Paint application: the most common mistakes

Recommendation points

• Foundation preparation
• System selection
• Application of paint and varnish coatings
• Tinting paint
• Exploitation

The last decade in the Russian construction market has been marked by the active appearance of a large number of new building materials and technologies. Their appearance has changed both the very approach to the execution of work, and the general trends in the decoration of interiors and facades. For example, the painting of walls and ceilings has become relevant again, but at a higher technological level. This is ensured, first of all, by the qualitative improvement of the decorative and operational properties of paint and varnish coatings and the expansion of the types of bases for painting..

Domestic builders have to master new, advanced technologies on the fly, often learning from their own mistakes. Unfortunately, there are practically no specialized training centers, competent sales support and technical support. As a result, when performing work, elementary technological rules are violated, and builders expect that high-quality finishing material will cover all the flaws of the preparatory stages of work. However, the statistics of paintwork complaints show that:

• about 70% of all causes of defects are improper preparation of the substrate,
• about 15% – wrong choice of paint system,
• about 10% – non-compliance with the application technology
• and only 5% – poor quality paint.

Foundation preparation

Before starting work, the painter must assess the quality of the substrate. For this, visual inspection is primarily used. At the same time, the type and condition of the base material, visible damages are determined, technological errors in its implementation are revealed. The type and composition of the base allows you to assess its effect on the coating and choose the right paint system. The base can be made of organic or inorganic materials, have a porous or dense structure. In addition, it is necessary to assess how clean and dry it is, there should be no form release agent on the concrete bases. By tapping on the plaster, possible voids or delamination are detected. If an old paintwork is used as a base, then its strength can be determined by testing with masking tape: it is necessary to stick it to the surface, and then tear it off sharply. If the coating is not broken, then its strength is sufficient.

It is very important for the correct performance of the work to check the absorbency of the substrate. For this, surface moistening is used. Depending on the rate of moisture absorption, they are distinguished: highly absorbent, normally absorbent and weakly absorbent bases. If water quickly goes into the base, then when applying water-thinned compounds, the film formation process is disrupted and the coating will not gain sufficient strength. Therefore, in this case, it is necessary to use special primers..

A serious problem is the uneven absorbency of different areas of the substrate. This can happen when different materials are used in the substrate. If this difference is not eliminated, then the transition boundaries will be noticeable on the finished paintwork. And if, as a result of inspection, chalking or crumbling of the base is revealed, then the presence of such a defect can lead to the fact that the topcoat will peel off along with the top layer of the base. When identifying such properties of the base, it is necessary to use special primers for them. They should be non-pigmented and finely dispersed, sufficiently liquid and well to penetrate the capillaries, not dry very quickly, provide adhesion for subsequent coatings, and not form a thick film. When applied, such primers should not form a glossy film. It is not necessary to treat surfaces with normal and uniform absorbency with special primers; it is enough to apply paint with a small addition of water (the percentage of dilution is usually indicated in the description). The final coat can then be applied without thinning. Substrates that are poorly absorbent are treated with pigmented primers that have a particularly high adhesion or form chemical bonds with the substrate. They are applied in a sufficiently thick layer and serve as a bonding bridge between the base and the next coating.

For decorative and gypsum plasters, primers are used with the addition of fine quartz sand. Then there is no need for outdated methods of improving the adhesion of the decorative layer to the base – applying notches or attaching a special mesh.

System selection

Choosing the right paint system will ensure optimum durability while avoiding unnecessary costs. The most common choice is between acrylic, silicate and silicone systems. When choosing a particular system, it is necessary to take into account the operational requirements for the coating, their physical properties, as well as the peculiarities of color design..

Acrylic dispersion paints contain acrylic polymers or copolymers as binder. Systems based on them are suitable for almost all substrates used in construction. Acrylic paint coatings have good vapor permeability, i.e. allow the base to “breathe”. Under normal operating conditions, they provide an optimal price / quality ratio. In addition, such coatings offer the greatest possibilities for the color design of surfaces..

