Pigments

  • Phasing out Zinc White?

    “I read a report from a manufacturer about using zinc white causing problems in oil paintings, and they are phasing out the usage of it. Any thoughts about it?”

     

    Indeed we have after much consideration decided to err on the side of caution and cease making it. It has also been removed from our mixed colours such as brilliant pink. For more information please feel free to contact us.

  • Download MH Oil Colour & Mediums Brochure

    Download and view the Michael Harding Oil Paint Colour Chart anywhere

    Please be aware of the limitations of screens and printers when you view the brochure; the colour value and saturation may differ from the colour within the tube. As Adobe say in “About Colours in Digital Graphics

    “Because each device has its own color space, it can reproduce colors only in its gamut. When an image moves from one device to another, image colors may change because each device interprets the RGB or CMYK values according to its own color space. For example, it is impossible for all the colors viewed on a monitor to be identically matched in a print from a desktop printer. A printer operates in a CMYK color space, and a monitor operates in an RGB color space. Their gamuts are different. Some colors produced by inks cannot be displayed on a monitor, and some colors that can be displayed on a monitor cannot be reproduced using inks on paper.”  — Adobe  “About Colour in Digital Graphics”

    Please be aware of the limitations of screens and printers when you view the brochure; the colour value and saturation may differ from the colour within the tube. As Adobe say in “About Colours in Digital Graphics

    “Because each device has its own color space, it can reproduce colors only in its gamut. When an image moves from one device to another, image colors may change because each device interprets the RGB or CMYK values according to its own color space. For example, it is impossible for all the colors viewed on a monitor to be identically matched in a print from a desktop printer. A printer operates in a CMYK color space, and a monitor operates in an RGB color space. Their gamuts are different. Some colors produced by inks cannot be displayed on a monitor, and some colors that can be displayed on a monitor cannot be reproduced using inks on paper.”  — Adobe  “About Colour in Digital Graphics”

    Please be aware of the limitations of screens and printers when you view the brochure; the colour value and saturation may differ from the colour within the tube. As Adobe say in “About Colours in Digital Graphics

    “Because each device has its own color space, it can reproduce colors only in its gamut. When an image moves from one device to another, image colors may change because each device interprets the RGB or CMYK values according to its own color space. For example, it is impossible for all the colors viewed on a monitor to be identically matched in a print from a desktop printer. A printer operates in a CMYK color space, and a monitor operates in an RGB color space. Their gamuts are different. Some colors produced by inks cannot be displayed on a monitor, and some colors that can be displayed on a monitor cannot be reproduced using inks on paper.”  — Adobe  “About Colour in Digital Graphics”

  • What do the numbers in the Details and Descriptions of Individual Colours mean?

    Details and Descriptions of Colours

    The individual colour descriptions provide assessments for certain determinable characteristics of all the colours presently in the Michael Harding Artist Oil Colours range as well as a few informal remarks by Michael on their qualities and idiosyncrasies when used.

    The Colour Index Number:

    This is the international system for classifying and identifying pigments by their (some times complex) chemical formulae (e.g. P(igment) R(ed) is expressed as Pr 106, Mercuric Sulphide known as Genuine Vermilion). The use of vague traditional or invented colour names is thus clarified and so in theory at least is the vexed matter of what pigment manufacturers actually put into their paints. If a colourman is honest, each constituent pigment in a paint can be specified precisely, and the practice of secretly adulterating or even completely substituting cheaper alternatives is made impossible. Assuming, that is, the colourman is honest . . . I can certainly state that there are no secret additions to any of the paints in my range. What you read as the C.I. number on the label is what you get.

    Estimated Drying Speed:

    Keep in mind that all drying speeds are affected by: temperature, humidity and light levels. The aforementioned conditions provide for a broad calibration of comparative speeds from: Very Fast, such as the Umbers, many of which if used neat (unmixed with other colours), will be touch dry within a warm summer day, to the Very Slow, which in an unmixed state, might take up to a week to cure. This is governed by how thickness of the paint layer. Please remember the thicker the layer the longer it will take to cure.

