Watercolor (US) or Watercolour (UK) (and "aquarelle" in French) is a painting method. A watercolor is the medium or the resulting artwork, in which the paints are made of pigments suspended in a water soluble vehicle. The traditional and most common support for watercolor paintings is paper; other supports include papyrus, bark papers, plastics, vellum or leather, fabric, wood, and canvas. In East Asia, watercolor painting with inks is referred to as brush painting or scroll painting. In Chinese and Japanese painting it has been the dominant medium, often in monochrome black or browns. India, Ethiopia and other countries also have long traditions. Fingerpainting with watercolor paints originated in China.
Despite this early start, watercolors were generally used by Baroque easel painters only for sketches, copies or cartoons (small scale design drawings). Among notable early practitioners of watercolor painting were Van Dyck (during his stay in England), Claude Lorrain, Giovanni Benedetto Castiglione, and many Dutch and Flemish artists. However, botanical and wildlife illustrations are perhaps the oldest and most important tradition in watercolor painting. Botanical illustrations became popular in the Renaissance, both as hand tinted woodblock illustrations in books or broadsheets and as tinted ink drawings on vellum or paper. Botanical artists have always been among the most exacting and accomplished watercolor painters, and even today watercolors -- with their unique ability to summarize, clarify and idealize in full color -- are used to illustrate scientific and museum publications. Wildlife illustration reached its peak in the 19th century with artists such as John James Audubon, and today many naturalist field guides are still illustrated with watercolor paintings.
From the late 18th century through the 19th century, the market for printed books and domestic art contributed substantially to the growth of the medium. Watercolors were the used as the basic document from which collectible landscape or tourist engravings were developed, and handpainted watercolor originals or copies of famous paintings contributed to many upper class art portfolios. Satirical broadsides by Thomas Rowlandson, many published by Rudolph Ackermann, were also extremely popular.
The three English artists credited with establishing watercolor as an independent, mature painting medium are Paul Sandby (1730-1809), often called "the father of the English watercolor", Thomas Girtin (1775-1802), who pioneered its use for large format, romantic or picturesque landscape painting, and Joseph Mallord William Turner (1775-1851), who brought watercolor painting to the highest pitch of power and refinement and created with it hundreds of superb historical, topographical, architectural and mythological paintings. His method of developing the watercolor painting in stages, starting with large, vague color areas established on wet paper, then refining the image through a sequence of washes and glazes, permitted him to produce large numbers of paintings with workshop efficiency and made him a multimillionaire in part through sales from his personal art gallery, the first of its kind. Among the important and highly talented contemporaries of Turner and Girtin were John Varley, John Sell Cotman, Anthony Copley Fielding, Samuel Palmer, William Havell and Samuel Prout. The Swiss painter Louis Ducros was also widely known for his large format, romantic paintings in watercolor.
The confluence of amateur activity, publishing markets, middle class art collecting and 19th century painting technique led to the formation of English watercolor painting societies: the Society of Painters in Water Colours (1804, now known as the Royal Watercolour Society), and the New Water Colour Society (1832). (A Scottish Society of Painters in Water Colour was founded in 1878.) These societies provided annual exhibitions and buyer referrals for many artists and also engaged in petty status rivalries and esthetic debates, particularly between advocates of traditional ("transparent") watercolor and the early adopters of the denser color possible with bodycolor or gouache ("opaque" watercolor). The late Georgian and Victorian periods produced the zenith of the British watercolor, among the most impressive 19th century works on paper, by Turner, Varley, Cotman, David Cox, Peter de Wint, William Henry Hunt, John Frederick Lewis, Myles Birket Foster, Frederick Walker, Thomas Collier and many others. In particular, the graceful, lapidary and atmospheric genre paintings by Richard Parkes Bonington created an international fad for watercolor painting, especially in England and France, in the 1820s.
Watercolor painting also became popular in the United States during middle 19th century; the American Society of Painters in Watercolor (now the American Watercolor Society) was founded in 1866. Major 19th century American exponents of the medium included William Trost Richards, Fidelia Bridges, Thomas Moran, Thomas Eakins, Henry Roderick Newman, John LaFarge and, preeminently, Winslow Homer. The popularity of watercolors stimulated many innovations, including heavier and more heavily sized wove papers and brushes (called "pencils") manufactured expressly for watercolor painting. Watercolor tutorials were first published in this period by Varley, Cox and others, innovating the step-by-step painting instructions that still characterizes the genre today; "The Elements of Drawing", a watercolor tutorial by the English art critic John Ruskin, has been out of print only once since it was first published in 1857. Commercial paintmaking brands appeared and paints were packaged in metal tubes or as dry cakes that could be "rubbed out" (dissolved) in studio porcelain or used in portable metal paint boxes in the field. Contemporary breakthroughs in chemistry made many new pigments available, including prussian blue, ultramarine blue, cobalt blue, viridian, cobalt violet, cadmium yellow, aureolin (potassium cobaltinitrite), zinc white and a wide range of carmine and madder lakes. These in turn stimulated a greater use of color throughout all painting media, but in English watercolors particularly by the Pre-Raphaelite painters.
