I finally managed to set things up to get decent looking gradients on a bottle of red wine.
(Except on the right hand side where the gradient does not look right where the bottle
curves up to the neck. That is because I have only one large 5'x7' diffuser that I used
on the left side, and I had to use a smaller diffuser on the right side.)

This is much better than the previous two bottle photos posted here. The next challenge will
be to do this with a bottle of white wine. That will require a back light to show the colour
of the wine. And probably I will need to composite at least a couple of exposures, with and
without the back light.

Best viewed at original size.