Can you make any material hydrophobic?

Seal surfaces with water glass

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Water glass is a chemical agent that is used in many areas. For example as a binding agent or in detergents. Water glass is also suitable for sealing surfaces in the construction sector. It is an aqueous solution that leaves a glass-like, dense surface on the treated materials when it dries.

Basically, water glass is nothing more than glass mixed with all kinds of chemicals, ground into powder and dissolved in water. The liquid can be applied with a brush, for example. If the water evaporates, water glass hardens and then has a glass-like, smooth surface. Depending on which chemicals are used, one speaks of potassium water glass or soda water glass, for example. Water glass is available as a solid mass and as a gel-like or dissolved in water agent.

Water glass is suitable for these purposes

There are many possible uses for water glass. Builders and do-it-yourselfers mainly use water glass in the following cases:

Water glass as a seal

Water glass seals masonry, concrete surfaces and other building materials. It is either applied directly or injected into drill holes under pressure. However, only potassium silicate is suitable for this purpose. Soda water glass loses its stability after a while and is then no longer waterproof. Water glass causes what is known as silicification in the pores of concrete, plaster or masonry. As soon as the water in the solution has evaporated, substances that are largely insoluble in water remain in the cavities.

Seal walls and hide stains

Water glass does not yellow. If nicotine stains are sealed in the wall with it, they remain hidden underneath. Then you can paint over it or re-wallpaper and the stains and smells no longer penetrate the surface. Corresponding stains can only come to light during the renovation. They still have to be sealed, because nicotine is stubborn and may take a while to get through wallpaper and layers of paint.

Prime porous substrates

The condition of a wall can only be seen once the paint, wallpaper and plaster have been removed. This is usually only the case in the course of extensive renovation work. Then the old clay bricks may turn out to be very absorbent. The joints may appear sandy and trickle, indefinable stains appear. Then water glass can help stabilize and prevent walls from sanding away.

In the past, water glass was occasionally used to make certain building materials, in particular wood, fireproof. The disadvantages: the material could become cloudy and brittle under the influence of heat and made wood significantly heavier. There are now more suitable methods for doing this. Water glass is used industrially today, for example to produce fire protection glass.

This is how water glass is used

Water glass is available from hardware stores as a concentrated and dilutable solution in a one-liter bottle. Internet dealers also sell larger quantities in canisters. However, water glass should only be diluted if it is used to stabilize highly absorbent substrates: the diluted water glass penetrates deeper into the pores.

If water glass is used for sealing, priming or sealing masonry, the surfaces are first cleaned. A high-pressure cleaner can be used outside, while a hard brush is used inside to remove loose material or dirt. Then you soak the wall or the plaster with potassium water glass. For example, you need a tassel, which is a large, brush-like paintbrush. However, a conventional coating roller can also be used. It is faster and more convenient with a sprayer. You apply the water glass several times, but you have to wait a few hours in between. It is recommended to let water glass dry for at least 24 hours before applying paint or plaster. If the temperature is below 5 degrees, the work should be postponed to warmer days.

According to the manufacturer, one liter of water glass should be enough for ten square meters of surface with a single coat. With a high absorbency of the substrate, you use significantly more.

The tools can then be easily cleaned under running water.

In some cases, water glass can also cause damage! Namely when the wall is damp and the water can no longer escape due to impregnation with water glass. In the worst case, the very part of the wall that was solidified with the help of water glass will crumble off. Water glass must not be used on plaster walls or paints containing plaster. The two substances react chemically, and the water glass flakes off after a while. On the other hand, water glass does not promote mold formation. Because the masonry itself is protected from water by the impregnation. Due to the high pH value of water glass, the surface does not form a suitable breeding ground for mold.

Protective measures

Water glass is a strong alkaline solution with a pH value of 11. The material is therefore similarly alkaline to household ammonia. Those who process it should protect their hands with gloves and their eyes with glasses. If you spray the agent on the wall, for example, you should never inhale the mist! If you still wet yourself, the only thing that will help is immediately rinsing off with plenty of water. In the event of eye contact, a doctor should be consulted. Anyone who spills water glass must immediately soak it up with paper towels, sawdust, sand or the like or bind it with suitable agents such as vermiculite or kieselguhr.

Steffen Malyszczyk


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