Aged and waterproofing Granite

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Created on Tuesday, 14 October 2014 12:20

Aged granite:

The color change in the granite can take place in two different ways:

  • Change of structural color.
  • Change of surface color.

The structural change of color is properly a chemical aged granite. The change of color is produced by the addition of soluble salts through the capillary network, which react inside the stone generating a new color into the stone. The intensity of the color depends on the salt concentration applied and the resulting color is associated to the chemical composition of the salts used in the process.

The final color is very different from the color of the applied solution, which is a very complex chemical process, that coloration could be surface­modified according to the intensity and tone required. This is doubtlessly not only the best way to age the granite, but also to match the color in a restoration work.

Once we get the desired result of the color, we would proceed to the sealing of the capillary network with silica and alumina amorphous. By the sealing of the capillary network, the color of the stone would be permanently fixed with a perfect crystalline granite definition. That means, there is no surface film and the granite can transpire through the micro­capillaries. The chemical and mechanical resistance increases and the capillary movement of water disappears (the granite would be structurally waterproofed).

The change of color on the surface it is made by pigmentation, and the chemical fixation of the pigments by consolidation. The film thickness is associated with the particle size of the pigment, that is an negligible thickness, as it transmits the crystalline form of the granite. That means, the quartz crystals, mica, etc. can be seen clearly.

With a proper chemical cleaning, we could remove the pigmentation and restore the original color.

These two techniques of color change allow us to identify the granite completely, as there is no concealment of the granite crystals. When a granite it is painted, either with normal paint or graffiti paint, a special coating is produced that prevents us to see the crystal structure of the granite.

Waterproofing of granite facades:

We will consider two types of facade:

  • ­Solid granite facade.
  • Granite facade plating.

When there is a proper execution on the wall, any leaks or filtrations will be produced inside the home.

facade bricks

In the picture it is seen the front of the forged and brick wall inside the house. There is a waterproofing mortar (in white) applied, and above, a previous formation of the channel. When we lift the outer wall over the slab it is possible to get filtrations through it by the following reasons:

  • If the wall is made of solid granite, by capillarity the water is deposited on the slab and leaks inside.
  • If the wall is layered and the bricks used for the construction are hollow, the water will be also deposited on the slab.
  • If the wall is layered and the used bricks are solid, the water slides down the facade.
  • If the wall does not rise above the slab, there will never be filtrations in the house.

Apparently there is not a construction issues in the execution of this wall. There is a waterproof made with a suitable mortar, but does this mortar prevent the water filtrations when the wall gets wet? . The response is overwhelming, it does not prevent leaks.

A waterproofed channel is made and aeration pipettes are added. Is it possible to explain how the water rises above the slab to the channel and goes out through the pipette? for what are these channels and pipettes for? I have been told it is to collect water from condensation. If the wall is properly insulated with polyurethane foam, extruded polystyrene, etc. When is the condensation happening?.

We do not understand the real meaning of these pipettes on a wall that it is not been painted. If the wall is painted with waterproofing paint, ventilation will be needed, as we are preventing the transpiration. What would it happen if we put a raincoat on in the summer and go to take a sunbath?, What happens if we put a raincoat on a building when the sun strikes?.

There are many buildings constructed with the start of the outer wall above the slab. These buildings will always have problems with damp and leaks due the capillarity of the granite. That would be resolved if the facade is properly waterproofed for avoiding granite ́s capillarity.

To seal the granite there is only the possibility of sealing the capillary network. The water repellents are not suitable for sealing the granite,as they do not seal the capillary network, they are simply oils that repel water and were developed to prevent moss on the north facing facades. On a sunny facade, the water repellent decomposes quickly and the hydrophobicity appears in a couple of months. If we read a technical sheet of any water repellent, we realize that the water repellent does not waterproof granite facades.

The sealing of the capillary network is something we can not explain without a chemical development, but in synthesis we have two different systems:

  • Inorganic Consolidants.
  • Organic Consolidants.

The use of effective consolidants it is only possible by experienced chemists professionals.