One of my contractors has recently installed 30, 000 sqft of blue stone. (Slate) They were required to have a certain amount of lime in the mortar mix. Now that the stone has been set it appears as if the lime is leaching into or on top of the edges of the stone. They tried lime away with a small brush and iy seemed to clear it up. Any ideas on what we can use to clean an area this large and neutralize the lime elements so as not to have this happen again after we finish??? Thoughts? As always, thanks in advance.