Until the mid-20th century, almost all paints used in America
could be divided according to the type of binder each had.
Chemists sought to improve paints, especially when the two
world wars made traditional paint components scarce and expensive.
Modern paints are far more complex chemically and physically
than early paints.
More ingredients have been added to the simple three-part
system of pigment, binder, and vehicle.
Fillers or extenders such as clay and chalk were put in to
make oil paints flow better and to make them cheaper as well.
Mildewcides and fungicides were prevalent and popular until
their environmental hazards were seen to outweigh their benefits.
New formulations, which retard the growth of the mildew and
fungi, are being used.
As noted, lead was eliminated after 1950 [after 1978]. Most
recently, volatile organic solvents in oil paint and thinners
have been categorized as environmentally hazardous.
A major difference in modern paints is the change in binder
from the use of natural boiled linseed oil to an alkyd oil
which is generally derived from soybean or safflower oil.
Use of synthetic resins, such as acrylics and epoxies, has
become prevalent in paint manufacture in the last 30 years
or so. Acrylic resin emulsions in latex paints, with water
thinners, have also become common.