De Mayerne.
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| silica gel mediums |
This is a more reliable gel based on adding fumed silica to the oil. When using tube paint, the oil used should be pre-heated. Many varieties of silica gel can be made by varying the amount of silica and the mix of the oil. The typical way of using this is as a glazing medium or in conjunction with the putty medium. The silica gel moves, or slides, easily, while the putty has more of a tendency to stick or grab. A fumed silica gel can also be used in a freer manner in alla prima painting.
Fumed silica is very light and should be handled with great care, using a quality respiratory mask. Once combined with the oil, it presents no further risk and can be tubed or kept in small glass jars.
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| the paint |
The quality of commercial paint is improving, the days of dark orange oil oozing from under the cap are on the wane. But it is still an excellent idea to compare brands, do research and yellowing tests of your paint, regardless of the brand's pedigree. Artist made paint will always have the potential advantage of being made with higher quality oil. No manufacturer, large or small, uses cold-pressed oil refined in a low-tech, non-invasive way and then aged in the light, as was the common older practice. In terms of linseed oil especially, this matters. On its own, commercial paint does not develop a strong enough film to resist oxygen or the subsequent sinking in of later paint layers. This is why the element of medium has become so important in modern painting practice: the pigment needs to be suspended and sealed from oxygen in a way that it cannot be using raw oil tube paint alone.
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However, if the paint is made with preheated oil, as in the illustration, a very different rheology is available from the start. Preheated oil is found routinely in older paintings by the researchers at the National Gallery, as reported in their yearly Technical Bulletins. The use of preheated oil creates a stronger and more stable paint film which is less likely to yellow. The increased body of preheated oil makes it less likely that the pigment will sink in. The oil used to make this paint was preheated to 100C for 48 hours. It also works to preheat the oil to 150C for 30-45 minutes..
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| fat over lean |
The structural rule of painting fat over lean is very important if raw oil is used with raw oil tube paint. It becomes less important the more the paint and medium are modified in the ways that are standard from sources such as the De Mayerne Manuscript and the findings in the National Gallery Technical Bulletins. This is because these methods -- principally pre-heating the oil, and introducing lead into the oil -- produce oil which is stronger, more flexible, and significantly less volatile in it's drying characteristics. Another great addition for long term stability is the addition of calcium carbonate to the paint through the use of the putty medium.
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| yellowing |
There are several different potential causes of yellowing in a painting. While lower quality linseed oil in commercial paint is on the wane, this has been a major cause of darkening in 20th Century paintings, and it is unfortunately possible to see this readily in major museums. Another culprit is turpentine which has been oxidized by exposure to light and air, the residue of this can yellow badly and affect everything it was a part of. If used, turpentine should always be high quality, and protected from both light and air by being stored in small size amber glass bottles. A thin application of a given oil may dry without yellowing, while a thick application of the same oil will darken. Oil which has been pre-heated or aged in the light has less of a tendency to yellow than the same oil, new and raw. Humidity is another factor often overlooked: an oil which dries without darkening in low humidity may dry with significant darkening in high humidity. In some climates, a dehumidifier is a studio necessity during the summer. Setting paintings to dry in moderate sunlight is a traditional remedy for short-term darkening, north or east windows work well for this: simple but effective. Paintings will darken naturally if not exposed to enough sunlight, this is especially true of work made with linseed oil. However, subsequent exposure to light will brighten the work once again. The darkening associated with resins is longer term. It is wise not to use a hard resin such as amber or copal in any but the most minimal amounts, and never as a final varnish. It is wise to keep all resin use to an absolute minimum: oil paint is so sensitive and these materials so strong that between 2-5% of a hard resin varnish in the paint layer will make a significant rheological and optical difference. This is enough. More may well be inviting trouble down the line. Oil paintings do not ever get lighter or brighter over time. Painting on a white ground is therefore a good idea, as is painting the values "up" somewhat, especially when working in layers.
