Machine used: Gaggia GX 3 group lever machine
The shots were pulled using
a commercial preroasted blend (Trucillo) that I use in
my trailer, and ground using
the Bregant grinder featured in the grinder section of my site.
Approximately 15 grammes were
dispensed and levelled off. The shot on the left was tamped using
my homemade brass tamper to
a pressure of approx 35lb using bathroom scales, and a polishing tamp of
110 deg.
The shot on the right
was tamped with the plastic tamper just sufficiently to level the grounds,
with no polish.
Picture on LEFT is with a 35lb approx. Tamp. Picture on RIGHT is with a slight levelling tamp with a plastic tamper
Interestingly there is less liquid volume on the untamped shot, possibly due to the way that the lever machine fills the void above the coffee with water, and the untamped grounds would take a little more space in the pf and possibly swelled more. Both shot times were almost identical and looked almost the same with there looking like a little more crema on the left shot, but the right shot having a nice striped effect when viewed from above (sorry, I drank it!).
Hard work this testing - I had to drink a few shots!
-UPDATE-
What happens with NO tamp at all - nothing,
zero, zilch, nada?
Whilst Alison was in Spain she saw more
than one cafe heap the portafilter
and insert it straight into the group!
There was a tamper on the grinder but it was never used.
Thought I'd try that, on the same grind
as required for my usual 20lb tamp:
Heaped as described by my witness.
shot doesn't look bad...
Slightly less crema and a slightly quicker
pour (but to be honest, I haven't cleaned
this group for a while)...
and virtually no mess. The grouphead
looked fine, and a quick pf wiggle
kept it clean.
Conclusion? Draw your own for now!
Later: I had another go...
Oops - doing well, then overextracted -
...how a shot shouldn't look
And how it should look.