Introduction to Art/Paints (Water-Based)
The broader term for water-based painting media is "watermedia". The term "watercolor" most often to refers to traditional transparent watercolor or gouache (an opaque form of the same paint), but also includes the use of thinned acrylic paint.
Traditional watercolor paint is made of finely-ground pigment mixed with gum arabic for body, and glycerin or honey for viscosity and to bond the colorant to the painting surface. Unpigmented filler is added to gouache to lend opacity to the paint. Oil of clove is used to prevent mold.
Watercolor paints vary in their transparency, some being less transparent (more covering) than others. The more transparent paints allow the paper (or an undercolor) to show through while others allow less of the undercolor to be seen.
As there is no transparent white watercolor, the white parts of a watercolor painting are most often areas of the paper "reserved" (left unpainted) and allowed to be seen in the finished work. White paint might be used to indicate snow on a fence or the foam in the sea, as examples, by using Chinese White or White Gouache. These are not transparent. Traditionally, such non-transparent paint is used sparingly so as not to lose the light and airy look of the work.
Some watercolor pigments are "fugitive", meaning they fade over time when exposed to light. An example is Alizarin Crimson. Some paint makers offer a different formulation of pigment as a less-fugitive alternative. These often have the word "hue" as part of the name. "Alizarin Crimson Hue" can be expected to be less fugitive than Alizarin Crimson.
"Staining" is another characteristic of certain watercolor pigments. A staining color is difficult to remove and persists on the paper. Less staining colors can be lightened or removed almost entirely when wet or when re-wetted by "lifting" with a wet brush, paper towel, tissue, sponge, or similar.
Commercial watercolor paints come in two grades: "Artist" (or "Professional") and "Student". Artist quality paints are usually formulated using a single pigment, which results in richer color and vibrant mixes. Student grade paints have less pigment, and often are formulated using two or more less expensive pigments. Artist and Professional paints are more expensive but many consider the quality worth the higher cost.
Paint pigments and formulation vary among manufacturers. Paints with the same color name from different makers can vary in hue, staining, and other characteristics.
Brushes for watercolor are made to hold water and softer as compared to the stiffer brushes used for acrylic and oil paint.
Watercolor brushes come in various shapes including flat, round, mop, and fan. There are numerous specialty brushes; for example, a long thin brush originally designed to paint the lines of rope (rigging) on a seascape is called a "rigger".
Artists typically have a few favorites and do most work with just one or two brushes. A single brush can produce many lines and shapes. A "round" for example, can create thin and thick lines, wide or narrow strips, curves, and other painted effects. A flat brush when used on end can produce thin lines or dashes in addition to the wide swath typical with these brushes.
Brush hairs come from a variety of sources including the very expensive hair of the Kolinsky Sable, the ear hair of the ox or other cattle, and others. "Camel" is used to describe hairs from several sources, none of which is from a camel.
Brush hairs can be natural, synthetic, or a combination. Brush prices vary considerably depending on the type of hair and the quality of the manufacture. A good brush will hold a fair amount of water and will keep and return to its original shape even after much use.
Brushes are numbered to indicate the size of the brush, the larger numbers for the larger brushes. A typical manufacturer's offering of brushes might go from a very small "0" to the larger size "20" or more. Flat, wide brushes are usually described by the width of the brush such as "1/2 inch" or "1 inch". There are no common standards for brush sizes. A "10" Round from two manufacturers might be slightly different in size.
Watercolor paper is designed to properly support the paint and be sturdy enough to withstand the painting action.
Heavier paper is much better than lighter paper if you are planning to make a brightly colored painting. Thin paper may allow pigments to soak through causing dampness and dull coloring.
The surface of watercolor paper can vary in its smoothness from very smooth to very rough. A watercolor painting on rough paper will result in quite a different look than a similar painting on smoother paper. The artist selects paper with a finish to give the desired effect.
Rough-surfaced paper is called "Rough", a smoother surface but still slightly rough is called "Cold Press" (aka "Not"), the smoothest surface is "Hot Press."
