Here's a 'sand on the green' question that came up last Sunday. What is the proper way to remove the sand from the putting line without being called for testing the condition of the green?
— Jim Dolliver, via Facebook
These days, super-tough greenside bunkers can let a few hackers turn the green into the beach in a matter of hours. Luckily, you have some recourse. The definition of "loose impediments" clearly states that "sand and loose soil are loose impediments on the putting green, but not elsewhere." This means that, so long as you're on the putting surface, you can treat sand just like you would rocks, leaves or twigs, which is to say that you can move them without penalty.
Rule 16-1a (i) does make it clear, however, that when removing a loose impediment from your line of putt, you may not press anything down into the green, and 16-1d forbids you from "roughening or scraping" the surface of the green (which refers to your question about testing the condition of the green). So, to put it more succinctly, feel free to sweep away the sand, but sweep carefully.