Here's what the MFG ought to tell you:

Porcelain tile is very hard and durable stuff and in the final
finishing process, microscopic pores are created that can trap a grout
haze if not sealed first. It really depends on the tile - if I am
installing a very dark tile with a very light colored grout (white
especially) I would absolutely seal it first. Otherwise, I would just
be very neat with my grout job and scrub it thoroughly without
disturbing the grout lines. Sometimes the haze is actually desirable
and it will give the tile a more even color and matte appearance, but
that's tricky stuff. Seal it first to be safe but only seal the TOP of
the tile FACE and try not to get too much sealer into the grooves in
between the tiles as it could actually diminish grout adhesion. I would
simply dab it on with a cheesecloth and wait 24 hours before grouting.

-Jeff


Mike wrote:
My buddy installed a new tile floor in his bathroom - Mannington Perugia
porcelian tile.
It's a very hard surface porcelain tile. Home Depot book on laying tile
states porcelain
tiles needs to be coated with a penetrating sealer before applying grout.
He called the
mfgr, Manninton, but did not get a direct answer. The Mannington website
did not have
any information on applying grout. Should he apply sealer to the tiles
before applying grout?
Should I post this message to another newsgroup?

Thanks,

Mike