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{{Short description|Deep blue purple color pigment which was originally made with ground lapis lazuli}}
{{About|the pigment and the color|other uses|Ultramarine (disambiguation)}} {{infobox color|title=Ultramarine|image=Ultramarinepigment.jpg|caption=Ultramarine [[pigment]]|hex=120A8F|spelling=color|source=ColorHexa<ref>{{cite news |title=Ultramarine / #120a8f hex color |url=https://www.colorhexa.com/120a8f |website=ColorHexa |access-date=2021-12-03}}</ref>|isccname=Deep blue}}{{Redir|Ultramarine blue|the RAL color|Ultramarine blue (RAL)}}'''Ultramarine''' is a deep [[blue]] [[color]] [[pigment]] which was originally made by grinding [[lapis lazuli]] into a [[powder]].<ref>''Webster's New World Dictionary of American English'', Third College Edition 1988.</ref> It's lengthy grinding and washing process makes the natural pigment quite valuable— roughly ten times more expensive than the stone it comes from and nearly as expensive as [[gold]].<ref name=":2" />

The name ultramarine comes from the [[Latin]] ''ultramarinus'' which means 'beyond the sea' because the pigment was imported by [[Italians|Italian]] traders during the [[14th century|14th]] and [[15th century|15th centuries]] from [[mines]] in [[Afghanistan]].<ref name="auto">{{cite dictionary |title=ultramarine |dictionary=Online Etymology Dictionary |url=http://www.etymonline.com/index.php?search=ultramarine |access-date=2011-06-30}}</ref><ref>{{Cite web |title=History of Ultramarine |url=https://www.york.ac.uk/org/seg/salters/ChemistryArchive/V_VisitHP/history.html |access-date=2023-04-12 |website=www.york.ac.uk}}</ref> Much of the expansion of ultramarine can be attributed to [[Venice]] which historically was the port of entry for lapis lazuli in Europe.

Ultramarine was the finest and most expensive blue used by [[Renaissance]] painters. It was often used for the robes of the [[Virgin Mary]] and symbolized holiness and humility. It remained an extremely expensive pigment until a synthetic ultramarine was invented in 1826.<ref>{{Cite web |title=Pigments through the Ages - History - Ultramarine |url=https://www.webexhibits.org/pigments/indiv/history/ultramarine.html |access-date=2023-04-12 |website=www.webexhibits.org}}</ref>

Ultramarine is a permanent pigment when under ideal preservation conditions. Otherwise, it can become susceptible to discoloration and fading.<ref name=":1" />

== Structure ==
The pigment consists primarily of a [[zeolite]]-based mineral containing small amounts of [[Polysulfide|polysulfides]]. It occurs in nature as a proximate component of [[lapis lazuli]] containing a blue cubic mineral called [[lazurite]]. In the [[Colour Index International]], the pigment of ultramarine is identified as P. Blue 29 77007.<ref>{{Cite news |title=The Color of Art Pigment Database: Pigment Blue - PB |work=Art is Creation |url=http://www.artiscreation.com/blue.html#pb29 |access-date=2018-10-11}}</ref>

The major component of lazurite is a complex sulfur-containing sodium-silicate (Na<sub>8–10</sub>Al<sub>6</sub>Si<sub>6</sub>O<sub>24</sub>S<sub>2–4</sub>), which makes ultramarine the most complex of all mineral [[Pigment|pigments]].<ref name=":0">{{Cite journal |last=Plesters |first=Joyce |date=1966 |title=Ultramarine Blue, Natural and Artificial |journal=Studies in Conservation |volume=11 |issue=2 |pages=62–91 |doi=10.2307/1505446 |jstor=1505446}}</ref> Some [[chloride]] is often present in the crystal lattice as well. The blue color of the pigment is due to the [[S3-|{{chem|S|3|-}}]] [[Radical (chemistry)|radical]] [[anion]], which contains an [[unpaired electron]].<ref name="Ullmann">{{Ullmann|doi=10.1002/14356007.n20_n02|title=Pigments, Inorganic, 3. Colored Pigments|year=2009|last1=Buxbaum|first1=Gunter|last2=Printzen|first2=Helmut|last3=Mansmann|first3=Manfred|last4=Räde|first4=Dieter|last5=Trenczek|first5=Gerhard|last6=Wilhelm|first6=Volker|last7=Schwarz|first7=Stefanie|last8=Wienand|first8=Henning|last9=Adel|first9=Jörg|last10=Adrian|first10=Gerhard|last11=Brandt|first11=Karl|last12=Cork|first12=William B.|last13=Winkeler|first13=Heinrich|last14=Mayer|first14=Wielfried|last15=Schneider|first15=Klaus|isbn=978-3527306732}}</ref>

