What is a solvent?
In general, solvents are liquids used to dissolve other components. In the paint industry, solvents are liquids or a mixture of liquids that dissolve resin and carry pigments and other paint components. In water-based paints, the solvent is water, but the resin (or latex) is emulsified in water, not dissolved in it. A small amount of other solvents is also added to water-based paints.
There are three major applications of solvents in the paint industry:
- As a cleaning agent to remove oily residues from a substrate in preparation for painting, and to clean equipment, spray guns, and spills after paint application.
- As an integral part of the paint formulation.
- As a paint thinner, added to paint to adjust its application method.
Common solvents used in paints include water, methyl ethyl ketone (MEK), white spirit, methylated spirits (a mix of methanol and ethanol), xylene, toluene, and acetone. Except for water, solvents are organic (i.e., carbon-based; derived from petrochemicals or plants). While water is a common solvent, the term "solvent" in this note refers to organic solvents.
Why add solvents?
The purpose of a solvent in paint formulation is to carry the paint from the container to the substrate in a way that allows the paint to be sprayed, brushed, or rolled evenly and helps achieve the required gloss level and dry film thickness. Solvents can be chosen to improve the balance between the paint’s application properties, such as viscosity, drying time, coverage, edge coating, and more.
What are the risks?
Safety
Almost all solvents are flammable, and even their vapors can ignite. Therefore, solvents should never be used near open flames, such as gas lights or lit cigarettes, or sparks.
Health
Inhaling solvent vapors can cause short-term health issues, such as:
- Nausea
- Eye irritation
- Headaches
- Dizziness
These risks dissipate when the source of solvent vapor is removed, or the applicator uses respiratory protection. Long-term health risks include cumulative effects on organs like the kidneys, brain, liver, and heart. There are clear exposure limits for each solvent, which are indicated on the Material Safety Data Sheet (MSDS).
Are paint solvent vapors dangerous?
They are not more dangerous than the solvents found in many other household products, such as nail polish, nail polish removers, cleaners (including natural products like citrus-based cleaners), some polishes, and furniture adhesives. All should be used in small amounts and safely.
How can I safely use solvent-based products?
Do not rely on your sense of smell to alert you to solvent vapor dangers, as not all solvents have strong odors. Additionally, the applicator can quickly become accustomed to many solvent odors and may become unaware of their presence.
When using a brush and roller, the hazards are largely limited to splashing or spilling paint directly onto unprotected skin and inhaling solvent vapors. The health risks associated with inhaling solvent vapor can be minimized by using proper face masks, whether solvent masks or positive pressure air respirators. Protective clothing includes, but is not limited to: coveralls, long sleeves, solvent-resistant gloves, safety footwear, and vapor masks.
When spraying, inhaling atomized paint (paint mist) presents a greater health risk than inhaling solvent vapors and should be avoided. Airborne paint particles carry a mixture of solids and liquids, including resin, pigment, hardener, and solvent, and are more hazardous to inhale than solvent vapors.
When spraying paint, avoid inhaling atomized paint by using a full-face positive pressure air respirator and wearing protective clothing, safety shoes, and solvent-resistant gloves.