    Lightfastness:

    This gives some indication of the resistance of a pigment to fading when exposed to very high light levels. Though the commonly used numerical system for this is the scale devised by the American Society of Testing and Manufactures (ASTM I-V), in practice the fade resistance of pigments is greatly affected by their concentration, or lack of it, in paint mixes. Thus an excellent lightfast pigment (ASTM I), if dispersed in a paint by the addition of fillers will in consequence show increased tendency to fade. As I have said before, there are no fillers added to the pigments in my oil paint range.

    Tint Power and Transparency:

    This characterizes the ability of a given paint to cover over the substrate onto which it is painted. Cadmiums are the most opaque and Indian Yellows are the least opaque. Transparency should not be confused with sheer strength of colour or Tint Power as it is revealed in mixes. Some transparent paints, e.g. the Phthalo Lakes, are ferociously strong when mixed with sturdily opaque hues.

    Oil Content:

    This indicates broadly how much oil has to be ground in with the dry pigment or the lake dye in order to make it into a workable paint. Paint with high oil content will generally, but with exceptions, dry to a glossier surface and that with low oil content will be leaner and tends to be less glossy.

    Toxicity:

    This subject must be taken seriously if you want a long and healthy relationship with oil paints.
    More advice is given in the Health and Safety section of the Michael Harding website.

     

    All Michael Harding Artist Oil Colours conform to ASTM D-4236 (always read the label).

  • Lapis Lazuli an article by the renowned authority David Margulies

    2B Lapis lazuli tileCopyright no sections to be used without permission.

    Lapis Lazuli an article by the renowned authority David Margulies

     

    Lapis lazuli was described by Pliny the Elder as ‘a fragment of the starry vault of heaven’. It is, and always has been, the most exotic of semi-precious stones and pigments. The best quality blue stone is to be found high in the mountains at Sar-i-Sang, Badakhshan province, north eastern Afghanistan. To our knowledge the oldest use of the lapis lazuli from that source dates back 9,000 years in the form of beads found at Mehrgarh, in present day Pakistan. Lesser quality stone can be found in the same mountain range in today’s Tajikistan. Another source for the stone is in the region of Lake Baikal, Siberia. There are deposits in Chile, Canada, America, Angola and Italy.

    Much of the writings about the stone and the pigment are surrounded with myth and mistakes, much by transmitted error. The first myth is that the word lazuli is derived from the Persian, ‘lajward’. In fact we do not know where the word originated from. The Old Persian word is ‘kasakaina’, while Middle Persian was ‘Kasken’. The word did find itself transmitted into New Persian. A similar word, ‘lazaward’, was transmitted into Arabic and thence into Medieval Latin as ‘lazzulum’ or ‘azzurum’. The word was translated into French as ‘azur’, and into English as ‘azure’. The pigment that is obtained from the stone is known in English as ‘genuine ultramarine’. The term ‘genuine’ is to assist in differentiating it with the synthetically made French ultramarine. French ultramarine was so called because it was a Frenchman, Jean-Baptiste Guimet who won a prize in 1828, offered by the Societe d’Encouragement for developing a synthetic alternative to the mined ultramarine. Ironically, it was the French who named the Holy States, ‘Outremer’, (in parts of present-day Syria, Iraq and Lebanon) during the First Crusades of 1096 to 1099,. The Latin for outremer was ‘ultra marinus’, ’beyond the sea’. The name of the pigment thus became ‘ultramarine’ in English. It should be noted that the word ‘azure’ was also used to describe another blue pigment. To confuse matters further, the lapis mines in Afghanistan are still translated by Afghan writers as the ‘azure mines’. The earliest known use of the stone is as beads found in Mehrgarh, in present day Pakistan, dating back to 7,000B.C. The first known use of the pigment was on an Egyptian funerary artefact, circa 1580 to 1550 B.C. and though found in a lime plaster paint mix with red iron oxide on a wall painting in Greece in the 13th century B.C., it is clear that such early finds are rare. The earliest known use of the pigment in England has been analysed by Professor Robin Clark in a manuscript, later restored in 920A.D. The first major use of the pigment was in the Buddhist wall paintings of the Kizil and Dunhuang caves in present day China from around the 4th to the 6th centuries A.D. During the 15th and 16th Century, one can find the very highest quality ultramarine being used by artists from Northern Europe, extending to Asia. One of the finest examples of the use of ultramarine is in a painting of the Italian Renaissance, ‘Bacchus and Ariadne’ by Titian, 1521 to 1523, National Gallery, London. The Divan of the Sultan Husain Baiqara, circa 1490, executed in Herat is a fine example of ultramarine so often found in Islamic art of the same period.

