Electric blue icing

A glacier dripping down the cliff in Scott Inlet

Some time ago I promised I would write about the icebergs and glaciers I saw this fall along the Baffin Island coast and in Scott Inlet.

In every gap between cliff faces in Scott Inlet, tongues of glaciers dripped in slow motion like icing on a cake of grey cliff. These weren't glaciers that could be accessed by fancy-big-wheeled buses like Columbia Glacier or even easily reached to trek across like these folks did. I wouldn't want to try to get up to the main part of the glaciers as even without the dripping ice, the cliff-gaps would have required us to use ropes to successfully scramble up.

Glaciers flow under their own weight, a direction that is obviously down hill. I have no idea how long it took, but a few of the glacier tongues had made it to the ocean calving bergy bits into the water. The icebergs in the inlet were tiny compared to the big icebergs moving south along the coast of Baffin Island.

Along the coast, the iceberg that sank the titanic once passed more than a century ago. Even knowing before I arrived that I would be heading into iceberg waters, I was surprised at how many there were. Some looked large enough to dwarf an aircraft carrier (as a tangent: there was a proposal in World War II to make aircraft carriers out of ice). Some that had grounded could easily be mistaken for an island. Many had wave-rounded forms reminiscent of modern sculpture, or ancient weathered architecture.

An iceberg glowing blue

What fascinated me about the glaciers and icebergs was their colour. Even under the grey skies parts glowed electric blue – almost like they were generating their own light deep within. Glaciers and icebergs don't actually glow, but under the right light it looks that way.

Snow looks white because of all the reflective edges from the layers of snowflakes. Once the snow is compressed into glacier, the edges merge and air is pushed out. However, any ice can look blue in time. Like the reflective snowflake edges, air bubbles scatter all the wavelength of light making young ice look white. Older ice looks bluer because air bubbles and other impurities have been pushed out.

Like water, ice absorbs the longer wavelengths of light as it passes through. That is, the red end of the spectrum is absorbed first, which is why a short distance underwater the seascape is dominated by blues and greens. Ice has the same effect on light, it filters colours as light passes through leaving blues. And it appears to glow because those blues have passed the whole way through – so the ice looks bluest from the inside.

Examples of iridescence from the fall fair

I caught these two beauties showing off their iridescent plumage at the fall fair. It always amazes me that such a range of colours can be produced from an optical trick.

An interesting take on blues and greens

I stumbled across this today. Colours and how we perceive them never ceases to fascinate me.

As a tangent: I realize it has been more than two months since I've written anything, work on another project has left me exhausted.

You are what you eat – the colour version

A flamingo from a local butterfly garden

Every kid knows that a flamingo is pink because of what it eats. They filter water through their beak to catch brine shrimp and algae. The beta carotene in their food is converted to the pink pigments in their feathers, without this pigment source the bird would be white. Unfortunately, flamingos aren't found on my Pacific island except in captivity. But, we do have critters using the same pigment trick.

Recently, I met up with the local Natural History Society (I'm a member) for a beach seine at night because that was when the best low tide was this time of year. Based on the wind storms recently, we were lucky the wind had dropped off and it wasn't raining. The surf was manageable with the net for people wearing hip-waders and dry-suits – so not me as I don't own either. Two people took the net out into the surf. The first seine was over sand resulting in hardly any fish. So, the net was taken out and hauled in a second time over eelgrass. All sorts of interesting intertidal creatures were pulled up.

Everyone gathered around to check out the fishes, crabs and shrimps. The fish catch included: walleye pollock, English sole, stary flounder, sharpnose sculpin, sailfin sculpin, sandlance, roselip sculpin, tubesnout, high cockscomb, a type surf perch, Pacific spiny lumpsucker (the cutest fish ever) and a penpoint gunnel. Each type was put into a clear ziplock bag along with plenty of water and passed around. By holding the bags up to my headlamp, I got a good look at each critter.

The penpoint gunnel intrigued me because it was neon green – a tropical water colour in our temperate zone. A picture can be found here, the fish looks like an eel, but isn't. This guy hangs around in eelgrass or sea lettuce beds waiting to ambush little crustaceans and mollusks. The bright green colour of the one we found would allow it to blend in almost perfectly (they also come in other colours to match other seaweeds). Like the flamingo, the penpoint gunnel gets it's colour through what it eats. The green comes from the sea lettuce.

Few of the fish and invertebrates were held on to for a local museum's tide pool, the rest were released. As we packed up our gear, another beach seine group arrived. In the darkness, all we could see of them was dark shapes and headlamps – it was like looking at ourselves a couple hours in the past.
  
As a tangent, my trips to the beach seem to coincide with when my rubber boots are muddy. Once again they are clean.

