Mineral spirits, a common petroleum-based solvent, is used for thinning oil-based paints, cleaning brushes, and degreasing surfaces. This substance definitely evaporates, though its rate is slower than many other solvents. This conversion from liquid to vapor is inherent to its function, allowing it to temporarily thin materials before disappearing. Understanding how mineral spirits volatilizes is important for effective and safe use.
What Makes Mineral Spirits Volatile
Mineral spirits, also known as white spirit, is a complex mixture of aliphatic hydrocarbons derived from the distillation of petroleum. These organic compounds typically have carbon chain lengths ranging from C7 to C12. The solvent’s ability to evaporate is directly tied to vapor pressure, which is the pressure exerted by a vapor in equilibrium with its liquid phase.
The molecules in the liquid are constantly moving, and those with enough energy near the surface escape into the surrounding air as vapor. Mineral spirits has a moderate vapor pressure, meaning it is volatile but does not evaporate instantly, unlike faster solvents such as acetone. Different types contain various chain lengths, resulting in a gradual evaporation profile. Longer hydrocarbon chains mean the solvent evaporates over time, which is beneficial for applications like paint thinning where controlled drying time is desired.
Environmental Factors that Speed or Slow Evaporation
The speed at which mineral spirits evaporates is strongly influenced by three main external conditions. Temperature is the most significant factor, as increasing it supplies more energy to the liquid molecules. For approximately every 18°F (10°C) increase, the evaporation rate roughly doubles. Warmer environments significantly accelerate the change from liquid to vapor.
Airflow, or ventilation, plays a substantial role by sweeping away the solvent-saturated air layer above the liquid surface. Without air movement, this saturated layer slows evaporation; moving air replaces it with fresh, solvent-free air, allowing more liquid molecules to escape. The total surface area also affects the rate of evaporation. Spreading the mineral spirits into a thin film exposes a much larger area to the air, accelerating the process compared to letting it sit in a deep pool.
Safety When Working with Mineral Spirits Vapor
Because mineral spirits readily evaporates, managing the resulting vapor is a necessary safety consideration. The vapors are flammable and can accumulate, creating a flash fire hazard, particularly in enclosed spaces. It is imperative to use the solvent in well-ventilated areas, such as outdoors or with local exhaust ventilation, to prevent the concentration of vapor from reaching dangerous levels.
Inhaling high concentrations of the vapor poses a health risk, potentially causing respiratory irritation, dizziness, or headaches. Prolonged or repeated exposure can lead to severe health issues affecting the nervous system. Users should wear appropriate personal protective equipment, including chemical-resistant gloves to prevent skin absorption, and ensure continuous fresh airflow. Keeping the solvent away from heat, sparks, and open flames is crucial, as the flammable liquid and vapor can ignite.