International Standard Tests
There is an ISO (international standard) test for testing staining on natural stone: ISO 16938-1. This is the more critical test, ‘with compression’. ISO 16938-2 is the same test without compression. If a sealant passes the test it can claim to be non-staining on a specific type of natural stone.
We tested several of our sealants on Carrara marble and (Belgian) Blue stone, which are common and well known natural stones. For products specifically intended for use in contact with natural stone, this standard is also mentioned in the Technical Data Sheet: ‘Tested according to ISO 16938-1 (Testing for staining on natural stone by sealants). Silirub MA, Fix All Flexi and Soudaseal 240 FC are all tested according to this standard.