Bubble colours

Who hasn't blown bubbles outside on a sunny day? If you haven't, devote some time to blowing bubbles the next time the sun is out - it's fun. As a bubble floats gracefully through the air, sunlight creates a virtual rainbow (actual rainbows are formed by a different process) of colours across the bubble's surface. The colour-making phenomenon at work is the same as what creates the colours on a slick of oil, a rooster's tail, a cardinal tetra or hummingbird's gorget – it's iridescence.

Bubble walls are constructed of several thin layers, two soap layers sandwich a layer of water between them. This wall encases a volume of air. As sunlight shines on a bubble, some of it reflects off the surface and some enters the soap film. Inside the bubble wall, light travels slower because both water and soap are denser than the air. At the interface between the soap film and the water, again some light reflects and some passes through. The reflected light may bounce back and forth between the two surfaces a few times or it may just pass back out of the bubble. Reflection or transmission of light occurs at every interface. Most of the light emerging from the interior of the bubble wall will be out of phase with the light that reflects off the interface. Out of phase means that the troughs from one wave line up with the crests from another so that the waves cancel each other out. Some of the emerging light will be in phase, that is, the crests and troughs line up with each other. These two light waves amplify each other, resulting in brilliant iridescent colours.

Layer thickness determines what wavelengths (thus colour) will be amplified. If you move and look at the bubble from a different angle, the colours will change. This is because your viewing angle has changed in relation to the layers. From different angles the distance the light has to traverse to reach you changes, thus the wavelengths that amplify each other also change.

Unfortunately, soap bubbles last only a short time. It doesn't take long before gravity pulls the liquid to the bottom and evaporation whisks fluid away. Bubble colours change as the bubble changes. When the bubble walls are thick, only red gets canceled out leaving blues and greens. As the walls thin, yellow is also canceled out leaving blue. Next green is removed and the bubble looks magenta. Blue goes last making the bubble look golden yellow. As the bubble wall's continue to thin, all the waves in the visible region cancel out and the bubble looks just clear. When the walls reach about 25 nanometres thick the bubble is in serious risk of popping.

Since the thickness of a bubble's walls aren't constant - the walls thicken towards the bottom (remember gravity acts to pull the water down), bands of colours seem to fall downwards on the surface. That pesky gravity also prevents us from dyeing bubbles. The dye will only mix with the water and drain to the bottom of the bubble. However, when gravity is absent dyeing bubbles becomes possible – so if you head out on a long voyage to Mars bring lots of bubble making supplies as you'll have years to perfect your bubble dyeing technique.

Another type of scattering

Clouds are mists drawn up by the heat of the sun, and their ascension stops at the point where the weight they have gained is equal to their motor power
- Leonardo da Vinci

The weather has changed outside. We had almost a week of beautiful but cold, sunny days. Now, clouds have rolled in, changing the sky from beautiful blue to drab gray. Have you ever looked up at a cloudy sky and wondered why the clouds are white? Alternately, have you ever looked at the foam of a dark beer and wondered how the foam could be white while the beer is dark? The answer lies in how light interacts with water droplets in clouds and tiny bubbles in beer foam.

The average size of a water droplet is between 0.01 and 0.02 mm, with the largest ones about 0.15 mm (from 'The Field Guide to Natural Phenomenon' by Keith Heidorn and Ian Whitelaw) and they are transparent. Cloud colour results from an optical phenomenon. Since water droplets are similar in size to visible light wavelengths, when light passes through the water droplets all wavelengths are affected the same way. This optical phenomenon is very different to the preferential blue scattering from gas particles in Rayleigh scattering that make the sky appear blue. The effect of scattering each wavelength of light in the same way is called Mie scattering after Gustav Mie, the German physicist who figured this out (there are others who independently came to the same conclusion but didn't get the phenomenon named after them). In Mie scattering all wavelengths scatter equally, making clouds appear white since all the wavelengths are present in the same amounts. In a thick bank of clouds, no direct light makes it through; instead all colour results from diffuse radiation. Thick clouds may appear in menacing shades of gray.

The foam atop of a freshly poured beer is composed of uniformly sized bubbles suspended in beer (from 'Does Anything Eat Wasps? And 101 Other Questions' edited by Mick O'Hare). Each tiny bubble is filled with air with a lower refractive index than the liquid around it. As a result, the bubbles act like magnifying glasses in reverse, where light that enters the bubbles is scattered in different directions – another example of Mie scattering. Reflections off the bubble's surface adds another layer of scattering. Both scattering effects created by each bubble is compounded in the foam. Since each wavelength of light is affected the same way, the fraction of light that makes it out will appear white, that is all wavelengths are equally present (The end result might be slightly yellow if the beer surrounding the bubbles absorbs some of the light).