    Lapis lazuli is not one mineral but the name given to a collection of up to nine different minerals, some sharing the same elements. The main minerals are lazurite, hauynite, sodalite, noselite, calcite and pyrite. The specific mineral that bears the blue of the pigment is named lazurite. Lazurite comes in two forms, though both are crystals. One form is rock-like, while the other has an isometric crystal structure with the appearance of blue nuggets sitting on a matrix of white calcite crystals. It is the latter that geologists name as lazurite.

    T. Highest grade lapis lazuli for jewellery, Afghan

    Fig.1. Grade 1A Afghan Rock.

    It is the quantity of sulphur radical anions trapped within the cubic holes in the lazurite lattice which determines the blue colouring. Even the chemical formulae for lazurite vary depending on location or even from seam to seam. Joyce Plesters, working at the Scientific Department of the National gallery, defined it as follows: 9Na, Ca) 8 (AlSiO4)6(SO4, S, Cl) 2 The main differences between synthetically produced French ultramarine and genuine ultramarine obtained from lapis lazuli are as follows: 1. The pigment particles of French ultramarine are very fine and uniform. 2. The crystals of French ultramarine are of a consistent blue colour. 3. Because French ultramarine crystals are smaller and more regular they diffuse light more evenly. 4. French ultramarine pigment has a strong electro-magnetic reaction, particularly visible if mixed into linseed oil. 5. Genuine ultramarine particles are irregular in size and the shape tends to be conchoidal, that is to say, shell-like. 6. The particles or fractures are more transparent in comparison with French ultramarine. This would explain the luminous quality of the reddish blue paint films of Renaissance, and post-Renaissance paintings. 7. Finally, the major characteristic of the crystal fractures of genuine ultramarine is that they are not uniformly blue. Examined under a microscope, the fractures can vary between those that possess a rich blue colouring, full of sulphur.

    Fig.2. Lazurite ‘crystal’.

    Fig.2. Lazurite ‘crystal’.

    Others may appear to be less and less blue; while some will appear to have no blue colouring. There are three ways of preparing pigment from the solid mass. 1. Crushing, grinding, washing and levigating. 2. The ‘pastille’ method, as exemplified by the recipe of Cennino Cennini, Italian, 15th Century. 3. The froth floatation method; the most common commercial process in use today. Many commentators throughout the past few hundred years have repeated the axiom that, however blue (or pure) the mass, it will not be sufficient to rely on grinding and washing in order to achieve the best results. ‘As Plesters [Joyce Plesters, Scientific Dept. National gallery, London, 1949-1987] has noted, unless the lapis lazuli from which the pigment is prepared is of exceptional quality, simply grinding and washing produces only a greyish blue powder’. Pigment Compendium, A Dictionary of Historical Pigments’. Contributors: Nicholas Eastaugh, Valentine Walsh, Tracy Chapman, Ruth Siddall. Publ. Elsevier Butterworth Heinemann, 2004. Page 219. “You can’t just take lapis lazuli, however good the quality of the colour and just grind it up and mix it with a paint medium to make a very satisfactory pigment. You actually have to extract the pigment from the mixture of minerals that constitute lapis lazuli.” Ashok Roy, Director of Scientific Research. Director of Collections. National Gallery, London. ‘The Story of Blue’. Nature Video. YouTube, published 14th August, 2014.

