All materials have a surface energy. It is a measure of how much a liquid or solid wants to stick together. A liquid with a low surface energy e.g. oil, is able to "wet" a material with a high surface energy e.g. stone. Dry-Treat’s sealers work by changing the surface energy at the surface of the building material so that it becomes lower than that of the liquid trying to wet it. That means that contaminating liquids such as oil and water are no longer attracted to that surface and are repelled. This is achieved by means of a semi-permanent chemical reaction between the sealer and the atoms of the building materials.
At the heart of a Dry-Treat sealer are molecules that consists of silicon, carbon, fluorine, hydrogen and oxygen atoms.
The main molecules have two main parts with quite different properties. Part of it is hydrophobic and/or oleophobic i.e. repels water and oil, while the other is hydrophilic and so attracted to water. When the sealer is sprayed onto the surface of porous building materials it immediately starts to react with moisture in the air and in the material. This causes the molecules in the sealer which are attracted to water to react and break off to form alcohol. A new compound is formed called alkyl silanol which is able to react with the surface layers of the masonry. The structure of the majority of masonry has an abundance of silicon, oxygen and at boundary layers oxygen and hydrogen atoms. The alkyl silanol molecule is very reactive and is able to break the oxygen-hydrogen bond. It then attaches itself to the masonry lattice.
Unlike surface coatings that rely on hydrogen bonding or mechanical holding, this bond is chemcial and very strong with the same strength magnitude as the bonds holding the masonry together. This bond causes the contact angle between water and masonry to change. It no longer acts like a 'hard sponge' but is able to repel liquids.
Depth of Impregnation
A good depth of impregnation gives the Dry-Treat sealer protection from weathering and traffic. It also can stop unsightly efflorescence salts reaching the surface of the building material. The uniform depth of penetration of the treatment can be measured relatively easily by breaking a sample piece of treated material that has had time to cure and measuring the "dry" section depth from the surface after it has been soaked in a water-based dye for a few minutes. The depth of penetration achieved will vary with the surface absorption and amount of product applied.
In addition, Dry-Treat sealers contain a relatively slow moving reacting liquid, with a viscosity similar to that of water. This means that even on slightly moist building materials over time it can displace the water and penetrate deep into the material. This is quite useful for those parts of a marine structure that are in the tidal zone.