== Visual Properties ==
The best samples of ultramarine are a uniform deep blue while other specimens are of paler color.<ref>{{Cite web |last=Roy |first=Ashok |title=Artists' Pigments: A Handbook of Their History and Characteristics |url=https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/artists-pigments-vol2.pdf |page=38}}</ref>

Particle size distribution has been found to vary among samples of ultramarine from various workshops. Numerous grinding techniques used by painters have resulted in different pigment/medium ratios and particle size distributions. Since the mineral lapis lazuli is ground in a purification process, the resulting ultramarine pigment often has particles of various geometries. Therefore, it is possible that different grades of pigment may have been used for different areas in a painting, a notable occurrence that may enable experts to determine whether paintings are authentic or not.<ref>{{Cite journal |last=Boer |first=J. R. J. Van Asperen De |date=1974 |title=An Examination of Particle Size Distributions of Azurite and Natural Ultramarine in Some Early Netherlandish Paintings |url=https://www.jstor.org/stable/1505730 |journal=Studies in Conservation |volume=19 |issue=4 |pages=233–243 |doi=10.2307/1505730 |issn=0039-3630}}</ref>

== Shades and Variations ==
{{Infobox color|title=Electric Ultramarine|hex=3F00FF|textcolor=white|r=63|g=0|b=255|c=100|m=75|y=0|k=0|h=255|s=100|v=100<ref>{{Cite web|url=https://toolstud.io/tools/color.asp?RGB|title=Free calculators and converters · toolstud.io|first=Peter|last=Forret|website=toolstud.io|accessdate=Dec 13, 2022}}</ref>|source=Maerz and Paul<ref>The color displayed in the color box above matches the color called ''ultramarine'' in the 1930 book by Maerz and Paul ''A Dictionary of Color'' New York:1930 McGraw-Hill;  the color ''ultramarine'' is displayed on page 105, Plate 41, Color Sample F12 and is shown as the color lying exactly halfway between blue and violet.</ref>}}
=== International Klein Blue (IKB) ===
[[International Klein Blue]] a deep blue hue first mixed by the French artist [[Yves Klein]].<ref>{{Cite web |title=All You Need to Know About the International Klein Blue {{!}} Widewalls |url=https://www.widewalls.ch/magazine/international-klein-blue |access-date=2023-04-12 |website=www.widewalls.ch |language=en}}</ref>

=== Electric ===
''Electric ultramarine'' is the tone of ultramarine that is halfway between [[blue]] and [[Violet (color)#Color wheel violet|violet]] on the [[RGB color model|RGB (HSV) color wheel]], the expression of the [[HSV color space]] of the [[RGB color model]].<ref>Maerz and Paul ''A Dictionary of Color'' New York:1930--McGraw Hill Color Sample of Ultramarine: Page 105 Plate 41 Color Sample F12 Ultramarine is shown as being one of the colors on the bottom of the plate representing the most highly saturated colors between blue and violet (the colors on the right of the plate represent the most highly saturated colors between violet and rose); ultramarine is shown as being situated at a position exactly one-half of the way between blue and violet.</ref>

== Production ==

=== Natural Production ===
Historically, [[lapis lazuli]] stone was mined in [[Afghanistan]] and shipped overseas to Europe.<ref name="auto" />

