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LuxeSci Show Notes: S2E6 - Red and Green

Hello again, welcome to LuxeSci, a podcast to reignite your wonder by exploring the science behind luxury items.


Well, it’s almost Christmas and we decided to do our holiday episode on the quintessential Christmas colors, Red and Green.  Now - I remember growing up visiting my grandmother and cousins in New Jersey and everyone really went over the top with the Christmas decorations.  But, you were just as likely to see green and blue Christmas lights as red and green, or white or colored.  I was always enthralled by it because 1) I thought the color combination was prettier than red and green and 2) growing up in a small town in CT, you didn’t see a lot of colored Christmas lights (except for our house).  Almost everyone had plain white lights. 


Dimos - any Christmas light stories


Why Red and Green

  • It’s thought that the red and green association with Christmas comes from the Roman celebration of Saturnalia

  • This was an agricultural celebration that happened around the Winter Solstice 

  • When the planting was done, the Romans would celebrate and decorate their houses with evergreens, including holly (which is red and green)

  • The use of evergreens has continued in Christian celebrations of Christmas

  • However, red and green weren’t the predominate colors as evidenced by Victorian Christmas cards, which has a number of color combinations

  • In the early 1930s, Coca Cola hired an artist to draw Santa for their Christmas ads and this is thought to be where the modern version of Santa was greeted, a jolly, fat old guy in red and white (coincidently Coke’s colors).  This association of Santa in red combined with the green of Christmas trees has led to red and green being the colors of Christmas

  • From Arielle Eckstut who co-authored The Secret Language of Color


Green pigments

  • Malachite

  • Ancient Egyptians (probably and others) used the mineral malachite to produce green pigment

  • Copper carbonate hydroxide mineral

  • Copper - turns green when exposed to oxygen

  • Carbonate - CO3-2 (carbonate ion)

  • Hydroxide - 

  • Mineral is a monoclinic crystal system - which forms a parallelogram prism

  • Found in fractures and deep underground spaces where water and hydrothermic fluids create chemical precipitation and as we know, if you’re not part of the solution, you’re the precipitate

  • Name is from Greek - molochites - mallow-like because it looks like the leaves of the mallow plant

  • Used for many years to produce copper

  • Used as a pigment until the 1800s and for other decorative uses as it is supposed to help with sleep

  • Made by grinding, washing and levigating the raw material or in the lab by mixing copper sulfate and sodium carbonate

  • Levigating - make a substance into a fine powder or paste

  • Not many examples in European paintings but you can find it in Raphael’s Sistine Madonna from 1512

  • Verdigris

  • Scheele’s green (Emerald green)

  • Invented in 1775 by Carl Whilhelm Scheele,  Swedish chemist.

  • Made by heating sodium carbonate and arsenious oxide and finishing with copper sulfate

  • It was cheap and easy to make and quickly took over as a dye for almost everything, toys, wallpaper, wax fruit, fabric, etc

  • A good example of it used in a painting is Madame Roulin Rocking the Cradle by Vincent Van Gogh

  • The deadly ingredient is copper arsenite

  • How arsenic is poisonous

  • Symptoms include vomiting, abdominal pain, encephalopathy, heart disease, numbness and cancer

  • So the main mechanism of arsenic poisoning is the inhibition of pyruvate dehydrogenase. This enzyme an essential reaction in cellular energy creation.  With it’s energy system disrupted, cells go through apoptosis

  • Apoptosis - programmed cell death

  • Arsenic prevents the use of thiamine (an essential amino acid) and thus the clinical symptoms mimic thiamine deficiency

  • Inorganic arsenic can also interfere with the potassium channels in cells, which disrupts the cell’s electrolyte function.  This can lead to high blood pressure, neurologic disturbances and cardiac episodes

  • Eventually use of the color waned as more and more deaths and illnesses were linked to its use

  • There was another green, though a more bluish green, that was in use called Viridian, thought to be invented in 1797 and put into use for painting around 1838

  • Chromate oxide - we mentioned chromium in our previous episode on yellow and orange and in our episode on emeralds and rubies

  • These pigments are chemically stable and can be mixed with other pigments

  • Renoir’s The Skiff (also mentioned last episode) is painted using viridian

  • Cobalt titanate green

  • Modern, non-toxic green pigment with a yellowish tinge (which apparently makes it good for landscapes)

  • Metal oxide of cobalt and titanium

  • Discovered in the 1930s and still used today

  • One interesting bit of green trivia.  Imagineers at Disney invented a shade of green called Go Away Green.  It’s a mix of the greenery in the area and a brown/gray/green hue that humans have a hard time registering (unlike last podcast subject, orange). It’s used to paint backdrops or construction or anything that Disney doesn’t really want you to “see” when walking around.

