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Home , Cerulean, Cobalt blue, Egyptian blue, Lightfastness, Light blue, Marking blue

Journal & Proceedings of the Royal Society of New South Wales, vol. 153, part 2, 2020, pp. 164–179. ISSN 0035-9173/20/020164-16

The history of in the Fine — , from the perspective of a maker

Steven Patterson CEO, Derivan Pty. Ltd., Sydney Email: [email protected]

Abstract In this text, I will introduce you to the colour blue, how and why we see it and when we, as a species, started to discover and use its various versions. I only cover blue pigments as opposed to . Many of the that I discuss are known by several names depending on locality, the age in which they were used and, at times, slight variations of their chemical makeup. I do not look at blue dyes mainly due to their inherent lack of (and, therefore, usefulness to the artist).

Introduction what was seen daily looking skyward or the he largest expanse of colour that any mottled of the never-ceasing oceans, Thuman is likely to have seen, or ever will, it is worth understanding just how we see is the blue of the sky followed by the blue colours. of the sea. Why then was this colour the In much the same way our ears tune in last to be named by Homo sapiens and one of to sound, or we use a radio to tune in to the least to have been reproduced in paint? a radio station, our detect different “The first new blue discovered in wavelengths of electromagnetic radiation 200 years” (Garfield 2017) — headlines from or energy. The various wavelengths falling just a handful of years ago. One has to ask on our eyes’ rods and cones send a signal to how flight, aeronautics, and nanotechnol- the brain commensurate with the particular ogy have all been discovered in the last 100 wavelengths which, if everything is working years and yet we have only discovered one correctly, we interpret as colour. new blue in twice that time. We can gain a better understanding of Is this recalcitrant frontier a sign that how colour works by understanding what we already know all that there is to know happens when colours are combined: blue about colour, or are we blissfully unaware of is a primary colour in both Additive and a plethora of unfound hues? An insight into Subtractive colour mixing. In other words, these questions may come from examining along with , it is not possible to add other the history of blue. To do this, we need to colours together to make blue. As a quick look no further than the discipline of Fine aside, Daniel Nelson asked in in 2018, “what Arts which has unknowingly documented two colours combine to make blue?” and the discovery of blue across the millennia. hypothesised that and mix to make blue. While this is true, many would How we see colour counter that cyan is indeed a blue; hence, in Before delving into the intricate past of mixing magenta with it, one is only chang- endeavour to produce a likeness of

164 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts ing the of a blue to another blue rather ries posit that did not really know than “making blue.” that blue existed until relatively recently. Additive colour mixing occurs when dif- Jules Davidoff, who worked with the ferent colours of are immitted from Himba tribe from Namibia as recently as an energy source in the . 2006, found that not only did the tribe not An example of this is an LCD screen where have a name for blue but they also found differing amounts of red, blue and it very hard to distinguish it. In a series of light are combined to form a vast array of tests to detect a blue , when presented colours. All three colours together produce with 11 squares, 10 of which were green and what we call light or a light contain- one blue, the surveyed tribe members were ing all the wavelengths of the visible light unable to distinguish the blue square that spectrum (i.e., ). Subtractive colour most people in the “outside” world would mixing can be most easily understood using readily pick from the line-up (Robertson the example of mixing . In the pres- et al. 2006). ence of sunlight (i.e., all wavelengths of the Indeed, when one thinks of it, back visible spectrum or white light), when two beyond 6,000 years ago there was very little colours, such as blue and , are mixed that was blue. The blue we see in the ocean together, their combination will result in a is due to the of water absorbing reflection of the resultant wavelengths of more of the red end of the spectrum and the yellow being reduced by the blue, the therefore producing what we perceive to combination of which produces what we be a blue hue, this of course can vary con- perceive to be green, which lies between siderably depending on impurities in the yellow and blue on the spectrum. water. High content can give the water a hue, as can tannin from leaves and Did we always “see” colour? trees leaching into a water course. However Now that we know how we see colour, we it is not possible to harness the blue of water may wonder why we have so few blues and to tint or colour, for instance, for use in a why it has taken so long to discover a new paint. one. As a matter of fact, it appears that we One may claim, “Of course the sky is may not have always “seen” blue, or at least blue!”, yet we can respond, “Hold on: we may not have always given it its status as a know that is not true!” — the sky appears colour. blue because the sunlight is diffracted by It is known that, as humans, we have tiny particles in the stratosphere. Subse- far fewer receptors for the colour blue in the quently, some of the sunlight is diffracted , compared with red and green. This was into the blue spectrum of visible light by par- thought to be due to the fact that there was ticles which are very close to the same size very little food coloured blue; hence, we as as the wavelength of blue, which explains humans did not need to concern ourselves why we perceive the sky as blue. Theories with this colour that much. Specifically, it for this phenomenon were first described is widely believed that early man could only by Lord Rayleigh,1 Richard Gans, and Peter recognise , white and red and then later yellow and green. In fact, many theo- 1 See Rayleigh scattering, [Ed.]

