I'm going to get a pro service in to clean my floor (doing a 1950's bathroom restore) - have a 50+ year old mosaic floor tile. In the Chicago area, there are quite a few companies that offer the service including franchises (e.g. Sir Grout) and independents. I'm probably going with an independent found via Angie's List. Can't comment yet on results, but videos show impressive results. Do a search on youtube for 'grout cleaning'. Below is an example.

I had also asked in my post for comments about experiences with grout cleaning companies and didn't get any responses. Most bathroom projects here are complete replacement.

Here is a link that might be useful: Grout Cleaning Video

This post was edited by DreamingoftheUP on Tue, Mar 11, 14 at 8:00

Try this: Spray it with pressurized foam carpet cleaner (Resolve or the WalMart house brand).

Let it sit a couple of minutes and then scrub hard with a stiff bristled brush and wipe off the dirty foam.

I was astounded at how much crud came off my grout and floor ti8lkes. It's several shades lighter.

Keep in mind they may also be unglazed tiles! If so they will never be shiny, and they may be a slightly off or grey white vs a bright white. But a good scrubbing can't hurt.

Google unglazed basketweave, and you can get an idea of what it may have originally looked like.

Always remember - respect the old house! ;-)

Always ;-)
Hunzi
Keeper of the Shrine of Our Lady of Perpetual Renovation (circa 1884)