Light hitting dust, smoke or pollen can also experience Mie scattering. This effect also explains why milk is white.

And now for something yellow

Turmeric stains – a fact that is made clear to me every time I make curry and a drop ends up on my light coloured counter tops (what were the previous owners thinking when they installed baby blue counter tops?). Turmeric seems to stain more than any other spice I use, why?

First, a bit about turmeric. Native to South Asia, turmeric plants thrive in the moist, hot conditions found there. It's a member of a tasty family including: ginger, galangal and cardamom. The name 'turmeric' may originate from the Latin terra merita, which means merit of the earth. The turmeric powder commonly used as a spice is derived from the rhizome, a horizontal stem that typically grows shallow beneath the soil. From this stem, roots and shoots are sent out. These rhizomes are harvested about nine months after planting, then boiled, peeled and dried in the sun. Once dry, it is ground into a power.

About turmeric, Marco Polo said “There is also a vegetable which has all the properties of true saffron, as well as the smell and the colour, and yet it is not really saffron.” In medieval Europe, this spice was called 'Indian saffron' and was commonly used as an alternative to the expensive saffron. According to 'The Flavor Bible' turmeric has a bittersweet pungent flavour. Today it's commonly used to make mustard yellow, and as a component in curries that adds both flavour and colour. At times, turmeric even been used to colour cheeses, margarine and chicken broth. I wouldn't mind at all if turmeric was used as a colourant in my iron pills because it can do some good. In fact, a long list of potential medicinal uses have been attributed to turmeric, one use that has been proven is that it reduces inflammation.

Turmeric's use as a dye probably dates back as long as it's been used. I can't imagine not to noticing that turmeric stains cooking implements once it's added to a dish, however, the first record of using turmeric as a dye comes from an ancient Assyrian herbal recipe dating back to 600 BC (a fact from The Cook's Encyclopedia of Spices). The yellow colour is caused by curcumin, a chemical component of turmeric. About 5% of the dry powder is curcumin. The colouring components of other spices like paprika are less than 1%, so, to answer why turmeric stains more, there is just more colouring potential in the turmeric. On the plus side, turmeric fades in sunlight – so if a drop of curry ends up on a favorite white shirt put it in the sun for the colour to fade.

Orange poo and red hats

It's officially a winter day where I live – it's raining. My backyard has turned into a monster mud pit. The sky is gray and everything else ranges from muddy green to brown. But, there is some colour – you just need to look closely. Close to home, the holly bush over my black fence is sporting a few red berries. In the forest there is other colourful natural stuff to be found, even this time of year. Looking through my photos of last winter I found these two colourful gems.

One of my favorites is what I always called 'orange poo'. I remember finding it the woods where I grew up and thinking it was poo of some magical creature. Anyway, by consulting my 'Common Mushrooms of the Northwest' book, I've found it called 'orange jelly' or Dacrymyces palmatus. It's a fungi and apparently edible but not too tasty – I'm not going to confirm this as I have a general policy of not eating wild mushrooms and this particular on is associated with poo in my mind.


If you look closely at a rotting log, you might find a tiny hit of red from the British Soldier lichen or Cladonia floerkeanna (this one I found in my 'Mosses, Lichens and Ferns of the Northwest North America' book). To me this lichen looks like a match.

In general, a lichen is a fungi that is living symbiotically with some sort of alga. Lichens can survive in all sorts of extreme places – some even survived being exposed to outer space for over two weeks (yes, an experiment was conducted on this). Reading the introduction section of my the lichen section of my book it says lichens are used to dye cloth, ferment beer, and in perfumes, lotions and toothpaste – some can even be eaten.


Even on a winter walk, if you observe carefully, there are all sorts of interesting colourful things to see.

I took both photos while on walks last winter

Red moon, blue moon

Based on my recent discussion of blues (colours, not moods), I though I should describe what a blue moon is. 'Once in a blue moon' is a common phrase for an uncommon event. However, the moon is never blue (unless there are smoke or dust particles in the atmosphere, then the moon can appear bluish).

I've seen the moon turn a blood red – a frightening event if I didn't know why it changed colour. On that night it was a lunar eclipse. The earth had moved between the moon and sun, casting the moon into its shadow. Normally, the moon reflects sunlight directly from the sun making it a bright feature in the night sky. When the earth is in the way, the only sunlight to reach the moon is refracted around the earth and as a result the moon takes on a blood red colour (at least it did on the night I watched).