165 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts

Debye and, more accurately, by Gustav Mie. wall.2 We will now look at when the first Intriguingly, their work was based on ear- blues were found and how. lier work carried out by Horace-Bénédict de Listed below, for completeness, are the Saussure and Alexander von Humboldt who blue pigments in general use over time. developed and used a “cyanometer,” which They are listed according to their Colour consisted of squares of dyed in gradu- Index pigment number, which is a general ating shades of (mixed with classification of colour by chemical type. A white or black) and laid out on a circle that more detailed list, maintained by The Soci- was then held up at a particular distance ety of Dyers and Colourists (UK) and The from the viewer and used to compare to the American Association of Chemists colour of the sky at that specific place and and Colourists (US), provides more specific time. five-digit numbers. Looking wider afield, peacock feathers appear to have blue in them; once again, this Ancient blues is not caused by a pigment absorbing and re- emitting particular wave-lengths as a colour, but rather by diffraction, or the slight bending of light waves known as structural colour. The wings of a blue-winged wasp and the wings of the blue morpho are all light diffractors, which can be best thought of as acting a little like layers of slits or grates that diffract the light to produce Han blue a blue. I will discuss this further with refer- ence to phototronic pigments. Smalt A timeline of blue pigment discovery Lapis lazuli PB29 and Egyptian blue — PB31 While there is evidence of very early use from around the world of naturally occur- Some of the earliest existing examples of ring and earths of red and Yellow. the use of blue for adornment is provided made from as a result of fire by the Egyptians, who used lapis lazuli for and in the form of carbonate ornaments and ceremonial artefacts. The and other compounds. All colourants that original blue made from lapis were readily found or easily dug up. These lazuli (Italian oltremarino; ultra: beyond, “pigments” are found in around the marino: sea) was so called as the lapis was world from France to Australia and date transported from literally back millennia. However we can see from “beyond the seas” (from a Eurocentric per- above that there were no naturally occurring spective, of course), and it was originally blues that were able to be found and easily ground into a paste and applied to a 2 There are no blues in the Indigenous works presented in B. J. Gillam, Figure-ground and occlusion depiction in early Australian Aboriginal bark paint- ings, JProcRSNSW 152: 251–267, 2019. https://royalsoc. org.au/images/pdf/journal/152-2-07Gillam.pdf [Ed.]

166 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts employed by the Egyptians in solid form for Egyptian blue is the earliest blue pig- ornamental use in . But there is no ment that we are aware of whose forma- record of them having successfully formu- tion is definitely based on a chemical reac- lating it into a paint, which was left to the tion. This reaction takes place when silica clever many centuries later. Due to (sand) is heated in the presence of a the processes of collection and manufacture compound and an alkali for several hours. through a series of manual kneading, wash- Egyptian blue, when studied at a micro- ing and filtering, it proved to be a highly scopic level, consists of blue crystals, with expensive pigment. There are many stories impurities of unreacted quartz and small in later years of well-known artists not fin- particles of . Some people thus refer to ishing pictures or saving their tiny amounts Egyptian blue as a . of ultramarine for the final application and Egyptian blue’s reaction can thus be only on especially important icons. described as Cu2CO3(OH)2 + 8 SiO2 + Although the Egyptians were never able 2 CaCO3 → 2 CaCuSi4O10 + 3 CO2 + H2O to incorporate lapis lazuli into a paint suc- As we will see with many other blues, the cessfully, there is little question that it was colour is derived from copper. However, they who first manufactured a blue pigment, looking at the formula, the starting com- using a chemical reaction. This pigment, pound is highly similar to that of azurite, now known as Egyptian blue, was used in which was also to be found in those times. paint in artwork and ornaments, and the Egyptians indeed referred to their discov- Azurite — PB30 ery as artificial lapis lazuli: “The term for Like lapis lazuli, azurite is a naturally occur- Egyptian Blue in the Egyptian language is ring mineral, and, when ground and washed, ḫsbḏ-ỉrjt which means artificial lapis lazuli it produces a powder reminiscent (ḫsbḏ)” (Pagès-Camagna 1998). of a clear blue sky. Azurite was most likely I argued that this is the first record of a also used when lapis lazuli was not on hand, manufactured blue, yet this applies if one namely earlier than Egyptian blue; however does not consider the incredible amount it does not appear as highly prized as lapis of work that goes into refining lapis lazuli. lazuli, as it is a light blue rather than the rich th As recorded in the 15 century by Cennini dark blue of lapis. It was still used in paint- (who devotes a several pages to detail its ing between the 14th and the 17th centuries precise handling extensively, including who in China, Japan and and was a major should do the work), “You must know also blue pigment in the Middle Age in . that it is rather the art of maidens than of Verditer blue and blue bice are synthesised men to make it because they remain contin- versions of a , simi- ually in the house and are more patient and lar in chemical composition to azurite. It is their hands are more delicate. But beware believed that these blues superseded azurite of old women.” (Cennini, 1899). On a more predominantly due to cost (Bristow 1996). serious note, the manufacture of lapis lazuli is mainly mechanical, as it involves taking a Han blue semi-precious stone and crushing and puri- Han blue was a manufactured copper fying it. silicate pigment found since the Chinese

