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Chrome Yellow: An Ancient Primary Color

Dec. 23, 2021

When chrome yellow was first introduced as a pigment in the early 19th century, it provided a bright, opaque yellow color on artists' palettes. However, it had a flaw in its original form - it darkened when exposed to light.

Chrome yellow had a brief history of widespread use among 19th century artists such as Turner, Manet, Cézanne, Monet, and Pissarro. Like Pissarro and Monet, Cézanne used the neutralizing effect of combining three primary colors - ultramarine, vermilion, and chrome yellow - to produce colored grays. Its popularity quickly faded due to the introduction of a more stable opaque pigment, cadmium yellow, in the middle of the century.

Impressionist mixtures of highly complex primary pigments were the solution to the problem of rendering airy light effects and modeling forms in space. The search for equivalents of light effects in material colors was based on the realization that "sunlight cannot be reproduced, but it must be expressed". Rather than the brilliance of each color, the juxtaposition of certain colors enhances each other's color and brightness, resulting in a high-key image. Renoir notes this effect, known to every good colorist.

"I used chrome yellow, which is an excellent color, but is obviously playing tricks. I tried chrome yellow; I found great difficulty in using it, it made me paint heavy. Then I wanted to do my little Rubens. I started painting with Neapolitan yellow, which is a rather dull color. It gave me all the brilliance I was looking for." 

Renoir mentions that chrome yellow darkens in the light. Although its history as an artist's color is short, modifications to the original form of the pigment discovered in the mid-20th century now make it light-resistant and resistant to change.


Medium Chrome Yellow

 

Chrome Yellow Pigment

Chromium yellow is a yellow pigment made by adding soluble lead salts (nitrates or acetates) to a solution of alkali chromates or dichromates. Its shade can vary from evening primrose yellow to orange, depending on the particle size, which in turn depends on the precipitation conditions. Lighter shades, such as chrome yellow evening primrose, usually contain lead sulfate or other insoluble lead salts. Intermediate shades are neutral lead chromate, and orange chromium is basic lead chromate. The pigment consists of very fine and opaque particles.

 

Durability and Compatibility

When chemically pure, chrome yellow is quite lightfast, but is often observed to darken and turn brown with age. Sometimes, especially when mixed with organic pigments, it takes on a greenish tint by reducing some of the chromium to chromium oxide (the basis of the green pigment chromium oxide).

By encapsulating the pigment with amorphous silica and other metal oxides, the resistance to discoloration when exposed to acids, alkalis and light can be greatly improved. Due to the inert nature of silica on the surface of the coated pigment particles, these pigments show excellent resistance to light, chemicals and heat. Modern light-resistant chromium pigments (based on monoclinic crystalline forms) are encapsulated by silica and various metal oxides. These encapsulated chrome pigment varieties are resistant to light, heat, weathering and sulfur dioxide.

Common types of chrome yellow may not be used with alkaline binders such as lime and water glass because they convert to red alkaline lead chromate. These varieties also tend to exhibit poor acid resistance. Lead chromate can be considered compatible with all common pigments, although older references sometimes warn against mixing with chalk because the latter is alkaline. However, the encapsulated variety of lead chromate pigments are highly resistant to acids and bases.

 

Toxicity

Although exposure to high concentrations of soluble chromate in industrial settings poses a potential health hazard, the use of small amounts of this pigment in paints does not appear to pose much risk. Because of its very low solubility in body fluids, the use of lead chromate in paints poses little potential hazard. Of course, ingestion and prolonged inhalation of the pigment dust should be avoided.


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