Diagnosis of Extraction Problems
Espresso is mostly defined in terms of shot time and volume, since
these are easiest to measure. By convention, the volume specifications
for espresso are total volume, combining crema and liquid. The dwell
time, the time it takes from turning on the pump to seeing the
first drops of espresso emerge from the basket varies from machine to
machine. So by convention, espresso extraction times are specified from
the moment the pump is turned on.
I will specify the diagnostics in terms of shot ending color and
volume, since these have the most intuitive correspondence to espresso
taste. This means you should end the shot at the specified color, and
then set the grinder to get the specified volume.
- Ristretto range: 1 ounce to 1.5 ounce doubles.
Compared to normales, the taste will be more intense and sweeter.
Ristrettos usually have less crema.
- Normale range: 1.5 to 2 ounce doubles.
- Lungo range: 2 ounce to 3 ounce doubles. Compared to
normales, the taste will be slightly milder and less sweet; with
certain blends, the crema on a short lungo can be better than for
- Dark stop: stopping the shot while the flow is still
foamy and brown. Compared to a normal stop with the same volume, the
taste will be slightly more intense, and balanced towards acidic.
- Normal stop: stopping the shot as the flow goes from
foamy and brown to more watery and tan. This point marks the optimum
extraction amount of 20% of the coffee solids.
- Light stop: stopping the shot sometime after the flow
has become watery and tan colored. Compared to a normal stop at the
same volume, the taste will be slightly less intense and balanced
- Optimum crema range: exact figures are basket
dependent, but generally, normal to high flow rates are best. Typically
1.33 ounces dark-stopped to 2.25 ounces normal-stopped has the highest
proportion of long lasting crema. Singles cannot extract at this flow
rate, so tend to have less crema.
- Start dump: initial few seconds of flow out of the
portafilter, which is black and without crema, is allowed to go into
the drip tray. The cup is inserted only as the flow gets brown and
- Center cut: a start dumped and dark stopped shot.
Diagnosing the Taste and Appearance of an Extraction
Diagnostics means tasting the espresso and correcting its
deficiencies by adjusting setup or extraction parameters. In a perfect
world, correcting for one deficiency would never interfere with
correcting for another. In the real world, there sometimes are
conflicts, and you must prioritize. The highest priority goes to gross
crema deficiencies, since these indicate that some parameter of the shot
is well outside proper espresso range. The next priority is taste flaws
that make a shot undrinkable. Finally, with these eliminated, you can
work on fine-tuning everything to get the most harmonious taste.
Gross Crema Deficiencies
Gross deficiencies in the crema point to something far out of whack
and have the highest correction priority. However, the blend itself may
have unusually light, dark or thin crema; so when you notice these
defects, taste the shot to confirm the problem.
- Too light and large bubbles: If the shot is less than
20 seconds, re-read the last section and set the grinder properly. If
the shot time/volume was correct, the machine is running drastically
cold and requires immediate correction. The taste will be very thin and
- Almost black, or a black outer ring with tiny bubbles and
thin crema: If the shot took forever to produce a few drops,
reread the last section and correct the grind. Otherwise the machine is
running drastically hot and needs immediate correction. The taste will
be very bitter and burnt.
- Good color, but thin and quickly dissipating: keep
the extraction in the optimum crema range, especially with dark roasts,
but usually it's old beans. Rarely, it can show a defective pump not
developing sufficient pressure. In this case, the taste will be
balanced, but weak and with a watery mouthfeel.
These taste flaws ruin the shot. Correcting them takes precedence
over working on the taste balance.
- Lemon peel: This can be a blending or roasting error
and irreparable. Short term, start-dump the shot. Long term, set the
temperature higher and make sure the grinder burrs are sharp. This flaw
comes from fines of very high quality coffees, and good blends tend to
flirt with it.
- Metallic: Recently cleaned machines or brand new ones
can have this. The taste is eliminated most quickly by flushing more
after cleaning, or for new machines, pulling a lot of shots and dumping
them. Dull burrs are another cause. Finally, a failure in the water
treatment resulting in almost distilled, low mineral water will cause
- 12 hours on the hot plate taste: Time to backflush
and clean the portafilter. Verify the frequency of your cleaning
- Instant coffee taste: The mark of overextraction.
Grind coarser and stop darker, so volume stays the same. If the bitter
taste is prickly-sharp rather than dull, also lower the temperature.