    2B. Lapis lazuli typical formation from Flores de los Andes mines, Chile

    Fig.3. Typical formation of lapis lazuli from the Flores de Los Andes Mines, Chile.

    Of course, one, if not the major issue, is the type and quality of the mass that one uses in the production of the pigment. Lapis lazuli from Chile may typically contain a very high percentage of impurities. It is believed that Cennino Cennini wrote ‘Il Libro Dell’Arte’, the most famous of artists’ treatises. Unfortunately there are no original texts in existence. We only have a copy of a copy, dated 1437. He wrote: ‘ And if you want to recognise a good stone, take that which you can see has a greater blue-coloured content, although it all has something like ash mixed in. That which contains less of the ash colour, that is better.’ Page90. Lara Broecke translation. Archetype Publications. 2015. Broecke writes in her foot note: ‘The ash coloured material to which Cennino refers consists of calcite and pyrites (and often other materials), which are present alongside the blue lazurite in lapis lazuli.’ Chapter 62. Page 90. It cannot be emphasized enough. Cennino was referring to the impurities that could be seen, the calcite and pyrites. He was not referring to what he could not see. It should therefore be considered that all of the sources that state that grinding solely will produce a greyish blue powder are in fact referring to lapis with a degree of calcite and pyrites left in the mix. However, many of the sources do emphasize that the choice of the stone in the first place will influence the quality of the pigment produced from it. It should also be pointed out that it is quite easy to pick out much of the calcite as the grinding proceeds. It is also possible to wash out much of the pyrites as it is broken off the lazurite particles.

    T. Afghan ultramarine.Ground & washed

    Fig.4. Afghan rock ground and washed into four grades at the Bodleian Library.

    In professor Yves Porter’s monograph, ‘Painters, Paintings, and Books’, he quotes Persian sources under the heading of ‘Techniques for Washing Lapis’. He states: ‘Several methods more or less sophisticated are suggested in various texts. Indeed crushed and unwashed lapis gives a bluish-grey colour, which is very far from ultramarine. The long and delicate process of washing lapis kept a whole body of professionals (lajvard-shuyan) occupied within the workshops.’ It would be correct to state that simply grinding lapis lazuli consisting of much calcite and pyrites, would produce greyish-blue powder. However, even those who recommend the pastille method clearly state that one should commence with the best quality lapis lazuli with the highest blue content (lazurite) and very least calcite and or pyrites. The second suggested method of producing the best quality blue pigment is through the ‘pastille’ method, first known reference is the method ascribed to Geber, the 8th century Arab alchemist. Since that time there were many authors who described a ‘pastille’ method. The most famous and most detailed recipe could be found in Cennino Cennini’s ‘Il Libro Dell’Arte’. The recipe refers to mixing the ground lapis lazuli with pine resin, mastic, fresh wax into a ball, then covered with linseed oil. This was to be left for a number of days and then kneaded in a warm bath of lye. The best deepest lazurite is meant to fall out of the ball into the lye, which is then poured off leaving the pigment to be collected. The kneading process would be done in a new bath of lye and yet more pigment would fall out into the lye. This would be deemed to be the second grade of lazurite pigment. This process would continue with another clean bath of lye yielding yet a further lower grade of blue, until the final yield which would be known as ultramarine ‘ash’ because of the greyish colouring. Cennini ends his section on the purification of the ultramarine by humorously advising: ‘ And know that it is more the business of lovely young girls than men to make it because they stay put in the house all the time and have more delicate hands; watch out for old women though.’ Lara Broecke translation. This method can only be confirmed as effective if it can be repeated. Unfortunately, there are a number of professionals who have found that this method produces extremely inconsistent results. The other issue with this method can best be illustrated by the most elegant experiments published. Following the closest recreation of Cennini’s recipe the results were as follows: Of a total of 50g of lapis lazuli mass, all that was yielded of Grade 1 quality was 0.45g- representing 0.9% of the total. Grade 2 yielded 0.45g – representing 0.9% of the total.