Unfortunately the careless and excessive adoption of brightly colored, petroleum derived aniline dyes (and pigments compounded from them), which all fade rapidly on exposure to light, and the efforts to properly conserve the 20,000 Turner paintings inherited by the British Museum in 1857, led to an examination and negative re-evaluation of the permanence of pigments in watercolor. This caused a sharp decline in their status and market value. Nevertheless, isolated exponents continued to prefer and develop the medium into the 20th century. In Europe, gorgeous landscape and maritime watercolors were produced by Paul Signac, and Paul Cezanne developed a watercolor painting style consisting entirely of overlapping small glazes of pure color.
In America, the most famous watercolor painters from this period include Maurice Prendergast, Frederick Childe Hassam, Charles Webster Hawthorne and John Singer Sargent, considered by many the finest watercolor painter of all time.
Among the many 20th century artists who produced important works in watercolor, mention must be made of Wassily Kandinsky, Emil Nolde, Paul Klee, Egon Schiele and Raoul Dufy; in America the major exponents included Charles Burchfield, Edward Hopper, Charles Demuth, Elliot O'Hara and above all John Marin, 80% of whose total output is in watercolor. In this period American watercolor (and oil) painting was often imitative of European Impressionism and Post-Impressionism, but significant individualism flourished within "regional" styles of watercolor painting in the 1920s to 1940's, in particular the "Cleveland School" or "Ohio School" of painters centered around the Cleveland Museum of Art, and the "California Scene" painters, many of them associated with Hollywood animation studios or the Chouinard Art Institute (now CalArts Academy). The California painters exploited their state's varied geography, Mediterranean climate and "automobility" to reinvigorate the outdoor or "plein air" tradition; among the most influential were Phil Dike, Millard Sheets, Rex Brandt, Dong Kingman and Milford Zornes. The California Water Color Society, founded in 1921 and later renamed the National Watercolor Society, sponsored important exhibitions of their work. Although the rise of abstract expressionism, and the trivializing influence of amateur painters and advertising or workshop influenced painting styles, led to a general decline in the popularity of watercolor painting after c.1950, watercolors continue to be utilized by important artists such as Joseph Raffael, Andrew Wyeth, Philip Pearlstein, Eric Fischl, Gerard Richter and Francesco Clemente. Modern watercolor paints are now as durable and colorful as oil or acrylic paints, and the recent renewed interest in drawing and multimedia art has also stimulated demand for fine works in watercolor. As art markets continue to expand, painting societies continue to add members and aging Baby Boomers increasingly retire to more contemplative hobbies, watercolors seem poised to enter yet another "golden age".
The term "watermedia" refers to any painting medium that uses water as a solvent and that can be applied with a brush, pen or sprayer; this includes most inks, watercolors, temperas, gouaches and modern acrylic paints. The term watercolor refers to paints that use water soluble, complex carbohydrates as a binder. Originally (16th to 18th centuries) watercolor binders were sugars and/or hide glues, but since the 19th century the preferred binder is natural gum arabic, with glycerin and/or honey as additives to improve plasticity and dissolvability of the binder, and with other chemicals added to improve product shelf life. Bodycolor is a watercolor made as opaque as possible by a heavy pigment concentration, and gouache is a watercolor made opaque by the addition of a colorless opacifier (such as chalk or zinc oxide). Modern acrylic paints are based on a completely different chemistry that uses water soluble acrylic resin as a binder.
