Cleaning grout

Sometimes you have to leave these cleaning products on for many hours without them drying out. One way to do this is to use toilet tissue as a sponge by soaking the tissue in the liquid and then squishing a wodge of it into the grout lines. The tissue will will remain "wet" for many hours. Remove and clean off before the tissue dries.

It is tedious to do and requires a steady hand but I have found a high quality tungsten carbide tile drill ideal for raking out stained grout.

Not one of the rubbish ones from a shed. They leave dark marks as the "tungsten carbide" material is nothing like a decent quality.

Yes its fungal spores in the pores of the grout. Brian

it might be worth a check on the technique used, many people do it in a way that doesn't work at first. It needs to go on without dilution, be left on all night and this be done several times before it comes clean.

The times I've had it not work there seems to be a soft muck layer that can be scraped off (unless the grout is disintegrating).

NT

....and use a good bleach. I find that only Domestos works.

I should have added that in my experience after soaking the grout line with bleach for hours the most effective way to fully clean the grout line was to use a new hard bristle tooth brush. Just using a cloth or scoring pad doesn't get into the grout line crack.

If it is disintegrating that makes it easy to scrape out and replace.