A blue moon is a completly different event, more of a bookkeeping phenomenon. A calander month is on average 30.5 days long, while the time between full moons is 29.3 days. Normally, there is one full moon a month but, on a rare occasion, a month can have two full moons. There are different ways of determining which of the full moons is the blue one. Typically, a season has three full moons, however when one of the months has an extra full moon, the third full moon is condidered a blue moon. This is so rare, a blue moon will occur only seven times in 19 years, which works out to one every two to three years. Mark your calenders as the next one will occur on August 21, 2013.

Been reading 'The Field Guide to Natural Phenomena' by Keith Heidorn and Ian Whitelaw – so far it promises lots of interesting tidbits.

What is it?

I was reading over a paper by John Peyssonel from the Royal Society's Philosophical Transactions (volume 50, 1757-1758, pages 585-589) titled 'Observations on the limax non cochleata purpur ferens, the naked snail producing purple.' It is about some sea creature and after reading it I have no clue what it is.

From the text (which is longest run on sentence I've ever seen):

Among the fish we meet with in the seas of the Antilles of America, we find, that this I am going to describe will appear precious, from the beautiful purple colour it produces, in the same manner, that the cuttle-fish produces its ink, if a means could be found to produce the liquor in a sufficient quantity to render it an article of commerce

The author goes on to describe this 'fish' as soft, viscous, without shells, scales or bones. It has no feet or fins. It acts like a slug when touched, in that it wreaths up as round as it can. In fact, they are so similar to snails and slugs the author calls them 'naked snails.' Their bodies are greenish in colour with black circular spots. They have two horns or antennae which might serve as eyes. Under a tough plate at the back of the body, it keeps a sack of purple juice. The purple juice can be deployed in defense just like a cuttle-fish uses it's ink.

Is this a description of a nudibranch? Or maybe a sea hare?

Part 4: Blue Eyes

Here is part 4 of my 4 part series on nature's blues. Part 1 is here, part 2 is here and part 3 is here.

Gaining an understanding why something is the way it is in nature is not always a direct path. We know the blues found in nature are often the result of the object's internal structure rather than pigments, however the actual blue making process can vary. Although the blue of the sky and the blue of a feather can look like the same colour, the actual mechanism involved is very different. The two optical phenomenon involved in making these blues are Rayleigh scattering and coherent scattering. The blues produced either way can look the same.

So, which of these mechanisms is responsible for blue eyes? Rayleigh scattering is the culprit this time. Eyes appear blue when there are only small amounts of melanin present in the iris. Melanin is the pigment that makes the iris brown – a complete lack of melanin results in the pink eyes of an albino. When light passes into an minimally pigmented iris, tiny protein particles in the eye act just like the gas particles in the atmosphere blue wavelengths are preferentially scattered and the eyes appear blue.

As a tangent – here is how Leonardo da Vinci explained blue skies 200 years before Lord Rayleigh:

'I say that the blue which is seen in the atmosphere is not its own colour, but is caused by the heated moisture having evaporated into the most minute and imperceptible particles, which the beams of the solar rays attract and cause to seem luminous against the deep intense darkness of the region of fire that forms a covering among them.'

Part 3: Blue Feathers

Here is part 3 of my 4 part series on the scattered blues. Check out part 1 here and part 2 here.

Blue feathers have evolved in many species of birds. A blue jay's plumage is an excellent example with blue and white. You can see the black and blue of a Steller's jay in your own backyard. A male mountain bluebird has blue plumage of this type along with the head feathers of the male lazuli bunting; both can be found in central British Columbia. We know that feathers don't contain blue pigment, so the colour must be a result of the feather's structure.

In the late 1800s, just after the discovery of Rayleigh scattering, naturalists used this new concept to explain why blue feathers were blue. Since they didn't have the tools to examine the nanostructure (structure in the order of a billionth of a meter) of a feather, naturalists assumed that within the feather there existed transparent cells full of particles that were tiny enough to create Rayleigh scattering. Like the sky, blue light would be more efficiently scattered. These transparent cells would also contain pigments to absorb the longer wavelength colours. As a result, to our eyes these birds would appear blue.

Because Rayleigh scattering is incoherent, it produces the exact same colour irregardless of the observation direction. Since blue feathers in natural light don't change colour depending on what direction the naturalists looked at them, the assumption that their colour was formed through Rayleigh scattering seemed valid. But, in the 1930's, scientists examined a a non-iridescent blue feather under a directional light source. Colour variations were observed as the light source was moved – an iridescent characteristic that called into question the hypothesis of Rayleigh scattering making the feather blue.