Watercolor painters before c.1800 had to make paints themselves using pigments purchased from an apothecary or specialized "colourman"; the earliest commercial paints were small, resinous blocks that had to be wetted and laboriously "rubbed out" in water. Modern commercial watercolor paints are available in two forms: tubes or pans. The majority of paints sold are in collapsible metal tubes in standard sizes (typically 7.5, 15 or 37 ml.), and are formulated to a consistency similar to toothpaste. Pan paints (actually, small dried cakes or bars of paint in an open plastic container) are usually sold in two sizes, full pans (approximately 3 cc of paint) and half pans (favored for compact paint boxes). Pans are historically older but commonly perceived as less convenient; they are most often used in portable metal paint boxes, also introduced in the mid 19th century, and are preferred by landscape or naturalist painters. Among the most widely used brands of commercial watercolors today are Daniel Smith, Daler Rowney, DaVinci, Holbein, Maimeri, M. Graham, Schmincke, Talens (Rembrandt), and Winsor & Newton.
Thanks to modern industrial organic chemistry, the variety, saturation (brilliance) and permanence of artists' colors available today is greater than ever before. However, the art materials industry is far too small to exert any market leverage on global dye or pigment manufacture. With rare exceptions, all modern watercolor paints utilize pigments that were manufactured for use in printing inks, automotive and architectural paints, wood stains, concrete, ceramics and plastics colorants, consumer packaging, foods, medicines, textiles and cosmetics. Paint manufacturers buy very small supplies of these pigments, mill (mechanically mix) them with the vehicle, solvent and additives, and package them.
Many artists are confused or misled by labeling practices common in the art materials industry. The marketing name for a paint, such as "cobalt blue" or "emerald green", is often only a poetic color evocation or proprietary moniker; there is no legal requirement that it describe the pigment that gives the paint its color. To remedy this confusion, in 1990 the art materials industry voluntarily began listing pigment ingredients on the paint packaging, using the common pigment name (such as "cobalt blue" or "cadmium red"), and/or a standard pigment identification code, the generic color index name (PB28 for cobalt blue, PR108 for cadmium red) assigned by the Society of Dyers and Colourists (UK) and the American Association of Textile Chemists and Colorists (USA). This allows artists to choose paints according to their pigment ingredients, rather than the poetic labels assigned to them by marketers. Paint pigments and formulations vary across manufacturers, and watercolor paints with the same color name (e.g., "sap green") from different manufacturers can be formulated with completely different ingredients.
Watercolor paints are customarily evaluated on a few key attributes. In the partisan debates of the 19th century English art world, gouache was emphatically contrasted to traditional watercolors and denigrated for its lack of "transparency" or hiding power; "transparent" watercolors were exalted. Paints with low hiding power are valued because they allow an underdrawing or engraving to show in the image, and because colors can be mixed visually by layering paints on the paper (which itself may be either white or tinted). The resulting color will changed depending on the layering order of the pigments. In fact, there are very few genuinely transparent watercolors, neither are there completely opaque watercolors (with the exception of gouache); and any watercolor paint can be made more transparent simply by diluting it with water. "Transparent" colors do not have titanium dioxide (white) or most of the earth pigments (sienna, umber, etc.) which are very opaque. The 19th century claim that "transparent" watercolors gain "luminosity" because they function like a pane of stained glass laid on paper -- the color intensified because the light passes through the pigment, reflects from the paper, and passes a second time through the pigment on its way to the viewer -- is false: watercolor paints do not form a cohesive paint layer, as do acrylic or oil paints, but simply scatter pigment particles randomly across the paper surface. Watercolors appear more vivid than acrylics or oils because the pigments are laid down in a more pure form with fewer fillers (such as kaolin) obscuring the pigment colors. Multiple layers of watercolor do achieve a very luminous effect because of less fillers obscuring the pigment particles.
Staining is another characteristic assigned to watercolor paints: a staining paint is difficult to remove or lift from the painting support after it has been applied or dried. Less staining colors can be lightened or removed almost entirely when wet, or when rewetted and then "lifted" by stroking gently with a clean, wet brush and then blotted up with a paper towel. In fact, the staining characteristics of a paint depend in large part on the composition of the support (paper) itself, and on the particle size of the pigment. Staining is increased if the paint manufacturer uses a dispersant to reduce the paint milling (mixture) time, because the dispersant acts to drive pigment particles into crevices in the paper pulp, dulling the finished color.
Granulation refers to the appearance of separate, visible pigment particles in the finished color, produced when the paint is substantially diluted with water and applied with a juicy brush stroke; pigments notable for their watercolor granulation include viridian (PG18), cerulean blue (PG35), cobalt violet (PV14) and some iron oxide pigments (PBr7). "Flocculation" refers to a peculiar clumping typical of ultramarine pigments (PB29 or PV15). Both effects display the subtle effects of water as the paint dries, are unique to watercolors, and are deemed attractive by accomplished watercolor painters. Regrettably the trend in commercial paints seems to be to suppress pigment textures in favor of homogeneous, flat color.