167 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts

Han Dynasty (208 BC–220­ CE). It is similar Vivianite in chemical makeup (BaCuSi4O10) to the Vivianite is also known as blue and Egyptian blue CaCuSi4O10. It has also been earth iron blue. Its is a phosphate referred to as Chinese blue, but the name of divalent iron with a significant amount Han blue is preferred to avoid confusion 2 of water: Fe +3(PO4)2(H2O)8. Vivianite has with other more common blues recognised been used for millennia by artists although as Chinese blue. Synthesised Han blue has a sparingly due to its scarcity in an agreea- similar chemical makeup to the rare mineral ble blue state and its known propensity to effenbergerite. (Eastaugh et al. 2004) change colour unavoidably. It is sometimes Subsequently, if we are to believe modern confused with azurite because it too changes pigment history, there was somewhat of a colour over time, but, unlike azurite that hiatus between the Egyptians’ discovery of changes into the green of , vivi- ḫsbḏ-ỉrjt (Egyptian blue) earlier than 3,000 anite tends to continue its process past the BC, Han blue by the Chinese around 200 green and through to a deep blue-black (as BC and the next blue in more modern times described below). It is found in many places over 2,000 years after that. Or was there? around the world — specifically, in ancient Other possible early blues wetlands or where deposits of peat are now found, rich in organic matter but lower in Thomas Katsaros, in his 2019 lecture at the oxygen and calcium concentrations. Symposium on the History of As is evident from his 1921 book The and Research of the Colour Blue at the Her- Manufacture of Earth Colours, Josef Bersch akleidon Museum in Athens, argued that in understood vivianite’s chemical compo- ancient Greece there was at least knowledge sition and was cognizant of its ability to of other blues as found in the records of oxidise; however, he still thought it to be Theophrastus of Eresos — the successor to stable. Eastaugh et al. (2004) touch on the Aristotle at the Lyceum — who wrote on pigment altering to a yellow, which pro- stones in 315 BC listing, among other things, duces an overall green pigment (p. 266); the colours of the painters of his time and however, the changing colour of vivianite recorded three types of cyanus (blue): Cyp- is best explained by Alfredo Petrov (2008) riot, Scythian and Egyptian. While it was in A Scientific Study of the Absorption of Evil generally accepted that Chrysopastos (Cyp- by Vivianite, where he describes the various riot) cyanus was lapis lazuli, doubt remains states of vivianite and how it transmorphs as to what the Scythian cyanus was: possibly into metavivianite: ? While there is no certainty as to Some people think vivianite darkens by the exact meaning, the jury is still wonder- oxidation — absorbing oxygen from the ing what blues Theophrastus was referring atmosphere — and then flakes apart along to; Thomas Katsaros posits that at least the the cleavages by “drying out,” i.e. losing Greeks believed that there was more than some of its 8 waters. They optimistically just lapis lazuli and Egyptian blue at that hope that both of these processes can time (azurite being included with Egyptian). be hindered by a thin coating of lacquer (which is why some specimens in old col- lections were varnished), or by dipping

168 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts

in oil, or sealing it in a glass jar. They are There are many other examples in China correct that both oxidation and water loss and Japan of blues made from either both are taking place, but not in the way they copper or/and — or at least that is imagine and not in any way that could what we know now is their main colour con- be prevented by a coating of lacquer no stituent. However, following the accepted matter how thick! To somewhat oversim- Western timeline, as a pigment plify and paraphrase the process, when (as opposed to a frit or ground glass) was (particles of light energy) enter yet to be discovered. Hence, we move on to a transparent vivianite crystal, they can Prussian blue, the next blue to be discovered. knock a proton (a hydrogen nucleus) out of one of the 8 water molecules, which Modern blues converts the water into a hydroxyl (OH) which has a negative charge. This Prussian blue extra negative charge is balanced by oxida- tion of one iron atom, whose valence state Cobalt blue changes from 2+ (ferrous) to 3+ (ferric). Notice that no interaction with the atmos- blue phere was involved — no oxygen entered the structure from outside, and no water molecule escaped to the outside — we are Ultramarine dealing with a completely internal reac- tion (oxidation by deprotonation). The Indanthrone blue liberated hydrogen (the proton) easily migrates through the crystal lattice, as Phthalocyanine blue in other species of proton-conducting crystals (which are currently undergoing blue intense study for potential industrial uses like fuel cells). No coat of lacquer is going Fluorescent blue to prevent this. Hence, while this is an intriguing colour, Mayan blue it is not one that is likely to see too many artists wishing to use it due to its inevitable Yin Min blue colour shift.

Smalt — PB32 Prussian blue — PB27 Concerning colourant in paint, early cobalt It was not until the very early 1700s that a blue was actually glass containing cobalt purely synthesised pigment was recorded and potassium (known as smalt), which as having been made in what we know as was ground and used as a colourant (smalt, Prussian blue. Swiss -maker Johann PB32) The earliest recording of its use has Jacob Diesbach, working in the Berlin labo- been found in by Hans Holbein ratory of his friend Johann Konrad Dippel, the Younger (1497–1543). was attempting to create red Florentine

