We use something like that to waterproof the sandstone walls of Adair Towers, it works really well. You just spray an aqueous solution containing the nano-particles on to the stone surface. It looks like milk and 1 litre covers about 6 Sq Metres. Leave it to dry and Robert is your Auntie. The nano-particles are sucked into the pores of the stone and provide a water repellent layer. It is not a sealed film, it allows the stone to "breathe" and pass water vapour. There's no change in appearance of the stone which is important in our Grade II listed home in a World Heritage Site.