  • Some guesses as to the shade of Go Away Green:

  • Aganthus Green, Benjamin Moore

  • Pale Jade, Glidden

  • Cooking Apple Green, Farrow & Ball

  • Relish, Sherwin-Williams

  • This takes advantage of what is called attentional bias, where we ignore things that we’re not focused on. 

  • Also - the cones (where we see color) are more focused in the area of the eye that is “seeing” what we’re focusing on and there are more rods (movement) in our peripheral vision, so we’re more likely to see the color of things we’re focused on and ignore color (especially a non-bright color) of things we’re not focused on

Red Ochre Natural inorganic pigment 20,000-15,000 BCE

History states that the first civilization of humans from archaeological evidence in southern africa from late stone age people scraped and ground ochre, a clay colored by iron oxide (rust!

The main color giving component of natural red ochre (ocher) is composed of hematite (∝-Fe2O3). The term red ochre (ocher) or red earth describes various kinds of iron oxide pigments such as Venetian red, mars red, English red, Indian red.

Iron oxides are stable at high temperatures but not resistant against acids. The pigment is absolutely stable as is documented by the cave paintings still in excellent condition after many thousands of years.



Wall Painting, Altamira cave in Spain, around 15 000 Years Old


Composition and Properties of the Madder plant 1500BCE

This pigment is prepared from the roots of the madder plant. The main coloring agents in the roots are alizarin, purpurin, and pseudo purpurin. All of them are derivatives of anthraquinone. Madder root has been used for dying cloth at least since 1500 BC.[2] Purpurin and alizarin were isolated from the root by Pierre Robiquet and Colin, two French chemists, in 1826. These were unfortunately prone to fading so they are not used as much as pigments for art.

To make:

Boil 1 part of madder in from 12 to 15 pints of water, and continue the ebullition till it be reduced to about 2 lbs. Then strain the decoction through a piece of strong linen cloth, which must be well squeezed; and add to the decoction 4 oz. of alum. The tint will be a beautiful bright red, which the matter will retain if it is mixed with a binder such as clay.

Interesting use: A study published in Nature journal Scientific Reports suggests that the purpurin could replace cobalt in lithium-ion batteries.[9] Eliminating cobalt would mean eliminating a hazardous material, allow batteries to be produced at room temperature, and lower the cost of recycling batteries. Extracting purpurin from farmed madder is a simple task; alternately, the chemical could be synthesized in a lab.[10]

 



Johannes Vermeer, Christ in the House of Martha and Mary, 1654-56

Carmine (Carmine Lake) Natural organic pigment from insects 

The name carmine is used for two similar pigments derived from different insects. Cochineal is produced from (Dactylopius coccus) a parasite on the cacti mainly in South America and Ethiopia. The main colorant of this pigment is carminic acid.The second pigment is derived from another insect called kermes which lives as a parasite on the tree Scarlet oak. The main coloring agent, in this case, is kermesic acid.


Dying textiles was done by Aztec and Mayans since 2nd century BCE and the pigments have been used as ink on manuscripts. Spanish conquerors in the new world brought these back but they were found to be lacking in color stability, ie they would change color under even diffuse sunlight:


“Beautiful and rich as are the colours prepared from cochineal, not one of them should ever find a place upon the palette of the artist. They all become brownish and ultimately almost disappear after a short exposure to sunlight or the more prolonged attack of strong diffused daylight” Arthur Herbert Church


Recent concerns over the safety of food additives have made the colorants from these natural sources quite popular but somewhat controversial as in the winter-spice latte from Starbucks. However safe, they run about 5 - 10x more costly than synthetic food dyes.


Peter Paul Reubens Samson and Delilah



Red Lead from 500 BCE

A dense, fine-textured red pigment comes from simple lead oxide Pb3O4. It has a good hiding power but only fair stability. Red lead was one of the earliest pigments artificially prepared and is still in use today. It was a favorite of Byzantine and Persian illuminators and commonly used in European manuscripts and paintings.


It is a mixed lead oxide containing Pb2+ and Pb4+ lead ions with an overall formula of Pb3O4. The pigment has been artificially prepared since antiquity but can also be found in nature as the mineral minium though quite rare and mostly visible if your lead mine catches fire as it is created under extreme oxidizing conditions. It is not very stable and cannot be used in fresco and in watercolor as it can blacken after prolonged exposure to air. It is not compatible with orpiment.


ORPIMENT Arsenic Sulfide (quite toxic, used as both a coloring and a poison)

For centuries, orpiment was ground down and used as a pigment in painting and for sealing wax, and was even used in ancient China as a correction fluid.[8] It was one of the few clear, bright-yellow pigments available to artists until the 19th century. However, its extreme toxicity and incompatibility with other common pigments, including lead and copper-based substances such as verdigris and azurite,[9][7] meant that its use as a pigment ended when cadmium yellows, chromium yellows and organic dye-based colors were introduced during the 19th century.

