What is Paint?

Paint consists of two things, pigment and binder. Pigment is what gives color to paint and in its raw form it is a fine powder. Binder is what holds the pigment and adheres it to a surface. The pigment particles are insoluble and merely form a suspension in the binder. There are a great many pigments in the world, from a variety of sources. Some pigments are earth pigments, or natural inorganic pigments—simply put, colored clumps of earth. These are the first pigments used by mankind and include such colors as Yellow Ocher, Slate Grey, The Siennas, and many more. Closely related are the Mineral Pigments (also natural inorganic pigments) which include colors such as Vermilion (Cinnabar/Mecuric Sulfide) and green Malachite. Artificial inorganic pigments, on the other hand, are colors that are produced rather than found. Many of these pigments were made and discovered by the alchemists of antiquity. Such colors as Verdigris, Naples Yellow and Sandarac fall into this category. Natural organic pigments have sources that are either vegetable or animal, rather than earth or mineral. These include colors such as Indian Yellow (cow urine from India), Sap Green, and Bone Black (calcined bones). Finally, there are the synthetic organic pigments, which saw their birth in the nineteenth century. When this type of pigment was first developed, it tended not to be very light fast and often faded in a short period of time. Eventually, this setback was overcome and color groups such as the Indanthren and Heliogen were invented.

There are a great number of binders for pigment. It is these binders that give us the many different types of paint such as Oil, Acrylic and Casein. Each binder imparts a unique quality to the pigment and adheres to the surface in a different way.

Beeswax is one of the oldest known binders for pigment. Encaustic paint is a very permanent media with a lustrous surface quality. Pigment is added to molten beeswax, which is then applied to a rigid support. Do to the brittleness of wax encaustic should be painted on rigid surface. Other types of wax such as carnauba wax can be used with the beeswax to achieve a higher melting point. There are modern forms of encaustic painting which do not require heating at the time of painting.

Casein is a milk-based product that forms a strong glue when mixed with an alkali (e.g. lime, borax, ammonia, etc.). Casein paint has a very dry, velvety surface which is rich in color. Casein is water soluble; however, it dries water insoluble which makes it possible to use it with glazing techniques. Casein is also an emulsifier, i.e. oil and varnishes can be added to the casein glue and still be thinned with water. Casein can be used as an underpainting for oils and can be applied to a variety of rigid surfaces.

Egg yolk is the binder for Tempera painting. Egg Tempera is a ancient tradition which offers rich results not duplicated by any other binder. It is famous for being used in icon painting. Egg yolk acts as an emulsifier, as well as allowing for oil and gum emulsions to be used.

Fresco is the painting of pigments into fresh (wet) lime plaster. In this case no binding agent is used for the pigments. They are made into a paste using water and are then brushed directly into the wet plaster surface. It is the plaster ground that binds the pigments during the carbonation (hardening) of the lime. It creates a bond so solid that it is nearly impossible to dissolve. Due to the extreme alkali of lime only those pigments which are alkali-fast can be used. Fresco technique was well evolved even 2000 years ago. Murals from Pompeii and Rome are still well preserved. Fresco retains an amazing vibrance of color not found with other media.

Gum arabic acts as the binder for booth water color and gouache paints. Gum arabic is produced by several species of acacia trees. It comes in lumps which are then dissolved in water to form a gum solution. It is into this solution that pigments are ground to produce paint. Gouache differs from water color on by the addition of chalk which allows the paint to be more opaque and imparts a dusty quality to the surface. Gum arabic is resoluble once it has dried, therefore it can be stored in cakes. Occasionally oxgall (a wetting agent) is added to water color to add in the even dispersion of pigment.

Rabbit skin glue or other hide glues act as the binding agent for distemper. Distemper paint has been used primarily in the painting of interiors. It has a wonderful matte finish and a soft feel to it. This paint however is very impractical to apply, because it is very runny, messy and needs to be applied while warm. Casein Paint has the same look and is much more practical to apply.

Oil paint evolved out of the use of Egg Tempera emulsions. Linseed oil (from the flax seed) acts as the binder. Linseed oil dries through the process of oxidation to a strong but flexible film. It is the flexible quality of the oil film that allows for its use on canvas. Cold pressed linseed oil is generally used in paint making though small proportions of poppy and walnut oils are also used. Oil paint has the longest drying time of all paints. It tends to be rather opaque though this varies greatly form pigment to pigment. With the addition of painting mediums, oil paint can be employed for glazing and impasto techniques. Oil is the most widely recognized artists paint in our time.

A recent invention, acrylic emulsion is the binder in acrylic paints. Acrylics are water soluble, but dry to a water insoluble and impenetrable flexible film. They are very fast drying and can be used as an under painting for oils. Originally thought to be a replacement for oil paints, acrylic paint has proven to be a unique and viable medium of its own.

There are a number of other materials that can be used to bind pigment to a surface. These include shellac, starch glue, gelatin, Dextrin, Tylose, plastic resins and more.

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