Watercolor paper is typically made of 100% cotton rag. Papers of lesser quality might be mixtures of rag (cotton) and other materials. Some artists use only better grade papers to get the effects they desire. The quality of paper can make a significant difference in the result.
The thickness of commercial watercolor paper varies from 90 pounds to 300 pounds (the weight of a ream of about 500 sheets of the paper.) A middle weight, common thickness, is 140 pound paper. While almost any paper of any thickness will buckle when wet, paper less than 140 pound thickness will buckle severely from the water and should be "stretched" before using. Even 140 pound paper will show some stress when wet watercolor is applied over large areas. 300 pound weight paper does not buckle severely and does not have to be stretched.
An alternate to this is to wet the water on a non-absorbing surface like plexiglass. Once the paper is soaked and lying flat on the surface, roll over the paper with a tightly rolled-up towel, squeezing and pressing the water out as you roll. The paper remains wet and stuck to the plexiglass with no bubbles. You can draw and paint right on the damp paper, and it will not buckle for usually up to an hour.
The paint is thinned before application to allow for lighter areas within the painting. This transparency provides watercolor its characteristics of brightness, sparkle, freshness, and clarity of color since light has passed through the film of paint and is reflected back to the viewer through the film.
According to a tradition, dating from at least the early 20th century, the white of the paper is the only white used in transparent watercolor. Opaque paint is seldom used for whites or to overpaint.
Watercolor techniques have the reputation of being quite demanding; it is more accurate to say that watercolor techniques are unique to watercolor. Maintaining a high quality of value differences and color clarity are typically the most difficult properties to achieve and maintain.
Watercolor proponents prize it as a studio medium for its lack of odor and ease of cleanup, and also as a plein air medium for its portability and quick drying.
Washes and glazes 
Basic watercolor technique involves washes and glazes. A wash refers to the application of a uniform color over an area of the painting. Typically, this might be a light blue wash for the sky, a uniform color on a field or other area. Washes can be "graded" or "graduated" if they gradually become lighter or darker in parts such the fading of color to show the lighter sky near the horizon. A "variegated" wash blends more than one color such as a wash with areas of blue and perhaps some red or orange for a sky at sunrise or sunset.
Wet in wet 
Two methods of applying paint to the surface for special effect are "wet-in-wet" (or "wet-on-wet") and "dry brush". Wet-in-wet is used to avoid a hard edge at the margin of the paint. Wet-in-wet paint flows on a wet surface. The paint is wet (diluted) and the surface of the medium is wet.
The surface of the paper or other medium is first "painted" with water, thinned paint is then dripped or lightly applied to the wet surface. The color flows along the wet area. More paint can be added to increase the area covered.
After the first wet application has dried, additional wet layers can be applied. The flow is controlled to some extent by the wetness of the surface; the amount, consistency, and placement of the paint; and by tilting the surface to encourage the paint to flow in the desired direction. The somewhat unpredictable results of the wet-in-wet technique can lead to some surprising but welcome effects.
Dry brush 
Dry brush is used to obtain a rough, textured appearance for the edges of beach grass, a rocky exposed hill surface, tree bark, sunlight skipping on the surface of water, are some examples. A brush is loaded with relatively thick paint then lightly pulled over the dry surface of the medium. Some artists hold the brush with just two or three fingers at the very end of the handle so just the weight of the brush glides along the surface.
The paint adheres and covers only the higher points and ridges of the surface but stays out of the deeper areas. The method is especially effective on Rough and Cold Press (medium rough) paper. It is not very useful on smooth surfaces.
Painting light to dark 
Watercolors are typically made darker on the paper by repeated application of the same color. These coats of paint are called "glazes. A glaze of a different color can also be used to create a combined color. It is also possible to achieve various lightness and darkness of a color (value) by diluting the paint in the mixing area before application.
Limited palette 
An artist might use a limited set of colors in his or her palette creating other colors by mixing two or three colors from the limited set. Mixing more than three colors can result in a muddy, unacceptable color.
