The ‘Escences' of Light: All About Color, Part IV

Peacock feather earrings

Yes, I know that "essences" is spelled with three S's, but that is not what we are featuring today. I want to discuss the subjects of iridescence, pearlescence, opalescence, luminescence, phosphorescence and fluorescence. We touched on these topics when we discussed structural color and observed iridescence in a peacock feather and a butterfly's wings (August 14, 2019 post). Now I want to treat iridescence and its related phenomena in greater detail.

Soap bubble

Iridescence is an optical phenomenon that appears  when certain substances seem to change colors as the viewer changes the angle of observation, or the angle of light changes. You have seen it on the surface of a soap bubble. feathers, insect wings, oil slicks on wet pavement and the insides of some seashells. Often the effect is the result of structural color caused by microstructures in the material that interfere with the direction of light rays. The word iridescent comes from the Greek word iris, which means "rainbow" and the Latin word escent which means "having a tendency toward". (Learn more about the origin of the word in our April 27, 2020 post.)

Oil slick on wet asphalt

The thickness of the layers of the iridescent materials influences the pattern of light interference. Thin films like oil slick or soap bubbles are most likely to produce temporary iridescence. In an oil slick, the different colors indicate different thicknesses in the layers of oil.

Hummingbird photos by J.J.

More permanent effects are caused by many layers of structure like those in a hummingbird's feathers, the scales of a butterfly's wing, or the layers of nacre in an abalone shell. The range of colors in natural iridescence may be narrow, shifting between only 2 or 3 colors, or as wide as the whole visible spectrum. The rainbow colors require quite elaborate arrangements of micro-structure.  A few minerals show this kind of iridescence. One of the most startling places to find the effect is from the iridescent scales on the abdomens of tiny male peacock spiders from Australia. This is easily mistaken as a threat display, but it is really part of an elaborate courtship routine. And he had better do it right or the female will kill and eat him! (You can see his performance on You Tube or BBC).

We can create artificial iridescence with diffraction, which in this case refers to the spreading of light around an obstacle or forcing it through a small opening, creating an interference effect.  We see the affects of this in DVDs, CD's, smart phones with iridescent back panels, and glitter nail polish.

Mother-of-pearl inside shell

Pearlescence is an effect related to iridescence where some or all of the reflected light is white and iridescent effects produce rainbow colors. The term pearlescence is used to describe the situation when a structure within a surface causes light to be reflected back, but some or all of the light that is reflected back is white light. However, pearls can be many colors besides white — pink, blue, green, gold, grey or rainbow-colored. Artificial pearlescence can be made with certain pigments and paints. This effect is largely used in the automobile industry.  Pearlescent paints and finishes can be found in craft paints and nail polishes, as well.

Fresh water pearl jewelry

Natural pearls occur in the soft bodies, or mantles, of mollusks like oysters and some species of freshwater mussels. The pearl is composed of calcium carbonate in response to the presence of an irritating intruder in the shell. Most people believe that the irritant is a grain of sand, but it is far more likely to be a parasite. A sort of allergic reaction by the mollusk causes a pearl sac to close around the intruder.  Tiny crystals are deposited around the sac in layer after layer. This process goes on as long as the mollusk is alive. Perfect pearls are round, but pearls come in many shapes, depending upon the shape of the irritant inside. Irregularly-shaped pearls are called baroque pearls. Cultured pearls are "grown" at pearl farms where small particles are inserted into the mollusks' bodies. In this way the size and shape of the resultant pearl can be controlled.

Opalescence is an optical phenomenon displayed by the gemstone opal. This is due to the layering, spacing, and size of the many crystals of silicon dioxide, in the form of microscopic spheres, and the included water and/or air in their microscopic structures. When the sizing and spacing of the spheres is small, refracted blue-green colors are prevalent, sometimes with flecks of other colors.  This is precious opal. You can see it in the opal set into the head of this silver fish pin. The dark spot in the "eye" is a bit of stone around which the opal formed.

