When we investigated the decanter, it was in a horrible state. There was rust at the bottom, very misty and covered in dust.
The solution we decided to do was, to clean it thoroughly, with soap and water. Afterwards, we sterilised the decanter many times and left it for a few days. Then we gave it a good brush in hot water.
After I poured my Taylor's port into the decanter, I had noticed over a period of time, the decanter starts to show a misty, some sort of blured reaction. Definitely in the inside of the decanter. Although, when I stir the port inside, it disappears for a while and then returns. Is it normal, or a cause for concern?
Here's a picture, althought it is not very clear, but you get some idea:

What do you reckon?