|Each side of the table above lists 4 common transparent and opaque pigments.|
by Naomi Ekperigin
Watercolor paints are those that use water-soluble, complex carbohydrates as a binder. Made of organic and inorganic pigments, today’s watercolor paints use a binder of 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 the shelf-life of the paint. Gum arabic is transparent and this is what gives watercolors their brilliancy, but not all paints have the same level of transparency. For example, the quinacridone pigments (oranges and reds) and the phthalocyanine pigments (greens and blues) are very transparent, while cadmiums and iron oxides are more opaque. It is important to know these differences when mixing colors.
Transparent Versus Opaque Pigments
Manufacturers generally label paints as transparent or opaque. When a transparent paint is applied to paper, much of the reflective white surface shows through. One method of testing your colors for transparency or opacity is to paint a strip of waterproof black ink down the paper. When it's dry paint each of your colors in separate bands across it. Let them dry then inspect each color for transparency and degrees of opacity. Top manufacturers are now supplying this sort of information in their color catalogues, along with permanency ratings and whether the color stains.
Beginners are often advised to begin with a palette of transparent colors before venturing into the opaques, because mixing opaques can result in muddy colors. However, some artists recommend having a few opaque earth tones on the palette. “I sometimes play translucent and lighter colors against the more opaque colors,” says artist-instructor Peggy Dressel. “For example, I can make the water in a landscape painting glow more if I play it against rocks and trees painted with more opaque paints.” It is also important to note that there are few completely opaque watercolors, with the exception of gouache. Gouache is made by mixing the standard watercolor with various amounts of an opacifying agent such as chalk. Watercolor paints do not form a cohesive layer on the surface; instead, they scatter pigment particles across the paper surface. Gouache, on the other hand, has a definite thickness and creates a paint layer. Because of its thickness, the effects of gouache paints do not depend on the color of the ground on which they are applied. Transparent watercolors require a highly reflective pure-white ground, which helps create a sense of luminosity; with gouache, the light-reflecting quality comes from the use of white pigments.
|Street Scene in Buena Vista, Colorado
by Brenda Turner, 2006, gouache, 22 x 30. Collection Community Banks of
Colorado, Denver, Colorado.
by Steve White, 2005, watercolor, 17 x 31. Private collection.
It is important to know the properties of each color so that color mixing is most effective. “When mixing a transparent pigment with an opaque or semi-opaque pigment, it’s important to keep the two well mixed,” advises watercolorist Lori Simons. “If the puddle of paint sits undisturbed, the larger particles sink to the bottom while the transparent small particles sit on top of the puddle, causing the mixture to separate.”
Staining and Granulating Pigments
The staining quality of a paint refers to the ease with which a paint can be rewetted once dry and then lifted or blotted off the surface. A staining paint is difficult to remove and 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 surface and on the particle size of the pigment. “Sap green and alizarin crimson are hard to lift because the particles are ground so finely,” notes Simons. “What I like about them is that they let the white of the paper shine through.” Staining is increased if the paint manufacturer uses a dispersant to reduce the time it takes to mix the paint, because the dispersant acts to drive pigment particles into crevices in the paper pulp, dulling the finished color.
Granulation refers to the effect given by some pigments when granules of pigment settle into the indentations of the paper, producing a “grainy” look. Some pigments notable for their watercolor granulation include viridian, cerulean blue, cobalt violet and some iron oxide pigments. Granulating colors also allow for the creation of textural washes, and show up best on rough papers. One can buy watercolor granulation mediums to create the effect in other pigments.
Naomi Ekperigin is the editorial assistant for American Artist.