169 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts lake — carminic which is extracted jar been labelled correctly, Diesbach might from and precipitated by alum, not have used it at all or discovered Prussian iron sulphate, and potash. blue, and he would have just continued to When Diesbach mixed what he thought make a boring old red! It took nearly another was potash with the iron sulphate, instead of 20 years for the formula to become public, the strong red he was expecting, he observed and, even then, both recorded early copies of a light pale colour. In attempting to con- the process continued to include the super- centrate the product, he first found it went fluous red cochineal dye. It is apparent no , and then a deep blue. Diesbach had one had worked out the true formula in that unknowingly, and by accident, produced time: how much longer might it have been the first batch of Berliner Blau, called many before it was discovered? other names such as Paris Blue, Antwerp Spare a thought for these poor guys who Blue but what we universally now know really had very little knowledge with which today as Prussian blue. to work, very few books, no internet of Digging a little deeper into this story, things, just a hunch and their observational Alexander Kraft, who believes that the most skills. We can only try to imagine what it probable year of discovery was 1706, has would have been like to work in a cold pieced together more details from several stone building, trying to solve a problem sources, namely letters and diaries from the and really not knowing where to start. They time. He found out that of one of Dippel’s lived in a time when the realm of science contemporaries, a younger friend named was the domain of gentlemen who could Senckenberg, recorded that Dippel had told afford the time and expense to experiment. him, concerning Prussian blue, that “he was Today, we might class them as great thinkers preparing a large amount of a ‘sal volatile’ or even as lunatics! Working by daylight or by dry distillation of calcined sal tartari candlelight, was very basic by our stand- (potash) and dried ox .” Dippel’s ards today, a furnace was just that — with assistant had not disposed of the remain- little or no idea as to the actual temperature ing mixture but rather stored and labelled to which compounds in an experiment were it only as sal tartari instead of noting it had being heated, accuracy would have been very other ingredients. This is the “potash” that difficult. (The first thermometer Diesbach used to make his discovery. Then was not developed until 1714.) he set about selling this newfound colour to Even under the most controlled condi- some local artists unbeknown to his friend tions of the time, many things were left to Dippel only to find out that, once his source chance. One can imagine lab benches with of what he thought to be potash ran out, he little on them in the way of apparatus, sun- could no longer make the colour. He then light filtered through smog-coated windows reported his problem to Dippel, who sug- being the only illumination, and suit-clad gested the use of bovine blood with potash. menfolk working away, hypothesising and This story makes one consider that, had experimenting with no boundaries and very Dippel not been aware of the mislabelling little clue as to what they were doing — a of the jar and exactly what was in it, the little like a child playing with a chemistry set formula might have been lost; or, had the before reading the instructions! And, bang,

170 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts here is a brand-new colour when you were ered essential to any basic healthcare system. not even expecting it! Hence, I guess it is Strangely enough, while Prussian blue is not a surprise to learn that Prussian blue used as a life-saving to heavy metal was discovered by accident. poisoning, when combined with acid and a Prussian blue is not only interesting for bit of heat, it gives off life-ending . the way it was discovered but also because “By itself it is only slightly toxic; however, it has played a role across many industries. it can produce extremely toxic hydrogen It is probably best known for its use in the cyanide gas in hot acid if heated to decom- blue of blueprints (since the mid-1800s), position or exposed to strong in which a sheet of paper is coated with radiation.” (McCann 1979, p.145) a mixture of ammonium iron citrate and For those with a technical interest, varia- potassium . The original draw- tions on the hue can be produced by varying ing (done on a thin paper, such as a tracing the reagents; an example of this is Turnbull’s paper) to be copied is then laid on top of the blue. Prussian blue continues to be used by coated paper and exposed to intense light. artists today although not to the extent of The light combines the two compounds, pro- other blues which have come after it. There ducing Prussian blue in the areas exposed are three variants of Prussian blue, and only to light and not protected by the drawn one of them will work in a water-based line on the design above. The coated sheet system such as acrylic or watercolour, which is then washed, and the unexposed areas still needs to be incorporated in a well-bal- washed clean to show the colour of the anced formulation. Many see Prussian blue paper through, as the white of the print. The as not as clean or brilliant as its successors. exposed areas are coated in the combined Nonetheless, it is still highly employed by compound being insoluble Prussian blue, artists and alike, although most resulting in a blue background, thus a blue paint manufacturers now offer a blend to print. A far easier and more precise way to achieve the colour rather than the original make copies than was the pre-existing prac- pigment.3 tice of tracing them by hand. Even when copies and copying were Cobalt blue — PB28 invented, large-scale technical and architec- I started with Prussian blue because it was tural drawings were still reproduced in this the first modern synthesised blue pigment. way for some time. However, the use of the cobalt as a colourant For anyone who has visited a dates back to the eighth and ninth centuries shop, Prussian blue is mixed with oil as and, in fact, far earlier when it was used “marking blue” or “engineer’s blue” to show to colour ceramics and jewellery, but as a high spots or areas that rub when “mating” colourant in paint, it was not commercially machine parts. produced for another century after Prus- In medicine, Prussian blue is used to very sian blue: around 1807 in France (where it effectively remove and radioactive from the body. In fact, it is included 3 Use of Prussian blue spread quickly around the in the World Health Organization’s list of world, even into Japan, despite its sakoku trade policy, essential medicines, namely those consid- where it is seen in Hokusai’s The great wave off Kanagawa (1830–1834), as Davies (2017) discusses. [Ed.]