At the beginning of the 13th century, a method to produce ultramarine from lapis lazuli was introduced and later described by Cennino Cennini in the 15th century. This process consisted of grinding the lapis lazuli mineral, mixing the ground material with melted [[wax]], [[Resin|resins]], and [[Oil|oils]], wrapping the resulting mass in a cloth, and then kneading it in a dilute ley solution, a [[potassium carbonate]] solution prepared by extracting [[wood ash]] with water. The blue lazurite particles collect at the bottom of the pot, while the colorless crystalline material and other impurities remain. This process was performed at least three times, with each successive extraction generating a lower quality material. The final extraction, consisting largely of colorless material as well as a few blue particles, brings forth ultramarine ash which is prized as a [[Glaze (painting technique)|glaze]] for its pale blue transparency.<ref>Lara Broecke, ''Cennino Cennini's ''Il Libro dell'Arte'': a New English Translation and Commentary with Italian Transcription'', Archetype 2015, pp. 89-90.</ref> This extensive process was specific to ultramarine because the mineral it comes from has a combination of both blue and colorless pigments. If an artist were to simply grind and wash lapis lazuli, the resulting powder would be a greyish-blue color that lacks purity and depth of color since ultramarine contains a high proportion of colorless material.<ref>{{Cite journal |last=Plesters |first=Joyce |date=1966 |title=Ultramarine Blue, Natural and Artificial |url=https://www.jstor.org/stable/1505446 |journal=Studies in Conservation |volume=11 |issue=2 |pages=62–91 |doi=10.2307/1505446 |issn=0039-3630}}</ref>

Although the lapis lazuli stone itself is inexpensive, the lengthy process of pulverizing, sifting, and washing to produce ultramarine makes the natural pigment quite valuable and roughly ten times more expensive than the stone it comes from. The high cost of the imported raw material and the long laborious process of extraction combined has been said to make high-quality ultramarine as expensive as [[gold]].<ref name=":2">{{Cite web |last=Roy |first=Ashok |title=Artists' Pigments: A Handbook of Their History and Characteristics |url=https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/artists-pigments-vol2.pdf |page=39}}</ref>

=== Synthetic Production ===
In 1990, an estimated 20,000 tons of ultramarine were produced industrially. The raw materials used in the manufacture of synthetic ultramarine are the following:

* white [[kaolin]],
* [[anhydrous]] [[sodium sulfate]] (Na<sub>2</sub>SO<sub>4</sub>),
* anhydrous [[sodium carbonate]] (Na<sub>2</sub>CO<sub>3</sub>),
* powdered [[sulfur]],
* powdered [[charcoal]] or relatively ash-free [[coal]], or [[colophony]] in lumps.<ref name="EB1911">{{EB1911|inline=1|wstitle=Ultramarine}}</ref>

The preparation is typically made in steps:

* The first part of the process takes place at 700 to 750°C in a closed [[Furnace (central heating)|furnace]], so that sulfur, carbon and organic substances give reducing conditions. This yields a yellow-green product sometimes used as a pigment.
* In the second step, air or sulfur dioxide at 350 to 450°C is used to oxidize sulfide in the intermediate product to S<sub>2</sub> and S<sub>''n''</sub> [[chromophore]] molecules, resulting in the blue (or purple, pink or red) pigment.<ref>{{cite web |title=Manufacture of ultramarine |url=http://www.freepatentsonline.com/2441952.pdf |website=www.freepatentsonline.com}}</ref>
* The mixture is heated in a [[kiln]], sometimes in brick-sized amounts.
* The resultant solids are then ground and washed, as is the case in any other insoluble pigment's manufacturing process; the chemical reaction produces large amounts of [[sulfur dioxide]]. ([[Flue-gas desulfurization]] is thus essential to its manufacture where SO<sub>2</sub> pollution is regulated.)

Ultramarine poor in [[Silicon dioxide|silica]] is obtained by fusing a mixture of soft clay, sodium sulfate, charcoal, sodium carbonate, and sulfur. The product is at first white, but soon turns green "green ultramarine" when it is mixed with sulfur and heated. The sulfur burns, and a fine blue pigment is obtained. Ultramarine rich in silica is generally obtained by heating a mixture of pure clay, very fine white [[sand]], sulfur, and charcoal in a [[muffle furnace]]. A blue product is obtained at once, but a red tinge often results. The different ultramarines—[[green]], [[blue]], [[red]], and [[Violet (color)|violet]]—are finely ground and washed with water.<ref name="EB1911" />