Precious (top) & common white opals

When the sizing and spacing of the molecules is somewhat larger, the colors yellow, orange, and red appear. This kind of gem is called fire opal. When the sizing and spacing is larger still, a milky, hazy sheen of light appears within the stone. This material is called common opal.  Exposure to heat can cause the water in the stone to break down and the fire and glow disappears. The stone is said to 'die'. During the Bubonic Plague, this effect was seen when the wearers fell prey to the extremely high fevers that the disease caused. Because people at that time did not understand diseases very well, the opals were sometimes blamed for the wearers' deaths. It became a forbidden gem and didn't regain its popularity until the 20th Century.

Honduran black opal

Opal can be found as inclusions in many different minerals. It can form in wood which later becomes petrified. It has also been found in fossil shell and bone. It is a fairly soft material, which is often "sandwiched" between a layer of dark stone, to reflect more of its brilliance, and a hard, clear quartz to protect it from wear.  It needs to be protected from heat, and opal rings or bracelets should never be worn while washing dishes.

Phosphorescent pigment before & after 'charging'

Phosphorescence occurs when the phosphorescent material is "charged" by exposure to light — usually ultraviolet light. Then the energy that has built up is stored for a period of time and released slowly.  Some minerals, including some diamonds, are naturally phosphorescent. Oddly, phosphorus, for which the phenomenon was named, is not one of them. These materials can sometimes be activated by body heat or by being vigorously rubbed. When the energy is released immediately after exposure to light, the phenomenon is called fluorescence. The study of phenomena like this led to the discovery of radioactivity in 1896.  There are practical applications, such as fluorescent lights and items like clocks that glow in the dark.

Scorpion fluoresces under UV light

Incandescent steel

Luminescence, sometimes called cold-body radiation, is a spontaneous emission of light from a substance that is not caused by heat.  It can be caused by electrical energy, chemical reaction, sub-atomic motion or stress on a crystal. This distinguishes it from incandescence, which is light being emitted by a substance that is being heated. For example, a fireplace poker left in the fire too long might begin to glow.

Luminescence has some interesting practical uses. Some examples are: lasers, light-emitting diodes (LEDs), dosimeters to detect harmful radiation, luminol to detect the presence of blood at a crime scene, and photoluminescence used in microbial diagnosis.  That last use is playing a part in the current fight against corona virus and other causes of deadly epidemics.

Fireflies (30 second exposure)

Bioluminescence is, to me, the most fascinating ‘escence’ of them all. It is light emitted from living organisms.  One summer night long ago I was riding around on dark rural roads with some college friends. Suddenly we saw an area ahead of us that was glowing and pulsing. We stopped, climbed over a fence, crossed a field and reached a tree-shaded place by a creek. On the ground were hundreds of small bodies flashing yellow, green, and a reddish light, more or less in unison. None of us had ever seen glowworms, but we realized that was what they were. Glowworms are the females of some species of fireflies (which we called "lightning bugs"). Their heads and eyes mature to adulthood, but their bodies remain in the larval state — unable to fly. We knelt down to watch. After a few minutes, we became aware of smaller pulsing lights overhead. The males had arrived. They flew intricate back-and-forth patterns before dropping down to mate with their choices of females. As mating progressed, the females went dark and the males flew away. They may have been an unnamed species, because they rarely flash red and the males are supposed to attract the females — not the other way around.  We walked in awed silence back to the car, aware that we had experienced something rare and wonderful.

Bioluminescent comb jellies

You may have recently seen film of surfers riding glowing waves at night along the California coast. The light was caused by algae in the water, disturbed by the rolling waves. It is a charming sight, but not a welcome one for scientists. The algae use up much of the oxygen in the water. If they stay around very long, this causes harm to the beds of giant kelp in the water, along with all the marine life that lives in their shelter. This can also be harmful to migrating marine animals like whales and dolphins.