By the 1940's, a cool new gadget came on the market – the electron microscope. Now naturalists could directly examine the internal nanostructure of blue feathers. Based on this first look, they interpreted the internal feather structure to contain randomly spaced objects. This meant scattered light would be incoherent leading giving support to the hypothesis of Rayleigh scattering. It took decades of further research to change this hypothesis and in the mean time many textbooks were written explaining that blue feathers were the result of Rayleigh scattering. By the 70's, scientists finally determined that the nanostructures were, in fact, not fully random. Instead they were a quasi-ordered matrix – not quite the perfect order of iridescence but not the full randomness required for Rayleigh scattering. Under natural light from all directions, like sunlight, these feathers appear to be the same colour from all directions. However when a directional light is shone on blue feathers the colour will change depending on the light direction.

Since the colour of a Steller's jay's feather comes from its internal structure on a tiny scale, a damaged feather would lose its blue colour. The dark pigments in the feather, that act to help show off the blue, would make damaged feather would look almost black. So if you are lucky enough to find a Steller's jay feather, take care of it.

Thanks to G. Hanke for the photo of mountain blue birds.

Part 2: Blue Skies

Here is part 2 of my 4 part series on the scattered blues. Check out part 1 here.

On a sunny day, we perceive blue blanketing the sky, but, in reality, the sky has no colour. When traveling towards us, sunlight first hits earth's atmosphere. Earth's atmosphere is primarily composed of nitrogen (78%) and oxygen (21%) with bits of dust, water vapour and some inert argon, among other things. Water vapour and dust are the physically biggest components of the atmosphere, and are relatively large compared to the wavelengths of light. When light hits the water vapour and dust, is reflected in different directions, but the light remains white. So why does the sky appear blue?

In 1810, Goethe gave this explanation: “If the darkness of infinite space is seen through atmospheric vapours illuminated by the daylight, the blue colour appears.” His theory said colour comes from something within the atmosphere during the light of day. About the same time a more scientific inquiry was being made into the nature of scattering light. John Tyndall showed in an 1869 lab experiment that the blue hues of the sky could be created when white light was scattered by tiny particles. A few years later in 1871, John William Strutt, also known as Lord Rayleigh, was the first to describe the actual mechanism that makes the sky appear blue was a result of the tiny gas molecules of the atmosphere instead of the larger dust and water vapour.

When light collides with a gas molecule the results are different than when light hits a relatively large dust particle. Gas molecules are tiny compared to the wavelengths of light – several thousand times smaller. When light strikes a molecule, that molecule absorbs a specific wavelength (or colour) of the light's energy and later re-emits the same colour in all directions; a process called Rayleigh scattering. This type of scattering is an example of incoherent scattering. Lord Rayleigh discovered that molecules absorb energetic light (blues) at a much greater rate than less energetic light (reds).

Most of the longer wavelengths of light pass through our atmosphere unaffected, resulting in the full spectrum of sunlight with a higher ratio of blue wavelengths from the scattering. For this extra blue light to make the sky appear a brilliant blue, a dark background is required. Fortunately, beyond our atmosphere is the blackness of outer space, which makes an ideal dark background. The combined effect of the extra blue light and the black of outer space results in a sky that appears blue.

If you shift your gaze towards the horizon, the brilliant blues give way to paler colours and perhaps even white. The light reaching you from near the horizon passes through much more atmosphere, so the scattered blue light is scattered again and again, reducing its intensity. This is another consequence of Rayleigh scattering. Preferential scattering of blue light by our atmosphere occurs everywhere, not just above us. For example, light reflected from your hand to your eye is affected by this scattering, but the effect is so minuscule we can't detect it. Over a longer distance, like to a range of distant mountains, there is enough atmosphere to superimpose a blueish haze on our view of the mountains.

Part 1: Blue Skys and Blue Feathers – The Scattered Blues

A while back I wrote about why the sky was blue and why some feathers are blue (here) – well I didn't quite get it right, so I'm trying again. I've written a more detailed explanation which I'll post in four parts.

When I look around, I see lush greens of temperate rain forest, rich browns of fertile soil, lively yellows in fluttering butterflies, and luscious reds in ripe berries – but, not a lot of blues. If the sky is clear, it's the biggest blue object around, extending from horizon to horizon. Water reflects the blue of the sky, adding another layer of blue. On a lucky day, I'll catch a glimpse of a Steller's Jay showing off it's blue and black plumage, or a shimmering silver-blue dragon fly will dart by. I might even see a rare blue flower. On a gray winter day, the blue eyes of my favorite companion may be the only brilliant blue around. Other natural places have their own blue components, but in general, blues aren't common in nature. In fact, world-wide there just isn't a lot of natural blue pigments, thus the blues we see are often the result of optical properties within an object. These colours created as the result of an object's structure are called, creatively, 'structural colours'. Blue is a very common structural colour, and to understand why we'll need to start with some optics.

