So I just finished my first tile job and grouted it. I got most of the grout off with the float then smoothed the joints with a sponge while getting some grout off. What I can't seem to find a clear answer on is when to wash off this grout Haze. I've read as little as 3 hours to as long as 3 days. Most of the how to is pretty similar, thinking I'm going to try vinegar and warm water sponge with 2 buckets, but how much longer do I wait? It's been 24 hours right now.
The longer you wait when trying to remove the grout the harder it gets, in your picture that is more than a haze, it should have been sponged more, but it's ok, you still need to remove the access by hard scrubbing with and plastic scraper, sponge with a corse side and water, if it does not have a high gloss look you can use a steel wool.
I just did this in my new laundry room. I compared using the sponge off method vs a microfiber towel, folded in quarters. No comparison. If you use your fingers to spread and keep the towel flat, it is amazing how much cleaner it gets the tile that a sponge. It is one of the best DIY tips I have ever discovered. I don't see why any professional would still use a sponge. The grout turned out perfect and there was so little haze left that I probably could have just let it be, but I did a post wash of vinegar and water to safe the next day.
Many years back we were tiling an area in a new shopping mall and a death in the family we let the haze set for ~5 days, we tried normal scrubbing but it was solid. We ended up using a weak muratic acid solution on the tiles just getting them slightly damp letting sit for a few minutes then wiping and rinsing with water it turned out great and this was a large area +500 1' tiles and you could not tell the difference from the previous section or the later ones when the job was done. Since then I have used. A dilute muratic acid solution ~5-10% by volume to water, it makes the cleanup much easier.