Commercial watercolor paints come in two grades: "Artist" (or "Professional") and "Student". Artist quality paints are usually formulated less fillers (kaolin or chalk) 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.
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. To preserve these white areas, many painters use a variety of resists, including masking tape, clear wax or a liquid latex, that are applied to the paper to protect it from paint, then pulled away to reveal the white paper. White paint (titanium dioxide PW6 or zinc oxide PW4) is best used to insert highlights or white accents into a painting. If mixed with other pigments, white paints may cause them to fade or change hue under light exposure. White paint (gouache) mixed with a "transparent" watercolor paint will cause the transparency to disappear and the paint to look much duller. White paint will always appear dull and chalky next to the white of the paper, however this can be used for some effects.
Brushes hold paint (the "bead") through the capillary action of the small spaces between the tuft hairs or fibers; paint is released through the contact between the wet paint and the dry paper and the mechanical flexing of the tuft, which opens the spaces between the tuft hairs, relaxing the capillary restraint on the liquid. Because thinned watercolor paint is far less viscous than oil or acrylic paints, the brushes preferred by watercolor painters have a softer and denser tuft. This is customarily achieved by using natural hair harvested from farm raised or trapped animals, in particular sable, squirrel or mongoose. Less expensive brushes, or brushes designed for coarser work, may use horsehair or bristles from pig or ox snouts and ears. However, as with paints, modern chemistry has developed many synthetic and shaped fibers that rival bristle and even hair for softness and flexibility. Until fairly recently, nylon brushes could not hold a reservoir of water at all so they were extremely inferior to natural bristles. In the past decade or so, each nylon bristle now has many small "hairs" off of it, each of which can hold a drop of water. Many artists now prefer synthetic brushes because of their superior points and durability.
There is no market regulation on the labeling applied to artists' brushes, but most watercolorists prize brushes from kolinsky (Russian or Chinese) sable. The best of these hairs have a characteristic reddish brown color, darker near the base, and a tapering shaft that is pointed at the tip but widest about halfway toward the root. Squirrel hair is quite thin, straight and typically dark, and makes tufts with a very high liquid capacity; mongoose has a characteristic salt and pepper coloring. Bristle brushes are stiffer and lighter colored. "Camel" is sometimes used to describe hairs from several sources (none of them a camel).
Natural and synthetic brushes are sold with the tuft shaped for different tasks. Among the most popular are:
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, and its brushmarks display the characteristic angle of the tuft corners.
The size of a round brush is designated by a number, which may range from 0000 (for a very tiny round) to 0, then from 1 to 24 or higher. These numbers refer to the size of the brass brushmakers' mould used to shape and align the hairs of the tuft before it is tied off and trimmed, and as with shoe lasts, these sizes vary from one manufacturer to the next. In general a #12 round brush has a tuft about 2 to 2.5 cm long; tufts are generally fatter (wider) in brushes made in England than in brushes made on the Continent: a German or French #14 round is approximately the same size as an English #12. Flats may be designated either by a similar but separate numbering system, but more often are described by the width of the ferrule, measured in centimeters or inches.
In general, natural hair brushes have superior snap and pointing, a higher capacity (hold a larger bead, produce a longer continuous stroke, and wick up more paint when moist) and a more delicate release. Synthetic brushes tend to dump too much of the paint bead at the beginning of the brush stroke and leave a larger puddle of paint when the brush is lifted from the paper, and they cannot compete with the pointing of natural sable brushes and are much less durable. On the other hand they are typically much cheaper than natural hair, and the best synthetic brushes are now very serviceable; they are also excellent for texturing, shaping, or lifting color, and for the mechanical task of breaking up or rubbing paint to dissolve it in water.
A high quality sable brush has five key attributes: pointing (in a round, the tip of the tuft comes to a fine, precise point that does not splay or split; in a flat, the tuft forms a razor thin, perfectly straight edge); snap (or "spring"; the tuft flexes in direct response to the pressure applied to the paper, and promptly returns to its original shape); capacity (the tuft, for its size, holds a large bead of paint and does not release it as the brush is moved in the air); release (the amount of paint released is proportional to the pressure applied to the paper, and the paint flow can be precisely controlled by the pressure and speed of the stroke as the paint bead is depleted); and durability (a large, high quality brush may withstand decades of daily use).