Sunlight is called 'white light' because it appears colourless. Within this colourless light lurks the full colour spectrum. Once, people thought white was the fundamental colour of light, and colours formed when something was added into the light. This theory was changed after the careful experimentation and observations of Sir Isaac Newton. Around 1670, Newton shone light through a prism creating a rainbow of hues on the other side. From this result, he concluded that white light contains all colours and that the prism simply separates them. Therefore, colour results from interactions between an object and light.

We now understand that white light is made up of tiny waves (which are simultaneously tiny particles if you want to add complexity). Light waves travel at the same speed but can have different wavelengths, that is, the distance between successive crests. Our brains perceive the different wavelengths as different colours. The longer wavelengths form reds, oranges and yellows, and the shorter wavelengths form greens, blues and violets. If you could watch waves of light pass by, more waves of blue would pass compared to waves of red – this means that the blue light has more energy. Light travels outward from its source, the sun, in a straight line until it collides with something. This collision could release all the hues in the spectrum or just a select few.

Scattering describes how light is diverted from its original straight path. Light scatters in two ways: coherent and incoherent. When scattering is coherent, spectacular effects such as iridescence can occur. Like a ball bouncing back from a flat wall, the light reflects precisely because the reflecting surface is geometrically regular. Similar colour light waves augment each other, further intensifying the effect. An iridescent feather's colour can change depending on viewing angle, a phenomenon easily observed in a Anna's Hummingbird gorget. Incoherent scattering resembles the result of throwing a rubber ball at a pole – it could bounce away in any direction. In this case, the scattering objects are randomly distributed relatively far apart. Scattering at one object occurs completely independently of the scattering at the other objects. Both coherent and incoherent scattering occur regularly in nature and can provide the mechanism for creating blue colours.

The photo is of a hyacinth macaw I took years ago at the San Diego Zoo.

A bloody green

Further to my post from yesterday, I stumbled across an interesting article from the 1818 edition of the Philosophical Transactions of the Royal Society of London, volume 108, pages 110 to 117. The paper was called 'A Few Facts Relative to the Colouring Matters of Some Vegetation' by James Smithson – an interesting person that I'm planning on digging up more information on.

I found this buried at the end in a section called 'Some Animal Greens':

There are small gnats of a green colour: crushed on paper, they make a green stain, which is permanent.

This brings to mind a child squishing bugs to see what colour their insides are. I've found no other reference to green dyes from gnats, so I'm assuming crushing gnats didn't make it into commercial production.

Actual bloody colours

I've been thinking about my bloody colours post of a little while back. Magenta and solferno were named because they reminded observers of the after effects of a battle. What about colours made from actual blood? That is, by killing a critter. These dyes exist, and some are still in use today.

Fantastic reds can be made from crushed insects. I wonder who was the first who thought of grinding up dried bugs to dye cloth? One of these dyes is Kermes, an ancient dye extracted from an insect (Coccus ilicis) that resided in the middle east. This bug lives as a parasite on oaks, producing carminic acid (the base component for a dye) to deter predators. Kermes is the root of the word crimson and predictably, cloth dyed with kermes turns out a bluish-red. Skilled dyers could even produce a scarlet cloth. About 70,000 insects are needed to make only one pound of dye – making a very bloody dye.

Cochineal, also known as carmine, is another ancient bloody dye produced from similar insect (Dactylopius coccus). This bug resides on cactus in Mexico and has been the foundation of a red dye for millennium. This dye is chemically the same as kermes except ten times stronger – less of them needed to die to produce the same amount of dye. When the Spanish brought this dye back to Europe in the mid 1500s, it quickly over shadowed kermes because it was a cheaper alternative. Both kermes and cochineal have been widely used to colour foods dating back to the middle ages, and cochineal is still in use now. As a food colourant it's called by many names, including 'natural red 4'.

Throughout the ages other similar insects have been used to make red dyes. Polish cochineal (Porphyrophora polonica), a insect that lives on the roots of herbs in Poland, was once used to make reds as an alternative to kermes. In India, a red dye was made from a secretion left behind by an insect in the same family (Laccifer lacca), I think the bug got to live in this case – but, I don't know for sure. In South East Asia, reds called lac, could be made from a whole family of related insects, which also provided the foundation for shellac (often used as a protective coat for wood).

Tyrian purple held the title of the most prestigious dye in antiquity. In Roman times if you were caught wearing clothing dyed this purple and weren't royalty it was considered a crime, of course affording this colour if you weren't royalty was virtually impossible. The complex technique for making this dye was discovered around 1500BC by the Phoenicians, an ancient Mediterranean seafaring traders. Tyrian purple is made from a pale yellow mucous secretion from some molluscs, commonly known as sea snails. It is possible to 'milk' these snails, in which case, they wouldn't be harmed – however, this is labour intensive so more destructive methods were used. Often the snails would simply be crushed to get their secretion. From one source, the snails were salted and left for three days to extract the liquid. The liquid was boiled for ten days after which fibers would be soaked in the resulting liquid for five hours. Finally, the resulting fabric would have to be exposed to sunlight where it changed colour from deep yellow, through green and blue to finally purple.