Synthetic ultramarine is a more vivid blue than natural ultramarine, since the particles in synthetic ultramarine are smaller and more uniform than the particles in natural ultramarine and therefore [[Diffusion|diffuse]] light more evenly.<ref>{{Cite web |title=Ultramarine-Blue-Pigment - Analysis, Applications, Process, Patent, Consultants, Company Profiles, Suppliers, Market, Report |url=http://www.primaryinfo.com/projects/ultramarine-blue-pigment.htm |access-date=2018-10-11 |website=www.primaryinfo.com}}</ref> Its color is unaffected by light nor by contact with oil or lime as used in painting. [[Hydrochloric acid]] immediately bleaches it with liberation of [[hydrogen sulfide]]. Even a small addition of [[zinc oxide]] to the reddish varieties especially causes a considerable diminution in the intensity of the color.<ref name="EB1911" /><gallery mode="packed" heights="150px">
File:Lapis-lazuli_hg.jpg|[[Lapis lazuli]] specimen (rough), Afghanistan
File:Natural_ultramarine_pigment.jpg|Natural ultramarine
File:Ultramarinepigment.jpg|Synthetic ultramarine blue
File:Pigment_Violet_15.jpg|Synthetic ultramarine violet
</gallery>

== Structure and Classification of Ultramarines ==
Ultramarine is the aluminosilicate [[zeolite]] with a [[sodalite]] structure. Sodalite consists of interconnected aluminosilicate cages. Some of these cages contain [[polysulfide]] ({{chem|S|''x''|''n''−}}) groups that are the chromophore (color centre). The negative charge on these ions is balanced by {{chem|Na|+}} ions that also occupy these cages.<ref name="Ullmann" />

The chromophore is proposed to be {{chem|S|4|-}} or S<sub>4</sub>.<ref name="Ullmann" />

== History ==
The name derives from Middle [[Latin]] {{lang|la-x-medieval|ultramarinus}}, literally "beyond the sea" because it was imported from Asia by sea.<ref name="auto" /> In the past, it has also been known as ''azzurrum ultramarine'', {{lang|la-x-medieval|azzurrum transmarinum}}, {{lang|it|azzuro oltramarino}}, {{lang|fr|azur d'Acre, pierre d'azur}}, {{lang|de|Lazurstein}}. The current terminology for ultramarine includes natural ultramarine (English), {{lang|fr|outremer lapis}} (French), {{lang|de|Ultramarin echt}} (German), {{lang|it|oltremare genuino}} (Italian), and {{lang|es|ultramarino verdadero}} (Spanish). The first recorded use of ''ultramarine'' as a color name in English was in 1598.<ref>Maerz and Paul ''A Dictionary of Color'' New York:1930--McGraw Hill Page 206</ref>

[[Venice]] was central to both the manufacturing and distribution of ultramarine. Other European countries employed the pigment on a somewhat less lavish scale than in Italy as the pigment was not used even by wealthy painters in Spain at that time.<ref>{{Cite web |last=Roy |first=Ashok |title=Artists' Pigments: A Handbook of Their History and Characteristics |url=https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/artists-pigments-vol2.pdf |pages=38, 41}}</ref>

The first noted use of ''lapis lazuli'' as a pigment can be seen in the 6th and 7th-century AD cave paintings in [[Afghanistan|Afghanistani]] [[Zoroastrian]] and [[Buddhist]] temples, near the most famous source of the mineral. ''Lapis lazuli'' has been identified in Chinese paintings from the 10th and 11th centuries, in Indian mural paintings from the 11th, 12th, and 17th centuries, and on [[Anglo-Saxon]] and [[Normans|Norman]] illuminated manuscripts from c.1100.

=== Middle Ages and The Renaissance ===
<gallery mode="packed" heights="300px">
File:The_Wilton_Diptych_(Right).jpg|The [[Wilton Diptych]] (1395–1399) is an example of the use of ultramarine in 14th-century [[England]]
File:Masaccio._Madonna_and_Child._1426._National_Gallery,_London.jpg|The blue robes of the [[Virgin Mary]] by [[Masaccio]] (1426) were painted with ultramarine
File:Pietro_Perugino_cat54b.jpg|[[Pietro Perugino]] economized on this painting of the Virgin Mary (about 1500) by using [[Azurite (pigment)|azurite]] for the underpainting of the robe, then adding a layer of ultramarine on top
File:Titian_-_Bacchus_and_Ariadne_-_Google_Art_Project.jpg|[[Titian]] made dramatic use of ultramarine in the sky and draperies of ''[[Bacchus and Ariadne]]'' (1520–1523)
</gallery>During the [[Renaissance]], ultramarine was the finest and most expensive blue that could be used by painters. The 15th century artist [[Cennino Cennini]] wrote in his painters' handbook: "Ultramarine blue is a glorious, lovely and absolutely perfect pigment beyond all the pigments. It would not be possible to say anything about or do anything to it which would not make it more so."<ref>Lara Broecke, ''Cennino Cennini's ''Il Libro dell'Arte'', a New English Translation and Commentary with Italian Transcription'', Archetype 2015, p. 89.</ref> Natural ultramarine is a difficult pigment to grind by hand, and for all except the highest quality of mineral, sheer grinding and washing produces only a pale grayish blue powder.<ref>{{cite web |title=Palette grinding and_materials |url=http://www.essentialvermeer.com/palette/palette_grinding_and_materials.html#.VINmSjGG-9E |access-date=December 6, 2014 |website=www.essentialvermeer.com}}</ref>

