Monday, December 9, 2019

Why Can't Flower Pigments Be Used in Paints?


Thom Rozendaal asks: "Why don't we use flowers to make pigments? I understand it would be hard to separate the biological matter from the pigments so maybe it would be possible to study how flowers produce these colors and recreate the processes in a lab? Has this ever been attempted before? Are there any pigments that are already made from flowers? It seems most are made of some type of mineral or something, and I guess I'm just worried we'll some day over-mine some of them as we are already doing with so many other things, whereas flowers are already being produced on a mass scale and are a renewable resource."

Thom, There are two main types of pigments in flowers: carotenoids and flavonoids. Scientific American says: "Carotenoids include carotene pigments (which produce yellow, orange and red colors). Carotene pigments are also found in vegetables, which is what gives carrots their colors. Flavonoids include anthocyanin pigments (which produce red, purple, magenta and blue colors)."

Both of these are natural organic pigment compositions that fade quickly because the large molecules are easily broken by ultraviolet light. You can make ink out of anthocyanin pigment, but it will be subject to photodegradation. People who collect dried flowers keep them pressed in books to protect them from ultraviolet light.

One organic pigment that has been traditionally been used as an artists' pigment or a vegetable dye is madder root, made from the dried root of rubia tinctorium. The root pigment is "laked" which means "bonded chemically to a colorless, transparent, insoluble salt that often acts as its own mordant — which turns the dye into an insoluble pigment. The gum arabic in watercolors then binds this complex but chemically stable pigment to the paper." (Source)

Natural organic pigments are rarely used in modern paints because of issues of lightfastness, so paint manufacturers use synthetic organic pigments or inorganic pigments. This webpage explains more about that process.
----
Scientific American: Springtime Science: Exploring the Pigments in Flowers
Anthocyanin pigments on Wikipedia


7 comments:

Susan Krzywicki said...

What a great question that was. Enjoyed your answer - nothing I had ever thought about before. It reminds me of a thought I had the other day, while watching a YouTube art restoration video. The restorer said in passing that he appreciated artists who prepared their canvasses well and used good techniques. It mean that restoration work, centuries or decades later could more easily help support the longevity of the work.

I'm not saying that the free-wheeling times from the 50s or 60s onward were wrong to break out of the strictures of a codified art establishment. It is interesting though, that this freedom has come at a later price: preserving flashes of genuine fresh creativity that were executed in spur of the moment methods and with materials grabbed from other realms that were not focussed on permanence - fading, etc.

Maybe this is part of the yin and yang of life: pops of new stuff, then a swing of making the new into the long-term standard that can be maintained over time.

arturoquimico said...

Maestro... I retired from 50 years as a chemical researcher, quality control consultant, and instructor at a local University and took up art as a hobby... not only am I impressed with your artwork, but also your straightforward explanation of plant pigments and artist dyes is very scientific and "chemical"... the only problem I had working with artists is that they thought brown was a color... and in chemistry there are only colors per se... so students should not answer a question about spectroscopy and name a pigment! i.e. violet exists, but not turquoise...

Susan Cushing said...

Walnut makes a fairly lightfast pigment used for inks, and has a long history of use.
I make it from the walnut husks and get a deep rich brown that works well with
watercolor and also other inks. In looking into how it has been used, some sources say
it is very lightfast. It's been around for hundreds of years.

Rick Majors said...

Can paint which has completely dried and hardened in its tube be rescued and reboended to an original consistency, after it has been stored too long?

James Gurney said...

Rick, I've heard some people say they've done it successfully. I've tried it without success so far—cutting open just made a big mess for me. Anyone have tips?

DeadSpiderEye said...

Very informative James, Rose Madder was used to dye uniforms in the British Army until 1873. Officers uniforms were generally dyed with cochineal, but they were responsible for supplying their own kit.

I wonder if you have view on the Emerald Green issue ie copper-acetoarsenite? It's sort of related to this topic, it being probably the most notable case of a toxic pigment.

Thom Rozendaal said...

Very interesting, there's much more depth to the matter than I expected. Especially that last link was incredibly informative, though I still feel a bit unqualified to understand most of it, having no knowledge of chemistry.