To dye a metre of cloth, 12,000 molluscs would be required (ie killed). Since they were making luxury fabrics, often a fabric would be dyed more than once to get the best shade. Different snails gave different shades, to get the best purple cloth would be first dyed in one species of snails then in another. Fortunately for the snails, synthetic dyes have completely replaced the original tyrian purple.

For more info check here, including some nice pictures.

Twilight - the space between day and night (without vampires)

How many painters have attempted to capture the gradiated hues of a sunset in pigments? It takes true mastery to get translucent fleeting colours from flat pigments; some artists do it exceptionally well, but most don't. Detailed observations of actual sunsets is the key: what colours go where? How do a few clouds change things? Cameras can capture some aspects of a sunset, but often miss the nuances. With my digital camera, I took this picture near the end of my drive to Winnipeg last summer – the sunset was much more stunning in person. However, nothing beats sitting on a patio somewhere with a view (perhaps with an accompanying beverage) and watching day turn to night.

Sunsets are a spectacular end to the day – however the entire process of shifting from day to night is called twilight. According to a book published in 1966 by Georgii Rozenberg (called 'Twilight' without a single mention of vampires – I like to read old science books): The term twilight refers to the entire complex of optical phenomenon that take place in the atmosphere when the sun is near the horizon. It occupies the interval separating daytime conditions of illumination from night.

I live far enough north to get reasonably extended twilights. The downside is that I live far enough north that twilight can start in the late afternoon on the shorter days of the year. Every twilight is unique and the shift from day time brilliance to more subdued hues feels almost magical. During twilight, the illumination at the ground decreases by a factor of a billion. If seen from space, twilight covers a global swath separating day from night. Twilight happens because the earth is rotating – so it will occur on every rotating planet with an atmosphere.

Looking up at the sky has been a pass-time for eons. However, early in the 21st century, before spaceflight was common, a keen interest in studying twilight emerged to provide details about the composition of the atmosphere – useful to know if you are trying to communicate by radio.

Many interesting phenomenon occur each twilight (I'll write more in other posts), however sunsets are the most obvious. Atmospheric optical properties are responsible for the vivid colours of sunset. Specifically, the amount of water vapour and dust play a huge role. In 1863, atmospheric scattering and attenuation of light were shown to produce the sunset colours. Since entire books have been written on sunsets, so my description will be brief.

When the sun drops towards the horizon, the sunlight must pass through more atmosphere. Since shorter wavelengths of light are scattered preferentially (see Rayleigh scattering post), the sun appears in redder tones (red is at the long end of the colour spectrum) and the near-by sky takes on yellow and orange hues. When the sun is about 5 degrees below the horizon (like in my picture above), it is out of sight to an observer on the ground. The sky above the horizon remains brightly coloured in deep reds while mountain tops and clouds are bathed with crimson and purple light.

A cool home experiment for generating a sunset in a glass can be found here.

Bloody colours

To a bloody war and sickly season - the traditional Thursday toast of the British Navy.

Since I've already written about blue (here and here), a friend suggested I write a post on redder colours, specifically ones named after bloody battles. I only found two: magenta and solferino – both are purplish red colours, perhaps even the same colour. Magenta and Solferino are both towns in Northern Italy that were caught up in the second Italian war of Independence at the same time synthetic dyes were being made from coal tar for the first time. Magenta as a colour name is still in common use, while Solferino was the more important battle. A witness to the battle of Solferino, Henry Dunant, found it so horrible he began a campaign that ultimately resulted in the founding of the Red Cross.

In 1859, Emmanuel Verguin's experiments with aniline dyes (ie the ones from coal tar) resulted in a rich crimson red. He called the colour fuchsine after the fuchsia flower and it was an instant hit. This was a prominent colour of the uniforms at both the battle of Magenta and Solferino, both in June 1859, so I don't know if the colour took these names because of the uniforms or the bloodiness of the battlefields (I've found references both ways). A few years later, the colour's name was once more changed, this time to rosaniline, but magenta is the name that stuck. A arsenic acid oxidation process was required to make this dye causing some of its wearers to be poisoned – leaving magenta even more bloody. (For more details of synthetic dyes 'Mauve' by Simon Garfield is a good read)

If you took a good look at the colour spectrum of light, magenta wouldn't be found. Magenta is considered an extra-spectral colour because it cannot be generated by a single wavelength of light. It is formed in our minds when there are equal parts of blue and red light (in truth colours only exist because our brains perceive them).

