As it follows from dictionaries and encyclopedias, mineral paints are inorganic compounds obtained either directly from minerals or artificially, as a result of chemical processes.
The word mineral means a natural chemical compound, a component of rocks and ores, occurring both as a solid and as a liquid (mercury, water).
The earliest paints were clays of different colors, chalk, natural yellow and red ochre (yellow and red mixtures of iron oxides with clay), coal, and soot.
Let’s define what mineral paint means in the modern sense.
Paint is a suspension of pigments and fillers in binders.
Paint composition includes at least the following components:
- Dyes are soluble organic (natural or synthetic) compounds used to make transparent colored varnishes, stains, and so on;
- Pigment – finely ground insoluble colored powder (mineral, synthetic, metallic), which with the help of a binder adheres to the surface;
- Fillers (organic and inorganic) – insoluble mineral substances that save pigments and give the composition certain qualities (strength, fire resistance, texture, and other properties), it may be fine kaolin, talc, rocks, and others;
- binders (water and non-aqueous compositions, emulsions) – are the basis of almost all paint-and-lacquer compositions, are used in the form of solutions, and are intended for binding pigment and filler particles to the surface; in some compositions, it is the only protective layer
- Solvents or thinners – liquids used to thin or dilute paint to the desired consistency.
According to reference books, mineral-based paint compositions include:
It turns out that it is not the pigment that makes the paint “mineral”, but the base. By the way, the most widespread classification in the construction industry combines the paint compositions by type of binder, but not by pigment.
Mineral lime paints are mostly used for exterior applications.
They are based on slaked lime, and the addition of alum or table salt increases the durability of the paint. Pigments used are alkali-resistant (mumia, minium, ochre, soot, sienna, umber, and others), and they must be used in the form of pastes of the consistency of sour cream, pre-moistened in water. Only in this form, they should be introduced into the paint composition.
Color palette – pastel, bleached. Hiding power determines the consistency of the solution and the number of layers.
They are not durable, their lifetime is 1-2 years. Easily washed off and reapplied.
Service life can be increased up to 4 years if the technology is followed:
- Clean and repair the surface,
- Prim it with a brush (paintbrush), rubbing the same, but more liquid lime compound (milk of lime) into all the cracks and pores,
- Apply the main coat of paint with a brush or spray gun.
Cement and polymer cement paints
Cement mineral paints are used for work on stone, concrete, brick, and plaster.
They are made on the basis of white cement, slaked lime, and calcium chloride (for the acceleration of setting) with the addition of hydrophobizing components that increase water repellency. As in the lime compositions, they use alkali-resistant pigments soaked in water.
Such compositions are applied only to unpainted surfaces. The old paint layer is removed and the walls are cleaned with hot water or 3% hydrochloric acid.
Polymer cement mineral paints are designed for painting concrete, aerated concrete, stone surfaces, plaster, asbestos cement products, wood fiber boards, metal, and wood.
Available in paste or liquid, ready to use. The composition includes white cement, pigments, lime, PVA, or latex. They differ from cement ones in elasticity, greater weathering resistance, and good penetrating ability.
Silicate paints are used for facades and interiors. They can be used on any surface with a mineral base. The coating is heat-resistant, fireproof, and resistant to atmospheric influences and UV rays, at the same time it has good air and vapor permeability.
According to the standards, silicate paints are a suspension of fillers, alkali-resistant pigments, and silicification agents* in an aqueous solution of liquid potassium glass. When applied to the surface, it creates a decorative and protective waterproof coating that penetrates the surface structure.
When Zn-dust or Al-powder is added as pigments the surface treated with such paint acquires anticorrosive properties.
The possibility of using additives and fillers (inflated perlite, ground chamotte, glass and others) allows you to create a variety of textured surfaces. But the use of special dyes limits the palette of colors.
A peculiarity of silicate compositions is the labor intensity of their application, compared to cement and lime compositions. Paints are available in two packages: potassium glass – in containers, and a mixture of fillers, and pigments – in bags. Components are mixed just before the painting. Special requirement is made to the working surface: it must not have old coatings, it must be primed with silicate paint or silicate primer.
In foreign practice, a four-layer surface treatment is applied: an etching, a primer, and two layers of decorative coating. When complying with this technology lifetime of the coating is about 20 years.
It is the silicate paint in foreign brochures called mineral paint.
Having considered the properties of mineral paints, it is impossible to ignore their significant component – pigments, especially since their certain qualities influence the properties of the paint composition with the same binder.
Natural mineral dyes are obtained by grinding rocks and minerals to powder form, in some cases, by subjecting them to heat treatment.
Here are some of nature’s pigments:
- Chalk is the best white pigment. It is used in aqueous, silicate, and adhesive compositions; it is the main filler in putties and putties; it is mixed with all types of dyes.
- Ochre – the range of colors of this natural pigment – from yellow to yellow-brown. Depending on the brand it is used in different paint compositions. Thermal processing makes burnt ochre brownish-red and dense, increasing the hiding power of paint. slit-resistant.
- Mumia is a yellow-brown-red mineral, it is produced in light and dark variants, it is used in gluey and lightfast oil paints.
Natural Sienna is a gray-brown-orange color; when heated strongly, sienna burns to auburn, the hiding power is low, and the coating is transparent. Acid-resistant.
- Iron Sulphur – a pigment of brown with a red tint. Available in different grades for different binders. Resistant to weathering, has good hiding power on all surfaces due to the presence of clay.
- Natural Umber is a brownish-greenish pigment, which turns red-brown when heated, and increases hiding power. It is used in all painting compositions, it is mostly applied in mastics and primers.
- Graphite gray is a dark gray to black color mineral. Black pigment with good coloring ability. Lightfast, flame retardant, chemically resistant – used as an anti-corrosive coating.
Today, mineral paints with natural dyes are the most environmentally friendly: compared with other paint compositions, they contain a very small amount of volatile organic compounds.
Hiding power – the ability of the pigment to hide the painted surface under the layer of the paint film; it is determined by the quantity of grams of the paint applied per 1 m2 of the surface.
Silicification agents are active substances penetrating deeply into the painted surface and reacting thereby forming water-soluble compounds. This leads to the clogging of pores, which results in the formation of watertight structures.