Yellow spots. Causes, methods of correction and prevention

This topic is especially interesting because it has already managed to acquire myths and conjectures. But then we like to understand the essence of the issue, and we will not miss such an important topic, and will not let alone the opportunity and to see what we have.

So, let's begin! Manifestations of yellow spots have never been observed on already dried liquid wallpaper. That is, it can only appear when liquid wallpaper is either just applied or they are in the process of drying out after application. As you understand, this clearly indicates the fact that yellowing occurs in the aquatic environment only. We continue to collect the facts.

It is important to understand that when we say "liquid wallpaper", we mean a dry mixture of their constituent components. As you remember, this is cellulose, CMC glue, textile fibers and decorative elements. Everything is carefully selected and tested hundreds of times for compatibility and lack of mutual reaction in the aquatic environment. Otherwise, then the very essence of liquid wallpaper is lost. As a conclusion: if any of the components of liquid wallpaper, by definition, does not give a reaction in the aquatic environment, then what is it then? Let's explore this further.

And so, the following components are involved in the application process: liquid wallpaper, water, and the surface on which we apply them - we will simply call it a “wall”. When we apply liquid wallpaper on a wall, each square meter contains 1.5-1.7 liters of water. That's quite a lot. At the same time, a properly prepared wall must get wet to a depth of 2 to 5 mm. And immediately after the wall gets wet, a physical phenomenon called “diffusion” begins to work, or, to put it simply, the mutual penetration of dissolved substances. Thus, the contents of the wall through diffusion begins to "float out" to the surface.

A logical question arises - what is inside the wall? It's just hard to predict in advance. For example, if you see a wall a plastered or, for example, painted with primer paint, it looks properly prepared. But how do you know what was done before the primer? Often this is simply not possible. Therefore, we approach the solution of this issue as a series of particular situations. And here's what they can be.

From practice, we noted the following main causes of yellow spots

Reason №1
The first reason is the use of COLORED PRIMER or PVA-based primer. I also have seen fakes of famous brands of acrylic primers with the addition of PVA.

Here is an example for you - Ceresit CT-17 acrylic primer. Its use gives yellow spots. And the reason is as follows - the instructions for CT-17 say that it is recommended to use it in general construction work, such as pouring a floor or gluing tiles, but absolutely nothing is said about using it for finishing such as painting or wallpapering. And all because the composition contains an additive that improves the properties of the primer, but it gives a shade that does not matter in general construction work. But this additiive gives yellowing. But for finishing Ceresit recommends CT-17 SUPER, which does not have coloring additives. It is colorless, and it is recommended specifically for finishing work, as indicated in the instructions, and yes, that's right, it does not stain.

However, those responsible for choosing materials often do not pay attention to the subtleties of primers, so such mistake may occur.

Reason №2
The second reason is the old wall, which in most cases was once long ago covered with chemically active substances. In the vast majority of cases that I have seen, this is COPPER SULPHATE. For a long time, about forty years ago, and earlier, its aqueous solution was used in finishing work as a primer and an antifungal agent at the same time. It was applied to the surface in the form of an aqueous solution of copper sulphate. Penetrated into the wall, and without going anywhere, copper sulfate was in the wall for decades in the form of small salt crystals.
When the wall gets wet, copper sulphate easily dissolves, and again turns into an aqueous solution, and then, through diffusion, freely “floats out” to the surface. At a low concentration in the form of yellow, and at a high concentration - in the form of aquamarine spots. Copper sulphate can penetrate even through putty applied in several layers.

Reason №3
Drywall. This is not a rule, but if liquid wallpaper is applied to drywall without technology preparation, namely, without putty, then there is a possibility of yellow spots. The fact is that, probably in the cardboard, on the front side of the sheet, there may be impurities that give color. However, here the easiest way out of all is to simply follow the drywall preparation technology. This will be enough.

Reason №4
Incorrect preparation of wooden surfaces. We have a separate article devoted to this topic. But in short - if such surfaces are not properly prepared, then there will definitely be yellow spots.

What can be done to prevent yellow spots?

First of all, of course, follow the technology for each of the surfaces, carefully read the instructions for the products used.

But for reason number 2, in the presence of copper sulfate, the way to isolate the wall from the applied layer of liquid wallpaper works perfectly, or in other words, to create a waterproofing layer. This method is also suitable for correcting other causes if a mistake in preparation has already been made. It helps to stop the "floating out" of the content of the wall, whatever it may be.

It is important to note that quartz primers, or as they are also called "primer paints" of any kind, do not have the property of waterproofing. They provide a white surface color and roughness due to the presence of quartz or marble sand in the composition. But not waterproofing.

How to create a waterproof layer?

Let's talk about the products that we tested ourselves, and we can vouch for the result.

1) AQUABLOCK from BIOPLAST – concentrated primer 1:10. To achieve waterproofing, it must be applied to the wall in a concentrated form, without dilution with water. In our opinion, the best option in terms of price and efficiency. Of the benefits - quick drying and no pungent odor.

2) OBJECT by ESCARO - insulating paint. It also gives the property of waterproofing, paints the surface white. There is no strong odor. However, the price is quite high. This is a special tool and can even be used to isolate soot spots.

3) Alkyd enamel PF-115. Produced by different brands. Paints the surface white. Of the benefits - relatively inexpensive, but it can dry up to three days and has a very pungent smell. It is necessary to ventilate the room during work.

What to do if yellow spots have already appeared?

There are two ways out of this situation:

• Remove the applied liquid wallpaper and prepare the waterproofing surface as described above. And only after that apply liquid wallpaper again.
• If the appearance of the stains is not very contrasting, then a repeated cycle of preparation and application can be avoided. To do this, it is enough to treat stains on liquid wallpaper with an aqueous solution of sodium hypochlorite, known as "Bleach". This tool is most often used in everyday life for bleaching and disinfection, due to its high oxidizing properties.

"Bleach" can be used both undiluted and diluted with water, depending on the contrast of the spots. But in a diluted form it may be less effective. "Bleach" is poured into a spray bottle, and sprayed onto the surface. The effect is visible immediately - the yellowness goes away within a few minutes after treatment. If the yellowness is gone, but not all, re-treat it.

IMPORTANT! When working with "Bleach" it is obligatory to protect the respiratory organs - with a respirator, eyes - with goggles, as well as the skin of the hands with rubber gloves. Ventilation is a must! The clothes are working, otherwise the oxidizing agent that has got in can ruin it.

For completeness understanding, it should be noted that "Bleach" does not affect the color of liquid wallpaper, because we use fibers that are dyed in a special way and have the highest color fastness. However, a strong oxidizing agent such as sodium hypochlorite can discolour some decorative elements, such as glitter. Therefore, before using "Bleach", consult with our specialists for complete information on the article of liquid wallpaper you use.

And in conclusion, one important point, all of the above will be fully true for liquid wallpaper of the BIOPLST trademark. As for liquid wallpaper from other manufacturers, in some aspects the properties may not coincide, because it is the components of liquid wallpaper that determine their properties. After all, it is not possible for us to track which components, which manufacturer uses, and even more so the stability of their quality.

Use materials from trusted manufacturers, follow the technology - and you will succeed quickly and easily. After all, your success is our reputation!