Bioluminescent sea creatures

Most bioluminescent animals live in the sea. Exceptions are the fireflies, some earthworms, and a few cave species that use luminescence to attract prey. Click beetles use flashes of light when in flight to attract mates, but they also flock together on the ground and appear to use the lights as a warning signal there. Some fungi are luminous, perhaps to attract animals that will carry some of the fungal spores away with them.  Bacteria may be luminescent. Many organisms produce their own light, but others harbor luminous bacteria in various parts of their bodies.

In the ocean, particularly at great depths, many — perhaps most — animals have some luminous features. As we develop better and better instruments to send back information on sea-floor dwellers, we are seeing some wild and wonderful luminous species. Animals use luminosity for a number of reasons. An obvious one is to identify mates of the correct species and attract them.  A sudden flash of light to confuse or startle a predator comes in handy.  Being able to mimic another animal — particularly one that is poisonous or just tastes bad — is a distinct advantage.

Angler fish (public domain illustration)

A marine animal that spends a lot of time close to the surface, like a firefly squid, may have luminous organs on the underside of its body that break up its outline and allow it to appear to be part of the surface waves. The angler fish dangles a luminous lure above and in front of its huge mouth to collect unwary prey. His stomach stretches so much that he can eat animals that are nearly as big as he is!  Some sea creatures use clouds of luminescent bacteria the same way the octopus uses ink — to provide a "smokescreen" while making a quick getaway. Animals that regularly eat luminous prey usually have opaque black stomachs. After all, it doesn't pay to advertise your last meal to a predator who might make you its next one!!

I hope you have enjoyed our excursion into the ‘escences’.

 This post by Annake's Garden is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Fog, Flashing Lights, and Flotsam: Seascapes, Part III

Surf & Rainbow, photo by J.J.

It is foggy this morning. Fog is essentially a cloud that has dropped to ground level. The tiny droplets of water that we feel on our faces as mist are not large or heavy enough to fall as rain, nor are they cold enough to start crystallizing into snowflakes.  Fog is relatively rare in this high, dry country. It is usually welcome because it brings the promise of rain or snow to this drought-damaged region. I can, however, remember a year when fog lingered from mid-December through mid-January,  leaving people short-tempered and depressed. Fog is an emotional thing.

Fog dampens sounds, distorts distances, and interferes with our sense of direction, making it easy to become lost. From an artistic standpoint, it reduces even a complex scene to a few basic shapes. That simplifies the scene and gets rid of a lot of clutter. Only the closest objects and the most distinctive shapes remain. Any source of light or reflection becomes a focal point. On the other hand, fog neutralizes the colors of everything. Fog is gray.

Grey-scale of photo by J.J.

In Part I of this series, we showed J.J.'s photograph of sunrise over the harbor. J.D. has shown it here in gray scale as it might have looked on a foggy morning. Old black-and-white snapshots could also give you more ideas for how things might appear in a light fog.

Much of my artwork lately consists of prints J.D. makes from detailed drawings I've done in graphite, charcoal, and black ink, so I am very interested in grays. I work with them practically every day. We think of grays as mixtures of black and white, but that is a very limited view. Very lively grays can be achieved by mixing complementary colors — the ones directly opposite each other on the color wheel. This technique can give you an array of warm grays, cool grays, soft grays, opaque grays, etc.

Simple color wheel

It is a good practice to mix complementary colors in needlepoint, particularly in shadows, which always show some of the complementary color of the object which casts the shadow. You might want to make some reference samples of this kind of work. You can do this with separate strands of floss or yarn. The strands can be twisted together or you can use them separately, side by side. Stitch fine lines of the colors close together on small swatches of fabric or canvas that you can keep for future reference. Hold the finished sample at arm's length to see how the blend appears. Keep and use the combinations you like best. Sometimes you may even get an iridescent effect. Orange and blue are complementary colors. Browns are grouped in the orange family of colors. I have gotten nice results with some mixtures of blues and browns. Try a cool greenish blue with a warm reddish brown, for example, or a purplish blue with a yellowish tan.*

