Grind setting change with basket diameter, at constant 1:2 ratio, 9bar, 30s

I used 4 baskets with different diameter to test the grind size adjustment. I kept all other variables constant, like flow rate, pressure and time of shot.

Some things of note:

• My 50mm basket is a high flow version - more on that later.

• 58mm basket is an IMS compeition

• 46mm is my GRAPH

• 36mm is a prototype made be me

• Please note, I have shown inside diameter of the basket - 36mm, 46mm, 50mm (aka 49 in the La Pavoni world where dimension was based on the tamper rather than ID), 58.5mm.

• I use a manual espresso maker so a bit of variability in all this

• I used my flat bur grinder, DF54 - so the numbers are relative to that

• I used puck screen in all tests

• I used a spring in 36, 46 and 50mm (tried spring with 58mm but ended up chocking it as no space for a spring)

Now to the results. Grind size and basket diameter have a power relationship - not linear.

Where it does appear to be linear is when plotting against basket area.

A note on the 50mm - the basekt is more of a fast flow design with straight walls and more holes per area at the base. It is really interesting to see how that enables a finer grind size at it's size.

That said as a basic rule of thumb one could approximate and say that for every 1mm decrease in grind size, when starting at 58mm, one needs to increase the grind setting by 0.93 units on a DF54. Or, if going even more general, 1 unit on the grinder for every mm.

Now here plotted without the higher flow 50mm basket - this shows a pretty linear relationship of area and grind setting.

Thanks for reading and welcome your thoughts on this. Any of you measured grind size between different basket diameters?

Other thing that is going round my mind is the effect of the spring. at 58mm there was no spring, so maybe this chart is all off the scale. Cheers! - Max