In silicate-based materials, liquid potassium glass is used as a film-forming glass, which is obtained by joint melting of potash and quartz, followed by dissolution of the resulting product in water. This binder belongs to the mineral. Film formation, unlike acrylic paints, occurs as a result of a two-step chemical reaction. Silicate paints are mainly used for painting mineral substrates, such as concrete, sand-lime bricks, etc., as well as surfaces previously painted with mineral paints. They have the highest permeability to water vapor and carbon dioxide, therefore they are the optimal solution for painting old buildings and architectural monuments..

An important property of silicate coatings is that they do not support the development of microorganisms and therefore do not require special biocidal additives. However, the high alkalinity of the paint makes it necessary to protect glass, aluminum, natural stone from splashes during application, which can leave indelible stains. For tinting, it is necessary to use only alkali-resistant and resistant to liquid potassium glass pigments, therefore the color range of silicate materials is very limited.

Silicone paints are among the most modern paints. They combine almost all the best properties of acrylic and silicate paints. First of all, it is a high permeability to water vapor and carbon dioxide (for silicone paints these indicators are close to silicate ones), but with a high water-repellency of the surface. They are suitable for almost all types of mineral surfaces and are well compatible with both mineral and synthetic paints. Silicone coatings, like silicate ones, do not support the growth of microorganisms. Therefore, they do not need the use of special fungicidal and algicidal additives..

Silicone paints currently have the best decorative and operational properties of coatings. The only drawback limiting their use is their high cost..

Application of paint and varnish coatings

As you know, the main functions of paint and varnish coatings are decorative and protective. Good hiding power and whiteness provide rather decorative functions. But in order for the coating to fulfill the requirements for moisture resistance, abrasion resistance, resistance to climatic influences, it is necessary to achieve a certain thickness of the dried film. For facade coatings, this is usually 100 – 120 microns, that is, approximately 200 ml of paint per 1 m2. The application of thinner layers leads to defects in the paintwork and, in the future, to damage to the enclosing structures..

If using liquid paints to obtain a thick film on vertical surfaces, a minimum of 4-5 coats will be required. If you use high quality, thixotropic paints, then such a coating can be obtained in one pass. (Thixotropic paints have a thick consistency in a calm state, under mechanical stress they liquefy, and after removing such an effect they again acquire a jelly-like consistency). In addition, thixotropic paints allow using the most progressive and productive airless spray method for painting – Airless.

Tinting paint

Tinting paint is one of the most important and very topical issues. For tinting, you can use both manual and computer tinting. Computer tinting is most convenient for builders, it requires a minimum of labor costs, especially when performing large amounts of work. For high-quality tinting, the material must have a very precise dosage both in volume and in individual components. Well-designed bases allow for accurate color matching, regardless of the amount of paint to be tinted, and guarantee the performance of the declared properties of the coating.

For small volumes, manual tinting is still relevant. Here you can choose between solid colors and universal pigment pastes without binder. Universal pastes can be used to tint both water-borne paints and solvent-based enamels. However, with the illiterate use of pigment pastes, the balance between the amount of binder and filler can easily be upset and, for example, instead of an abrasion-resistant coating, a surface that gets dirty when rubbed dry, or an easily fading coating can be obtained. The use of full-color paints containing a binder is possible only for materials with the same binder. But the reliability and quality of this method is higher, so they are preferable for manual tinting..

Exploitation

During operation, it must be borne in mind that there are no eternal paint coatings. Protecting the base from harmful influences, it wears out. However, a properly applied coating will provide a quality coating with a long service life. The service life of coatings depends on many reasons: this is the application technology and the effect on the coating during operation. For example, facade coatings on acrylic II serve 8-10 years, and under sparing conditions – much longer (for example, the facade is in the shade or is covered by a visor). But if all the technological aspects were observed during the work, then the coverage update can be performed without large financial costs. As a result, painted structures will serve for a long time and not create additional problems for their owners..

Therefore, starting a new construction, it is wiser to immediately perform all stages of work with high quality, without falling into excessive savings. This will allow you to avoid significant costs later on repair and restoration work.