Making Blue - part 2

Further to my last post, another synthesized blue lurks in my paint box – Prussian Blue. It is a complex dark blue pigment that was first synthesized around 1706 by the paint maker Diesbach (whose first name I couldn't find) in Berlin. Since its discovery, Prussian Blue has been used extensively in making paint, and is the traditional "blue" in blueprints. Strangely, It has been used as an antidote for certain kinds of heavy metal poisoning – perhaps a story for another day.

The synthetic Prussian Blue filled a gap left by the loss of knowledge of how to make Egyptian Blue. It is a stable and relatively light-fast blue that is cheaper than ultramarine made from lapis lazuli. Artists were waiting for a pigment like this, so within two years of it's discovery it was already being traded across Europe. Prussian Blue is a strong colour that tends towards black or dark purple when mixed into oil paints. Interestingly, the particle size of the pigment creates the exact hue.

Prussian Blue is a complex chemical including iron and cyanide. It's not particularly toxic because the cyanide is bound tightly to the iron. I was surprised to learn about the number of applications where this pigment is used. In medicine, Prussian Blue is used to detect iron in biopsies like bone marrow. It is also the basis for laundry bluing, that is, it's used to add a slight hint of blue to someone's washing to combat yellowing of whites.

Once children's crayons contained a Prussian Blue, but now that has been changed to Midnight Blue. It has been a long time since I've looked at crayon colours – I think the last time was when I melted them to colour wax for candle making.

Making Blue – or what to do if you don't have enough lapis lazuli

'Through the atmosphere the universe tones towards us in the colour blue and according to the thickness of the air, takes on every grade of blue until it goes over to black-violet on the mountain tops'

-Goethe 'Theory of Colours'

The above quote makes me think of the Van Gogh painting 'The Starry Night' – one of my favorites. I love the shades of blue (I love the swirls too but, that makes up a different story). So what makes paint blue? Typical pigments used include Azurite, Cerulean Blue, Cobalt Blue, Prussian Blue and Ultramarine which was once made from lapis lazuli.

Although there are other natural blues that can be used in pigments, lapis lazuli intrigues me the most. Years ago, I read a book on natural colours where the author journeyed to Afghanistan (in safer times) to find lapis lazuli. I don't have the book at hand, so I can't quote from it, but ever since then I've thought lapis lazuli had a fantastic story, I even like saying 'lapis lazuli'. Powdered lapis was used as eyeshadow by Cleopatra – what could be more exotic than that?

Lapis lazuli has always been prized for its intense blue color. It has been mined from Afghanistan for over 6,000 years and there are other sources around Lake Baikal in Siberia. Lapis lazuli is classified as a rock composed of more than one mineral. Since it polishes well, it can be made into jewelry, carvings, boxes, mosaics, ornaments, and vases. In ancient Egypt, lapis lazuli was favored for inclusion on amulets and ornaments such as scarabs. To answer my paint question, lapis lazuli was also ground and processed to make the pigment ultramarine.

So what if lapis lazuli wasn't available (or too expensive)? Before modern synthetic colours became available there were several options.

Egyptian Blue is a pigment that was made and used by Egyptians for thousands of years and may even be the first synthetic pigment. In Egyptian it's called 'hsbd-iryt', which translates to 'artificial lapis lazuli'. Although it's only one of many components, copper is what makes Egyptian Blue blue. The exact hue of blue can range from light to dark depending on how it is made. Egyptian Blue coloured stone, wood, plaster, papyrus, and canvas. It was also used in objects like cylinder seals, beads, scarabs, inlays, pots and statuettes. Unfortunately, when the Roman era ended, knowledge on how to make Egyptian Blue was lost. Egyptian blue has been found on objects from all over the Roman Empire and may have been independently discovered in places like ancient China.

At least 2,000 years ago a synthetic blue turned up in China. Chinese Blue and Egyptian Blue have the same basic structure and have very similar properties. The difference is that Egyptian Blue contains calcium where Chinese Blue has barium. Was this Chinese Blue produced from knowledge of Egyptian Blue making it's way along the silk road? There are theories that lean both ways.

Another ancient blue comes from pre-columbian mesoamerica and examples are still blue today. Maya Blue is a organic-inorganic hybrid that was made by heating indigo and a fibrous clay together. This method worked so well it is an active area of research today.

Back to lapis lazuli. Lapis lazuli's use as a pigment in oil paint ended in the early 19th century when a chemically identical synthetic variety, often called French Ultramarine, became available.