Sealing Concrete

Hi, I have just finished my first floor tiling effort with 400 x 400 polished porcelain tiles. As these are bloody expensive I followed all the instructions to a 'T' using davco flex. They recommend using a sealer so I got their brand from Bunnies in the tiling area. Not much to it, looks just like watered down PVA glue which was rollered on and only takes 20 minutes to go off - don't know what it does or if it works but better to be safe than sorry if you are a newbie. It was also suggested not to leave it down too long before tiling over it to prevent dust and dirt contaminating the finish. Good luck, Ron