For only one stone, two buckets for now. It is a shame that none are provided here... [As if he were surprised to see nothing of the sort around.... because he was. Well, they were so common place, at home, after all.]

Thankfully, once cleaned, so long as they are attended to yearly, they should never require so much ever again. Of course, for all the work we do today, these stones have been quite damaged. Try as you might, you will not be able to fully restore them without more in depth means, the pitting will remain as will traces of dirt, and stains.