The pigment was most extensively used during the 14th through 15th centuries, as its brilliance complemented the [[vermilion]] and [[gold]] of illuminated manuscripts and Italian panel paintings. It was valued chiefly on account of its brilliancy of tone and its inertness in opposition to sunlight, oil, and slaked [[Calcium oxide|lime]]. It is, however, extremely susceptible to even minute and dilute mineral [[Acid|acids]] and acid vapors. Dilute HCl, HNO<sub>3</sub>, and H<sub>2</sub>SO<sub>4</sub> rapidly destroy the blue color, producing [[hydrogen sulfide]] (H<sub>2</sub>S) in the process. [[Acetic acid]] attacks the pigment at a much slower rate than mineral acids.

Ultramarine was only used for [[Fresco|frescoes]] when it was applied ''[[Fresco-secco|secco]]'' because frescoes' absorption rate made its use cost prohibitive. The pigment was mixed with a binding medium like egg to form a [[tempera]] and applied over dry plaster, such as in [[Giotto di Bondone]]'s frescos in the [[Cappella degli Scrovegni]] or the [[Arena Chapel]] in [[Padua]].

European artists used the pigment sparingly, reserving their highest quality blues for the robes of [[Mary (mother of Jesus)|Mary]] and the [[Christ child]]. As a result of the high price, artists sometimes economized by using a cheaper blue, [[azurite]], for under painting. Most likely imported to Europe through [[Venice]], the pigment was seldom seen in German art or art from countries north of Italy. Due to a shortage of azurite in the late 16th and 17th century, the price for the already-expensive ultramarine increased dramatically.<ref name="The blue color">{{cite web |date=2012-03-28 |title=The blue color |url=http://artelisaart.blogspot.se/2012/03/famous-blue-history-of-color-in-middle.html |access-date=December 6, 2014 |publisher=artelisaart.blogspot.se}}</ref>

=== In The 17th and 18th Century ===
<gallery mode="packed" heights="300px">
File:Sassoferrato_-_Jungfrun_i_bön.jpg|[[Giovanni Battista Salvi da Sassoferrato|Sassoferrato]]'s depiction of the [[Blessed Virgin Mary]],, ''[[The Virgin in Prayer]]'', c. 1654. Her blue cloak is painted in ultramarine.<ref>{{cite web |title=assoferrato-the-virgin-in-prayer |url=http://www.nationalgallery.org.uk/paintings/sassoferrato-the-virgin-in-prayer |access-date=December 6, 2014 |publisher=www.nationalgallery.org.uk}}</ref>
File:Johannes_Vermeer_-_Girl_with_a_Pearl_Earring_-_WGA24666.jpg|''[[Girl with a Pearl Earring]]'', by [[Johannes Vermeer]] (c. 1665)
File:Johannes_Vermeer_-_Lady_Standing_at_a_Virginal.jpg|''[[Lady Standing at a Virginal]]'', by [[Johannes Vermeer]] (c. 1675)
</gallery>[[Johannes Vermeer]] made extensive use of ultramarine in his paintings. The turban of the ''[[Girl with a Pearl Earring]]'' is painted with a mixture of ultramarine and lead white, with a thin glaze of pure ultramarine over it.<ref>[http://www.girl-with-a-pearl-earring.info/palette.htm Description of the painting at www.girl-with-a-pear-earring.info/pallette.htm]</ref> In ''Lady Standing at a Virginal'', the young woman's dress is painted with a mixture of ultramarine and green earth, and ultramarine was used to add shadows in the flesh tones.<ref>{{Cite web |title=National Gallery of London discussion of Vermeer's palette |url=https://www.nationalgallery.org.uk/research/about-research/the-meaning-of-making/vermeer-and-technique/vermeers-palette |accessdate=Dec 13, 2022}}</ref> Scientific analysis by the [[National Gallery]] in London of ''[[Lady Standing at a Virginal]]'' showed that the ultramarine in the blue seat cushion in the foreground had degraded and become paler with time; it would have been a deeper blue when originally painted.<ref>{{Cite web |title=National Gallery essay on the altered appearance of ultramarine in the paintings of Vermeer |url=https://www.nationalgallery.org.uk/research/about-research/the-meaning-of-making/vermeer-and-technique/altered-appearance-of-ultramarine |accessdate=Dec 13, 2022}}</ref>

