Don,

Confusion arose in the last thread ("press size") as to whether you
were talking about whole cluster pressing or crushed grape pressing.
There is a significant difference (both in terms of quantitative AND
qualitative extraction).

On press technique:
> > 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?

They are most likely using crushed grapes, which already have much of
their juice released. This means that the crushed grapes added to the
press already has some free run in it which can run out of the press
without any actual pressing action. In this way, volumes of crushed
grapes larger than the actual capacity of the press can be added to
the press before actual pressing begins.

> > 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.

That is not normal practice.

> So a #25 press would be adequate for one or two 23l carboys?

Yes. Using crushed grapes you could certainly manage that with a 25
diam x 33 cm height press.

Ben