171 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts was discovered in 1802). It is the effect of bias, and is very stable when formulating the element cobalt in rich blue in the now and lightfast in use. Furthermore, when used ubiquitous blue and white ceramics from in standard proper artist practice, it is quite China (although, apparently, early on, the safe, as most modern versions have no free blue was seen as too ornamental for local bio-soluble cobalt. Chinese tastes; hence it was not used much for local production but rather for export). Cerulean blue — PB35 (PB36) The amazing blue that we see in As cobalt blue was being released to art- churches and cathedrals across Europe owes ists in the early 1800s, a new blue was in its distinctive lightfast blue to the element development, once again making use of cobalt as well, which is somewhat ironic cobalt: the compound originally composed when considering that the word “cobalt” is of cobalt magnesium stannate (1789). In derived from “Kobold”, the name of a dev- antiquity, the term “caerulum” was used ilish sprite well known in German folklore to describe blue pigments in general, par- for mischief-making. Miners in the Saxony ticularly mixtures of copper and cobalt: the region discovered the silver-like ore which main chemicals in azurite or malachite and after smelting formed a “useless” lump and smalt. Cerulean blue production was then produced noxious and lethal fumes. The irri- further perfected by a process developed by tated miners thus dubbed the ore Kobold, Andreas Höpfner in in 1805 by and the name stuck. This was around 1500 heating that roasted cobalt and tin AD. together. However, the colour only appeared Nearly 200 years later, a Swedish chemist, available to artists in a catalogue from the Georg Brandt, at Uppsala University, began 1860s under the name of caeruleum. Ceru- researching the rejected substance. Suspect- lean blue is an inert, lightfast pigment that ing that the core of the material was in fact a can act as a drier in oil paints. It is quite previously unknown element, Brandt tested stable in both watercolour and acrylic and his theory on an ore from Sweden, separat- is referred to as PB35 cobalt stannate. PB36, ing the metal via fire assay, thus isolating which is a cobalt chromate, is also used and the same substance that the Saxony miners sold as Cerulean blue for those who prefer had stumbled upon and discounted. Brandt a slightly greener or cooler hue. stuck with the miners’ name for the mate- rial and called the newly discovered element Artificial ultramarine — PB29 cobalt. We now have a bit of a backtrack in our As a synthesised pigment, a purer alu- timeline!: Artificial Ultramarine Blue. The mina-based version of cobalt blue was dis- original ultramarine blue made from lapis covered by French chemist Louis Jacques lazuli was employed by the venerable Egyp- Thénard in 1802. Leithner of Vienna is also tians in solid form for ornamental use in recorded as having developed a cobalt arse- jewellery, as remarked above. Due to the nate as early as 1775. Cobalt blue is a favour- processes of collection and manufacture ite of artists: although more expensive than through a series of manual kneading, wash- copper-based blues, it gives a vibrant but ing and filtering, it proved to be a highly opaque blue, slightly leaning to the green expensive pigment. While paint made on

172 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts remarkably high-quality lapis is a roman- subdued and shadow hues. Modern tic idea to produce, it was still feeble in ultramarine blue is a soft pigment that quite strength in comparison to what was to come often does not need much milling to disperse and vastly expensive to produce even now. into a paint formulation. It is non-toxic, Finding a way to make artificial ultra- with generally accepted good lightfastness. marine (lapis lazuli) was going to assure its However, recent research conducted during inventor fame and fortune, but, even with the restoration of Michelangelo’s work in that promise, it was still a long time till the Sistine chapel has thrown some doubt the birth of artificial ultramarine blue. Sir on the lightfastness of lapis lazuli in Arthur Church (1915) recorded that, “I[i]n the (lapis blue and ultramarine are very simi- year 1814, a blue colouration, subsequently lar in chemical composition). Specifically, proved to be due to ultramarine, was noticed it seems that sulphur, which is one of the in the soda (black ash) furnaces of St. Gobain.” constituents of the colour, has been moving Artificial ultramarine blue was not born until out of the pigment molecules, resulting in 1824, when the Societé d’Encouragement fading. Certainly, most colour chemists offered a reward of 6,000 francs to anyone would have struck occasions where they who could develop a synthetic alternative to have observed sulphur off gassing from ultramarine. It was a troublesome birth. Two formulations, which smells very unpleas- men came forward within several weeks of ant. Clearly, this is a space to watch. one another: Jean-Baptiste Guimet, a French It would be remiss of me not to add in chemist, and Christian Gmelin, a German Yves Kline blue here — if only for com- professor from the University of Tübingen. pleteness of the story. Kline’s blue was just The prize was fiercely contested. Gmelin artificial ultramarine which was under- claimed that he had arrived at a solution a year bound — namely, presenting too much pig- earlier but had waited to publish his results. ment and not enough binder — which gave Guimet countered by declaring that he had a striking finish extremely rich in colour conceived his formula two years before, but, and texture, which is how the raw pigment like Gmelin, had opted not to publicise his presents. However, it does not take much of findings. The committee awarded the prize an imagination to work out what happened to Guimet, and the artificial blue became to those works: by producing a coating that known as “French ultramarine.”4 did not have enough binder, the resulting This new method of production was based colour was not going to hold on well. This in part upon chemical analyses of natural still happens today, as there can be found ultramarine (lapis lazuli), and in part on more than one story of gallery staff coming a study of the conditions which produced in each day to find more ultramarine pig- the first observed accidental manufacture ment on the floor to be cleaned up below a at St Gobain. This very rich red-blue was Kline artwork. developed and revolutionised the way art- ists could now mix their and violets, Indanthrone blue — PB22 and PB60 while also allowing for a full new range of Indanthrone blue (PB22 and PB60, also known as indanthrene blue), was first pat- ented in 1901 by Rene Bohn. It belongs to 4 See Mertens (2004) for details of this rivalry. [Ed.]