It is becoming more common for painters to pay attention to conservators, and this is by and large a good development. But sometimes conservators become obsessed by yellowing. In oil painting, there is a profound difference between normal, visually comfortable mellowing and an overall darkening which is fact disfigures the work. It is important to keep in mind that the dire warning of the conservator about a material "yellowing over time" might be a little overstated, some conservators simply like to terrorize painters. Conversely, it's possible to see before and after photos of paintings where old varnish was removed which show that the painting clearly benefited from the warming effect of the varnish layer: as perhaps the painter intended. So, the issue is to know one's materials. A lower chroma earth color palette, such as used by Rembrandt or Velasquez, can be used safely with quality linseed oil, as was in fact the case for both painters. Raphael's early higher chroma palette may well have benefited from his use of walnut oil. The more the color depends on a cool, neutral light, the more the color is focused on pure color in the midtones, the more the painter needs to be concerned with yellowing in the choice of the oil. However, as will be seen below, it is possible to paint in such a way that the relative warm-cool dimensional distance of the painting remains constant or in fact increases as the painting ages.
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| color |
Color is the great chameleon, it's behavior is always contextual and relative. Modern painting practice tends to feature more color as opposed to wise color. Older painting practice often featured great discipline with regard to the use of white and the separation of warm and cool tones on the palette, resulting in the illusion of brighter color and greater dimension from a relatively to extremely limited palette. For more details on this extremely powerful tool, go here.
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Color is organized into triads. For realistic painting a primary triad that is warm and a primary triad that is cool are all that is necessary in addition to white. There are many possible triad combinations that can be mixed and matched for various situations, rather than resorting to a greater variety of colors. Exploring this helps to assure harmony and a convincing spacial envelope.
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A relatively warm, low chroma triad composed of three earth colors: Yellow Ochre, Venetian Red, and Ivory Black.
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A cool, high chroma triad: Primary Yellow, Primary Magenta, and Primary Blue.
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| white lead |
White lead is capable of a great many different rheologies or working characteristics depending on how it is made and how it is modified. Paint made with simply pigment and oil is more responsive than commercial paint.
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| solvent |
Solvent is unfortunately considered necessary to oil painting when in fact is is only necessary to the type of painting which uses a soft resin medium such as dammar. Older painters kept their brushes in oil, not solvent. Long term solvent use in an unventilated studio leads to significant health issues, Denmark has in fact labeled this "Painter's Dementia". Solvent should always be kept in small amber glass bottles which are full, protecting the contents from both light and air. This is especially crucial with turpentine. Both the traditional putty medium and the more recent silica gel medium offer a variety of solvent-free painting options. Solvent is also unnecessary when using a small amount of hard resin varnish in the medium or a fused soft resin and oil medium. A higher quality solvent for general use may well be spike lavender, but it is important to get this without adulteration. If you find surprisingly inexpensive spike, it is probably cut with mineral spirits.
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| final varnish |
Whether or not to varnish a painting and how long to wait before varnishing it are complex subjects, depending on on how much paint was put on, the medium used, and the amount of time the painting took in total to complete. It's important to understand that the atmosphere in houses and urban areas is now generally much cleaner than it was during the time when houses were heated with wood or coal: varnish then made the inevitable cleaning safer and easier. Not all paintings are seen the way their maker intended: Monet liked the matte quality of the surface of his paintings, almost all of which have now been varnished. At one point a high-gloss, enamel-like surface was desirable for a painting, no matter how large. Now larger paintings are often finished with a more matte overall surface. The safest varnish is one which is easily reversible, so that it can be removed if anything goes wrong: mastic varnish, in spite of it's inevitable yellowing, was actually preferred for this quality. The final varnish is an area where modern products from quality manufacturers may perform better than older materials, almost all of which have been proven to yellow significantly over time. Possible exceptions are discussed below. It is always best to test the final look of a varnish first on a painting which is unimportant: someone else's idea of the perfect look may not exactly be yours.
A painting made using the all oil system can, with experience, be engineered to any desired level of shine. This certainly solves the problem in the short run, possibly even for the painter's lifetime. The more paint you use, and the richer the medium that can be used safely, the more the painting will be resistant to the destruction of the oil by oxygen. This is an advantage offered by painting on panels over unsupported canvas.
