What is household paint?

The following is a summary of the major components that go to make up household paint products sold to consumers.

VOLATILE VEHICLE
This is the part of the paint or coatings product which evaporates. Its role is to keep the paint as a liquid for ease of application. Once applied to the surface it evaporates leaving a uniform film which then dries to form a protective coating.

Latex Paints
Latex paints use water in them with small amounts of other materials (glycols, etc.) to keep the paint uniform. The water is essentially non-toxic and the other materials are present in such small amounts in the paint product that they do not present any significant toxicity.

Solvent Paints
Solvent paints use organic solvents as the volatile vehicle. These may be a variety of solvents such as mineral spirits, alcohols and esters. They may present two health concerns: that of inhalation by people and their inherent flammability.

NON-VOLATILE VEHICLE
The non-volatile vehicle is often called the binder. It is a resin or polymer which actually forms the film of the finished paint product. Once dried, it is a fairly non-toxic material and presents no real health hazard.

Latex Paints
The non-volatile vehicle or binder in water-based latex paints is most often an "emulsion polymer", commonly referred to as latex. These latexes (or latices) are very small particles of the polymer dispersed in water (the emulsion). When the paint dries they come together to form a continuous film which holds to the surface and forms the paint film.

Solvent Paints
The non-volatile vehicle or binder in solvent-based paints varies much more than in latex paints. The most common is alkyd resin or alkyd. Alkyds are made from drying oils reacted with chemicals. They form a film by oxidation (taking oxygen from the air) and cross-linking. Alkyds may be "modified" with acrylics, urethanes or epoxies. Additionally, there are solvent-based paints that are catalyzed. These involve mixing two components together just before application.

PIGMENTS
The pigments found in paint are most often bound or encapsulated in the resin. Therefore, they are not readily available to be dispersed into the environment. The pigments used in paint serve several purposes. The pigments help: (1) to hide the surface on which they are being applied, (2) to provide a decorative effect through the particular colour of the paint film, and (3) to provide durability as well as other surface characteristics such as washability, gloss, etc. The pigments used in both latex and solvent-based paints are typically the same. A few comments about several types follow.

Hiding Pigments
The major hiding pigment used in paints, is found in white or pastel paints and is known as titanium dioxide. Titanium dioxide is relatively non-toxic and indeed is used in food and personal care items such as toothpaste.

Specialty (Extender or Inert) Pigments
These pigments are added to the paint to provide certain characteristics such as thickness, a certain level of gloss, and durability. They are usually naturally occurring products which originally were in the ground and were mined and purified for use in paint. Such pigments as calcium carbonate, talc and clay, for example, are all used extensively in paints.

Coloured Pigments
There are a variety of coloured pigments used in paint, both to impart a certain colour to it and also, in the deeper shades, to provide hiding. There are two basic kinds of coloured pigments: organic and inorganic.

Inorganic Pigments
A number of the inorganic pigments are in themselves naturally occurring. For example, iron oxide, found in many metal primers (giving it a red colour), is either of the same chemical composition as rust or its first cousin. Other pigments found in paints are the product of different chemical processes but are in themselves rather inert and would not dissolve or break down upon disposal.

Organic Pigments
Organic pigments are those which contain carbon. These provide a wide variety of colours and have relatively low levels of toxicity, not providing any major environmental concern.