Paint is a mixture of pigment and adhesive. There must be some mechanism that allows the paint to be liquid during application, but then solidify or "set" after application. This may be accomplished by dissolving the adhesive in a solvent which evaporates into the air, or through some polymerizing chemical reaction. The component that allows a paint to flow is refered to as the vehicle. Chemicals added to paint for the purpose of decreasing the paint's viscosity and shearing properties are referred to as thinners. Chemicals added to paint for the purpose of lowering the paint's concentration are referred to as reducers. The component of paint that is not the pigment is referred to as the paint medium, and is sometimes mixed with paint to reduce the concentration of pigment without altering the paint's physical properties. A paint's medium is also referred to as a paint's base in certain contexts, but the ubiquity of the term can lead to ambiguity.
The set of pigment chemicals used in paint is small, and in general, spans all types of paint. Paint is categorized by the nature of the paint's medium.
As the name suggests, watercolor paints are dissolved in water. Watercolor paints set by drying, and may be redissolved with water any number of times. As a result, watercolor paint is vulnerable to moisture. Unlike other paints, where the pigment is held in suspension, pigments for watercolors are generally selected to be soluable in water. This allows the pigment to be embedded into pourous material (e.g. paper) instead of lying on top of it.
Watercolors are translucent, and are commonly layered to produce various effects. Watercolors that are formulated to be opaque are known as gouache.
Oil based paints are pigments suspended in drying oil, a specific category of oils that harden as they oxidize with the air. Oil paints have reduced in popularity with the advent of acrylic paints which can offer many of the same properties with a more managable drying time, and lower cost.
Acrylic paints utilize acrylic polymers suspended in a solvent, usually water. Unlike watercolors, acylic paints polymerize as they dry, and can thus provide some degree of waterproofing. Acrylic paints are sold with a variety of additives that give the paint a wide variety of different properties, such as thickness, flexibility, gloss, and drying time.
Originally, lacquer referred to paints made from resins extracted from the Lac bug and dissolved in alcohol. Later, lacquer was used to refer to nitrocellulose based paints, thinned with solvents like alcohol, acetone, or ether. In modern usage, lacquer may refer to any paint that uses some form of lacquer thinner as a vehicle. Lacquer thinner can be any sort of combination of Volatile Organic Compounds (VOCs). Lacquer paints are less commonly used, due to environmental and health concerns.
Enamel (modern usage)Edit
Enamel is a generic term referring to any paint that sets to a hard coat. Enamel paint is generally thinned with paint thinner. Products sold as "water based enamel" are generally acrylic paints formulated to set hard with a higher than average degree of waterproofing.
Enamel in the original usage of the term are pigments suspended in materials that, when properly heated, polymerize into a ceramic coating. This includes most "powder coats", such as those seen on industrial machinery and products that must withstand high heat.
Polyurethane paints cure via the polymerization of polyurethane. This paints may be devided into two subcategories, 1k (meaning one part) and 2k (meaning two part). 1k polyurethane paint reacts with the atmosphere to cure. 2k polyurethane is used by mixing the paint base with a "hardener" immediately before application. The two ingredients react causing polymerization. 2k polyurethane is extremely durable, and is the standard for modern automotive paint. another benefit of 2k polyurethane paint is that both components are liquid prior to the reaction, meaning little or no VOCs are needed.
Epoxy paints are also 2 part paints. The properties of epoxy make it more durable against weather damage than polyurethane paints. This makes it popular for use in marine applications. Epoxy paints are also able to withstand higher temperatures than most categories of paint. High material cost, and difficulty of cleanup make epoxy paint less popular overall than polyurethane paint.
Latex paints are water-based, and rely on the polymerization of natural or synthetic latex. Latex paint is the standard housepaint. The latex component allows the paint to be extremely flexible. Latex paint's characteristic oder comes from ammonia, an additive that stabilizes the latex. Latex paint is useful in that painting stores or painting departments are set up to color match and mix pigment to produce any color desired in just moments.
A common use of latex paint in propwork is for painting open-celled foam. A good example of this technique can be seen in the costumes and props used by the band Gwar.
- The ingredients must be non-toxic and non-irritating to the skin
- The cosmetic must be settable, such that the product is at least moderately resistant to removal or smearing by sweat and natural body oils
- There must be some means of removing the cosmetic when it is no longer needed. An exception to this point is makeup that is permanently tatooed to the skin. This is a stain, not a paint, and is in general beyond the scope of Special FX cosmetics.