biology zoology blog benno meyer color dye animal

Famous Because of their Colour

Some animals really are

I had once bought quite a nice shirt in Funchal Madeira (incidentally the place star footballer Cristiano Ronaldo was born) and I wore this shirt on the day I handled some fresh squid. Squid, as most people know, have the ability to secrete a dark liquid, often referred to as “ink”. It’s their form of defence against an attacker and a way to disappear behind a black cloud when the squid’s ink is released in the water. Little did I know that this ink is almost indelible: my squid-ink-stained shirt was probably washed a dozen times, but the stains remained as “brownish reminders” of the time I once handled the squid.

As a matter of fact, I was told that some painters had used squid ink in some of their paintings as the colour “sepia brown” and it also found use as a dye. Far more famous as a dye and an animal-derived colour is purple. It is obtained as reddish drop from primarily a Mediterranean marine snail formerly known as Murex brandaris and now going by the name of Bolinus brandaris. A few other species like Hexaplex trunculus and the rock-shell Stramonita haemastoma can also be used. So sought-after was this colour that only the wealthiest clientele could purchase items that were treated with the snail’s liquid. In more northerly seas the dogwhelk Nucella (Purpura) lapillus has historically been used to obtain a scarlet dye whose colour turns more radiant with age. Purple snail dyes all contain bromine.

A reddish-violet secretion is obtained from some lac-insects, principally Kerria lacca. It used to be in demand in India and China to dye silk and wool, but nowadays the reddish insect lacs are used mainly in connection with candies, refreshing beverages, jams and sauces. An even brighter ruby-red colour, often referred to as “carmine”, is still widely used in the food industry and is the product (known as cochineal dye) of crushed scale insects of the species Porphyrophora hamelii and P. polonica. Depending on the species and treatment different shades of red, ranging from pink to bloodred are used in the cosmetics industry, for example in lipsticks and eye shadows. The substance is not very stable in oil paints.

Animal blood has been used in some paintings and the contemporary artist Vincent Castiglia paints with blood, which, however, loses its red colour rapidly and turns brown due to oxidation and then cracks. Indians have been reported to use cow’s urine as a yellow dye, but egg yellow has been more popular. It retains its colour well, but dries quickly and then becomes brittle if not treated before being used as a colour for paintings. Traditionally egg yolk had to be mixed with vinegar and water. Another animal-based colour that painters have used widely is black, based on charring of animal bones. Charcoal was, of course, one of the 6 colours ancient Egyptians used for their famous paintings, the other 5 being white (chalk), blue (copper salts), green (malachite), yellow (arsenic trisulphide) and red (iron oxide and ochre), but there were no animal-based colours. Some red paints were plant-based and so were their brushes, consisting of bundled fine reeds. European painters used (and still use) brushes made from hog, badger, goat, mink, or squirrel hairs. Of course, there is nowadays a wealth of synthetic materials for both brushes and paints, but water colourists still love ox gall (= bile) as a paper wetting agent.

After reading this blog, perhaps the next time you look at paintings or admire the colours of an ‘Indian sari’ or a ‘Japanese kimono’, you might wish to think about where the colours could have come from -and (if by chance you squashed a caterpillar) if its fluid mightn’t perhaps work as a dye for “green”!

© Dr V.B. Meyer-Rochow and, 2020.
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