We pressed 50 microliters of sap from 0.3 g of leaf,
and are trying smaller samples. The leaf was about 70% water.
Different sizes of hardware can be used for different
quantities of leaf.
For this small sap press we used 0.5 inch (1.25 cm) plastic plumbing fitting.
The hole was drilled (once from each side) using a hand drill,
once from each side, after making a small starting dent with a sharp screw.
We have found that placing in a -80° freezer for a few hours,
then thawing, works instead of liquid nitrogen.