http://www.hgtv.ca/holmesmakesitright/article/holmes-on-tiling/
这里说不建议seal grout。有些tile需要seal。
“ You can’t let your contractor tile, grout, then seal the whole thing---it’s a huge mistake. And I don’t recommend sealing grout. In my opinion, grout needs to be able to breathe, so any moisture that gets in behind your tile is able to escape. If you seal the grout, that can’t happen.
Grout will get dirty over time and it can be tough to keep clean—that’s why many contractors suggest sealing it. I think a better solution is to tint the grout so it matches the tile and hides discolouration. Don’t try and solve your stained grout problem by sealing in moisture. You will only create a bigger problem.”