> So a 25 cm in diameter by 33 cm high (usuable height of 13 in)
> press is adequate for a couple of 23l carboys of wine. When
> someone says one press will fill a 23l carboy are they filling
> the press with grapes and completely pressing out or are they
> pressing one load, opening the press up again and adding more
> grapes and pressing again? In other words, the first would be
> one full load completely pressed, the second would be a couple
> of loads squeezed down and more added before fully pressing.

I assume you are talking about pressing *whole grapes*. In which case:

Even if all your grape matter was 100% liquid/juice (which they are
not of course), you can't get 46 L (2*23) from that kind of volume
press/grapes *from a single pressing*:

(usable height = 13 in = 2.54 * 13 = 33.02 cm)
pi*r^2*h = pi * (25/2)^2 * 33.02 = 16.2 L

So even if all your grapes were actually liquid which all got
extracted, you'd still only get 16.2 L out of that single pressing.

Grapes usually yield about 600-700 ml/kg juice, so you'd need a press
which could fit about 65-77 kgs in it to be able to press out 46 L in
a single pressing operation.

Ben