173 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts the class of pigments described as “vat pig- world, this type of blue was first marketed ments.” It is a very red shade, ranging from by ICI in 1935 under the name Monastral blue to pigment. However, due to blue, which is still available today. the high cost relative to the artificial ultra- marine pigments, uptake and use have been Manganese blue — PB33 limited. A synthetic green-blue pigment is formed “when an aqueous solution of permanga- Phthalocyanine blue — PB15 nate of potash yields, with baryta-water, a Phthalocyanines were discovered in 1907 mixture which afterwards becomes by Braun and Tchermiac in London. With- colourless and deposits a blue precipitate.” out understanding the importance of their (Eastaugh et al. 2004, p.44). This was first finding, they noted the results, but did not mentioned in the late 1800s. Manganese follow them up. Then, in 1927, the Swiss blue only became commercially available chemists Von der Weid and de Diesbach in the 1930s when IG Farbenindustries AG (no relation to our Prussian blue inventor patented it in 1935. However, its produc- that I could find) accidentally obtained a tion appears to have been phased out in form of copper phthalocyanine whilst trying the 1990s probably due to the higher cost to produce phthalonitrile. Then, in 1928, at when compared to other pigments on the Scottish Dyes Ltd., iron phthalocyanine was market, such as cobalt and phthalocyanines. found as an impurity during the preparation Furthermore, it contained barium and was of phthalimide, a fine white solid produced deemed to be toxic. Therefore, at present, by reacting phthalic anhydride and urea. A any artist-paint manufacturer who offers crack was spotted in one of the glass lin- the colour produces a blend to arrive at the ings of the reactors which was leading to same hue. an unwanted blue impurity in what was supposed to be a whiteish end product. The Fluorescent blue Scottish dyers had the foresight to follow Although most artists do not use fluores- through and find out what was going on. cent pigments due to their fugitive nature, With experimentation, they produced iron I will mention them here for completeness phthalocyanine, and, in 1929, Scottish Dyes and because how they were developed is was granted a patent for the preparation an interesting story. In the summer of 1933, of phthalocyanine produced from phthalic Rob Switzer had taken a summer job before anhydride, a metal and ammonia. he started medicine at UC Berkeley. In a Since then, several phthalocyanine varia- terrible twist of fate, he suffered an accident tions have been produced on various metals, which him spend a prolonged period in together with a metal-free version, the most hospital, followed by doctor’s orders to rest popular being the green tone based on in a dark room. Rob and his brother Joe had copper, which is used across many indus- a love of magic: during Rob’s time of con- tries, as it is very lightfast, incredibly strong valescing confined to darkened rooms, he in tint strength and very stable in formula- and Joe found that their parents’ pharmacy tions. It is worth noting that while at pre- provided an Aladdin’s cave of compounds sent there are many producers around the that glowed under black light, which gave

174 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts them the idea to enhance their magic show angle at which the pigment is viewed will with the addition of fluorescent costumes, dictate what colour is observed. which earned them a prize for best illusion “The development of pearlescent pig- at a magicians’ convention in Oakland. Rob ments only started in the 20th century using and Joe were to go on and build the com- mercury and salts, but there were no pany now known as Day-Glo Corp., substantial advancements until the inven- and in 1957, they were awarded a patent to tion of coated with metal oxides in produce the first commercial fluorescent 1963. From that point onward, new discover- pigment. ies were made in this field, as the production As early as 1944 artists started using of -based pearlescent pigments fluorescent colours, which were dyes and in the 1990s.” (Rossi and Russo). not very stable (De Winter 2010); however, they became more popular in the 1960s as Mayan blues — PB82 and PB84 they became commercially available in more A fairly recent addition to the modern range stable paint forms. Blue was not one of the of pigments, the MayaCrom and MayaPure first fluorescent colours developed but did blues (PB82 and PB84) are a recreation start appearing in catalogues for fluorescent of an ancient blue pigment composed of pigments by the late 1960s. clay and indigo which was used by the ancient Mayans throughout Mesoa- Pearlescent, Iridescent and Interference blue merica between the 6th and the 8th centu- Pearlescent pigments are made by coating ries. Research has shown it to be very stable mica with metal oxides and diox- when exposed to , alkalis, and chemical ide and may contain other blue pigments. solvents. Artefacts recovered from a well at The pearlescent pigment does not contain Chichen Itza along with over 100 skeletons any pearl but rather has a lustre similar to gave further weight to the theory that Maya that of a pearl that gives it its name. The blue was an essential colour in Mayan cul- colour, however, can be considered to be ture. It is believed that, at some time in the homogenous. This is in contrast to irides- Mayan history, blue was produced by burn- cent blue pigments which are produced in ing incense, which was found to contain a similar way yet appear to the observer to palygorskite and indigo, during sacrificial “change” colour around a limited spectrum. ceremonies and applied to the sacrificial Interference colours go one step further and victims just before their still-beating heart tend to emit two definite homogenous col- was cut out and they were thrown into the ours, depending on the angle of view. well as an offering to the rain god (Arnold In each of the above cases, the observer et al. 2008). sees colours which are developed through Using multiple modern analysis tech- the result of interference between rays of niques, the chemical makeup of the blue was light. The light is reflected off the top and discovered and then recreated by a group at the bottom of particular layers (platelets or the University of Texas around 2006. Unfor- flakes) within the pigment, which collide tunately, it seems at writing, the company or combine to form particular colours. The that was to commercially produce the pig- ments is now defunct. I have formulated

