What is the tone of Pip and Joe's reunion?

In Chapter Twenty-seven, Pip and Joe's reunion is awkward at best. After Hoe arrives, Pip immediately notices a change in him, as Joe begins calling Pip sir and acting formal around him. When Herbert shows up, Joe seems to be even more uncomfortable. When they are alone again, Pip asks Joe why he calls him sir. Joe tells him that he is a gentleman now and must be treated that way.