Paint thinners arediluents —solvents used to adjust theviscosity ofpaint, as well as similar preparations such asvarnish andlacquer, by dilution.[1][2]Organic solvents labelled "paint thinner" are usuallyturpentine orwhite spirits / mineral spirits for the use of dilutingoil-based paints only. Forwater-based paints, such asacrylic paints,water is the primary solvent, but notably, may not always be the only solvent.
Principally, paints are either acolloidal suspension of solidpigment particles or are anemulsion of dense viscousdye gel or paste with afiller all dispersed through a lighter free-flowing liquid medium — the solvent. This solvent also controls flow and application properties, and in some cases can affect the stability of the paint while in liquid state. Its main function is to act as the carrier to ensure an even spread of the non-volatile components. After a long period in storage, the dense paint pigment and filler settles out over time and it can lose some of its solvent due to evaporation, becoming so thick and viscous that it does not flow properly when used. By the addition of more solvent, it can be diluted or re-dissolved to restore the paint to an appropriate consistency for use. The diluent acts to reduce theviscosity and so making a more free-flowing liquid, so in this context, "thinning" is the act of dilution.
These solvents can also be used as paint-brush cleaners to remove or to clean items that have become caked in dried-on paint. With improvements in paint manufacturing have led to the reduction of use of organic solvents in preference for water, means that paint clean-up can be done with water and commonsurfactants anddetergents.
Common organic solvents used historically as paint thinners arevolatile organic compounds — forms ofhydrocarbons — and include:[3]
Less common organic solvents used as paint thinner — likearomatic organic compounds that are more hazardous, so more heavily regulated and restricted in use — but still used in theconstruction industry include:[4]
Some paint thinners can ignite from just a small spark in relatively low temperatures. These solvents arevolatile organic compounds (VOCs), with white or mineral spirits having a very lowflash point at about 40°C (104°F), the same as some popular brands of charcoal starter. All such solvents with low flash points are hazardous and must be labelled asflammable.[5][6][7][8][9]
Prolonged exposure to VOCs emitted by paint containing these solvents or its clean-up using paint thinner are hazardous to health. VOCs exhibit highlipid solubility and for this reason, theybioaccumulate inadipose / fatty tissues.[10]Extensive exposure to these vapours has been strongly related toorganic solvent syndrome, although a definitive relation has yet to be fully established.[11]For safety reasons, the use of substances containing these solvents should always be done in well-ventilated areas, to limit the health consequences and minimise the risk injuries or fatalities.[12] In countries with poor environmental protection regulation, workers commonly experience a high exposure to these chemicals with consequent damage to their health.[13]
TheAmerican Conference of Governmental Industrial Hygienists has establishedthreshold limit values (TLVs) for most of these compounds. The TLV is defined as the maximum concentration in air which can be breathed by a normal person — i.e. excluding children, pregnant women, etc. — in the course of a typical Americanwork week of 40 hours, day-after-day through their work life without long-term ill effects. Globally, the most widely accepted standard for acceptable levels of VOC in paint isGreen Seal's GS-11 Standards from the US which defines different VOC levels acceptable for different types of paint based on use case and performance requirements.[14][15]
Due to their hazardous nature and environmental threat of damaging pollution —persistent organic pollutants from aromatic organic compounds that are resistant to degradation are often found in wastewater with poor handling and disposal resulting in them seeping into groundwater, contaminating public water supplies[16][17]— so in recent decades, laws from legislatures like theEuropean Parliament inEU regulations have extensively reduced the usage of these VOC solvents in favour ofwater-based paints — that is, using ones likeacrylic paints that have been reformulated to be made with water as the primary solvent, with only low levels of hydrocarbon solvents, if any — which perform in a very similar way as oil paints, but also are much less polluting, so have a much lower environmental impact.[18]
Paint thinners are often used as aninhalant, due to its accessibility and legality as a drug. Many teenagers become addicted to thinner and due to lack of knowledge, parents and caregivers do not notice it or give it much attention. By using paint thinner a person could experience hallucinations, sensitive hearing (for the first time), speech deformation, memory loss, etc.[19]
