Lesson 21. Pigment

In this lesson we move on to the study of pigments — the key component of decorative material that determines its appearance. The entire variety of colors in decorative plaster depends precisely on pigments, which is why understanding their properties is especially important for the decorator. You will learn what pigment is, in what forms it is used when working with decorative plaster, and also become familiar with its nature and origin.

Pigment is a finely ground solid substance that gives color to paints, decorative plasters, and other materials. It does not dissolve in the binder but is distributed in it in the form of tiny particles, coloring the entire mass.

Pigment in the composition of the material has two main, inseparably connected functions. The first and most obvious is color — the ability to selectively absorb and reflect light waves, which we perceive as a particular shade (the wave nature of light will be considered in a separate part of our training course). The second, no less important function for the craftsman, is opacity: the ability of the coating to completely hide the color and pattern of the substrate on which it is applied. This ability directly depends on the type, size, and quantity of pigment particles in the composition.

In the work of a craftsman, pigments are encountered in two main forms:

• Dry pigments: This is pure, concentrated powder. A traditional method of tinting that requires thorough mixing. It is better suited for tinting mineral materials sold in dry form.
• Liquid colorants (pigment pastes): This is the most common and convenient method for manual or machine tinting, used everywhere today.

Liquid colorant is essentially the same dry pigment, but already pre‑mixed in a special liquid medium. This medium is not a binder. Its task is not to form a film but only to ensure even distribution of pigment particles and their good compatibility with the main paint or plaster. That is why pure liquid colorant cannot be used to paint anything: after the liquid dries on the surface, only unbound pigment powder remains, which will rub off at the first touch.

Now that we understand what pigment is and what it is responsible for, let us look at their main types, which determine the durability of color and the opacity of your future coating.

All pigments are divided into two large groups, differing in their origin and behavior in decorative material — inorganic (mineral) and organic (synthetic). This division resembles the classification of binders, where we also distinguished mineral and polymer components. Understanding the difference between these two types of pigments is of great importance for the craftsman, since they differ in color, opacity, lightfastness, alkali resistance, and other characteristics. We begin with inorganic pigments — the traditional and most stable option.

1. Inorganic Pigments (Mineral)

These are the oldest pigments that humanity has used for thousands of years, from cave paintings to modern decorative finishes.

Inorganic pigments are essentially colored “stone dust.” They are obtained by finely grinding natural minerals or synthesizing their analogs — oxides and salts of various metals (iron, titanium, chromium, cobalt). Their chemical structure is simple and very stable, like stone.

Main representatives:

• White: Titanium dioxide — the king of white pigments. This is the main white pigment in the world of paints, decorative plasters, and other coatings. It is called the “king of white pigments” thanks to its exceptional whiteness, high opacity, and lightfastness. It does not yellow over time, does not react with other components, and is suitable for almost all systems — from water‑based to solvent‑based.
• Black: Carbon black (technical carbon) and black iron oxide are the two main black pigments used in decorative materials.

1. Carbon black can be classified as an inorganic pigment because industrial carbon black (its purified form) consists of 99% pure elemental carbon. Carbon is an inorganic element. It is distinguished by its deep, saturated color, good opacity, and stability. Thanks to the microscopic particle size, the pigment disperses easily in all systems — from water‑based to solvent‑based.
2. Black iron oxide is an inorganic pigment that is slightly inferior to carbon black in depth of color but surpasses it in lightfastness, alkali resistance, and heat resistance. It is excellent for facade decorative coatings, plasters with alkaline reactions (lime or cement‑based), and materials requiring high durability and color stability under sunlight.

• Yellow, red, brown: This entire range consists of iron oxides, known as ochre, red lead, umber, sienna. Depending on chemical composition and degree of hydration, the same metal (iron) produces a palette of natural shades. Simply put, all these colors are based on ordinary “rust” in its various forms.
• Green: Chromium oxide — the main inorganic green pigment used in decorative coatings where high color stability is required. It gives a characteristic “muted,” natural green shade reminiscent of moss. The pigment is obtained by high‑temperature oxidation of chromium compounds, resulting in fine, chemically stable particles. Chromium oxide is highly lightfast, heat‑resistant, and alkali‑resistant.
• Blue: Ultramarine and cobalt pigments — two classic inorganic pigments used to obtain stable blue shades in paints and decorative plasters.

1. Ultramarine is a historic pigment originally obtained from the semi‑precious mineral lapis lazuli. Today it is produced synthetically from components at high temperatures. It provides a rich, “warm” blue color, often with a violet tint.
2. Cobalt pigments, particularly cobalt blue, are obtained from cobalt and aluminum salts through sintering. They produce “cooler,” deeper, and purer blue tones, with high lightfastness and chemical stability.

Inorganic pigments are a reliable foundation in working with interior and facade decorative materials. Their environmental friendliness, resistance to light, moisture, and alkaline environments makes them indispensable for tinting lime, cement, and other mineral coatings. They do not fade, do not change color over time, and ensure a uniform shade for many years. But despite all their advantages, they are limited in palette: you will get natural, calm tones, but you cannot create bright, saturated, or neon shades. Therefore, working with inorganic pigments is always a balance between ecological durability and expressiveness of color.

2. Organic Pigments (Synthetic)

These are modern pigments, born in chemical laboratories. Their appearance created a real revolution, giving us colors that could not be obtained from natural minerals.

Organic pigments are complex synthetic compounds based on carbon. Unlike mineral pigments, their molecules consist of complex and long carbon chains and rings. This complexity simultaneously gives them incredible brightness but makes them vulnerable to aggressive influences.

Unlike inorganic pigments, which are classified by the metal at their base (iron, chromium), organic pigments are better considered by color groups, since their chemical names are too complex and do not provide practical information for the craftsman.

• Red, pink, orange: Organic pigments make it possible to obtain the purest and juiciest shades that cannot be created with iron oxides: from scarlet and orange to fuchsia and magenta. They have exceptional brightness but often fall short in opacity and lightfastness compared to inorganic analogs.
• Yellow and green: Organic synthesis gives us the purest lemon‑yellow and light green shades, which cannot be achieved with ochre or chromium oxide.
• Blue and violet: Phthalocyanine blue is one of the most popular organic pigments in the world. It provides a very pure, bright, and saturated blue color, which has become the basis for most modern blue paints.

Organic pigments are the key to creating bright, modern, and expressive interiors. Their almost limitless palette allows any design idea to be realized. However, this brightness comes at the cost of durability and resistance. They are sensitive to UV radiation (fade), degrade in alkaline environments, and often have lower opacity. Therefore, working with organic pigments is a choice in favor of maximum color brightness for interior work on chemically neutral binders (polymers).

After becoming familiar with the nature of pigments and their main properties, we can move on to the next lesson and consider which varieties are used in working with decorative materials.