Pigment is a chemical compound that changes the color of the dyed substance. This effect of changing the shade is based on a change in the composition of the base, as a result of which the wavelength of the light wave reflected from the painted object is adjusted. This physical process should not be confused with fluorescence, phosphorescence, and other forms of luminescence in which the material itself emits light.
What is pigment and how does it work?
Pigments are dyes. Unlike dyes, they consist of particles and are practically insoluble in the medium to be colored. The medium to be colored is the substance into which the pigment is introduced. In biology, the term "pigment" refers to all coloring substances in a living organism.
Pigments reproduce their colors because they selectively reflect and absorb certain light waves. White color is approximately equal to a mixture of the entire visible part of the light spectrum. When such a wave of light encounters a pigment, some of the waves are absorbed by the pigment's chemical bonds and substitutes, while others are reflected. This new spectrum of reflected light creates an appearance of color. For example, dark bluethe pigment reflects blue light and absorbs other colors.
It has become a little clearer what a pigment is, but we need to understand that pigments, in comparison with fluorescent or phosphorescent substances, can only absorb the waves of light they receive, but not emit new ones. Other characteristics of a color, such as its concentration or brightness, can be formed from other substances that interact with pigments. Pure dye transmits very few wavelengths of white light, providing rich color.
History
Naturally occurring pigments such as indigo, ocher, alizarin and iron oxides have been used as dyes since the prehistoric era. Archaeologists have found evidence that primitive people used them for aesthetic purposes, such as decorating their bodies. Between 350,000 and 400,000 years old pigments and tools for their production have been found in a cave in Twin Rivers, near Lusaka in Zambia.
Before the Industrial Revolution, the variety of pigments available for artistic and other decorative uses was limited. Most of the dyes used then were of natural origin. Pigments from non-traditional sources such as plant matter, insects, and shellfish were also produced and traded. Some colors were difficult or impossible to prepare using the available shades.
Rare color pigments were generally difficult to obtain, and technologytheir production was kept strictly secret by the inventors. Such a product was expensive and difficult to manufacture, and objects painted with it were a symbol of power and we alth.
Use of pigments
Different colors have been used for a long time and have been the main materials in the fine arts throughout history. The main natural pigments used are of mineral or biological origin. The need to obtain less expensive colors, given the scarcity of certain shades, such as blue, has led to the emergence of synthetically created substances.
Pigments are used to give color to paint, ink, glass, plastics, textiles, wood, cosmetics, food and other products. Most of them used in industry and in the arts are dry dyes in the form of finely divided powders. Such a composition is added to the "carrier" or "base" - a neutral and colorless material that acts as an adhesive. For industrial and artistic applications, permanence and stability are desirable properties.
Pigments, which, according to some physical characteristics, cannot be permanent, are called volatile. These types of dyes fade with time or exposure to ultraviolet light, while others eventually turn black.
How to choose a pigment?
The following are some of the characteristics of dyes that make them suitable for certain manufacturing processes and applications:
- Toxicity.
- Color power.
- Light resistance.
- Dispersion.
- Heat resistant.
- Opacity and transparency.
- Resistant to aggressive environments, including acids and alkalis.
- Reactions between mixed pigments.
The choice of pigment for a particular application is determined by its price, as well as the chemical properties and physical characteristics of the color substance itself. For example, a pigment used to color glass must have very high heat resistance to withstand the manufacturing process. On the other hand, a glass product must be durable so that it can be used, for example, in the transport industry. The resistance of glass to acidic or alkaline materials is not so important.
In artistic painting, heat resistance is less important, while resistance to light and aggressive environments is fundamental. Another example is the pigment used for pavement tiles. Such a color element must be resistant to fading and destruction under the influence of ultraviolet radiation and precipitation.
Some types and names of pigments
This will help you figure it out:
- Carbon pigments: carbon black, black ivory, black vine, black smoke. These are pigments often used in cosmetics. They are an excellent source of dark tint.
- Cadmium pigments: cadmium green, cadmium red, cadmium yellow, orange. These pigmentshave good resistance to acids and high temperatures.
- Pigments of iron oxides: red oxide, ocher, red ocher, Venetian red. Essential pigments for paints. Including mineral.
- Chromium pigments: chrome green, chrome yellow. Such pigments are widely used in painting. Very well proven in combination with acrylic.
- Cob alt pigments: cob alt azure blue, violet, cob alt yellow. Such substances are very durable and have high opacity. However, the price of this type of pigment is high.
- Copper pigments: Parisian green, verdigris, Egyptian blue. These pigments have been used since time immemorial in the painting and artistic fields. Nearly obsolete now due to their toxicity.
- Biological pigments: alizarin, alizarin-carmine, indigo, cochineal, tiropurpura, phthalocyanine. Universal pigments that are used everywhere: in everyday life, and in the food industry, and in the fine arts.
It can be said that pigments are widely used in the modern world.
