Frequently Asked Questions
Careful preparation of the substrate is the most important factor for successful painting. Even if the preparation of the substrate requires much more time than the painting itself, it is worth the effort. For successful painting, the substrate should be clean, free of grease, rust, rot, without crumbling and firm.
If the old coating has deteriorated so that it has cracked or is mostly peeling off the substrate, it needs to be completely removed. Removal is performed in several ways, depending on the type of coating and substrate: mechanical, chemical or heat.
Resting of paint in the packaging usually leads to partial separation of the paint and the appearance of “liquid” on top. The paint should be mixed with a stick, until achieving a uniform mixture.
The optimal temperature for applying the paint is usually around 25 ± 5oC, at a relative humidity of around 65%. Solvent-based paints can be applied at lower temperatures but with slower drying. However, depending on the coating you apply, it is important to follow the manufacturer’s instructions.
Proper choice of tools facilitates painting. The brush is used for smaller surfaces, door and window frames, for wall corners and joints of walls and ceilings. The roller is used for large areas. In many cases, the paint can be applied with a gun, but the manufacturer’s specifications on the possibility of applying a specific colour should be followed.
Efflorescence is the appearance of white crystals or deposits on mortar, plaster or brick. Efflorescence increases in the presence of moisture. No paint should be applied to such substrate. The deposits should be removed and if they do not return within 14 days, the substrate may be painted. If re- efflorescence occurs, the surface should be sanded and moisture removed.
Synthetic fibre brushes are mainly used for water-based paints. They are not recommended for alkyd paints, because the paint stays on them and a less glossy coating is obtained. Brushes made of natural fibres are recommended for alkyd paint, but they are not recommended for water-soluble paint, because natural fibres can swell due to water absorption.
A quality brush has thick and long bristles, does not shed and facilitates the application of the paint.
The paint can adhere poorly if the substrate is wet, dirty, powdery, crumbly, improperly prepared or when inappropriate primer is used. If the paint adheres poorly, remove it completely, properly prepare the substrate and select the appropriate colours.
Paint dripping occurs on vertical surfaces due to excessive application of paint to the substrate being coated or the paint is too thin. It is necessary to check whether the paint is dripping during the application of the paint. If the paint has dried and has not diffused well, the surface should be sanded and re-coated.
Ripple occurs if a second coat of paint is applied over a previous coat of paint that has not dried. If the coating has rippled, it is necessary to completely remove it from the substrate and start painting again.
Brush marks appear if the paint dries quickly or is applied in a thicker layer. Sand the parts of the surfaces where traces are visible, using fine sandpaper so that the surface becomes smooth. Apply paint again.
The most common cause of slow drying of solvent-based coatings is poorly prepared substrate, use of inappropriate thinner or inadequate application conditions (low temperature or high humidity). With water-based coatings, slow drying occurs due to the application of paint in cold and humid weather conditions.
Swelling is defined as the undesirable separation of the coating from the substrate in the form of small or large bubbles. Blisters can occur if the coating is applied to a wet surface or is applied at high humidity. In places where bubbles appear, the coating peels off. Blisters also occur if the coating is applied at high air temperatures. Blisters that contain water are formed when water vapor penetrates through the pores on the coating, which condenses and “inflates” the coating. Surfaces that peel and where blisters appear should be sanded and re-painted.
It usually occurs when the paint is applied unevenly. It is necessary to sand the surface and apply another layer of paint.
Unpainted parts appear when the paint is applied to a surface that is stained with oil, grease or wax. To remove stains, it is necessary to dry the coating completely, and then sand the surface with waterproof sandpaper and warm water to which a little detergent has been added. The surface should be well rinsed and dried. Apply paint again.
Loss of gloss (matting) can occur if the coating is applied to a poorly prepared porous substrate or in conditions of high humidity. It is necessary to lightly sand the coating and apply another layer of paint.
The particles on the coating usually appear due to dust in the atmosphere during and after the application of the paint. Also, dirty tools can be the cause. It is necessary to dry the coating, and then sand and clean the surface. Reapply the paint.
Powdering (chalking) occurs due to the decomposition of the coating under the influence of atmospheric influences and air pollution. All coatings are characterized by chalking if they are exposed for a longer time to these effects than the one required for repair. Chalking can occur if an inappropriate paint choice is made, e.g. interior paint is applied to the exterior, etc. If the coating is a little chalky, remove the parts of the coating that are sprayed by wiping and re-apply the paint. If the chalking is more pronounced, completely remove the coating.
Cracking occurs on the surface of the coating and all the way to the substrate. Cracking can occur due to the use of old paint, if an inappropriate paint is selected, or if the paint is applied over a coating that has not dried completely. Completely remove the coating, clean the substrate and apply the paint again.
It is a property of a material that prevents or slows down the corrosion process by physical or physical -chemical means.
It is a continuous and relatively thin layer on the substrate, which is formed by single or multiple application of a coating agent or other film-forming material. The thickness of the coating film is measured with devices on a mechanical, optical or magnetic principle (Elcometar, Permascop, PIG device), and there are also electronic digital instruments with high precision. The thickness of the wet coating film is up to twice the thickness of the dry film.
By applying special coatings that contain metal pigments (eg aluminium) and create relief indentations during application and drying, creating the effect of wrought iron (Hammerschlag Effect) is achieved.
It is a special group of coatings, whose film does not have a uniform optical effect, and often neither a uniform nor a smooth surface. The surface of the film has special decorative effects.
A protection system is a group of products which, when used together, provides the substrate with protection in the intended conditions of exploitation and decorates it. The protection system usually consists of a base, interlayer and cover paint.
Trivial name for the basic paint for wood. Oil paint as a binder contains vegetable oils, such as soybean and linseed oil. This paint is usually dissolved in petrol for varnish.
Alkyd paint is a type of oil paint. Alkyd is the name for a synthetic resin based on vegetable oil, which is used as a binder.