An early varnish used in Italy was made from sandarac, either dissolved in spike lavender or used an an oil varnish. The National Gallery has found specimens of both these in good condition, although the varnish in oil has yellowed more. The varnish used on most 17th Century paintings was mastic, a soft resin dissolved in turpentine. While this was known to yellow, it also aged to the point where it crumbled easily away, making it simple to remove. When dammar came into the picture in the 19th Century, mastic was still preferred due to it's lower level of shine. Writing on the experience of older varnish removal from the National Gallery makes it clear that copal, because it both yellows and dries irreversibly, should not be used here.
There are many modern synthetic varnishes available now which may well offer a more reliable final finish, or have at least been engineered to be easily removed should something go wrong. These include the MSA (Mineral Spirit Acrylic) family, and the various other acrylic resins in the Paraloid family, although the latter involves the use of relatively toxic solvents.
Genuine Silver Fir Turpentine, or Olio d'Abezzo, is quite light in color and can be used as a final varnish when diluted with solvent, 1 part resin to 3 or 4 parts solvent. It dries quickly and yellows minimally. However, it is brittle, and quite glossy. Sandarac can be dissolved in pure spike lavender and used in a similar way, this is a very old material, and should be used on panels. This also dries in a few hours, with slightly less shine, and is reversible.
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| caution! |
A while back I read a couple different articles on the internet about oil painting materials, both of which advocated caution in strong terms. The interesting thing about both these articles was that, for all the elegant and elliptical prose involved in both, I couldn't seem to find a single thing -- process or material -- that was actually being recommended. Which seemed to be the absolute apogee of caution! There was a definite righteous tone to both these articles that I found fascinating -- both were written by Americans -- as though there is one ethically and morally correct way to make a painting and it is The Cautious One, whatever that actually is, and that incautious painters go to...well, you get the idea. Caution isn't wrong: with regard to commercial art materials, for example, experience dictates tremendous caution. But to exercise caution appropriately it needs to be balanced with a genuine understanding of the materials. This understanding is not about comparing one brand of flake white to another on a forum, it's about making your own flake white. Not once, for years. This is the fundamental difference between the old world view and the modern one: they made it, we buy it. The modern view is a cul-de-sac with regard to the craft of painting because, if you buy it, what do you know? Only what they tell you, and it is often, all too often, a stretch to call it the truth. Once one comes to terms with the few simple materials that were used historically and begins to combine them within the context of one's own painting process, fascinating developments can occur, developments which are outside the realm of what can be tubed or bottled by the manufacturers. Yes, there is a learning curve, yes, there will be some chaos, and yes, some materials are better than others. The hope is that the information here will be helpful on all of those fronts, saving you some of that most precious of all mortal commodities, time.
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| research |
Beyond advice, or personal opinion, a great deal of research has been done into painting materials at this point. In evaluating the potential worth of anything written, it is always helpful to examine the subtext. Research, like the people who do it, is rarely as detached or empirical as it presents itself to be. In this way it is like a hammer: neutral as an object, but wielded with a specific intent. Is the intent to build, or destroy? That is, are positive examples of quality process given, or a complex labyrinth of negation? Does the research prove that one should purchase products made by the researcher? Does the researcher paint, or simply claim to paint? If there are paintings, what do they look like? If someone presents themselves as in sole possession of the facts, whence cometh this divine authority? Is it the result of a lifetime spent as a painter? Or within the ivory tower? And finally, does the researcher name drop the Old Masters as though they all play pinochle together on Saturday night?
Asking questions such as these may well provide a more reliable method of navigating the material on offer than the de facto worship of authority. Human beings have an unfortunate tendency to extrapolate observations into facts, facts into theory, and theory into a set of rules. But even a casual examination of the National Gallery Technical Bulletins -- now, in 2009, in thirty volumes -- shows that older paintings were reliably made in a variety of ways. In painting, as in life, the guidelines need to be broad, not puritanical, in order to incorporate the crucial creative element. This element is always personal, extra-logical, unscientific. Yet it is also responsible for anything genuinely exciting, or actually new.
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Mitigating the modernist miasma.