Re: Any Hope For Old Grout?
The perfect way to clean grout is with a household steamer such as the SteamFast SF275. You can clean and sanitize at the same time, without the use of caustic chemicals such as bleach. The SF275 comes with many attachments to clean any heat tolerant surface, for your tile I would recommend one of the nylon scrub brushes. This really gets ground in dirt and oils to release from the grout. Once the grout is clean and dry, you can apply a sealer that will help to keep the grout clean and protected.
The great thing about this particular steamer is that it not only works very well, it is very reasonably priced at only about $100, so you can get to know what steam cleaning is all about without a huge investment. If and when you're ready for a bigger and better machine, I can recommend one of those as well.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!