Many construction works are inextricably linked with such a type of finish as putty coating. And when it comes to a non-new building or premises, then often there is already a layer of paint on its walls. Then a logical question arises: is it possible to apply putty on the paint? The answer to it depends on what type of paint you are dealing with.
How to determine the type of paint on the walls
To determine the type of paint applied to the surface, a simple test is carried out - soak it with a sponge soaked in warm water. If it is covered with foam and begins to wash off, then this is a water-based paint; when putty is applied under the influence of moisture, it will definitely come off in layers.
Apply to such a coating putty pointless, which means that it will have to be removed completely. This is done simply: the surface is moistened with a sponge or a spray gun with ordinary water and left for 10-15 minutes. After that, the paint can be easily removed with a spatula, and the surface can be wiped with a damp cloth and dried.
If, after moistening, the color coating does not come off, then it is an enamel based on drying oil or other non-aqueous solvents. Puttying on oil paint is possible after appropriate preparation, if, of course, the painted layer is well-kept. To check this, scratch the surface with a metal spatula in several places. If the paint comes off in layers and falls off, it should be scraped off.
Ways to remove paint from a wall
Distinguish the removal of the colored layer by chemical, thermal and mechanical methods. The first method is associated with the use of special compounds that soften the enamel to such an extent that it can be easily removed with a spatula. This method is inconvenient only because the product consists of toxic solvents, that is, they can only be used in a room with good ventilation. By the way, a household replacement for such a tool can be, in extreme cases, a solvent.
The effectiveness of the thermal method is due to the property of the old layer of paint to soften when heated. The paintwork is heated with a building hair dryer or a soldering iron, after which the paint begins to bubble and melt, and then removed with a spatula.
Tip: in the absence of a building hair dryer, you can use a blowtorch, but this is much more dangerous and requires strict adherence to safety measures.
Mechanical methods can be varied and quite unusual. You need to start with an ordinary peeling off a layer of paint with a spatula. Of course, this work is labor-intensive and highly dusty, so if the coating does not peel off over the entire area, but only in certain places, it is better to clean them up. The rest the surface is treated with a primer.
If the layer is too firmly attached to the surface, use a metal brush to scratch the coating with it - this will help increase adhesion before filling. Another option is if there are no voids under the paintwork, make notches with a sharp object (for example, an ax) (the main thing is that their depth reaches the surface under the paint).
This contributes to a better adhesion of the solution to the surface when puttying is done on the paint. For the same purpose, paint stripping with coarse-grained emery is used manually or using grinder.
Tip: after such processing, be sure to brush off the resulting dust layer from the surface.
What to do if the paint cannot be removed
If it is not possible to remove the paint, a special primer is used, which contains microscopic particles, it is they who improve the adhesion of the base to the putty. Quartz sand is often used as such particles, the liquid component of the agent has the property of penetrating deeply into the paint layer, while simultaneously connecting with it. A similar primer designed to cover smooth surfaces is called Concrete-Contact. Its main purpose is to provide a smooth plane with roughness that will facilitate the application of putty.
If there are cracks in the coating, they are “embroidered” with a spatula, that is, the peeling paint, as well as the plaster under it, is removed to a durable coating. In the process, large recesses may form, they need to be leveled with putty over the paint layer, and then, after preliminary priming, begin leveling the entire surface.
After applying the primer with a roller or brush, it is advisable to make plaster mesh installationwhich will make the job much easier. It is especially necessary if the future plaster layer on the walls exceeds 10 mm.
How putty is applied to paint
Further actions are identical to those performed when leveling and finishing a conventional plastered surface. However, there are also specific features of this work.
- With a significant deviation of the wall from the level or the presence of serious defects, the surface is first leveled with a starting putty, which has a coarse-grained structure;
- The putty on the treated paint will hold on stronger if it is applied in several layers, the thickness of which is up to 2 mm. Each subsequent layer can be applied after the previous one has completely dried;
- After the final drying of all layers, the surface is cleaned with a sandpaper or a special mesh so that the sags and traces of the spatula can be removed.
After that, according to the same principle, finishing putty. After the last layer has dried, it is also sanded to a perfectly smooth surface. This operation is especially relevant if painting is to be done.
As for the plastering technology, first a small part of the solution is sprayed on to form a reliable base. When this base dries, proceed to the main leveling procedure with a plaster rule or trowels.
At the final stage, a primer is applied to the walls. After that, you can paint them or wallpapering.
By following all these recommendations, you will quickly forget that a perfectly even layer of putty hides a peeling coating underneath.
