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Blue The noble color of the sky
Blue has always been associated with royalty, it is cool, soothing, a reminder of infinity and things spiritual. it gives a sense of stability. It is no co-incidence that big financial institutions often have blue colored emblems. Although the sky and the sea are both rich in blues, blue coloring is rare in natural minerals, Azurite and Turquoise being almost the only ones used for art until modern times. Ancient Britons covered their faces in Woad, and around the mediterranean Indigo was used for dyeing textiles. The scarcity of good and affordable blues meant both were employed by artists from time to time. The Egyptians developed Blue Frit to meet the need for a good blue but it was too weak and coarse to last until modern times. When the Europeans began importing ground Lapis Lazuli they thought they had found the perfect blue finally. It was except that it cost more than the same weight of gold. It wasn't until the synthesization of Ultramarine in the 1820's that artist had what they really needed all those years, an affordable, permanent, and useful deep blue of great beauty.


Ultramarine PB 29   ASTM   l
Previously known as ground Lapis Lazuli  and also Lazuline Blue
Chemical type and description
Inorganic synthetic silicate. Made by heating clay, soda, sulfur, and coal in a furnace. The original product had been a semi precious stone ground up and treated chemically to remove all the non colored stone in a process developed in Persia in the 12th century. It cost more than gold and eventually the French Government offered a large prize to anyone who could synthesize it. All attempts failed until a French foundry accidentally produced a deep blue color as a by-product of something else. An intense analytic process backtracked through the steps taken to arrive at a workable formula. The synthesization of Ultramarine was one of the  most important color discoveries in the history of artists pigments. The synthetic Ultramarine is chemically identical to the Lapis Lazuli but has a different crystalline structure which means it does have some differences. The original is still available at a price.

For a discussion of the historic Lapis Lazuli click here

Ultramarine is now produced industrially in about 30 different shades from a green through blues to a violet. The color called Ultramarine Yellow is not related except by name. All the Ultramarines are equally permanent and only the green is difficult to find. Ultramarine naturally goes very stringy in oil and can be erratic in behavior. Manufacturers make up for this by adding large amounts of waxes and other 'stabilizers'. The maker of paint in the studio usually puts up with the difficult painting qualities of Ultramarine to get the extra intensity of the pure pigment. Nowadays Ultramarine is so cheap that it is even used as a major pigment for roof tiles due to its light fastness. It is susceptible to bleaching in the presence of even weak acids and their vapors. It cannot be used for Fresco but is suitable for all other media. It is a slow to moderate drier and makes a fairly hard but brittle oil paint.
Toxicity
Not considered toxic. Do not breath dust.
Media suitability
Linseed oil,  Alkyd, Acrylic, Watercolor, Gouache, Tempera, Encaustic, Pastels, Chalk.


Cobalt Blue PB 28   ASTM   l
Also called Thenard's Blue
Chemical type and description
Inorganic synthetic mixed metal oxide. Discovered 1802 by Thenard in France it did not become available as an artist's color until about the time of the introduction of artificial Ultramarine. Always expensive its price has increased over recent decades because Cobalt is used as a coating on high performance jet engine turbine blades which has lead to an ongoing shortage of the metal. Cobalt Blue is as permanent as Ultramarine and has few defects. It can be used in all media including Fresco with the exception of dry media such as pastel due to toxicity. It is a good drier and makes a hard and fairly flexible oil paint.

Cobalt Blue has an interesting history going back past Thenard in 1802. The first Cobalt based pigment was Smalt, a color that was developed in Saxony in previous centuries. It was an improved version of Egyptian Blue Frit that used cobalt to replace the copper colorant of the older pigment. The cobalt was mined as an ore in 2 forms that were later to be called Smaltine and Cobaltine. The miners believed there were spirit beings in the mines and they were called in the local tongue 'Kobalds'. Cobalt is named after these spirits that inhabited the mines.
Toxicity
Considered toxic. Do not breath dust.
Media suitability
Linseed oil,  Alkyd, Acrylic, Watercolor, Gouache, Tempera, Encaustic, Fresco.


