Grout cleaning question.

[lindapendant]

I have a mosiac ceramic tiled bathroom floor that was laid in the early 1960s, and the grout is stained/dirty to the extreme maximum and I'd like to clean it if not to white, then something that resembles white and not the muddy gross putty colour it is right now. I do not want to retile the floor, I love this old style that you don't see much anymore, plus there is nothing wrong with it other than dirty grout.

I have tried several DIY 'recipes' and not one of them can touch this.

I am looking for a grout cleaner that really works, and I don't care if it's corrosive, I don't care that it's not 'green', I don't care if I have to seal off the bathroom for three weeks because of the fumes. Really, I don't.

Please don't leave comments saying that I am killing the planet to save my grout because global warming and/or the startling death (and potential extinction) of mass amounts of bees that are vital to our food chain production is going to be what kills us all.

So have any of you actually used a product that has cleaned beyond hope of being cleaned grout and can vouch for it? I'm looking at commercial grout cleaning products and I really don't want to end up having to buy several before I hit on one that works.

Failing that, can any of you recommend a product that you 'paint' onto the grout lines to give them the illusion of clean, and that will last for longer than a month?

Thanks in advance.