I have a Thurlow leather jacket I had custom made sometime in the 1990's. A few years ago I began to notice that my wrists were picking up some mysterious black goo every time I wore the jacket. Now there is goo dripping out of the cuffs - here's a pic of it - anyone have any idea what it is and how I might stop it? Seems odd that it was fine for 25 years or so and then this started. I have it hanging in the garage so it won't drip on the floors in the house - never heard of a jacket that wasn't housebroken but here it is...