Water-based paints include water color, acrylic, gouache, tempera and casein. Water is used for thinning and cleanup.

Watercolors:

Watercolors (dry cakes) are composed of pigments, preservatives (often paraformaldehyde) and binders such as gum arabic or gum tragacanth. Liquid watercolors may also contan water, glycerine, glucose and other materials. Both liquid and dry watercolors may give off small amounts of formaldehyde, but generally need no exhaust ventillation.

Gouache is an opaque watercolor which contains pigments, gums, water, preservatives, glycerine, opacifiers and other ingredients. The opacifiers may be chalk, talc or other substances. Formaldehyde may be used as a preservative.

Acrylic Paints:

Acrylic paints contain a small amount of ammonia. Some sensitive people may experience eye, nose and throat irritation from the ammonia. Acrylics and some gouaches contain a very small amount of formaldehyde as a preservative. Only people already sensitized to formaldehyde would experience allergic reactions from the trace amount of formaldehyde found in acrylics. The amounts can vary from manufacturer to manufacturer.

Acrylic paints (Water-Based Emulsions) are composed of synthetic acrylic resins and pigments with many additives usually including an almmonia-containing-stabilizer and formaldehyde preservative. The small amounts of ammonia and formaldehyde released during drying can cause respiratory irritation and allergies.

Acrylic Paints (Solvent-Based) are synthetic acrylic resins and pigments dissolved in solvents. The solvents should be identified and ventilation sufficient to keep the solvent's concentration at a safe level should be provided.

Casein Paints:

Casein paints use the protein casein as a binder. While soluble forms are available, casein can be dissolved in ammonium hydroxide which is moderately irritating by skin contact and highly irritating by eye contact, ingestion, and inhalation.