    Grade 3 yielded 0.47g – representing 0.94% of the total.

    Grade 4 yielded 0.22g – representing 0.44% of the total.

    Of the 50 g, the method yielded 1.59g of pigment– representing 3.18% of the total.

    This means that 48.41 grams would remain lost in the pastille, a shocking loss of 96.82%. This would strongly suggest that this method would not be commercially viable. The third way of producing ultramarine from the ground lapis lazuli is through the froth ‘floatation’ method. The intention of this method is to be able to create an economically viable way to separate the lazurite particles from the impurities that are found in the mass. The mass (rock) is ground and then placed in a bath of water which can be heated, aerated and agitated, creating bubbles. The procedure is carried out in three stages.

    1. The removal of iron pyrites.

    2. The removal of calcites.

    3. The removal of mica, quartz and other silicates.

    The process is under patent pending. Much of the details of the alkali reagents, and more surprisingly, acid reagent, added at the different stages, are still a matter of trade secret. These reagents consist of a hydrophilic and a hydrophobic group called ‘foamers’. In the first stage the pyrites cling to the surface of the bubbles and are then skimmed off and away.

    7. Detail. Hydrophobic iron pyrites floating on the surface of the bubbles.Email version

    Fig.5. Hydrophobic pyrites clinging to the surface of the bubbles, ready to be disposed of.

    Using different reagents the carbonates are then skimmed off. In the third stage an acid reagent is rapidly introduced to decompose the poly-sulphates. An alkali is added to neutralise the acid before it can damage the lazurite particles. The water plus the reagents are washed out of the container leaving the lazurite lying at the bottom of the container. The lazurite particles are washed out thoroughly to remove any traces of the reagents and left to dry.

    Earlier it was mentioned that the greyish appearance of the pigment described by Cennini et al was because of the visible impurities such as calcite and pyrites. There is another reason why the powder may have a greyish blue appearance. With the use of a petrographic microscope It is possible to observe pigment structures invisible to the naked eye which may also explain why the powder can appears greyish blue.

    When examining the pigment particles microscopically, from all three of the above-mentioned production methods, it is clear that they share one characteristic in common. The conchoidal fractures contain different amounts of the sulphur anions.

    Fig.6.Lazurite-laden bubbles being paddled off from the unwanted silicates.

    Fig.6.Lazurite-laden bubbles being paddled off from the unwanted silicates.

    There are those that will contain a large quantity of sulphur, and are of the richest blue. There are those fractures with less sulphur and will appear to be of a paler blue, and there will be fractures that have no colour. The presence of partially blue and transparent particles of genuine ultramarine will dictate whether the pigment, in dry form, appears more or less blue to greyish blue. Even if the lazurite mass appears to be pure blue, with no calcite and pyrite present, it will contain varying grades of chroma, depending on the source (from which mine and from which country). The quality and chroma will even vary from seam to seam in the same mine.

    Froth flotation method. Grade1 lazurite. Mag. x10. Note remaining impurities. Email Version

    Fig.8. Froth flotation method. Mag.X10. Grade 1 lazurite. Note the remaining impurities.

    Washed and Blotted lazurite. Email version

    Fig.7. Washed and blotted ultramarine after the froth flotation method.

    The finest blue pigment comes from a rock which is dark blue, almost blackish purple with the least amount of impurities. And even then, one cannot anticipate the quality of the pigment before the rock or crystal is broken up and ground.

    David Margulies

    London 2015

    Copyright no sections to be used without permission.