175 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts artist colours on these recreated pigments, this pigment may concern a variety of com- and while they are generally not as strong mercial products, such as paint coatings for as other synthesised pigments, such as the buildings and roofs. Specifically, the coat of phthalocyanines, they do have a wonder- paint would help to keep buildings cool by ful hue for painting. Formulating can be a reflecting light. tedious process and takes time as they are In artistic terms, Yin Min blue (or based on clays and time needs to be given YlnMnBlue, as it is quoted in research to wet these out sufficiently to avoid post- notations) has a brilliant, almost shim- thickening. mering look with a, maybe, very slight red undertone. Research notes from evaluation Yin Min blue testing of samples indicate a higher optical In 2009 the discovery of Yin Min blue, the reflectance (vividness) than other blues in first truly new blue pigment in two centu- the colour spectrum due to the compounds ries, was the result of a happy accident in in the structure of the pigment particles. the research for new materials that could be Another crucial factor to consider, and in used in electronic applications. In the course direct relation to health and safety, is that of research by an Oregon State University none of this pigment’s compounds is toxic, team led by chemistry professor Mas Subra- which cannot always be said for copper or manian, his then-graduate student Andrew cobalt. Yin Min Blue has just as vivid an E. Smith took manganese mixed with appearance, providing an alternative to other compounds — (Y) and ultramarine blue with the added benefits (In) — and heated it at high temperatures to of refracting infrared wavelengths, which test for structure. They noticed that one of makes it highly lightfast, in archival terms, their samples turned out into a very vivid with no toxic compounds — specifically, brilliant blue colour. Despite not being spe- a very safe pigment to use either in paint cifically developed for artistic purposes, the form or dry. Yin Min has gone through ini- characteristics of this newly created inor- tial approval in the US to be used in artist ganic pigment undoubtedly make it possible paints only in bound form in July 2020.5 for it to have applications in art. One of the most remarkable structural Forthcoming blues? characteristics of this pigment is that it absorbs red and green wavelengths of light Quantum blue while at the same time only reflecting the blue wavelengths in the light spectrum. This new inorganic pigment has been described Deepwater blue as an intense blue colour with high solar Presently, I have no more information than radiation (IR) reflecting properties. As has the one referenced below from Ruth Sid- been observed, the resulting vibrant blue dall’s article; however, I have made contact appears to be very durable, and its core with Professor Dobson and, on his return compounds are said to be so stable that “the from hiking in Scotland (whilst socially colour does not fade” (Subramanian 2018). distancing I am sure), I hope to find out The initial application and use intended for 5 To read further, see Kupferschmidt (2019). [Ed.]

176 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts more about his discovery, however I find conservators alike. In theory; they could be this quote from a recent article very excit- a real game changer! ing. “Here in UCL Earth Sciences, we are attempting to develop synthetic structures Quantum blue which mimic the unusual ferric iron struc- From his lecture at the Symposium on the ture of ringwoodite but which are stable History, Technology and Research of the at atmospheric pressure. So far we have Colour Blue at the Herakleidon Museum shown that we can make blue pigments in Athens in 2019, Jason Hartlove, CEO of from iron-bearing oxides and are now inves- Quantum Dot Leader Nanosys put the ques- tigating how much Fe3+ the structures can tion: “What if paint pigments could actively take before they become unstable. That will emit light instead of merely absorbing it? A determine just how blue we can make them. new type of nanotechnology called Quan- The prospects are bright … blue.” tum Dots is changing the way artists work with colour and light. Quantum Dots are Phototonic blue tiny nanocrystals — 10,000 times narrower The concept of phototonic colours, a colour than a human — that can be tuned to produced through the modulation of light actively emit light at any colour in the vis- pigments a form of structural colours, is ible spectrum. This exciting new material not new; as discussed previously, the way is enabling artists to explore a new mode we see the sky is a form of structural blue. of expression — painting with light. Light- Birds, insects and flowers have been using emitting pigments open new artistic possi- this form of colouring forever — the wings bilities for unique colour combinations and of the morpho butterfly being a perfect surprising perceptual manipulation through example of a bright blue caused by light additive light mixing.” diffraction, which is the bending of light Artist Olga Alexopoulou is already work- rather than generation or absorption and ing with quantum dots. It will be interest- reflection or generation or reflection. The ing to watch how quantum dots evolve over latest iteration of this exciting method of time and just how the artistic community producing colour has been reported in 2019 will embrace and use them to create work as taking place at Wageningen University we cannot probably even imagine at present. in the Netherlands where they have pro- duced photonic pigments, which they refer Conclusion to as suprapigments — free-standing water- Ancient or Modern blue pigments — one dispersible spheres entirely made of silica, does not need to be a paint maker or an an abundant, (photo)chemically stable and artist to appreciate how we see them or non-toxic material, with an ordered, macro- indeed the various ways they came into use. porous structure that interacts with inci- An understanding of the development of dent light to endow the pigments with a one of the three basic primary colours, how- colour. Theoretically, these colours should ever, is a window into human development be very stable and very lightfast — an utter over the ages. With hopefully more to come. dream for formulators, artists and hopefully It seems that we are not at the end of the discovery of all things blue, but partway

