Having just been out in my back garden, I noticed that there are gaps in the sealant which bridges the gap between the window frame and the brickwork. These gaps are most of the way around the frame almost as if the sealant has shrunk. With a view to making this water tight again, what is the best way to remove the old sealant prior to resealing? By hand or are there any good chemicals to break it down? Thanks in advance.