ARCHITECTURAL RESTORATION placeable, made of unique materials for which no standard method is adequate. Each cleaning intervention must be carefully planned, on the basis of deep diagnostic analysis and preliminary cleaning testing to identify the best cleaning techniques for each specific case. Indeed, in compliance with the legislation, “The materials and processes to be used must be chosen based on the results of necessary assessment carried out by qualified and industry-specialised laboratories to determine the effectiveness and/or any side effects”2. All the different analyses carried out on the Malta stone, under the supervision of the local superintendence, have identified only two possible viable cleaning processes: manual cleaning with broomcorn brushes following treatment with chemical agents or selective cleaning with micro-air-abrasion system with helical vortex nozzle by IBIX. Any process involving the use of water during cleaning was categorically excluded. The outcomes of the preliminary tests and previous knowledge on the Malta stone - its characteristics and damage - have led to the choice of cleaning through IBIX air-abrasion systems, taking into consideration the enormous amount of time saved and, as a consequence, the reduction of labour costs. Furthermore, an higher safety and uniformity of the intervention was guaranteed by the possibility to “customize” the system functioning parameters of working pressure (as low as 0.1 bar), nozzle size (as little as 0.8 mm), grain size of the abrasive material (as small as 38 micron), flow type (vertical or tangential) etc. HELIX® is a special gun able to give a rotatory motion to the abrasive exiting the micro sandblasters. This exclusive IBIX patent has been developed and produced in Italy. Thanks to this special technology the impact of the abrasive on the surface is not vertical but tangential, so that the abrasion is more gentle and respectful of the treated surface, increasing at the same time the contact area and the machine effectiveness. The HELIX® system offers, for the same nozzle dimensions, an increased tangential contact area, maintaining 2
Uni Beni Culturali 11182:2006
The Malta stone
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Restoration, removal of black crusts and salt efflorescences with HELIX® air-abrasion technology
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