Most natural hair brushes are sold with the tuft cosmetically shaped with starch or gum, so brushes are difficult to evaluate before purchasing, and durability is only evident after long use. The most common failings of natural hair brushes are that the tuft sheds hairs (although a little shedding is acceptable in a new brush), the ferrule becomes loosened, or the wood handle shrinks, warps, cracks or flakes off its lacquer coating.
Every watercolor painter works in specific genres and has a personal painting style and "tool discipline", and these largely determine his or her preference for brushes. Artists typically have a few favorites and do most work with just one or two brushes. Brushes are typically the most expensive component of the watercolorist's tools, and a minimal general purpose brush selection would include:
Reputable watercolor brush manufacturers include DaVinci, Escoda, Isabey, Raphael, Kolonok, Robert Simmons and Winsor & Newton. As with papers and paints, it is common for retailers to commission brushes under their own label from an established manufacturer. Among the best of these are Cheap Joe's, Daniel Smith, Dick Blick and Utrecht.
All art papers can be described by eight attributes: furnish, color, weight, finish, sizing, dimensions, permanence and packaging. Watercolor painters typically paint on paper specifically formulated for watermedia applications. Fine watermedia papers are manufactured under the brand names Arches, Fabriano, Hahnemuehle, Lanaquarelle, Saunders Waterford, Strathmore, Winsor & Newton and Zerkall; and there has been a recent remarkable resurgence in handmade papers, notably those by Twinrocker, Velke Losiny, Ruscombe Mill and St. Armand.
The traditional furnish or material content of watercolor papers is cellulose, a structural carbohydrate found in many plants. The most common sources of paper cellulose are cotton, linen, or alpha cellulose extracted from wood pulp. To make paper, the cellulose is wetted, mechanically macerated or pounded, chemically treated, rinsed and filtered to the consistency of thin oatmeal, then poured out into paper making moulds. In handmade papers, the pulp is hand poured ("cast") into individual paper moulds (a mesh screen stretched within a wood frame) and shaken by hand into an even layer. In industrial paper production, the pulp is formed by large papermaking machines that spread the paper over large cylinders -- either heated metal cylinders that rotate at high speed (machinemade papers) or wire mesh cylinders that rotate at low speed (mouldmade papers). Both types of machine produce the paper in a continuous roll or web, which is then cut into individual sheets.
The basis weight of the paper is a measure of its density and thickness. It is described as the gram weight of one square meter of a single sheet of the paper, or grams per square meter (gsm). Most watercolor papers sold today are in the range between 280gsm to 640gsm. (The previous Imperial system, expressed as the weight in pounds of one ream or 500 sheets of the paper, regardless of its size, is now obsolete.) Watercolor papers are typically almost a pure white, sometimes slightly yellow, though many tinted or colored papers are available. An important diagnostic is the rattle of the paper, or the sound it makes when held aloft by one corner and shaken vigorously. Papers that are dense and made from heavily macerated pulp have a bright, metallic rattle, while papers that are spongy or made with lightly macerated pulp have a muffled, rubbery rattle.
All papers obtain a texture from the mould used to make them: a wove finish results from a uniform metal screen (likea window screen); a laid finish results from a screen made of narrowly spaced horizontal wires separated by widely spaced vertical wires. The finish is also affected by the methods used to wick and dry the paper after it is "couched" (removed) from the paper mold or is pulled off the papermaking cylinder.
Watercolor papers come in three basic finishes: hot pressed (HP), cold press (CP, or in the UK "Not", for "not hot pressed"), and rough (R). These vary greatly from manufacturer to manufacturer.
These designations are only relative; the CP paper from one manufacturer may be rougher than the R paper from another manufacturer. Fabriano even offers a "soft press" (SP) sheet intermediate between CP and HP.
Watercolor papers are traditionally sized, or treated with a substance to reduce the cellulose absorbency. Internal sizing is added to the paper pulp after rinsing and before it is cast in the paper mould; external or "tub" sizing is applied to the paper surface after the paper has dried. The traditional sizing has been gelatin, gum arabic or rosin, though modern synthetic substitutes (alkyl-ketene dimers such as Aquapel) are now used instead. The highly absorbent papers that contain no sizing are designated waterleaf.
Most art papers are sold as single sheets of paper in standard sizes. Most common is the full sheet (22" x 30"), and half sheets (15" x 22") or quarter sheets (15" x 11") derived from it. Larger (and less standardized) sheets include the double elephant (within an inch or two of 30" x 40") and emperor (40" x 60"), which are the largest sheets commercially available. Papers are also manufactured in rolls, up to about 60" wide and 30 feet long. Finally, papers are also sold as watercolor "blocks" -- a pad of 20 or so sheets of paper, cut to identical dimensions and glued on all four sides, which provides high dimensional stability and portability, though block papers tend to have subdued finishes. The painter simply works on the exposed sheet and, when finished, uses a knife to cut the adhesive around the four sides, separating the painting and revealing the fresh paper underneath.