     

  • Stack Lead White the Reincarnation of Rembrandt’s Lead White? By Michael Harding

    Stack Lead White the Reincarnation of Rembrandt’s Lead White? 

    Imagine for a moment that we are in Rembrandt’s studio. What would we learn, what would we see? Obviously genius in the making! To some he may be on a human scale of a god in his domain. On a more grounded level what can we glean from his studio practices? His materials for me would unlock many secrets to magnificent oil painting.

    Artist’s are constantly in search of methods, materials, shortcuts and even some “legitimate tricks” with which to improve ones painting, I think our eyes would dart around Rembrandt’s studio trying to find a clue as to how he produced the extraordinary paint strokes he rendered. When I study Rembrandts very closely, I examine his brush strokes and I try to imagine what he was thinking, not just about his subject, which was often himself. I feel he knew exactly where and how every dab should be placed. As is so often the case with geniuses they make it look incredibly simple.

    Rembrandt close

    Many scholars have noticed there is something different in the nature of Rembrandt’s oil paints, particularly his whites that cannot be simulated with any white today. There are many writings about this and I do not intend to claim to be the first to notice this or to regail you with the same observations. The realities are that the method by which whites, and in this case lead whites, were made has changed. Until the industrial revolution lead whites were made roughly in the same way, suspending lead over vinegar in a container and then burying under horse dung, yes that’s right its not a typo! The chemistry that takes place is well understood and quite simple in broad terms. First, vapors of acetic acid from the vinegar attacks the lead then, the carbonic acid from the warm horse dung converts the white corrosion into lead carbonate. This is a method traced back well before the time of Christ. The Dutch literally scaled up this process and built huge stacks of vinegar, lead and horse dung filled containers, which to this day is still referred to as the ‘old Dutch stack process’. For me to be able to recreate the actual white pigment that would have been familiar to Rembrandt and masters of this pre-industrial process is something of a hunt for the holy grail. I have been researching Rembrandt’s lead whites and the old Dutch stack process for many years. So how does it vary from other man made lead whites?

    I believe when nature comes into play, as with snowflakes, every molecule is randomly different, and then every conglomeration of pigment particles on a nano scale is different. With industrially made pigments every particle tends to be uniform, every bit of colour is deliberately made to be consistent. In our modern world we are “trained” to want bright white things, paper, bleached loaves of bread, white chicken meat, the list goes on. Consistency matters in the modern world for example, imagine frustration if wall papering a wall to find the colour varied from one roll of paper to the next. How many bright white acrylic primed canvases can you see in the art stores around the world? For me this is crazy not only is bright white completely unnecessary it is difficult to paint upon because of the extreme contrast. Most experienced artists start by obliterating this crisp white surface to a more neutral sympathetic hue as a first step.

    So, what looks different in the Rembrandt whites? They have a unique texture almost a goopy, syrupy quality. I try and imagine what he was thinking about when painting his paint. Did he like it? Did he have to fight to get it to do what he wanted? I think not. I think he knew exactly how to make his paint behave.

    Many artists of the pre-industrial age appear to have been able to throw wonderful passages of white light as if it magically flowed from the brush. An example is the wonderful painting of ‘woman bathing’ in London’s National gallery. (photo 1)

     

    Making stack lead white has been a 25-year mission for me. How am I doing it? I start by deliberately hunting the horse fields to gather the freshest horse poop I can. The warm steaming type is best, because it’s the most active biologically. I also visit the horse dung piles that are mixed with straw which been cleaned out of the stables by the people who lovingly take care of these generous animals. Straw is a good addition because it helps aerate the mixture. I then take strips of roofing lead cut it to strips, 6 inches by 24, and roll it in a spiral and then place this in a small clay container over a small amount of vinegar settled at the bottom. I then bury the pots in the horse dung. After a number of weeks magically nature runs its course producing the most beautiful white flakes resembling something more along the lines of the paper one finds in a wasp nest or something made by an insect. The process in itself I find beautiful! This process takes approximately eight weeks depending on time of year and other weather variables.