=== 19th Century – The Discovery of Synthetic Ultramarine ===
The beginning of the development of artificial ultramarine blue is known from [[Goethe]]. In about 1787, he observed the blue deposits on the walls of lime kilns near [[Palermo]] in [[Sicily]]. He was aware of the use of these glassy deposits as a substitute for lapis lazuli in decorative applications. He did not mention if it was suitable to grind for a pigment.<ref>{{cite book |last1=Goethe |first1=Wolfgang |url=https://archive.org/stream/goethesitalienis00goetuoft#page/264/mode/2up |title=Italiensche Reise |date=1914 |publisher=Insel Verlag |location=Leipzig, Germany |page=265 |language=de |trans-title=Italian Journey}} From p. 265:  {{lang|de|"Doch wissen sie, außer diesen beiden, … andern kirchlichen Verzierungen mit Glück angewendet."}} (Yet they [viz, the stone cutters of Palermo] know, besides these two [types of stone], still more about a material, a product of the fire of their lime kilns.  In these is found, after roasting [the lime], a type of glassy [[flux]], which passes from the brightest blue color to the darkest, even to the blackest.  These lumps, like other rocks, are cut into thin slabs, appraised according to the level of their color and purity, and, with luck, used instead of lapis lazuli in the inlaying of altars, tombs, and other church decorations.)</ref><ref>{{cite journal |last1=Elsner |first1=L. |date=1841 |title=Chemische Untersuchung über die blaue Färbung des Ultramarins |trans-title=Chemical investigation of the blue color of ultramarine |url=https://babel.hathitrust.org/cgi/pt?id=njp.32101076785466;view=1up;seq=399 |journal=Journal für Praktische Chemie |language=de |volume=24 |pages=385–397 |doi=10.1002/prac.18410240157}}  From pp. 385–386:  ''"Allein es scheint weniger bekannt zu sein, … von Altären u.s.w. gebraucht würde."''  (Yet it seems to be less well known that von Göthe in the year 1787 during his stay in Palermo (see his ''Italian Journey'') cited a similar observation, as he recounted that in the Sicilian lime ovens, a product of fire, a sort of glassy flux, is found, [which is] of a light blue to dark blue color, [and] which was used as ''lapis lazuli'' by local artisans during the inlaying of altars, etc.)</ref>

In 1814, [[Tassaert family|Tassaert]] observed the spontaneous formation of a blue compound, very similar to ultramarine, if not identical with it, in a [[Calcium oxide|lime]] [[kiln]] at St. Gobain.<ref>Tessaërt gave a sample of the pigment to the French chemist [[Louis Nicolas Vauquelin]] for analysis:  {{cite journal |last1=Vauquelin |date=1814 |title=Note sur une couleur bleue artificielle analogue à l'outremer |trans-title=Note on an artificial blue color similar to ultramarine |url=https://babel.hathitrust.org/cgi/pt?id=nyp.33433062722727;view=1up;seq=98 |journal=Annales de Chimie et de Physique |language=fr |volume=89 |pages=88–91}}</ref> In 1824, this caused the {{lang|fr|[[Société d'encouragement pour l'industrie nationale|Societé pour l'Encouragement d'Industrie]]}} to offer a prize for the artificial production of the precious color. Processes were devised by [[Jean Baptiste Guimet]] (1826) and by [[Christian Gmelin]] (1828), then professor of chemistry in Tübingen. While Guimet kept his process a secret, Gmelin published his, and became the originator of the "artificial ultramarine" industry.<ref>See:

