cleaning slate tile outdoors

Sorry if I didn't look closely enough but what do you recommend for cleaning honed slate tiles on an outdoor covered patio. It's very dusty! I've used water and brushed it lightly with a gentle detergent but it's not doing the job. Thank you

 

Dear Tina:

Maybe you need something more heavy-duty, like MB-2 to hit those tiles a little harder.

Maybe they're not dirty…

Could you please explain in more details what seems to be the problem and, if possible, send me a couple of pictures?

Are those tiles set on a cement slab on grade?

Was a water-proofing barrier ever applied to the cement slab prior installation?

How does the soil on the tiles look like?

Knowing all that and seeing pictures would help me.

Ciao and good luck,

Mauri z io Bertoli