Grouting slate floor tiles

I have grouted my slate floor, but I can't seem to get the tiles completely clean, there remains a light cloudy dust on the tile itself.

I've gone over the tiles several times with a clean sponge, clean water and I can't seem to get that cloudy dusty look off from the grout.

Once it dries it goes back to the dusty look. Have spent an easy 2 hours on a small portion just trying to get it clean. How do I get it off?

Once the final seal is on will it just cover it, or will it show up?

Is there some sort of solution I should buy to clean with? Is it possible that I didn't put enough initial seal on and therefore the slate is absorbing in the dirty water?

So far it sounds like you have done everything right, all you have left now is grout water residue. As long as the heavy clumps of grout have been removed & 99.9% if the grout is off the surface then you are ok to give the floor a final coat of sealer.

For the inexperienced DIY'er fitting a slate floor for the 1st time this would look quite worrying but it is completely normal. The final coat should Overseal the residue & make it disappear leaving a beautiful looking finished slate floor.

Again our advice would be to try a test area before proceeding.