Some ideas:
*Black plexiglass underneath, will reflect rear light and appear almost white, but will not throw as much light back up onto the glass. May need some PS work to remove the edge of the plexi against the background. If the edge is "hard" you need to change something, as that will be a bigger PS job than a small change in lighting or camera position would provide.
*Transparent glass underneath, and lit through, would give you some rim lighting on the rounded surfaces of the glass towards the floor, but may be tricky with the wineglass as there are several "layers" of glass (a tumbler would work fine...)
*As mentioned, black card on both sides. Needs to be quite tall, or else you will see a reflection of where the "card ends" in the glass. The wider/deeper the card, the "thicker" the edges will seem. Start fairly wide, and trim to perfection.
*As mentioned, a good polarizer. Cuts down on glare and makes the glass "pop" a bit more.
*As mentioned, paper, card or reflector directly behind the glass. This works well in bottles etc. but i suspect it to be difficult with your wineglass. Getting it to sit perfectly behind on either just the liquid, or the entire glass, would need a very, very cood cutting job.
*You can try any number of different frontal white card combinations. Id make only one very tall and thin to have them follow the entire line of the glass. This can create a running highlight along the vertical to better show the viewer how round it is and that it is "lit" from some angle. A striplight is also good, but expensive and needs to be very tall.
*Photoshop... cut down on the rear lighting, makes the stem disappear. Get the stem back, and trace it in PS (if you need it surrounded by white.)
*Bubbles, fewer?
Some tips can be found at Strobist:
http://strobist.blogspot.com/2007/03/on-as...red-vodkas.html
