You can see that I was woefully unprepared to cope with glossy glass surfaces. You can see the extent of my paper background; it's suggesting that this piece is two-tone with the lighter band in the lower half. You can also see me in the reflection taking the photo and using the built-in flash in commander mode to drive the off-camera flash at camera left. You can see how little diffusing a piece of paper does. The umbrella, seen at the right edge of the pot, is a better diffuser of light but boy is it obvious in the reflection. Here, the umbrella is serving as a reflector.
The only way to really cope with this is to enshroud the scene in white, with a little hole for the lens.