JR8 wrote:Grout cleaner... in hand luggage ? Wow, I'm surprised you got through with that.
In any case IME there are two variants of products, one DIY, like a toothpaste, apply, leave a few hours, scrub-off. That works pretty well. The other (more dangerous one) is the full on solvent one, which has more of a bleaching action IIRC.
Good luck!
p.s. Deffo straight-up horseradish, over 'cream of horseradish'....
Ah got it, no its not the bleach version we buy that locally here in Singapore. This one you leave on the grout then just wipe the excess from the tiles.