Types of pigments for paints and application features
Pigments for paints are finely ground powders diluted with special substances, which are added to paints and varnishes. Multi-colored paints (colors) are made by mixing different pigments.
Pigmenting agents can be broadly classified as artificial and natural.
By the way, the latter can be divided into inorganic and organic, and there are not so many natural substances, but they are actively used in construction, because their use will be much cheaper than the production of artificial components ..
The following types of pigments can be used to obtain different colors:
- Yellow - ocher or crowns.
- White - lime, chalk or whitewash.
- Blue - azure or ultramarine.
- Red - mummy, red lead (lead or iron), and also cinnabar.
- Green - lead or chrome green.
Next, consider what types of pigments are, in more detail.
So, let's take a closer look.
Pigments made on a natural base are extracted from oxides and metals. Sources for obtaining dyes also include inorganic elements with such colors as:
Mineral-type dyes are characterized by a high degree of strength, are resistant to light, excellent miscibility and compatibility with binding components.
Characteristics of certain inorganic pigments:
Products with ocher are perfect for coloring wood, concrete and metal products. The pigment has excellent hiding power, strength and resistance to alkalis, as well as to light.
Sienna is resistant to alkalis, lime and is used in almost all types of paints. When mixed with oil, sienna gets glaze characteristics, and the compositions are also often used when finishing works on expensive wood species.
The pigment is extracted by fine grinding of iron ores. The substance itself is not poisonous, but its dust may contain toxins. Different grades of red lead are used to add to alkyd types of primers and paints and varnishes for special purposes (for painting ships and anti-corrosion compounds). Red lead also found application in oil compositions for coloring metal products that are located in the open air. The cost of manufacturing the element is small, and therefore it is used for enamels and glue paints.
The addition of umber allows the oils to dry much sooner, and the coloring agent is used to paint plaster, wood and metal products.
The pigment can be added to all kinds of pigments and chromium oxide is used for critical coatings in the chemical plant, pipe surfaces and equipment that are constantly exposed to high thermal stress.
Red lead is characterized by low resistance to all kinds of acids.
The component is used with binders in non-aqueous and aqueous formulations.The coloring agent is used for painting wood and metal products, as well as plastered surfaces.
In this case, the color is bright blue, and the substance is resistant to light, and also perfectly tolerates the effects of atmospheric precipitation, is characterized by high glazing and siccative properties. Cobalt blue is distinguished by its increased oil capacity and low hiding power.
Next, consider another type of dyes.
The pigments added to the dyes can be organic, in which case the organic is extracted from plants and insects.
These types of dyes, in contrast to the same mineral dyes, can dissolve in water, alcohol and oil. For organics, a lower degree of strength will be characteristic compared to mineral dyes, and since such pigments do not create a layer of paint, but fall into the surface structure, they are most often used when dyeing fabric. The most popular type of organics will be kraplak, which is extracted from the roots of krap or madder. Another plant-derived substance is indigo, which is obtained from woad. With modern industry, synthetic indigo can even be made.
Light brown pigments are obtained from sea molluscs, and black colorants are obtained from organic materials by calcining.
Coloring synthetic substances are distinguished by the maximum degree of resistance to moisture, atmospheric precipitation, light and gases. They are characterized by the brightness of colors, and due to this set of qualities, artificial pigments have long been able to take a leading place among other types of dyes. Synthetic pigments can be classified as mineral or inorganic. The latter dyes are produced through complex chemical reactions, and synthetic inorganic pigments are characterized by a constant chemical structure, pure and bright color.
Please note that the cost of manufacturing such components is quite expensive compared to natural coloring compositions. Used inorganic synthetics for the construction industry to make non-aqueous paints and varnishes.
Synthetic type mineral pigments are made by combining two or three components. According to the manufacturing method, such dyes can be divided into precipitated from metal solutions and salts or made by calcining.
It can be classified as inorganic synthetic dyes.
It contains sulfur and sodium aluminosilicate.Ultramarine is often used in the construction industry and in paints, non-aqueous and waterborne paints. Metal, concrete, wood and plastered surfaces are also painted with such paints. Ultramarine is rarely used in its pure form, and if it does, the goal is usually to neutralize the yellow color from chalk or lime. Ultramarine is also used as a glaze dye.
The pigment is resistant to alkalis and light. But the addition of a coloring agent to the mortar is undesirable, because in this case the substance will lose color. Ultramarine is suitable for interaction with all types of binders when performing external and internal finishing work.
This dye is characterized by a bright red color, but it can also be in dark tones. Cinnabar can be used to produce all types of paints and varnishes that are used to paint brick, concrete, wood and plastered surfaces.
It can be used for both interior and exterior finishing works.
A binder will be quite an important element of paints and varnishes component. Its function will be to combine pigment particles and fix them on the surface. Binders will also affect color because they differ in the refractive index of the light rays. An extremely important indicator for oil paints will be the oil absorption of the dyes.
This is an indicator of the amount of oil that will be needed to make paints for a certain level of pigment. The oil capacity indicator will depend on the total surface area of the particles, and moreover, on the physicochemical characteristics of the oil, which is used as a binder. Another significant indicator that pigments affect will be the drying rate of paints. Some pigments, such as white lead and cobalt, make the drying process more intense. Some pigments (kraplak, gas soot and others), on the contrary, will make drying longer.
Please note that the pigment for paints must correspond to the standard of a colored background, which will be determined by the structure of its particles, their capabilities for refraction, absorption of sun rays and reflection.
Another requirement for the pigment is the desired degree of dispersion. Such quality is understood as the degree of fineness, which is achieved by crushing by a mechanical method, settling, precipitation in a solution mixture (wet method) or due to heating in a special oven (dry method). The lower the dispersion index, the more transparent the paint and varnish material. The dispersion of the dye in certain paints determines their shade, for example, finely ground zinc white gives a blue tint, and sienna increases the saturation of tones.
In oil-type compositions, an increased level of dispersion will lead to a decrease in plasticity indicators.
Dispersion also affects another indicator of the pigment - the degree of hiding power. This characteristic shows the number of dye required per square meter of the treated surface. This will mean that the primer / surface to be treated will not be visible under the layer of material. The index depends on the internal structure of crystals, which are characterized by different refractive indices of light rays.
Dyes with low dispersion are in the base of body and opaque paints and varnishes, and pigments with a high index are included in glazing (that is, more transparent) paints and varnishes. Intensity, as a pigment characteristic, is the ability to change the tonality of the paint layer when interacting with other pigments. The highest intensity is characteristic of organic dyes with a high level of dispersion.
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