This vase is created through a process called raku - a type of low-fire that is inspired by traditional Japanese raku firing. The piece was fired and taken out of the ~1500 degree kiln and placed in a container of newspaper, allowing the material to ignite quickly and easily. A lid was then put on the container, creating a carbon atmosphere and dramatic coloration. The raw black area is a result of the smoke.
I highly recommend watching a video on raku - it's on of my favorite processes because of the spontaneity.