Mineral spirits and paint thinner are essentially the same product, except mineral spirits is more refined and costs more than paint thinner. According to The Family Handyman, both chemicals are petroleum substances, but paint thinner has different solvents that make it more volatile and pungent.
Mineral spirits and paint thinner are both used to clean oil-based paint, remove varnish from surfaces and soak paintbrushes to remove pigment. Because more hydrocarbons are removed from mineral spirits, it is less smelly. Paint thinner contains more solvents than mineral spirits, so the odor is stronger and the chemical is more volatile. Paint thinner is generally cheaper than mineral spirits because less work is done to produce it.
Paint thinner is better for cleaning brushes because the quantity of paint removal is far less than a surface with dried paint. Mineral spirits is more effective in small quantities because it is more refined.
These hydrocarbons are poisonous and should be handled with caution. Exposure to such paint-cleaning chemicals can cause skin irritation. Inhalation leads to difficulty breathing. Accidentally ingesting mineral spirits or paint thinner causes severe pain in the throat and stomach. Both mineral spirits and paint thinner require well-ventilated areas during usage. Safety precautions should be taken to ensure no one is injured trying to remove paint.