Blueness makes me happy

 kw: book reviews, nonfiction, colors, nature, blue

When I was ten years old my parents bought a set of four drinking cups of different colors to use in the bathroom, and sets of similarly-colored breakfast plates. I was the oldest of four boys; the others were 6, 4 and 2. Mom had prepared for the coming moment by questioning each of us privately, what was our favorite color. The 2-year old didn't understand the question, the 6-year old said, very definitely, "Red!" and while I had also said "Red" at some point, I also liked blue, so when she showed us the four cups, I was quite happy to pick the blue one—it was really a lovely, dark blue—leaving green and yellow to the two youngest boys. The 4-year old was happy enough with green, so the youngest got yellow by default. In later years, I learned that blue is the most common favorite color. It made me wonder, if that is so, why does "feeling blue" mean sadness?

That latter point is scarcely touched in Blue: In Search of Nature's Rarest Color by Kai Kupferschmidt, but the book abounds with lore and learning about Blue: how we see it, use it, and value it. I did wonder, how is it so rare, when the sky is blue? As I soon learned, "blues you can use" are hard to come by. Thus, there are a number of blue minerals, also many blue flowers and fruits, but stable blue pigments made from minerals are historically scarce and thus highly valued, and blue dyes from plant sources even more so.

It's true that though there are a number of blue minerals, only one or two make useful pigments, and the primary one is lapis lazuli (lazurite to a mineralogist). It's scarce and hard to produce because it seldom occurs with much purity, being intergrown with pyrite and other minerals of similar solubility. One must almost pick it apart with tiny tweezers to get the blue mineral grains separated from all the others.

It's also hard to grow, unlike chalcanthite, AKA hydrated copper sulfate. I grew this specimen of copper sulfate in a jar, rather quickly. It is very water soluble, so as a mineral it only occurs in deserts, associated with copper deposits. Good pigments aren't water soluble!

I happen to favor blue minerals, as does Dr. Kupferschmidt. The two pictures below show one natural mineral, light blue fluorite, and a jar-grown phosphate (apatite, chemically).

There is also a chapter on color perception, with quite a discussion of the way some languages have only one word that covers both green and blue hues. Does this mean that some people can't see the difference, or that it just isn't important in some cultures? I do know this: my wife says the phosphate crystals are clear; she doesn't see the aqua color that is so distinct to me. She also tends to see some of my clothing as green, which I see as blue, but the Japanese language has quite distinct words for blue and green colors (she is Japanese).

Another chapter deals with plant dyes, which seem to produce every color except blue, with two exceptions: woad, Isatis tinctoria, and the indigo bean, Indigofera tinctoria. The Latin word tinctoria is from tinctura, meaning "dye". The two plants' extracts are the same chemically, but that from the indigo bean is more concentrated. Denim is dyed either with natural indigo, or a synthetic version. It has the charming characteristic of gradually coming out in the wash, so that older blue jeans and jean jackets (etc.) fade with many washings. If you want blue underwear, wash it with new blue jeans!

I was surprised that mollusk dyes were not mentioned (I happen to work in the mollusk collection of a natural history museum). Of course, "royal purple" is the most famous dye to be made from snails of the genus Murex. It was even more surprising to me because I found this statement, quoting philologist Lazarus Geiger, that "the Bible found 'no opportunity' to mention the color blue." This is blatantly false! viz:

The Hebrew word tekelet occurs 50 times, and nearly every version translates the word as "blue". Historically the word describes the blue dye produced from a secretion of the cerulean mussel; both Mytilus edulis and Mytilus galloprovincialis are found on the Phoenician coast where the purple-yielding Murex species are found. Jewish sources describe the color of "Tyrian purple" from Murex snails as having a range of colors, depending on how much ultraviolet the dye solution is exposed to during processing. The more UV, the bluer the result. Apparently, in the mix of dye chemicals, the red one(s) are bleached by UV. Thus, begin making dye in the late afternoon to get a more magenta, almost reddish color, or begin early in the day to get a sky-blue dye. The dye from the mussels tends more toward blue hues than from the snails. The common name "cerulean mussel" refers to sky blue, which is the color of the fresh shells. And here we mean the darkish blue of a clear winter sky.

The tapestries of the Hebrew tabernacle and later of the temple in Jerusalem, as well as the garments of the priests, were to be of linen embroidered with "blue and purple and scarlet", all colors that can be produced from mollusks. Now, perhaps Lazarus Geiger only had a New Testament available; the word "blue" does not occur in the Greek New Testament, where either kyanos or galazios would have been used. The NT does mention red, scarlet, green and purple.

On a further note, some consider the Hebrew word cappiyr, translated "sapphire", may refer to lapis lazuli, but from the root of the Hebrew word, it refers to the extreme hardness of the stone, and can only refer to corundum; sapphire is blue corundum. The "sapphire pavement" before the throne of God is intended to appear as the blue sky seen from above.

All that aside, It was great fun to read this book. There is much to learn about blue, including why its manufacture was so hard in the past, but is so common now. So I could have a dark blue plastic cup to use when brushing my teeth as a child. P.S. I still have that cup, and still use it!