This from Alan Frew at Coffeeco, a lot of common sense stuff here, should be compulsory reading for neophytes.
May 2018 Newsletter
Fundamentals are an often overlooked aspect of brewing coffee. I get
a fair bit of correspondence from non-customers, usually from
overseas, asking for solutions to brewing problems. In most cases
the problems come down to mechanical failures in coffee brewers or
ignorance of some fundamental aspect of brewing.
I thought it would be worthwhile to go over some of the simpler
things that can cause problems, starting with good quality fresh
roasted beans (of course). You can store beans in a sealed
container for about 2 weeks, in anormal fridge freezer (-4°C)
for 4 to 6 weeks, chest freezer (-18°C)for 3 months and dry ice
temperature (-78°C) for up to a year.
Then comes grinding, and I'd say about half of all the problems I
see are grind based. One of the most common espresso problems is
simply not adjusting the grinder when the beans change, either by
type, season or roast level. A slightly lighter roast needs a finer
grind; slightly darker a coarser grind. Filter brewers can be more
forgiving, but some of the latest models require precision grinding,
as does the Aeropress.
The least grind sensitive brewing methods are plunger and syphon,
because it's easy to adjust the brewing time to accommodate grind
variations. That's another fundamental rule, the finer the grind the
shorter the brewing time, with the exception being middle eastern
coffee brewed in an Ibrik.
Finer grind equals greater surface area equals faster extraction. Of
course, with filter brewing a finer grind may slow down the passage
of coffee through the filter, lengthening the extraction time, which
is why precision is needed. Overextraction leads to undesirable
Temperature is the next fundamental variable. My personal preference
is a water temperature between 88°C and 92°C, regardless of process,
but again dependant on roast level. In my experience, very dark
roasts extract best around 88°C, but very light "Scandinavian"
roasts can require up to 96°C to get a drinkable result. Remember,
this is the temperature of the water as it first contacts the ground
coffee, and things will immediately get cooler. This is why I like
Coffee Syphons so much, and all my "final" cupping for the specials
is done with syphon brewed coffee.
Once you've standardized the grind, the temperature takes care of The final fundamental is origin, i.e. where is the coffee grown, and
itself, allowing you to adjust the brewing time as necessary.
where did it originate. There is a new book, The Coffee Atlas of
Ethiopia, by Dr. Aaron Davis and his Kew Gardens UK team which gets
down to the DNA level of the origins of coffee. In his words,
"Ethiopian Arabica DNA diversity has a distinct geographical
pattern, which, in combination with the diverse local climates of
each origin, yields a cornucopia of flavour profiles.. It became
clear that there are many unique and interesting flavour experiences
that are hardly known outside Ethiopia, and that there are several
origins barely touched upon, if at all, by specialty coffee