177 Journal & Proceedings of the Royal Society of New South Wales Patterson — The history of blue pigments in the Fine Arts along the course; therefore, next time you Microscopy of Historical Pigments, Amsterdam: look up at a never-ending blue sky or across Elsevier. the vast plain of the ocean, your inner artist Garfield, Leanna (2017) A chemist discovered the first new blue in 200 years — now will realise that you are not really seeing Crayola is turning it into a crayon, Business blue … or are you? Insider Australia, May 12. https://www. businessinsider.com.au/new-blue-discovery- References 2017-5?r=US&IR=T Arnold, D., Branden, J., Williams, P., Feinman, Katsaros, Thomas (2019) “Re-thinking the G., and Brown, J. (2008). The first direct nomenclature of blue mineral pigments evidence for the production of : described by Theophrastus of Eresos: rediscovery of a technology. Antiquity, 82 The case of Sapphirus,” presented at the (315), 151–164. doi:10.1017/S0003598X00096514 “Symposium on the History Technology and Bersch, Josef (1921) The Manufacture Research of the Colour Blue” Herakleidon of Earth Colours, London, Scott, Museum, Athens. https://www.nanosysinc. Greenwood. https://archive.org/details/ com/events/2019/9/17/symposium-on-the- manufactureofear00bersrich/page/n7/ history-technology-and-research-of-the- mode/2up colour-blue Bristow, Ian C. (1996) Interior House-Painting Kraft A. (2008) On the discovery and history Colours and Technology, 1615-1640, Yale U.P. for of Prussian blue. Bull. Hist. Chem. 32: 61–67. the Paul Mellon Centre for Studies in British http://acshist.scs.illinois.edu/bulletin_open_ Art. access/v33-2/v33-2%20p61-67.pdf Cennini, Cennino (1899) Chap. 62, On the Kupferschmidt K. (2019) In search of nature of azzurro oltre marino (ultramarine blue, Science, 364 (6439): 424–429, 3 May. blue), and how it is prepared. The Book of doi:10.1126/science.364.6439.424 the Art of Cennino Cennini A Contemporary Lindblom K. (2012) DayGlo® Fluorescent Practical Treatise on Quattrocento Painting, Pigments Brighter, Longer Lasting Color, Trans. by C. J. Herringham. London: George American Chemical Society, National Allen. https://warburg.sas.ac.uk/pdf/ Historic Chemical Landmarks Program. cnh925b2209242.pdf https://www.acs.org/content/acs/en/ Church A. H. (1915) The Chemistry of Paints and /whatischemistry/landmarks/ Painting. London: Seeley Service & Co., 4th ed. dayglo.html https://www.amazon.com/Chemistry-Paints- Mangla, Ravi (2015), , The Paris Painting-Arthur-Herbert/dp/1142141829 Review, https://www.theparisreview.org/ Davies, Hugh (2017) “Prussian blue: From the blog/2015/06/08/true-blue/ Great Wave to Starry Night, how a pigment McCann M. (1979), Artist Beware: the Hazards changed the world,” The Conversation, 21 July, and Precautions of Working with Art and Craft https://theconversation.com/friday-essay- Materials, New York: Watson-Guptill. from-the-great-wave-to-starry-night-how-a- Mertens, Joost (2004) The history of artificial blue-pigment-changed-the-world-81031 ultramarine (1787–1844): Science, industry De Winter, Stephanie (2010) “Conservation and secrecy, Ambix, 51:3, 219–244. problems with paintings containing Nelson, Daniel (2018) “What two fluorescent layers of paint,” CeROArt, combine to make blue?” Science Trends, EGG 1 | 2010, http://journals.openedition. November 29, https://sciencetrends.com/ org/ceroart/1659 https://doi.org/10.4000/ what-two-colors-combine-to-make-blue/ ceroart.1659 Pagès-Camagna S, (1998) “Bleu et vert Eastaugh, Nicholas, Valentine Walsh, Tracey égyptiens en question: vocabulaire et Chaplin and Ruth Sidda (2004), The Pigment analyses” in La couleur dans la peinture et Compendium A Dictionary and Optical l’émaillage de l’Egypte Ancienne, CUEBC,

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