Beef gallbladder
Adding ox gall to watercolor or tempera paint is useful for evenly coloring large areas (known as a “flat wash”), as well as for paints that are harder to dissolve and spread or that form round droplets on the paper. Examples include earth tones, whose pigment particles are heavier.
In chemical terms , ox bile is a surfactant that reduces surface tension—in this case, between the wet watercolor paint and the water. It exhibits a dispersing (scattering) property, causing the watercolor pigments to instantly disperse into the water with a “blooming” effect. Since it acts as a wetting agent, one could jokingly say that it makes the water or the wet paint “wetter.” 🙂
Ox bilecan be dissolved in the water used to wet the flowers and leaves, or mixed directly with the paint on the palette. Applying it to a damp area of color gently shifts the color, creating a paler trace. Ox gall exhibits its beneficial properties best when painting wet-on-wet. Usually, 3–4 sparing drops per glass of water are sufficient, but this depends on the type, as different manufacturers offer products with varying concentrations. Too much of the additive diminishes its effect.
Another use for it is as a degreaser for the palette— a few drops are spread in the mixing tray, then wiped off with a cloth. The surface becomes noticeably smoother, making it easier to mix colors. Ox bile is a detergent, which explains why adding soap or regular dishwashing liquid (which are also detergent-based) to the paints produces a similar effect.
It is also used in lithography, engraving, fabric dyeing, and marble-effect painting— the bile helps the colors float on the surface of the water instead of sinking.
Ox gall, which is available at art supply stores, comes in the form of a liquid or a solid cube ranging in color from clear to dark brown. Natural ox gall tends to become cloudy and form a sediment over time, but this does not affect its quality, and it can be used for years.
Gum arabic
Natural gum arabic is a sweet, edible resin extracted from two species of acacia trees; it is widely used in food production, in the textile industry, and in the manufacture of cosmetic and industrial products, where it acts as a stabilizer and binding agent.
In watercolor painting, natural gum arabic has the opposite effect of ox gall—it It slows down the spread of the paint on the paper, giving the artist more control and the ability to create precise strokes. Once dry, gum arabic also stands out for its subtle sheen, which can be used to highlight an otherwise matte watercolor.
Gum arabic can be added to water or directly to the paint. It is the traditional binder in watercolor paints ( or the substance that binds the dry pigment particles into a homogeneous, water-soluble mixture) and Adding it increases adhesion, that is, how well they stick to the paper. It makes the colors more ethereal and easier to rewet and remove. (English: “lifting“). It imparts transparency and a slight sheen to gouache and tempera paints, as well as elasticity, which prevents them from cracking when layered.
Undiluted gum arabic can be used to achieve a resist technique with softer outlines than those left by masking fluid, including on thinned acrylic and oil paints on canvas. To achieve this, the gum is allowed to dry, then painted over; to remove it, it is carefully moistened with a brush and blotted with a cloth once the paint has dried thoroughly.
Moderate use
Both ox bile and gum arabic are additives that exhibit their unique properties only when used in moderation.
For example, it should be noted that adding too much gum arabic to watercolor makes it difficult to rewet and lift the colors after they have dried, as it causes the paint to penetrate too deeply into the fibers of the paper.
Too much gum arabic in the paint, in turn, causes it to separate at the edge of the color drop or field, hardening and remaining as a very fine and shiny flaky layer.
The key to mastering the flavor profile of arabica coffee and ox bile lies in perfecting their moderate use —a skill that comes with experience.
Masking fluid
Watercolor masking fluid , also called liquid rubber or latex milk, is the surest way to leave clean, crisp marks on paper, completely isolating the sheet from the paint or one color from another.
The eraser can be applied with any tool, from a brush, to a pen handle, to a simple toothpick, or by spraying, then peeling off by rubbing with a finger or eraser. Since the bristles of the brushes stick together from the liquid, a specially designed, cheaper, or old brush can be used for this purpose. Its life will be extended if it is lightly soaped before dipping in the masking fluid.
Liquid rubber is usually white, gray, or blue and dries in about 10 minutes. It’s best not to leave it on the paper for more than a few days, as this makes it harder to remove later. When applied to a colored area, it removes some of the color when peeled off.
The biggest enemy of the masking fluid is air— to minimize air entering the bottle and the hardening of the rubber, it can be stored with the cap facing down.
We take a closer look at the possibilities offered by this liquid in another article of ours.
Varnishes and Protective Coatings
The traditional way to preserve watercolor and gouache paintings is to place them behind glass, but they can also be displayed without a protective barrier by varnishing them or sealing them with a wax medium. Made with a solvent base, specialized varnishes and waxes for watercolor protect against moisture and dirt and do not re-dissolve the pigments when applied. There are matte and glossy varnishes available in liquid and spray forms that have virtually no effect on the appearance of watercolors and tempera, nor do they alter their color over time. Varnishes, which often contain added UV protection, usually appear milky due to the wax in their composition, but they also dry to a clear finish.
This way, the watercolors can be mounted and displayed on stretched canvas or a rigid surface to create a more three-dimensional effect. This storage method is also suitable for small souvenir paintings such as cards, bookmarks, and miniatures.
Author: Martina Petrova
Research: Radoslav Hristov