* {{cite journal |last1=Gmelin |first1=C.G. |date=1828 |title=Ueber die künstliche Darstellung einer dem Ultramarin ähnlichen Farbe |trans-title=On the artificial preparation of a pigment similar to ultramarine |url=https://books.google.com/books?id=ZjArAAAAcAAJ&pg=PA191 |journal=Naturwissenschaftliche Abhandlungen. Herausgeben von Einer Gesellschaft in Würtemberg (Scientific Essays. Published by a Society in Würtemberg) |language=de |volume=2 |issue=10 |pages=191–224 |bibcode=1828AnP....90..363. |doi=10.1002/andp.18280901022}}
* {{cite journal |last1=Gmelin |first1=C.G. |date=1828 |title=Ueber die künstliche Darstellung einer dem Ultramarin ähnlichen Farbe |trans-title=On the artificial preparation of a pigment similar to ultramarine |url=https://babel.hathitrust.org/cgi/pt?id=umn.31951d00316722w;view=1up;seq=377 |journal=Annalen der Physik und Chemie |series=2nd series |language=de |volume=14 |issue=10 |pages=363–371 |bibcode=1828AnP....90..363. |doi=10.1002/andp.18280901022}}
* {{cite book |last1=Watts |first1=Henry |title=A Dictionary of Chemistry and the Allied Branches of Other Sciences |date=1869 |publisher=Longmans, Green, and Co. |volume=5 |location=London, England |page=937 |chapter=Ultramarine |chapter-url=https://books.google.com/books?id=WVNOaYdeSXgC&pg=PA937}}</ref><ref name="EB1911" />

== Permanence ==
Easel paintings and illuminated manuscripts have revealed natural ultramarine in a perfect state of preservation even though the art may be several centuries old. In general, ultramarine is a permanent pigment. Although it is a sulfur-containing compound from which sulfur is readily emmited as H<sub>2</sub>S, historically, it has been mixed with lead white with no reported occurrences of the lead pigment blackening to become lead sulfide.<ref name=":1">{{Cite web |last=Roy |first=Ashok |title=Artists' Pigments: A Handbook of Their History and Characteristics |url=https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/artists-pigments-vol2.pdf |pages=44-45}}</ref>

A plague known as "ultramarine sickness" has occasionally been observed among ultramarine oil paintings as a grayish or yellowish gray discoloration of the paint surface. This can occur with artificial ultramarine that is used industrially. The cause of this has been debated among experts, however, potential causes include atmospheric sulfur dioxide and moisture, acidity of an oil- or oleo-resinous paint medium, or slow drying of the oil during which time water may have been absorbed, creating swelling, opacity of the medium, and therefore whitening of the paint film.<ref name=":1" />

Both natural and artificial ultramarine are stable to ammonia and caustic alkalis in ordinary conditions. Artificial ultramarine has been found to fade when in contact with lime when it is used to color concrete or plaster. These observations have led experts to speculate if the natural pigment’s fade may be the result of contact with the lime plaster of fresco paintings.<ref name=":1" />

== Notable Occurence ==
Color infrared photogenic studies of ultramarine in 13th and 14th-century Sienese panel paintings have revealed that historically, ultramarine has been diluted with white lead pigment in an effort to use the color more sparingly given its high price.<ref>{{Cite journal |last=Hoeniger |first=Cathleen |date=1991-01-01 |title=The Identification of Blue Pigments in Early Sienese Paintings by Color Infrared Photography |url=https://doi.org/10.1179/019713691806066782 |journal=Journal of the American Institute for Conservation |volume=30 |issue=2 |pages=115–124 |doi=10.1179/019713691806066782 |issn=0197-1360}}</ref>

Synthetic ultramarine, being very cheap, is largely used for wall painting, the printing of paper hangings and [[calico]], etc. It also as a corrective for the yellowish tinge often present in things meant to be white, such as [[linen]], [[paper]], etc. [[Bluing (fabric)|Bluing]] or "laundry blue" is a suspension of synthetic ultramarine, or the chemically different [[Prussian blue]], that is used for this purpose when washing white clothes. It is often found in make-up such as [[Mascara|mascaras]] or [[Eye shadow|eye shadows]].<ref name="EB1911" />