    What does the pigment look like once it is washed of impurities, ground by hand with pestle and mort and then ground in linseed oil? Firstly, the colour is that of a soft gentle non-brilliant white more like the colour of parchment, soft and subtle. The other fascinating observation compared to an industrially made lead white is in the handling quality. When the paint has been left standing and one takes a pallet knife to it and starts to manipulate the paint, at first it is very short and produces only abrupt wisps of paint.

    Stack lead knife

     

     

    Here you can see the stack lead white, which has been standing is thick enough to support the weight of the pallet knife.

     

     

     

    Stack Lead white jpg

     

     

    If you manipulate the stack lead white further for a few seconds the paint starts to become what seasoned oil artists refer to as “ropier” and produces long dragged wisps of paint below.

     

     

    It even has what could be described as “flow” for a moment. From a more scientific point of view its whats known as “thixotropic” or put briefly for the lay person a material that become more fluid when agitated or stirred.

    I am very proud of my stack lead white as it is what I envision Rembrandt to have used as his white oil paint. My output at the moment is very limited due the labor intense process.

    Michael Harding

     

    In addition I am very proud to include these quotes by the well known American artist David Leffel

    In all these many years I have been painting, which is synonymous for me as studying the art of painting, brushstrokes and paint quality have been essential concerns. David Leffel portrait

    The quality of Rembrandt’s white has always been a source of fascination. As Mr. Michael Harding has already stated, “his whites cannot be simulated with any white commercially manufactured today.”

    Try as I might—adding various mediums to my tubes of lead white, as well as grinding my own lead paint—I could never produce a white which would enable me to achieve the paint quality I sought. And now a new door is opened—stack white! This white allows an artist—any artist—long limpid descriptive brushwork, brushstrokes that reveal the workings and understandings of the mind behind the hand. The long supple quality of stack white that allowed Rembrandt the freedom and expressiveness that enthralls us to this day is, at last, at hand.

    As with all of Michael’s colours, quality and integrity are in every tube.

    David Leffel

     

  • Composition of Paint

    If you think of paint as a two-part material, with the oil being the glue that binds the pigment particles into place, it is the pigment that is responsible for delivering the colour. The pigment must therefore have the following qualities:

    • it must be light-fast to a reasonable level (i.e. far more light-fast than would be acceptable for house-paint)
    • it must not be soluble in oil or in thinners like turpentine
    • it must have the right pH balance (i.e. acid to alkaline) with the linseed oil or other oil into which it is ground, otherwise the pigment might have little resistance to the bleaching effect of an acidic oil (which would cause a marked colour shift)
    • it must not, in normal circumstances, react chemically with other pigments in the range

    So paint manufacturers choose pigments which have these properties, or rather the ability to resist these forms of attack. Broadly speaking we divide pigments into two groups: inorganic and organic.

  • Inorganic Pigments

    Natural

    These are pigments not made from the tissues or chemical residues of animals or plants. They can be further divided into those which are natural and those which are man-made. The natural are a simple matter to discuss. All our predecessors did was to dig them out of the ground or from rock faces. In most instances these were dry ground with a pestle and mortar until they made a fine powder. In the case of Lapis Lazuli (the original version of Ultramarine Blue) excessive grinding simply causes the blue colour to disappear! There are many books which tell romantic stories of the mystique which, sometimes inappropriately, surrounds these pigments. Vermilion, for instance, in its natural form was called Cinnabar, a granular terra-cotta-like mineral which was gathered by shooting arrows at seams exposed in cliff faces.

