Paint
Some cave paintings drawn with red or yellow ochre, hematite, manganese oxide, and charcoal may have been made by early Homo sapiens as long as 40,000 years ago.
In 2003 and 2004, South African archeologists reported finds in Blombos Cave of a 100,000-year-old human-made ochre-based mixture that could have been used like paint.
[6][7] Further excavation in the same cave resulted in the 2011 report of a complete toolkit for grinding pigments and making a primitive paint-like substance.
[7][8] Interior walls at the 5,000-year-old Ness of Brodgar have been found to incorporate individual stones painted in yellows, reds, and oranges, using ochre pigment made of haematite mixed with animal fat, milk or eggs.
The works are located in cave-like rooms carved from the cliffs of Afghanistan's Bamiyan Valley, "using walnut and poppy seed oils.
The Flemish-trained or influenced Antonello da Messina, who Vasari wrongly credited with the introduction of oil paint to Italy,[14] does seem to have improved the formula by adding litharge, or lead (II) oxide.
It was only when the stimulus of World War II created a shortage of linseed oil in the supply market that artificial resins, or alkyds, were invented.
This is the proportion of the wet coating weight that is binder, i.e., the polymer backbone of the film that will remain after drying or curing is complete.
Classic nitrocellulose lacquers fall into this category, as do non-grain raising stains composed of dyes dissolved in solvent.
The paint type known as Emulsion in the UK and Latex in the United States is a water-borne dispersion of sub-micrometer polymer particles.
The film formation mechanism of the simplest examples involves the first evaporation of solvents followed by a reaction with oxygen from the environment over a period of days, weeks, and even months to create a crosslinked network.
Recent environmental requirements restrict the use of volatile organic compounds (VOCs), and alternative means of curing have been developed, generally for industrial purposes.
[25] So-called "catalyzed" lacquers" or "crosslinking latex" coatings are designed to form films by a combination of methods: classic drying plus a curing reaction that benefits from the catalyst.
For example some decorative pigments protect the substrate from the harmful effects of ultraviolet light by making the paint opaque to these wavelengths, i.e. by selectively absorbing them.
When MIO pigments are ground into fine particles, most cleave into shiny layers, which reflect light, thus minimising UV degradation and protecting the resin binder.
[32] Besides the three main categories of ingredients (binder, diluent, pigment), paint can have a wide variety of miscellaneous additives, which are usually added in small amounts, yet provide a significant effect on the product.
Car manufacturer Nissan has been reportedly working on an electrochromic paint, based on particles of paramagnetic iron oxide.
When subjected to an electromagnetic field the paramagnetic particles change spacing, modifying their color and reflective properties.
Gouache is an opaque variant of watercolor, which is based around varying levels of translucency; both paints use gum arabic as the binder and water as a thinner.
As a solid (usually used in industrial and automotive applications), the paint is applied as a very fine powder, then baked at high temperature.
In a gas phase application, the coating composition is introduced (if gaseous), vaporized (if liquid) or sublimed (if solid) then deposited on a distant substrate, often under vacuum.
Dipping used to be the norm for objects such as filing cabinets, but this has been replaced by high-speed air turbine-driven bells with electrostatic spray.
Defects or degradation can be attributed to: Volatile organic compounds (VOCs) in paint are considered harmful to the environment and especially for people who work with them on a regular basis.
[54][55] In the US, environmental regulations, consumer demand, and advances in technology led to the development of low-VOC and zero-VOC paints and finishes.
These new paints are widely available and meet or exceed the old high-VOC products in performance and cost-effectiveness while having significantly less impact on human and environmental health.
A polychlorinated biphenyl (PCB) was reported (published in 2009) in air samples collected in Chicago, Philadelphia, the Arctic, and several sites around the Great Lakes.
PCB is present in consumer goods including newspapers, magazines, and cardboard boxes, which usually contain color pigments.
This assessment is driven by accumulating evidence that underscores the role of paint as a significant contributor to microplastic pollution.
Further, a 2022 study by Environmental Action revealed that approximately 58 percent of the microplastics found in oceans and waterways could be traced back to paint.
Efforts to mitigate this environmental issue have spurred the development and exploration of alternatives to plastic-based paints, such as those derived from linseed, walnut, milk, and limewash.
