Yes, that’s the mod I mean. It’s not as scary as it might look!
If you have a backflushing plate then you can do the following:
With the back flush plate in the portafilter, collect water from the over pressure hose (I think it’s the shorter of the two in the water tank, the other being the pump feed). Use this chart to set the pressure to approx. 9bar. This means that you’re aiming to get about 130ml from the pump (through the over pressure hose) in 30 secs.
I’d suggest doing a test first to see what you currently get from the pump in 30 secs. Then reduce the pressure on the Over Pressure Valve and take another 30 sec sample. Play about until you’re satisfied.
The pressure doesn’t need to be totally spot on, but higher pressures bring out the bitterness, not enough pressure won’t extract enough flavour. 8-10 bar is acceptable for me.
Brewhead being too warm is also a big cause of overly bitter coffee.
Remember water and electricity will try their best to kill you 😕 don’t let them!
More info: Link
With regard to coffees there is no “good” or “bad”, just try lots of different ones until you’re happy! Don’t keep your beans or ground coffee in the fridge or freezer as this exposes it to a high humidity environment and the person who roasted them took a lot of effort to get the water out in the first place! Even if you keep it in an airtight container in the fridge, condensation will form on the surface when you take it out.
I’d say that it’s good to go along to a place who roast their own coffee and get them to grind it straight into an airtight container for you. I keep mine in small jam jars – this means they’re only opened/closed about 4 or 5 times in total so minimal air exposure.
I could ramble on . . .
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