Finally, the best art papers are designated archival, meaning they will last without significant deterioration for a century or more. Archival means that the papers are made entirely of high alpha cellulose or 100% cotton or linen fiber (that is, they are lignen free, as lignen causes the darkening and embrittlement under light exposure), pH neutral (meaning there is no residual acidity left from the chemical processing of the pulp), buffered (a small quantity of an alkaline compound, usually calcium carbonate, is added to the furnish to neutralize the effect of atmospheric acids), and free of any artificial paper brighteners or whiteners (e.g., ultraviolet dyes). The content designations "100% cotton" or "100% cotton rag" have little significance to the actual quality or handling attributes of the paper. (A wide range of papers using alternative plant fibers, some of them not archival, are available from Asian manufacturers; some watercolor painters even employ sheets of printable plastic, sold under brand names such as Yupo.)
A useful test of paper quality is simply to burn a small piece of the paper in an ashtray: pure cellulose completely burns away to a wispy, whitish gray ash. The absorbency of a paper is assessed by licking it. The mechanical strength of the paper is assessed by repeatedly folding it back and forth along a single crease. The stability of the paper (amount of cockling when soaked) and its response to lifting paint (the paper should not shred or tear) is best tested by making a painting on it.
All cellulose fibers absorb moisture and expand along the length of the fiber when wet; this produces the familiar buckling or warping called cockling. Evenly wetted, machinemade papers typically curl along one dimension, revealing the curvature of the cylinder they were formed on; some mouldmade papers and all handmade papers cockle in a random, uneven pattern. Handmade papers typically have four natural deckles (feathery, uneven edges) left by the paper mould; mouldmade papers have two natural deckles along the edges of the web, and two simulated deckles produced by cutting the sheet with a jet of compressed water; machinemade papers have no deckles.
In the 19th century, before modern high quality and heavy weights of paper were available, watercolor painters preferred to "stretch" papers before painting on them, to minimize or eliminate cockling and to provide a firm painting support. The paper was first completely immersed in water for 10-15 minutes, then laid completely flat on a board. The paper edges were fixed with gummed tape, starch glue or tacks, and the paper was left to dry. (As paper dries it shrinks, producing a high tension across the paper surface; when painted on, this tension takes up the expansion produced by the paper cockling, so that the paper remains flat.) When the painting was finished, the gummed or glued edge of the paper, including the deckle (which was considered unsightly) was trimmed away. Many watercolor painters still stretch their papers, but because natural deckles are appreciated today for their decorative, handmade effect, the modern preference is to work on unstretched papers, either by using a heavier weight of paper, by allowing paper to dry out before it becomes too saturated, or by exploiting the artistic effects that cockling can produce.
Watercolor painting has the reputation of being quite demanding; it is more accurate to say that watercolor techniques are unique to watercolor. Unlike oil or acrylic painting, where the paints essentially stay where they are put and dry more or less in the form they are applied, water is an active and complex partner in the watercolor painting process, changing both the absorbency and shape of the paper when it is wet and the outlines and appearance of the paint as it dries. The difficulty in watercolor painting is almost entirely in learning how to anticipate and leverage the behavior of water, rather than attempting to control or dominate it.
Many difficulties occur because watercolor paints do not have high hiding power, so previous efforts cannot simply be painted over; and the paper support is both absorbent and delicate, so the paints cannot simply be scraped off, like oil paint from a canvas, but must be laboriously (and often only partially) lifted by rewetting and blotting. This often induces in student painters a pronounced and inhibiting anxiety about making an irreversible mistake. Watercolor has a longstanding association with drawing or engraving, and the common procedure to curtail such mistakes is to make a precise, faint outline drawing in pencil of the subject to be painted, to use small brushes, and to paint limited areas of the painting only after all adjacent paint areas have completely dried.
Another characteristic of watercolor paints is that the carbohydrate binder is only a small proportion of the raw paint volume, and much of the binder is drawn between the hydrophilic cellulose fibers of wet paper as the paint (and paper) dries. As a result, watercolor paints do not form an enclosing layer of vehicle around the pigment particles and a continuous film of dried vehicle over the painting support, but leave pigment particles scattered and stranded like tiny grains of sand on the paper. This increases the scattering of light from both the pigment and paper surfaces, causing a characteristic whitening or lightening of the paint color as it dries. The exposed pigment particles are also naked to damaging ultraviolet light, which can compromise pigment permanency.