Complementary colors from the wheel with their mixed grays

People have been going to sea for thousands of years. Many must have perished in fog, perhaps tragically close to safe harbors. Seacoast cities began building tall towers with large fires burning on top of them to serve as beacons.  The most famous one of these lighthouses was on the island of Pharos by the mouth of the harbor at Alexandria, Egypt. Built by Pharaoh Ptolemy II between 290 and 280 B.C. (BCE),  it was one of the Seven Wonders of the Ancient World.  It survived for more than 16 centuries before it was destroyed by an earthquake. Writers described it as 450 feet (135 meters) tall. Focused by huge polished bronze mirrors, its light could be seen 40 miles (65 km) at sea. There has recently been a magnificent computer reconstruction of it.

A U.S. lighthouse (public domain photo)

Many of these lighthouses were built along the coasts of the United States and some of the Great Lakes to guide ships by their fixed or flashing lights.  Their use has declined since World War II because so many vessels now use SONAR and GPS positioning systems. A few, mostly remotely controlled, are still in use. Others have become converted to tourist attractions, maritime museums, even private homes.  But the lighthouse is still a romantic structure, loved by painters, photographers, and fiction writers. Lighthouses are a popular subject for large photograph calendars. Now that 2019 has already begun, you may find these handsome pictorial calendars on sale for a reduced rate. They are good references for creating your own lighthouse design. Those of you who prefer landscapes to seascapes may be content with the small amount of ocean visible around a lighthouse.

Lighthouse collage by Annake

This picture is one of my collages, now belonging to J.D. Those of you who are quilters can probably imagine stitching a scene like this on top of a patchwork background. It would also be attractive done in trapunto, a type of decorative raised quilting, on a pillow top. In trapunto, two parallel lines are stitched through at least two layers of material to outline the design. Then the bottom layer has slits made in it and stuffing is inserted between the lines. If the lines are quite close together, a heavy cord,  instead of stuffing,  can be worked into the space between the lines.

Watercolor study for a wall hanging

The word flotsam comes to us from maritime law, where it referred to items deliberately dumped into the ocean from ships. Over the years it has come to mean anything that floats on the water. Much of this flotsam eventually washes up on beaches. Most of it is just garbage that needs to be removed in order to keep the beaches clean and safe. It is unsightly; some of it is dangerous. Nevertheless, an attentive person walking on a beach will find something attractive: pretty seashells, branches of coral, deep-sea fishing lures, glass floats, etc. These objects can be put together in collections or made into artistic arrangements.

The picture at the side of this section of the article is a watercolor sketch for a quickpoint wall hanging. It is 23 inches (58 cm) long and 9 inches (23 cm) wide. When the wall hanging is completed, it could be hung either horizontally or vertically.  I think I prefer to hang it vertically, so that is the way I have shown it here. A sketch in progress for a similar composition is shown horizontally, below. I have not chosen a final background color for that composition yet. Those of you who enjoy doing still life designs should enjoy putting together an assortment like one of these. A pattern like one of these, with a wider background, could also be used for a latch-hook rug.

Another watercolor study of flotsam

Think of a foggy day as a fortunate time to spend with a good book (or sketchbook) or to read blog posts like this one.

* Look for more on this subject in our series on using color, coming this spring,

 This post by Annake's Garden is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

An Interview with Our Jewelry Artisan

Carnelian Bead Necklace with Hand-formed Copper Links

Those of you who have read my earlier posts, visited our Etsy shop's "About" page, or checked out our Gallery site know that Annake's Garden (the business!) is a collaborative effort of several artisans; and while you've heard quite a bit about my -- Annake's -- methods and work in progress, you haven't really met the rest of our motley crew.

This time I'm interviewing one of the Annake's Garden's artisans who makes original jewelry from wire and natural gemstones. And, no, I'm not going to introduce her; for that, you'll HAVE to check our Etsy shop's "About" page!

How long have you been making jewelry?   "I did quite a bit of beadwork as a young adult. Later I taught my daughter and some of her teenaged friends to make beaded jewelry. I've been making wire and gemstone jewelry for about five years now."

