I just looked at a job that has a very light sandstone (Indian but looks like Himalayan) and it was well sealed with 3 coats of Dry Treat stain proof at construction close.  Now, on one of the floors it is staining. It is a high use floor and has been hit hard with various cleaners. Owners are saying stone is not fit for use.

Other than a rilem tube test, does anyone know how to test for sealer? Looks like the sealer has been stripped out. When I water tested it absorbed after 10 minutes, took 50 mins to dry out. My tailgate test is 10 mins soak time, and if the dark spot is gone after 10 it is okay and this is just surface wetting. This is very informal. Is there anything to back up my findings with this type of water test?