    We live in a modern world where the word ”natural” is normally associated with superior quality. Yes, you could take a natural earth as did the colour makers of the Renaissance and laboriously grind it, but the result, unromantically, may well be unstable physically, and contain such impurities as to make it colorifically impermanent. To be honest, as an artist’s colourman, I find the natural earth pigments a nightmare to use in making paint, and if possible I avoid them! But for Terre Verte and Raw Sienna there are no manufactured substitutes. Both have been micronised to give them consistency. I find that Terre Verte is very stable, in that adverse changes in consistency can be avoided after a few days. But Raw Sienna is a different matter: not only does it contain “free radicals” (other elements) which are wild cards awaiting something to react with, but it has a tendency sometimes to flocculate, which means that particles, once evenly dispersed, might later regroup like miniature magnets and form lumps. You have been warned!

    Manufactured

    Unsurprisingly, paint makers, over thousands of years, have attempted to regularize supplies of stable pigments by initiating chemical processes (until quite recently, without fully understanding them) which create more reliable versions of such “found” materials. A good example of this is Lead Carbonate, which is a naturally occurring chemical, but which has been made for centuries by the “stack” process, and is of course the constituent pigment of the uniquely handling Lead Whites. Most of the earth colours are in fact mixtures of Iron Oxide and Manganese or Magnesium salts, and modern chemistry allows these to be manufactured to the highest standards of consistency and purity. As such chemical knowledge developed, other metal compounds were found to be useful. Between 1780 and 1900 chemists progressively discovered that Zinc, Chrome, Cobalt, Manganese, Titanium and above all Cadmium based compounds provided the basis for some of the most brilliant and durable colours you will find on your palette today. I find that man-made inorganic pigments are a dream to make paint from – and to paint with. The only disappointment was the Lead Chromates (not to be confused with Chromium Oxide) which have been abandoned due to their tendency to darken and to react with other colours. The rest have been unqualified successes.

  • Organic Pigments

    As I said, organic pigments are constituted of what was, at some time, plant or animal matter. And again they divide into the natural and those resulting from sophisticated manufacture. The natural ones were made simply by crushing up insect or vegetable tissue (e.g. Cochineal, Gamboge, Indigo, Madder).As you might expect, these were hardly a safe bet for reliability, and except for restoration purposes they have long since been replaced by more stable compounds. I suppose that the one survivor into widespread modern use is Ivory Black, now made from charred animal bones, originally from ivory scraps.

    The story is different with the manufactured or synthetic versions. The basis for these pigments is the residue of plants compressed in strata of rock millions of years ago – the hydrocarbon compounds we know as crude oil. In the 18th century chemists were starting to experiment with “coal tar” in order to make lake pigments, that is, coloured liquids which have to be given body with inert powder so as to be used as paint. The results were usually disastrously impermanent, as some portraits by Joshua Reynolds demonstrate. Throughout the 19th century manufacturers produced many “coal-tar” or aniline dyes for industrial purposes but lacked the means to test their permanence. Often, artists would use these brilliant lakes, only to find they would fade in 5-10 years. As a result, by the 1930’s their reputation stood very low. Twenty years later, three synthetic organic lake pigments were regarded as stable enough for artistic purposes: Alizarin Crimson, and Phthalo Blue and Green. The big change came with the adoption of uniform rigorous lightfastness tests by the American Society of Testing and Manufactures (i.e. the AMTS ratings you might be familiar with), the huge expansion of the plastics and chemicals industries in the 1950’s, and the demand for pigments lightfast enough to stand up to, say, tropical sunshine on a car body. Consequently the last fifty years have seen the development of brilliant and very lightfast organic pigments, many with names I find difficult to pronounce.

    The quality of pigment that I, as a colourman, can obtain, has never been higher. And as I aim to produce what Chris Ofili has described as “beautifully honest” paint I intend to take advantage of all the advantages of modern paint chemistry. I am not in the business of making twee “old master” colour which will disappoint. Unfortunately, for many large paint manufacturers, the incentives have never been stronger to counter these advances in raw materials by favouring their own cost-benefit at the expense of the ultimate quality of the product. I aim to benefit artists, and not my accountants. Just thinking about making Burnt Umber on a three roll mill excites me. Perhaps I’ll just stop for the day, go home and start painting!