Pthalo Blue PB 15 & 16   ASTM   l
Also known as Monastral Blue
Chemical type and description

Organic synthetic Pthalocyanine. Available in copper and metal free versions, Pthalo Blue has steadily replaced the less reliable Prussian Blue as the artist's primary dark blue since its introduction in 1936. Having all the good qualities of Prussian Blue without its major defects it is a useful blue especially for mixing greenish blues and greens. It is an unusual pigment in that it is so strong as manufactured that it is actually improved by the addition of 50 and 75% Alumina Hydrate or Blanc Fixe. Normally this would constitute adulteration in other pigments but in this case the extenders improve the workability of the pigment, eliminates a tendency to 'bronzing' and reduces the tendency of the color to overpower all mixtures it is a part of. This admixture of inert filler will be already in the pigment at time of purchase. Average to slow drier, it makes a hard and fairly flexible oil paint. Suitable for all media. Pigment is available in 'Floc' and 'non-floc' versions which refers to a tendency of a pigment to flocculate (an undesirable clumping of pigment particles) choose 'non-floc' if there is a choice.
Toxicity
Copper may be a slight hazard. Do not breath dust.
Media suitability
Linseed oil,  Alkyd, Acrylic, Watercolor, Gouache, Tempera, Encaustic, Fresco, Pastels, Chalk.


Cerulean Blue PB 35   ASTM   l
Chemical type and description
Inorganic synthetic mixed metal oxide. Oxides of cobalt and tin. A bright sky blue color of great permanence. invented in 1805 it was not introduced as an artist's color until 1870 due to its high cost. it is one of the most opaque colors on the palette. Very useful for the landscape artist.It is an excellent drier and makes a fairly flexible oil paint. Do not confuse with the cobalt chromate also marketed under the name Cerulean Blue but tends to be greener (it comes in beautiful turquoise versions) and a little darker. Its color index number is PB 36. While it shares many excellent properties the chromium version lacks the unique sky blue character of PB 35 although it does tend to be cheaper and has its own beauty.
Toxicity
Cobalt is considered toxic. Do not breath dust.
Media suitability
Linseed oil,  Alkyd, Acrylic, Watercolor, Gouache, Tempera, Encaustic, Fresco.


Other Blues Both past and present
Prussian Blue (PB 27) also called Antwerp Blue, Paris Blue, Milori Blue, Iron Blue, Chinese Blue, and Bronze Blue.
A deep intense dark blue that was the first significant pigment produced as a result of the Industrial Revolution. Quality and permanence varied considerably according to the grades used. Now totally replaced by Pthalocyanine Blue which is superior in every way.

Azurite (PB 30) also known as Bremen Blue.
A copper blue associated with Malachite was mined from Ancient Egyptian times. Still produced in Central Asia and available through calligraphy supply stores that have Chinese connections, it is a beautiful sky blue color but is a very poor pigment in oil so fell out of favor despite its permanence. The pure blue skies of Titian's paintings are often pure Azurite.

Indanthrone (PB 22)
A clear deep blue organic pigment of excellent light fastness. Not as overpowering as Pthalo Blue.

Egyptian Blue (PB 31) also called Blue Frit
The first industrial attempt to produce a deep blue it was made for 3000 years before largely disappearing in the 18th century. Made by making a deep copper blue glass then pulverizing the glass as a pigment.

Smalt
Considered a direct descendant of Egyptian Blue, it was developed in the 17th century when cobalt ores replaced the copper of the older pigment. It was popular until the synthesization of Ultramarine. Coarse, weak, but very permanent.

Zirconium Cerulean Blue (PB 71)
A beautiful semi opaque light Blue (available from Kremer).


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References
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Muther, R,    The History Of Painting From The Fourth Century To The Early Nineteenth Century,    1907 (Putnam)
Parkhurst, D B,    The Painter In Oil   1898 (Lothrop, Lee & Shepard)
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Roy, A      Artist's Pigments: A Handbook Of Their History And Characteristics,      1994 (Oxford University Press)
Taubs, F,    A Guide To Traditional And Modern Painting Methods,    1963 (Thames & Hudson)
Theophilus,   On Divers Arts,    1125 (Dover)
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