The St. Patricks Cathedral utilized the Rotec Vortex to clean the antique marble. This method was chosen because it is very gentle on the stone, and works with friction as well as minor abrasion (crushed glass) to clean the soft marble without harming it. Link to a restoration of the St Patrick Cathedral in New York City using the Rotec Vortex http://vimeo.com/71035329
Mend was asked about removing efflorescence from the concrete block facade at the Selkirk Montessori in Victoria, BC. Sand blasting was not an option, as it would blow out the mortar in between the blocks, and pressure washing did not touch the problem areas. We showed up with our Rotec Vortex system and successfully removed the efflorescence that was seeping from the lime based mortar in quick fashion.