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Coral polyps with their tentacles extended. Photo by Nbharakey, via Wikimedia Commons

The polyps are usually small, with tentacles surrounding a mouth-like opening* and stomach.  The polyps extend their tentacles(usually at night) to catch food floating by in the water and pull it into their mouths.  They retract their tentacles for protection.  The polyps share the nutrients from their food with algae that live inside their bodies. Algae are like plants–they get their energy from the sun–and the algae inside coral polyps share nutrients with their hosts.  The algae help the coral grow, and the coral help the algae.  The algae are so important to the coral, that corals have a very difficult time building their skeletons without their algae partners.

*It’s not exactly a mouth.  The polyps’ food enters through this opening, but it exits through it as well.

** Some corals whose polyps don’t divide and remain singular throughout their lives, but the majority of corals do form colonies.

1. They can squirt ink to distract and confuse predators allowing them to escape danger.
2. They can change the color of their skin, to camouflage themselves.
3. They can change the texture of their skin, also for camouflage.
4. They are very intelligent, capable of solving complex problems.

But don’t take my word for it, check out this video from National Geographic:

Photograph by Richard Ling via Wikimedia Commons

To understand how they do it, it’s first important to understand what a coral is.  Many people mistakenly believe them to be a plants (like plants, they grow in one place and can’t move from that spot on their own), but corals are actually animals.  There are two kinds of coral, hard(or stony) and soft corals.  Hard corals build reefs, so those are the ones that I am going to write about now.

Hard corals have limestone (calcium carbonate) skeletons that are covered by tiny polyps.  I’ll describe polyps in more detail in my next post, but for now you can picture them as miniature sea anemones.  The polyps live on the surface of the skeleton, and as they grow, they add more limestone to the skeleton.  On hard corals, only the polyps on the surface are alive and the structure beneath the polyps is stone.

When a coral dies, it’s polyps decay, leaving its skeleton, which becomes a place where a new corals can attach and grow.  Over time, new corals pile atop old corals and that’s how the reef grows.  Over thousands of years, corals build their skeletons, and then die, their skeletons becoming part of the reef structure, and over time an underwater mountain of limestone of formed: a coral reef.

This photo shows the cross section of a coral. The white center is limestone, and the outer edge is where the polyps grow. It has been stained purple by scientists studying its growth rate. Photo by Hannes Grobe, via wikimedia commons.

I’ve just finished work on Coral Reefs, which is slated for publication in Fall 2011.  The book is similar to Redwoods (not a sequel, but more of a companion) and I’m really excited about it.  Did you know that coral reefs are the largest structures on earth created by living things?  Far bigger than the pyramids, the largest sky scrapers, or the great wall, corals literally create mountains of limestone under water.

While I was working on Coral Reefs, I learned many, many exciting facts — far too many to fit into the book.  So I’m going to write about them on my blog over the next few months.  Hopefully, it will get everyone excited to learn about coral reefs!

At the end of step three, I left off talking about building up layers of paint.  As I add layers of color, I also add more and more detail.  The painting begins with with blocking in large areas of light color (see step three) and slowly adding in darker and darker colors, in more and more detail until I’m satisfied.

When the painting is nearing completion, I remove my frisket masks. In this painting they were on the the girl, crab and ceiling.  I paint the previously masked areas in carefully, paying careful attention to the edges.  With friskets, it’s easy for the masked off portion to have a “cut out” feel, so I usually soften the edges slightly by rubbing over them with a damp brush, so that the girl looks like she belongs in the painting.  When all the areas are painted in, it’s time to add the finishing touches .  I darken the darkest darks (the bars in the window, and the deep shadows) and lighten any areas that I feel need it by wetting an area and using a towel or q-tip to pull out the paint (the beam of sunlight coming through the window).  I use white gouache to cover some areas that need to be very light, like the highlights on the puddles of water.  When I’m satisfied, I get to do my favorite part: remove the tape that I used to mask off the edges of the piece, and voila, a nice clean edge on the finished painting.

In this picture you can see the masked areas, and my first layers of paint.  I start with light washes and block in major areas of color.  From there, it’s a process of slowly building up color until I reach the right value and hue that I want.  I constantly refer back to my original sketch to check how dark or light I intended to make an area.  I don’t finish one area, then move to the next, but instead do a little here a little there so that the all areas of the scene progress evenly.  The exception, of course is the masked areas, which I generally leave until near the end to paint.  Stay tuned, I’ll discuss more of that in the next post.

After I’m finished with my preliminary drawing my next step is to transfer that drawing to a nice piece of watercolor paper.  I use a 300 pound hot-press paper, made by Fabriano.  It’s a very thick paper with a flat surface.  The flat surface is much easier to draw on than the rougher cold-press papers and the thickness allows it to absorb a lot of water and paint without buckling.

I use a lightbox to help me trace the drawing onto the watercolor paper with a hard (H or 2H) pencil.  I like the harder pencil in this case because leaves a light line which I can easily erase.  When I’m tracing, I try to do it quickly and accurately, but I try not to get to hung up in details, because with the light shining from behind the image I can’t really see the paper very well.  After I’m done tracing, and I take the paper off the lightbox, then I very carefully add details, and adjust the drawing.  This is the final step before I start applying paint, and I want to be sure everything is just the way I want it.

When the drawing is done, I soak it in water for 5 minutes and then staple it(while  it’s still wet) to my painting board.  The board is 1/2″ plywood.  After the paper dries, it will be ready for painting.  Because it’s been presoaked, the paper the surface will remain flat as I paint on it.

This preliminary drawing is the last thing I do before I start painting and I try my best to work out as many details as possible in this drawing.  Since I work in watercolors, it’s very hard to go back and change things after I start to paint.  When the drawing is finished, I use a lightbox to transfer it to a nice piece of watercolor paper…but that’s step two, and I’ll write more about that tomorrow.