You need a hydraulic press for this. I recently designed a "bunch
of grapes" as a holiday ornament for a client. I used Delrin to
carve out a realistic looking grouping of grapes, in reverse,
complete with stem. This delrin slab became the mold for my
ornament. I then used a form box and my hydraulic press, placed a
26ga. sheet of copper cut to size in the box, pressed to 6500 lbs.
and voila, a bunch of grapes. For this project, I only pressed
once. For your project, you will probably want to press a few times
to get the depth of the grapes right, annealing between pressings.
If you want realistic 3-d grapes with two sides, you will need to
create a reverse mold, press the back, and then solder.
As for color, I found that cleaning with Simple green, lightly
sanding with scotchbrite green, and placement in a standard oven at
around 350 degrees for 20-30 minutes gives a wonderful, hearty
patination. Variations on the temperature give wonderful results.
regards, Donna Blow, dzines by donna