How to clean outdoor porcelain tiles?

[windsor-tg]

I recently had 20mm porcelain tiles laid outside on a new patio. I did notice the tile installers did not take a great deal of care in ensuring tile adhesive and grout were thoroughly removed off the tiles.

The patio has been pressure washed but the tiles still look dirty and unattractive. I had attached a photo of part of the patio. Can anyone advise what I can use/do to clean the porcelain tiles so that the tiles look as good as new?

 

[Tile mad]

A mild acid solution should do the trick. Start with a very weak solution mix 10 parts water to 1 of acid. Apply with a brush and try and keep it out of the joints.