Why can liquid wallpaper swell? Part one. The reasons

In practice, for more than 16 years of work, we have had to deal with various situations, including problematic ones. They can occur both when applying liquid wallpaper by beginners and professionals. And today we will consider such a phenomenon as swelling of liquid wallpaper. We will deal with the reasons for its occurrence, and also consider the methods that can be used to avoid such situations.

How does swelling manifest itself?

Swelling looks like a bubble on the surface of applied and smoothed liquid wallpaper. This bubble always appears on the surface of not completely dried liquid wallpaper. When pressed, even on a dried bubble, it sags. At the same time, there is always a feeling similar to breaking through a fragile eggshell. Why this happens, we will consider a little later. Such a bubble on the surface can be either a single one, or the entire surface can be covered with such bubbles. On the surface of liquid wallpaper, which has dried up, and one that has been in operation for a long time, such a phenomenon has never been observed before.

What is useless to do when bubbles occur?

Those who have not encountered such a phenomenon before, first of all decide to soak the liquid wallpaper, giving it additional plasticity, and try to smooth it out, thereby smoothing the bubble, or even pressing it down. This will only be a waste of time and effort. And why exactly, you will understand after considering the causes of bubbles.

Bubble anatomy

Most clearly, the structure of the bubble, and hence the determination of the cause of its occurrence, can be considered after it has completely dried. When opening any, and I emphasize this, any of my bubble practice, we observed the following picture: The layer of dried liquid wallpaper is firmly, as it should be, held on to the putty layer.

1. The putty under it is either still wet or already dried, similar to an eggshell.

2. Next, we see an empty air space behind the putty layer, separating the putty from the base on which this putty was applied. It was this empty space that created the volume of the bubble. And, it was the exfoliated putty that, when pressed on the bubble, gave the feeling of a breaking shell.

3. The base on which the putty was applied can be: a concrete slab, cement-sand plaster, another layer of putty, etc. We have always observed the following picture: if you run your finger over such a base, the finger is covered, one might say, with white powder or white dust. The main thing for us is that the finger always gets dirty.

That's exactly the fact that the base, from which the putty has exfoliated, gets dirty - and this is what we were looking for. It turns out that the putty was not placed on a clean, dust-free base bonded with acrylic primer, as required by the technology. If we draw a parallel with the gluing process, it turns out that the putty was glued to a dirty, dusty surface. And what happens in this case, I think everyone understands perfectly. It is a well-known fact that if the surfaces to be glued are not degreased, dirt is not removed, then gluing will not work.

In finishing work, there is an immutable rule: before any next stage of finishing work, it is necessary to cover the surface with acrylic primer - before applying a new layer of plaster, putty, before painting or applying liquid wallpaper. It is acrylic primer that acts as an agent that binds dust on the surface. It impregnates and binds the particles of gypsum putty, preventing them from "limp" under the influence of water. It is the primer who provides the binding of particles and layers, makes them resistant to water.

The reasons

And so, considering the totality of the material obtained during, let's call them so, "field studies", we get the following picture. When applying liquid wallpaper with a standard layer, 1.6-1.7 liters of water are applied per square meter of the surface to be coated. Part of this water remains on the surface in the fibers of the liquid wallpaper itself. It is this majority of the water that will evaporate in 48 hours with standard drying. At the same time, some of the water will still be absorbed into the putty. The amount of water absorbed will depend on the composition and thickness of the putty layer, and the concentration of the primer with which it was treated.

If the surface is prepared according to the technology, then the putty layer (or layers) will absorb water, but, being properly treated with primer, they will not lose their bonding properties.

If, at any stage, the primer was applied with gaps, or was heavily diluted with water, or not applied at all, then as a result, the putty is guaranteed to peel off under, the influence of water.

Another reason may be poor-quality removal of whitewash from the surface on which the putty was applied. About 30 years ago it was used in finishing works. The fact is that whitewash is chalk powder diluted in water. Not completely washed off whitewash is, in fact, the dust that remains on the surface. And there is not a single agent that can bind it into a monolith, so the whitewash must be washed off in the most thorough way. If this has not been done, then even the highest quality primer treatment will not help. And if putty is applied to it, it is guaranteed that delamination will occur in the form of bubbles.

In both cases, this is inadequate surface preparation for applying putty and the result will be the same - bubbles.

How to avoid the possible occurrence of bubbles on liquid wallpaper, as well as how to correctly repair damaged areas, read our next article on this extensive topic.