Large quantities are used in the manufacture of paper, and especially for producing a kind of pale blue writing paper which was popular in Britain.<ref name="EB1911" /> During World War I, the [[Royal Air Force|RAF]] painted the outer [[Roundel|roundels]] with a color made from ultramarine blue. This became BS 108(381C) aircraft blue. It was replaced in the 1960s by a new color made on [[phthalocyanine blue]], called BS110(381C) roundel blue.<ref>{{Cite web |title=Ultramarine blue 464# (P.B29)_MEI DAN PIGMENT |url=http://m.mdpigment.com/product/40.html |access-date=2023-04-12 |website=m.mdpigment.com}}</ref>

== General Terminology ==
Ultramarine is a blue made from natural [[lapis lazuli]], or its synthetic equivalent which is sometimes called "French Ultramarine".<ref name="dic1">{{citation |last=Paterson |first=Ian |title=A dictionary of colour |pages=35, 169, 228, 396 |year=2003}}</ref> More generally "ultramarine blue" can refer to a vivid blue.

The term ultramarine can also refer to other pigments. Variants of the pigment such as "ultramarine red," "ultramarine green," and "ultramarine violet" all resemble ultramarine with respect to their chemistry and crystal structure.<ref>{{citation |last1=Eastaugh |first1=Nicholas |title=Pigment Compendium – A Dictionary and Optical Microscopy of Historical Pigments |pages=585–587 |year=2008 |isbn=978-0-7506-8980-9 |last2=Walsh |first2=Valentine |last3=Chaplin |first3=Tracey |last4=Siddall |first4=Ruth}}</ref>

The term "ultramarine green" indicates a dark green while [[barium chromate]] is sometimes referred to as "ultramarine yellow".<ref name="dic1" /> Ultramarine pigment has also been termed "Gmelin's Blue," "Guimet's Blue," "New blue," "Oriental Blue," and "Permanent Blue".<ref>{{citation |last1=Kelly |first1=Kenneth Low |title=Color: Universal Language and Dictionary of Names |issue=440 |page=150 |year=1976 |publisher=U.S. Department of Commerce, National Bureau of Standards |last2=Judd |first2=Deane Brewster}}</ref>

== See also ==

* [[Blue pigments]]
* [[RAL 5002 Ultramarine blue]]
* {{annotated link|International Klein Blue}}
* {{annotated link|List of inorganic pigments}}

== Notes ==
<references group="" responsive="0"></references>

== Further reading ==

* {{cite book |last=Bomford |first=David |url=https://archive.org/details/colour0000bomf |title=A Closer Look – Colour |publisher=National Gallery Company Limited |year=2000 |isbn=978-1-85709-442-8 |url-access=registration}}
* {{cite book |last=Broecke |first=Lara |title=''Cennino Cennini's ''Il Libro dell'Arte'': a New English Translation and Commentary with Italian Transcription'' |publisher=Archetype |year=2015 |isbn=978-1-909492-28-8}}
* Mangla, Ravi (8 June 2015), "[http://www.theparisreview.org/blog/2015/06/08/true-blue/ True blue: a brief history of ultramarine]", [[The Paris Review|''Paris Review''—Daily]].
* Plesters, J. (1993), "Ultramarine Blue, Natural and Artificial", in ''Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 2'': A. Roy (Ed.) [[Oxford University Press]], p.&nbsp;37-66

== External links ==
{{Commonscatinline}}

* [http://aic.stanford.edu/jaic/articles/jaic30-02-001.html Discussion of ultramarine] in an article on blue pigments in early Sienese paintings from ''The Journal of the American Institute for Conservation''
* [https://web.archive.org/web/20130719191247/http://www.nationalgallery.org.uk/paintings/research/meaning-of-making/vermeer-and-technique/altered-appearance-of-ultramarine National Gallery essay] on the altered appearance of ultramarine in the paintings of Vermeer
* [http://colourlex.com/project/ultramarine-natural/ Ultramarine natural], ColourLex
* [http://colourlex.com/project/ultramarine-artificial/ Ultramarine artificial], ColourLex
* [https://www.htmlcsscolor.com/hex/120A8F Shades and tints and color harmonies of ultramarine], HTMLCSScolor.com
* [https://www.htmlcsscolor.com/hex/3117A7 More shades and tints and color harmonies of ultramarine], HTMLCSScolor.com
* [https://www.pantone.com/color-finder/17-4037-TPX An alternative ultramarine color (#5A7CC2) from] [[Pantone]], pantone.com
{{Shades of blue|Ultramarine}}{{Authority control}}