Watercolor paint is traditionally and still commonly applied with brushes, but modern painters have experimented with many other implements, particularly sprayers, scrapers, sponges or sticks, and have combined watercolors with pencil, charcoal, crayon, chalk, ink, engraving, monotype, lithography and collage, or with acrylic paint.
Many watercolor painters, perhaps uniquely among all modern visual artists, still adhere to prejudices dating from the 19th century rivalry between "transparent" and bodycolor painters. Among these are injunctions never to use white paint, never to use black paint, only to use transparent color, or only to work with "primary" color mixtures. In fact, many superb paintings flout some or all of these guidelines, and they have little relevance to modern painting practice.
Perhaps only with the exception of egg tempera, watercolor is the painting medium that artists most often compound themselves, by hand, using raw pigment and paint ingredients purchased from retail suppliers and prepared using only kitchen utensils. Even with commercially prepared paints, watercolor is prized for its nontoxic, tap ready solvent; lack of odor or flammability; prompt drying time; ease of cleanup and disposal; long shelf life; independence from accessory equipment (jars, rags, easels, stretchers, etc.). Its portability makes it ideal for plein air painting, and painters today can buy compact watercolor kits -- containing a dozen or more pan paints, collapsible brushes, water flask, brush rinsing cup and fold out mixing trays -- that fit neatly into a coat pocket.
A glaze is the application of one paint color over a previous paint layer, with the new paint layer at a dilution sufficient to allow the first color to show through. Glazes are used to mix two or more colors, to adjust a color (darken it or change its hue or chroma), or to produce an extremely homogenous, smooth color surface or a controlled but delicate color transition (light to dark, or one hue to another). The last technique requires the first layer to be a highly diluted consistency of paint; this paint layer dissolves the surface sizing of the paper and loosens the cellulose tufts in the pulp. Subsequent layers are applied at increasingly heavier concentrations, always using a small round brush, only after the previous paint application has completely dried. Each new layer is used to refine the color transitions or to efface visible irregularities in the existing color. Painters who use this technique may apply 100 glazes or more to create a single painting. This method is currently very popular for painting high contrast, intricate subjects, in particular colorful blossoms in crystal vases brightly illuminated by direct sunlight. The glazing method also works exceptionally well in watercolor portraiture, allowing the artist to depict complex flesh tones effectively.
The essential idea is to wet the entire sheet of paper, laid flat, until the surface no longer wicks up water but lets it sit on the surface, then to plunge in with a large brush saturated with paint. This is normally done to define the large areas of the painting with irregularly defined color, which is then sharpened and refined with more controlled painting as the paper (and preceding paint) dries.
Wet in wet actually comprises a variety of specific painting effects, each produced through different procedures. Among the most common and characteristic:
Watercolor painters also learn to apply paint to paper and then, when the paint has dried to the right point, brush along the edge of the paint with a flat, mop or sky brush charged with a moderate amount of clear water. This new area of water pulls the wet paint outward in a diffusion fan that is controlled by judging the wetness of the paint and the amount of water applied; if excessive water is used, this brushing produces both an outward diffusion and a backrun into the drying paint. This method is useful to produce transitions in value or color within narrow bands, such as the locks of hair in a portrait head.
Scumbling (in the 19th century, called "crumbling color" or "dragging color") is an unrelated technique of loading a large, moist flat or round brush with concentrated paint, wicking out the excess, then lightly dragging the side or heel of the tuft across the paper to produce a rough, textured appearance, for example to represent beach grass, rocky surfaces or glittering water. The amount of texture that can be produced depends on the finish or tooth of the paper (R or CP paper works best), the size of the brush, the consistency and quantity of the paint in the brush, and the pressure and speed of the brush stroke. Moist paper will cause the scumbled color to diffuse slightly before it dries.
Tube paints are normally used with a flat palette that provides compartmentalized paint wells (for holding separate paint colors) and a large mixing area for mixing or diluting paints; pan paints are arrayed in enameled metal paint boxes that provide shallow mixing areas in the folding cover or in a fold out faceted tray. With tube paints, the excess paint remaining in the palette paint wells should be cleaned out only if the paint has become dirtied with another paint; otherwise the paints should be allowed to dry out promptly and completely, as this prevents mold from forming. Despite the common misconception, there is no visual difference between the viscous paint packaged in tubes and the dried paints in pans. Tube paints left to dry in paint wells are used in exactly the same way as pan paints -- the painter simply drips or sprays water over the paint a few minutes before starting work. The only notable difference is that some tube paints, such as viridian or cerulean blue, produce a gritty, uneven paint mixture when left to dry and then rewetted.