The "palette" refers to the array of colors used in a painting and also refers to the tray, dish, or other implement used to hold and mix the paints.
Other considerations 
When using watercolors, it is a good idea to think of using the medium in the consistency as it comes from the tube. Using dried out "cake" watercolors will prevent the user from being able to take full advantage of the medium. When the colors are tube fresh, one can go from totally thinned with water to create the most elusive effects and in an instant to very dense full bodied mixtures for deep dark passages. The best way to keep colors from drying out would be to use a covered palette such as the "John Pike Watercolor Palette" which has plenty of colors "wells" and sufficient mixing space. A great tip for squeezing paint from the tube is as follows: Squeeze an amount about the size of a lima bean or slightly larger. Do not leave the paint in a "mound", but rather spread it through the area of the designated color well. The logic behind this method is that since watercolors are resoluble with water, one can simply spray water on the surface of dried color to refresh it as it came from the tube. If the colors are left in a mound, the water will roll off; but if the colors are spread evenly, the water has no place to go but into the color bringing it back to life. Do this twenty minutes or so before painting if your colors are dried out or if time does not allow just squeeze a little fresh color over the exsisting dried out color and spread. The new color will interact with the old making all the color usable. Do not put a damp sponge in the palette for storage as this can lead to mildew and mold. The primary thing to remember is to take full advantage of the wide range of consistentcies watercolor has to offer.
Though there seem to be endless colors available in tubes, one need only a very limited palette. Consider a primary color palette to include: Lemon Yellow; Cadmium Yellow; Cadmium Red; Alizarin Crimson; Cerulean Blue; French Ultramarine Blue; Phtalo Blue; and perhaps Burnt Sienna and Raw Sienna. These nine colors will give you the ability to mix virtually any color possible. A brief summary of color mixing is: A red and a yellow make orange; yellow and blue make green; blue and red make violet. A red, yellow, and blue make gray and if mixed dense enough, black. It's simple color theory of primary color mixing. Primary colors being: red - yellow - blue. Secondary colors (mixing any two colors): orange - green - violet. and Tertiary colors (three color mixes): any gray imaginable and black. When mixing three colors, avoid muddy mixtures by "undermixing" on the palette. Pull the colors into the mixing space and simply "swish" the colors together. Your darkest darks can be very exciting so long as you are sure to not "overmix." Another reason for muddiness comes from excessive brushing. Apply the washes with conviction being sure to limit your brushstrokes.
Making other colors 
If you don't have the color you want, you don't have to buy that color, you can simply mix it! Here are a few mixtures:
Yellow+blue=green Yellow+red=orange Red+blue=purple Red+green=brown
Why mixing paints doesn't produce the color white . The accompanying figure represents the artist's color wheel. Colors opposite one another are called complementary colors. Those next to each other are adjacent colors.
A dab of paint is an opaque body. Its color is due to reflection. No paints are pure colors; they reflect light over a narrow wavelength band. Yellow paint reflects yellow light, but also reflects small amounts of orange and green light, while absorbing red and blue light. Red paint absorbs blue and yellow light, but reflects a bit of orange. When yellow and red paints are mixed, the yellow paint absorbs the red light and the red paint absorbs the yellow light, but they both reflect orange. So the mixture appears orange. When two paints mix, the color produced is the color that both paints reflect. Add some blue paint, which absorbs orange, to the red and yellow mixture and the paint loses its hue. By mixing all your paints together, each pigment absorbs a particular wavelength and therefore no colors are reflected and the paint mixture appears a dark, dull gray.
Blue, red, and yellow are primary colors. Violet, orange and green are the secondary colors (colors made from two primaries). The array of browns, mauves and grays are the tertiary colors (colors made from a primary and a secondary, in other words, colors made from all three primaries). It is interesting to note that the tertiary colors are the most common colors in the landscape, followed by secondaries, with pure primaries being ever so rare in the natural landscape--rainbows, sunsets and the aurora borealis, to name a few.