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  • Writer's pictureMichael Skalka

Green Pigments

Updated: Jun 17

A lot has transpired since my last blog post. We recently returned from an 18-day trip to the Republic of Ireland and Northern Ireland. The island is a paradox of diversity and unity.  We marveled at castles both intact and in ruins. We drove through areas of flat lands and undulating hills and cliffs. We navigated super highways and roads that by American standards would be considered driveways, yet they were intended for two-way traffic.  We stayed at fairly small hotels and a grand castle surrounded by lavish landscaping and a sprawling lake.


The one unifying factor was how amazingly green the countryside is in Ireland. It almost hurts your eyes to see such an intense green color. Despite numerous sheep munching away in fields of grass, the color was never dull. In many instances, the sheep were the only things that added color to the landscape.  While it might appear to some that the sheep were victims of graffiti tagging, the colors were intentionally put on the sheep to denote ownership.  The various marks of red, purple, green, or yellow will eventually be bleached from the wool in the process of making yarn.  While it might have been thought that the native sheep provide most of the wool that supplies the numerous sweater shops that dot the country, we were told that the wool of merino sheep from Italy supplies the yarn for the soft sweaters sold in Ireland.


Coast of Northern Ireland


So it is fitting that today’s essay focuses on the color green. As a color found in the paint box of many artists, especially those residing in the eastern part of the United States where green is a dominant part of the landscape, digging into the variety of types of green colors and the pigment choices that create the green paints sold becomes a complicated exercise.


As a secondary color, green is defined as combining both blue and yellow hues. Technically, green occupies the range of 520 to 570 nm in the visible light spectrum, coming right in front of blue and blue-green wavelengths and ending where yellow begins.


This essay will not focus on the history of green which by all accounts goes from obscure origins in antiquity starting with Malachite and Earth Green, continuing on into the Middle Ages and the Renaissance with Sap Green, Verdigris, and copper resinate compounds. Green rises to a crescendo of intrigue with the advent of a host of copper arsenate pigments like Emerald Green and other derivatives that were the cause of fashion and home decorating related deaths.  All good reading, but not useful when dealing with what a contemporary artist faces with when purchasing green paint. 


Green paints sold today can serve as an example of some of points made in several previously posted Syntax of Color essays.  Historical color name as well as color names derived from a pigment name do not necessarily have common, uniform formulations.  That will become painfully obvious upon examining the following chart.


Color Name Composition Chart


Chart of green paints by manufacturer
Color Name Composition Chart

This examination is composed of a selection of 6 common green colors sold today  using  3 domestic and 3 of foreign brands.   The colors are Cobalt Green, Cadmium Green, Phthalocyanine Green, Chromium Oxide Green, Viridian, and Sap Green. 


The selection is divided into 3 cool greens: Cobalt Green, Phthalocyanine Green and Viridian, and 3 warm greens: Cadmium Green, Chromium Oxide Green and Sap Green.  However, this warm and cool division is heavily influenced by the pigments selected or the ratio of pigments used, which makes the cool/warm designation manufacturer-dependent rather than color-name-dependent.


Only 3 out of the 6 green colors have manufacturers agreeing on what pigment should be used to make the color formulation.  Phthalocyanine Green, Chromium Oxide Green, and Viridian are consistent regardless of brand.  Phthalocyanine Green is made using PG7 (Chlorinated Phthalocyanine), Chromium Oxide Green is composed of PG17 (Chromic Oxide), and Viridian is made of PG18 (Green-Black Hematite)


There is no agreement on how to formulate Cobalt Green, Cadmium Green, or Sap Green. Each manufacturer has their own way of making the colors in their line of oil paints.


Cobalt Green can be made with PG19 (Cobalt Zinc Oxide) PG26 (Cobalt Chromite Green) and PG50 (Cobalt Titanite Green). 


Cadmium Green can be made with PY35 (Cadmium Yellow ) PG18 (Viridian) and PW4 (Zinc White PW6 (Titanium White).  Note that Cadmium Green is a convivence color so each manufacturer has the liberty to craft it their own way. Two manufacturers don’t even have Cadmium Green in their inventory of oil colors.


As expected, Sap Green is both an old historical color name originally made from an organic plant substance (buckthorn berries) so the expectation of uniform color is a matter of interpretation.


The pigments that are employed to make Sap Green run the gamut starting with:

 PY83 (Diarylide Yellow) and PB15:1(Phthalocyanine Blue),

PB 15 (Phthalocyanine Blue) and PY110 (Isoindoline Yellow),

PG7 (Phthalocyanine Green) along with PY42 (Iron Oxide Yellow) and PY129 (Irgazin Yellow),

 PG7 (Phthalocyanine Green) and PY110 (Isoindoline Yellow),

PY95 (Diazo Yellow) PG7 (Phthalocyanine Green) PBk7( Lamp Black),

PG7 (Phthalocyanine Green) PBk9 (Bone Black) and PY75 (Arylide Yellow)


So the takeaway from all this is that artists need to evaluate their choice of any green colors they intend to incorporate into their palette.  Even the single pigment green colors should be examined carefully.  Manufacturers may use different suppliers and the hue can be slightly different depending on the manufacturer.  Mixed greens are selected with personal color mixing strategies and subject matter in mind. 


Artists may have a preference for a warm or cool green that matches their requirements. Of course, artists are free to make green hues without the use of single pigment green colorants.  The range of blue and yellow colors each with their own characteristics can provide all the green colors required.  The green colors discussed in this essay can be modified with more yellow or blue.  The addition of red, orange or violet can broaden the range of color temperature in greens that may be required to suit the needs of an artist.


The spectral signatures of the colors discussed in this essay are posted in the section (green spectra) in this website.  They can provide an indication of the underlying color bias of the pigments and give a preview of how they may react when mixed with other colors. 

Understand that even though a color appears to be an easily recognizable hue,


underlying spectral intensity in an unexpected area of a color’s spectral signature will play a role in how a mixture will behave. Example:  Ultramarine Blue and Cadmium Yellow will never yield an intense green hue because Ultramarine Blue has a powerful red reflectance that subdues the ability to make the combination of Ultramarine and Cad Yellow a forceful, vibrant green.  The “redness” of Ultramarine Blue neutralizes the mixture.


More fun awaits as other hues are explored in the future.


Syntax of Color

 

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2 comentários


azcrazy
13 de jun.

Greens are the bane of my existence...still interesting to try to mix. Thanks for this article!

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Michael Skalka
Michael Skalka
13 de jun.
Respondendo a

If you paint landscapes on the east coast of the USA you can't avoid learning how to make a variety of green hues and to control their color temperature based on lighting at the time being depicted. Check out the spectral curves in the website. They provide a peek into color bias and why some mixtures are easy to make and why some thwart you from achieving the color you want. Thanks for the feedback.

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