There are three finesses to color mixtures with watercolors. First, the raw or "pure" paint in the paint wells should never be discolored with any other paint. To ensure this, colors are mixed by picking up the desired quantity of dissolved paint from the prewetted paint well, using a moist, clean brush, then applying the paint onto the flat mixing area of the palette. Then the brush is rinsed before picking up any other paint. Once all paints are on the mixing area, they are mixed and/or applied to the painting.
Second, colors can be mixed in at least four ways: (1) by completely mixing together on the palette the paints that exactly match a desired color; (2) by loading together in a large brush the separate paints that approximately match the desired color, then letting these partially mix as the paint is applied to the paper; (3) by laying down first a single paint color, then "dropping in" the remaining paint colors with the brush while the painted area is still wet; (4) by glazing the paints as separate layers, one over another. Each technique has its purpose -- the first provides color accuracy (for photorealist painting), the second provides color variety (especially in dark colors), the third produces many "wet in wet" effects between wetter and drier paint areas (for greater color expressiveness), the fourth can produce a variety of luminous, iridescent or "broken color" effects, similar to mixtures with pastel chalks.
Third, watercolors should be used confidently: applied with a single stroke or joined strokes, then left alone to dry. Color muddiness or dullness typically comes from excessively brushing wet paint after it has been applied to the paper, or adding new layers of paint onto paper that has soaked water into its pulp (capillary action draws the paint inside the paper, dulling the color, rather than letting it dry on the surface). Overbrushing and "color soaking" are the most common flaws of novice watercolor paintings.
Though commercial watercolor brands offer selections of up to 100 or more paint colors in tubes, subtractive pigment mixtures can produce a complete range of colors from a small number of specific paints. In the 19th century a six paint "split primary" palette became popular and is still advocated by older painters. It is based on the three subtractive primary colors (red, yellow and blue), each in a "warm" and "cool" version:
The reason for this intricate selection was that bright or saturated mixtures were only produced by related primary colors, e.g. the brightest orange is the mixture of a yellow with some red in it (warm yellow) and a red with some yellow in it (warm red); the brightest green is the mixture of a yellow with some blue in it (cool yellow) with a blue with some yellow in it (cool blue); duller mixtures are produced by mixing contrasted primaries, and the dullest mixtures by mixing three primaries.
The modern approach (the hexachrome palette) also relies on six paints, but spaces them more equally around the hue circle so that their mixtures automatically produce the most saturated color in every hue:
Both palettes obtain dull or darkened colors, including a "neutral" (dark gray or black), by mixing together paints or colors on opposite sides of the hue circle -- especially orange or scarlet with cyan, and carmine or magenta with green.
As a matter of convenience, painters typically also add one or more paints made with an iron oxide pigment (the so called "earth" pigments, many of them manufactured as concrete colorants or wood stains) and sold under the names yellow ochre, raw sienna, raw umber, burnt sienna, burnt umber and/or venetian red. Exactly the same brown or ochre colors can be matched with either of the six paint palettes, but it tedious to do. As dark colors also require inconvenient mixing, most painters prefer to add a premixed dark neutral paint containing a carbon (black) pigment, usually sold under the marketing names indigo, payne's gray, neutral tint or sepia.
Unfortunately, paint manufacturer lightfastness ratings are not always trustworthy. However, because they have been demonstrated to be impermanent in watercolors, certain pigments (paints) should never be used under any circumstances. These include: aureolin (PY40), alizarin crimson (PR83), genuine rose madder (NR9), genuine carmine (NR4), genuine vermilion (PR106), most naphthol reds and oranges, all dyes (including most "liquid watercolors" and marker pens), and paints premixed with a white pigment, including paints marketed under the names naples yellow, emerald green or antwerp blue. Most of these are colorants invented in the 19th century or before that have been superseded by far more durable modern alternatives, and these are usually sold as "hue" paints (e.g., "alizarin crimson hue" is a modern pigment that resembles alizarin crimson). Industry labeling practice is to include a lightfastness rating on the paint packaging, and painters should only use paints that have a lightfastness rating of I or II under the testing standards published the American Society of Testing and Materials (now ASTM International).