At work on a current project

How did you get started?   "It all goes back to my love of the outdoors. My older son and I like to spend time in the forests and on the hills. While he fished, I'd look for rock specimens. He found that he enjoyed being a “rockhound”, too, and we soon acquired a lot of specimens. I began to use a tumbler to polish promising rocks. Soon we had a large number of tumbled stones. Then a friend sold my son a rock saw and he began cutting slabs from larger specimens. In no time, it seemed, we had buckets full of slabs. I returned to our friend and asked what we should do with them, since the situation was getting out of hand. He handed me some silver wire and a pair of pliers and told me to make jewelry."

Some of the artisan's tools and materials

Where have you and your son hunted for gemstones?   "In Colorado, of course, but also in Oregon, California, Montana, New Mexico, Arizona, South Dakota and Nevada. We've particularly enjoyed hunting in Nevada because the people there were so helpful and welcoming. People have also contributed specimens to our collection from as far away as Panama. We would like to plan future trips to the diamond crater in Arkansas, to North Carolina, and to Alaska."

What IS she doing?

You obviously enjoy making jewelry. What attracts you to it?   "The materials themselves. The feel of gemstones is very important to me. Not only do the stones have different colors and textures, they seem to have different temperatures. Stones like garnets, labradorite, and carnelian feel warm to me. Turquoise, jade, and tiger eye --- despite its warm colors --- feel cool. I don't believe I have ever combined 'warm' and 'cool' stones in the same piece, but it will be interesting to try. Lately I have been working also with shell, pearls, and other oceanic materials. Pearls are especially touchable. I love to use copper wire because of its warmth and color, as well as its malleability. I use silver because it is so versatile. In fact, I have plans to combine the two in some future pieces."

Closeup of  the artisan's hands at work

How do you begin a project? Do you make sketches?   "No. I take two approaches. If I have a definite design in mind, I look through my collection, choosing stones that look and feel right for that design. I like to start with a pendant and later make compatible pieces like earrings, rings, and bracelets. Once I have laid out the stones, I cut and shape all the metal pieces. Lastly, I position beads, pearls or other small elements. If I need inspiration, I just get the stones out and “play” with them until a pattern quickens in my mind. It is challenging to see a project through from idea to artifact."

A simple Silver Pendant strung with Jasper Beads

What part of the process do you find the hardest?  "One of the harder things is to find or make a clasp that goes well with the finished piece. I'm always looking for new clasps and clasp designs. I re-purpose clasps from older and out-of-style pieces. I know a lot of older people who have virtually given up wearing jewelry because they can no longer manage the fasteners. I think that's a shame. For those people I use a lot of magnetic clasps. I also don't mind recycling pieces --- “orphan” earrings, for example--- and incorporating them into new pieces of jewelry."

Crocheted Copper Wire Bracelet with Pearls

What new projects are you working on?   "I've brought one along to show you how I'm working on it. I've combined my interest in crochet with my interest in jewelry-making. This will be a cuff bracelet crocheted from a fine gauge of copper wire that has small pearls worked into it. I think a matching collar would be another fascinating project. Perhaps I'll do that next."

How do you feel about man-made gemstones? "There are many beautiful ones available and I'm sure technology will produce more. I think there is a need to define what “natural stone” means. Do we include reconstituted and laboratory-grown? I believe that stones actually found in Nature will become increasingly valuable as sources dwindle and access to them becomes restricted. I think we will see more use of agates, jaspers, quartzes, etc. Personally, I prefer to work with natural stones. They feel right to,me, whereas many of the man-made materials do not. It's as if they have no 'soul'."

Any other benefits of your work?  "It's therapeutic. And (laughing), of course, I now have more jewelry than I could ever wear. "

I hope you enjoyed hearing from someone besides me, for a change --  I'll be interviewing more of our artisans in coming months, and may even be able to talk some into guest blogging here. As always, your comments and suggestions are eagerly awaited...

Annake

Cowrie Necklace and Earring Set, now available in our Etsy shop

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