Dragon’s Blood and Vermillion 1st Century BCE

From the sap of wounded trees from the species Dracaena , Vermillion is from the elements HgS Mercuric Sulfide, a source is from the mineral Cinnabar.

An orangish red pigment with excellent hiding power and good permanence. It was used from antiquity through to the present but handling the dust is dangerous. Made artificially from the 8th century it was the principle red in painting until the manufacture of its synthetic equivalent, cadmium red.


 This is also known well throughout Asia as the color of chinese red.


Cadmium Red 1818

The range of cadmium pigments, yellow, orange, red are basically cadmium yellow (cadmium sulfide) with some selenium added in place of sulfur (cadmium selenide). Therefore cadmium sulfide can be made in various shades ranging from yellow, orange to red. Mineral pigment produced from cadmium sulfide when heated with selenium becomes red. It has very high hiding power and good permanence. A cadmium red was available as a commercial product from 1919. The pigment was used sparingly due to the scarcity of cadmium metal and cost


From Cadmium Sulfide and Selenium. Toxic

Henri Matisse, Interior with Black Fern 1948


Chrome Red Beginning of 19th Century

The mineral is deep orange, a natural form of lead chromate. It was analysed in the late 1790s by the eminent French chemist Nicolas Louis Vauquelin, who identified the new element chromium as the source of the colour. Vauquelin studied the compounds of chromium, and found that he could make bright yellow and rich orange versions of lead chromate, both of which he proposed as potential pigments. Chrome orange became the first pure orange pigment since the medieval use of realgar, a highly toxic compound of arsenic. The chromium colours did not become widespread, however, until the discovery of chromium-containing mineral deposits in France, USA and Britain. By replacing the lead in chrome yellow with other metals, such as zinc and strontium, the colour could be tuned to paler or more acidic hues, such as ‘lemon yellow’. Vauquelin also commented on ‘un vert extremement beau’ made by roasting crocoite to form chromium oxide. In 1838 this was modified (by incorporating water in the crystals) to make the vibrant green called viridian, a colour that became almost emblematic of Paul Cézanne. Chrome orange was introduce as a pigment in 1809. The world production of chrome orange ceased few years ago.


PbCr04 Lead Chromate, not very stable but used in impressionist painting


MODERN REDS

PR 170 – Naphthol Red


Colour Description: Ranges from orange-red to blue-red

Transparency/Opacity: Semi-opaque to semi-transparent

PR 170 covers a wide range of shades, and the name of the paint usually gives away what kind of shade you can expect. Naphthol Red Light indicates an orange-red, while Naphthol Red Deep is usually a more violet shade. Its lightfastness varies between pigment manufacturers.



PR 83 – Genuine Alizarin Crimson


Colour Description: Rich blue-red

Transparency/Opacity: Transparent

Alizarin crimson is a synthetic lake pigment that was developed as a replacement for Genuine Rose Madder (NR 9). It is a deep, cool red with a high tinting strength and, despite concerns about its lightfastness, many artists find the colour indispensable. With Viridian (PG 18) or Phthalo Green (PG 7) Alizarin Crimson makes a deep-valued chromatic black. PR 83 is more muted and natural-looking than most of the modern Quinacridone pigments which now dominate the blue-red pigment market, but for those who are concerned about its lightfastness there are many Alizarin Crimson hue paints that are often offered alongside the genuine pigment in many paint ranges.




RED Facts

Use in Iconography:

Red is one of the most frequently used colors in icons. This is the color of heat, passion, love, life and life-giving energy, and for this very reason red became the symbol of the resurrection - the victory of life over death. But at the same time it is the color of blood and torments, and the color of Christ's sacrifice. Martyrs are depicted in red clothing on icons. In red celestial fire blaze the wings of the Seraphim - angels stationed adjacent to God's throne. Sometimes icons were painted with a red background as a symbol of the celebration of eternal life. 



Red light is used to help adapt night vision in low-light or night time, as the rod cells in the human eye are not sensitive to red.


Bull Fighters use a red cape but Bulls are color blind anyway so it is only the movement that agitates them.


As for the colors used in early televisions; Primary red in the original color TVs is generated from the red-emitting Mn2+-activated phosphate, Zn3 (PO4)2.


Glossary

  • Levigating - make a substance a fine powder or paste

  • Attentional bias - ignoring things we’re not focused on

Cocktail party facts

  • Who invented a very toxic but very beautiful shade of green pigment

  • How did red and green become associated with Christmas


Thank you for listening to this episode of LuxeSci.  Please rate and review us on Apple Podcasts, Spotify or wherever you listen.  This is the best way to help us get noticed and find new listeners.  A special thanks as always to my audio engineer Dimos.  Our theme music is Harlequin Mood by Burdy.

This holiday season, if conversations get tense around the dinner table, just start talking about paint colors.  Happy Holidays!


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