Butyl rubber caulk is used mostly for outdoor projects, such as roofs, storm windows and exterior doors. It is usually the caulk of choice for cracks or gaps that are ¼-inch wide or larger. According to Fix All Roofs, butyl caulk is durable and strong and, when applied properly, it can last 10 years or longer. For a caulk that is known for its strength and long life, you'd think it would be difficult to remove once it has been applied, but the opposite is true. Given the right technique and tools, you can remove butyl caulk like any other caulk.
Run a utility knife down each side of the bead of caulk to loosen it from the edges of the surface.
Lift the caulk up with a putty knife. Slide the putty knife under the loosened caulk at a 45-degree angle; lift it up and out.
Grab the caulk with your fingers and pull it up and out.
Repeat steps 1 to 3 until you have removed all the caulk.
Scrub the surface with steel wool soaked in mineral spirits. According to Tom Silva of This Old House, you must get rid of any caulk residue after removing the old caulk or the new sealant won't stick to the surface.