Listen to part of a lecture in a studio art class. The class has been discussing the painting medium called watercolor.(male professor) We\'ve been painting with watercolors for a few weeks now, and we\'ve seen that with watercolor, you create variation in brightness by mixing different amounts of water and paint.Now, we\'re going to try a type of watercolor called gouache.Gouache is, well, you know how the regular watercolor we get that transparent effect?Well, gouache is an opaque paint. You usually can\'t see through it to the paper underneath.That\'s because gouache has a higher percentage of pigment than regular watercolor, which is much thinner.Now, one big difference between painting with gouache versus regular watercolor is the way that lighter colors and whites are worked into a painting.So far, if we want something white in our watercolor paintings, some clouds, say, what have we been doing? Katie?(female student) Mainly, I just don\'t paint those areas, like for white clouds in a blue sky. I paint blue for the sky part and just leave blank spaces for the clouds.Or I paint clouds with a really thin, extra, transparent layer of paint. So, the white of the paper still shows through.(male professor) Good. Now, you can use those methods with gouache, too. Same as with regular watercolors.But one big advantage of gouache is that, since you\'re dealing with opaque paint, it\'s possible to apply white or light highlights on top of darker colors, which you haven\'t been able to do so far.There\'s a variety of different ways you can work with light colors and gouache.Take the work of Hank Compton. Hank Compton didn\'t start out as an artist. He was a marine biologist.He worked on research vessels, collecting specimens of marine life.And during these expeditions, Compton taught himself how to paint many of the sea creatures he encountered.And even though he had no formal artistic instruction, his illustrations are so accurate that they\'re often published in guides and books.And most significant, especially considering his lack of training, was his compelling depictions of bioluminescent fish. Are you familiar with bioluminescence?(female student) Oh, yeah, bioluminescence. Kevin and I are in the same biology class. And we learned about that earlier this semester.Certain marine animals like fish give off light in all kinds of different ways.(male student) Yeah, uh, like some fish produced light through small organs along their sides, or even in their mouths or on their jaws.(female student) And there are these other fish where like colonies of bioluminescence bacteria on them.So, the fish have these bioluminescent dots. Bioluminescence is particularly common in deep sea animals where sunlight doesn\'t really penetrate the water.(male professor) Excellent. Thank you both. Now, Compton use multiple techniques for painting the light the bioluminescence fish give off.He was adapted using gouache to add bright highlights to his paintings, like bioluminescent dots.And he used extra thin, transparent paint to transition from darkly shaded areas to brighter ones.He also used a third technique called masking.Masking is when you paint a rubber-based material onto the paper temporarily to preserve lighter colors. The masking material repels wet paint.So, to paint bioluminescent fish, Compton would start by masking off areas that had been painted light colors.The light colors had been allowed to dry, and then they were masked off with the rubber material.Then once the masking material was dry, Compton would apply a dark color on top of the painting.The dark color would become the dark of the deep ocean.When the dark layer dried and he scratched the rubber off, the bright layer below was revealed. The part represented an animals’ bioluminescence.(male student) So, actually, masking is a little bit like what we\'ve been doing already.(male professor) I like that comparison. You\'ve been working on preserving light parts of the background of your paintings. So, in a way, yes.(female student) Um, can I ask a question? Maybe this is off topic, but are contents paintings considered art, or just scientific illustrations?(male professor) Um. Hard to say. They\'re kind of in between.Interestingly, while Compton had first-hand experience with specimens of a fishy painted, he wouldn\'t have seen them in their natural habitat.Some of the fish he studied were from as far as 800 meters beneath the surface. He just had to invent the backgrounds for his paintings.His paintings are this interesting combination of precise, scientific depiction of the fish themselves, and creative imaginations about the settings they appear in.