Types of Cleaning

Before any cleaning is carried out the following should be considered

Place all cleaning work in the hands of specially trained staff. Consult an expert before beginning any cleaning work. Before selecting the most appropriate cleaning method, the following steps should be taken: The surface to be cleaned should be thoroughly studied; a lab analysis should be conducted and a sample surface should be examined. Prior to cleaning the condition of the mortar should be ascertained, and if need be restored or repaired.

High pressure cleaning
The use of high-pressure cleaning devices is more effective in removing dirt than a method not involving pressure. It can be conducted using hot or cold water. For the better removal of greasy or oily dirt layers surfactants can be added. The waste water must be captured, treated and controlled.

Ultra-high-pressure cleaning
This method is restricted to only a handful of applications as it involves large amounts of water and generally results in enormous loss of substance. The waste water must be captured, treated and tested

Sandblasting / particle blasting
With all blasting methods involving sand/air, sand/water or sand/water/air mixes there will always be a more or less substantial loss of substance.

Although "more gentle" blasting methods (mist blasting, particle blasting and even the "eraser method" are offered) incur less loss of substance than classic sandblasting, they are very expensive as the machines are expensive to purchase and maintain. Also when used properly they provide less area covered per time unit.

Sanding agent remnants can lead to the pores becoming blocked, and this in turn may affect the subsequent hydrophobing / impregnation. As such, the right choice of sanding system and sanding agent is of key importance.

Chemical cleaning methods
Should the type and extent of soiling be such that cleaning using water does not suffice then one option is to break up the encrusted grime using special cleaning chemicals that facilitate its removal.

Cleaning stone facades with cleaning chemicals is a specialist task that should be performed by an expert whose knowledge will rule out severe errors from the start, ensuring that substances are employed in a proper and safe manner.
We also recommend that tried-and-tested finished products by renowned manufacturers be used as highly concentrated acids or leaches can cause serious, irreversible damage (dissolving the binding agents in the stone, forming new salts harmful to the building or the formation of other chemical compounds not found in stone). It is advisable to check the competence of both the person employing the chemical agent and the chemical manufacturer.

ETRAS has long-standing experience in cleaning stone facades and has the right cleaning agent for every application.

Cleaning with acids

This method is frequently used for cleaning facades. Acid-based cleaning agents are largely used to remove the following: airborne soot, grout residue, blooming, sinter deposits (obstinate, encrusted grime), corrosion- and oxidation products, light oil- and grease soiling, algae and moss.

For smooth surfaces it is often advantageous to first remove as much of the dislodged soiling or paint possible using a spatula. Following a pre-defined waiting period water is applied under pressure. This rinsing water must not be hotter than 40° C. The water jet should point away from the treated area and the distance between jet nozzle and wall should not exceed 15 cm. Care should also be taken that the underlying facade sections are always kept wet so that the dirty water running down does not penetrate into dry areas
Rinsing should be carried out until foaming ceases and the stone cleaner applied has been completely removed. If necessary use litmus paper to check the neutral reaction of the stone). In many instances it is advisable to use a stone neutralizer (containing diluted organic acids. Finally, the cleaned areas are thoroughly rinsed from top to bottom.

Waste water must not under any circumstances enter the soil or surface water and where there are separate canal systems must not be fed into the rainwater sewer system.The dirty water must be captured, treated and disposed of pursuant to local waste water regulations.

Cleaning with organic solvents
Some soiling (e.g., tar, bitumen) is best removed using suitable organic solvents. Cleaning should always be effected swiftly as there is a danger that solvent particles may be sucked deep into the subsoil.

Cleaning follows in two steps: The soiled area is soaked in the solvent and then rinsed with water at high pressure. Façade sections located lower down must be kept wet during the procedure. The dirty water must be captured, treated and disposed of pursuant to local waste water regulations.