What camera are you using? It sounds like an autofocus problem, ie your camera is focussing on somehing beyond the transparent vessel. See if you can switch to manual focus.
Put the "transparent vessel" in front of a dark background and light it with large soft box so that you get rim light and nice reflection. Set camera to manual focus and manual exposure.
uhm.. i'm using a lousy digi cam.. a mavica, actually...
and vessels as in vases and bottles.
uhm.. soft box.... okok, thanx, will give it a try. been using natural light and the reflection is terrible.