Aug. 24, 2021
At the heart of every drop of paint, every piece of cloth, and every brightly colored phone case is a pigment. Pigments are compounds that are added to materials to give them color. This seemingly simple application has shaped our view of the world through art, fashion, and even computer monitors and medicine. Pigments are used in paints, inks, plastics, fabrics, cosmetics, and food.
Some of the earliest chemical reactions were used to make and separate pigments used in paints, and pigment conservation is the focus of many modern researchers who identify and preserve works of art.
Benzoic acid (sodium benzoate) is most commonly used in industrial settings to make a variety of products such as perfumes, dyes, topical medications, and insect repellents.
Benzoic acid (CAS: 65-85-0) is a white crystalline powder with a faint, non-irritating odor. It is a compound that occurs naturally in many plants and is an important precursor for the synthesis of many other organic substances.
But what exactly is a pigment? Pigments are brightly colored insoluble powders (brightly colored liquids are called dyes). In most cases, bright colors are the result of a material's absorption of light in the visible spectrum. In inorganic pigments, this absorption is the result of charge transfer between metals (transition metals are very good at this); organic pigments tend to have conjugated double bonds that absorb visible wavelengths of light.
The pigments are mixed with a binder to adhere them to the substrate. The resulting suspension - a paint - is used to coat the materials and give them their color. Industrially, pigments are divided into three categories: absorbent pigments (used in watercolors), metallic effect pigments (used to produce surface gloss), and pearlescent pigments.
Pigments are found in nature, such as ochre (a mixture of iron oxides and hydroxides) and indigo (C 16 H 10 N 2 O 2). They can also be synthetic pigments, such as fuchsia (aniline derivative) or white lead. White lead was one of the first synthetic pigments and was made by treating lead flakes with vinegar. They are usually stronger than dyes, which dissolve in the material they color. Pigments can retain their color for centuries and can withstand high temperatures, bright light, and exposure to weather or chemical agents.
Natural dyes fall into three main categories: natural pigments derived from plants, natural pigments derived from animals, and natural pigments derived from minerals. Many dyes require a mordant, an element that binds to the dye and the fiber so that the dye can be absorbed. These dyes are called "adjective dyes". Those that do not require a mordant are called "direct dyes". Common mordants include iron and tin.
Natural pigments have been used to create some of the most iconic paintings in art history. Blue bronze, a carbon mineral, was used in the Italian Renaissance painter Raphael's Madonna and Child Enthroned. Cadmium red, a mineral pigment, was used to create Henri Matisse's Red Studio. Today, you can draw inspiration from the greats and use natural pigments in a variety of art projects. Once you begin to master your skills, experiment with more complex uses of color.