- Thin and sourish: The mark of underextraction. Grind
finer and stop lighter, so the volume stays the same. If the taste is
extremely sour, also raise the temperature.
- Salt or MSG: A common defect in Indonesian or slower
roasted coffees, and difficult to correct. It is ameliorated by high
crema content and sweet, ristretto shots, so dial-in exactly to 1.5
ounce, normal-stop color shots. If that fails, also start-dump, since
the taste is slightly more concentrated there. Finally, strong flavors,
particularly acidic ones, can cover the salt taste. Consider lowering
the temperature to enhance these, if the blend's flavor balance
permits. The best solution is to find higher quality Indonesians for
the blend and/or speed up the roast finish.
- Ashiness: Usually a flaw in rapidly dark roasted, low
grown coffees. Drop the temperature to the low end of the espresso
range. Dial in to the lungo end of the optimum crema range and dark
stop the shot (you may be under 20 seconds when you do this, that's
OK). These measures will not much reduce the ashiness, but will mask
the problem with a little more brightness and crema. The real solution
is to change blend.
- Rubber or Iodine: Buying cheap coffee? This is the
classic reason for start-dumping.
- Sewage, decay, mold, sausage or cabbage smells: This
is from badly fermented coffee. If the blend is normally good, it's
from a stinker bean. Clean out the doser and burrs. If it keeps
happening, there's nothing you can do except get new coffee. The
importer slipped the roaster a bum bag, and the problem has to be
When the crema is right and the shot has no taste flaws, you can
fine-tune the setup and extraction to provide the most harmonious and
balanced taste possible. Although everyone wants balanced taste, the
exact combination of sweet, bitter and sours tastes that any person
considers balanced is extremely variable. So these adjustments will be
subjective; and there may be more than one optimum set up for the blend,
especially if it is complex in taste.
- Not sweet enough: Do more ristretto shots, grinding
finer and stopping at the same color. This will take the shot out of
the optimum crema range, so it has to be a good crema blend. You can
also center cut the shots, however, this will reduce the distinctive
flavors and can lead to blandness. On the other hand, somewhat bland
center cut shots are good way to serve newcomers to straight espresso;
or those who prefer more subtle flavors.
- Over-intense flavors: Lower the pump pressure. If
this is because there's not enough sweetness to balance the bitters and
sours, use the previous fix. Also consider going more lungo with the
same stop color.
- Pallid Flavors: Raise the pressure. Also consider
going more ristretto with the same stop color.
- Overly sour: Raise the temperature. Short term,
trying stopping lighter and grinding finer to keep the volume the same.
If it's really bad, start-dump.
- Overly bitter: Lower the temperature. Short term, try
stopping darker and coarsening the grind to keep the volume the same.
Pursuing the Godshot
If you've never tasted great espresso, you may have read the last
section and asked yourself how you can do all the diagnostics. You have
good taste, otherwise I can hardly imagine how you've read this far.
Good espresso isn't a punch in the mouth, but tastes wonderful. Expect
that, trust your taste and judgment, and make the adjustments
accordingly. Then taste the results. You'll improve very quickly.
To further develop that taste, it greatly helps to sample top flight
espresso and get a feel for all its possibilities. Take every
opportunity to visit good cafés and roasters, and try their
espresso and blends. Ask the coffee people there what you are tasting
and how to tell if it's right. Don't worry about getting bad
information—it's a lot easier to recognize a good coffee person
than a good coffee because their enthusiasm gives them away.
You can go further by drinking top flight estate coffees brewed
regularly and learning how the coffees from different places in the
world vary. In comparison to wine and other gourmet items, coffee is the
most economical of the truly great taste experiences. Deepen your
appreciation even further by home roasting you own coffees and blending
them for espresso, or taking part at tastings conducted by roasters.
There is a large variety of espresso equipment, and it's useful to
know something of the possibilities. These are discussed in great detail
on the coffee Internet sites (see the resources and
the rest of this site). If this interests you, participate in these
discussions. There are frequent get-togethers that are organized via
these sites, so you will also get some hands on experience.
Espresso is a social world. If you want to turn this into a serious
hobby, join the Specialty Coffee Association of America (SCAA), attend conventions
and barista competitions, get to know others like yourself, as well as
the stars of the business. If you like espresso and coffee, I guarantee
you'll enjoy the activity and like the people you meet.
Finally, coffee is a big global business. It encompasses large
numbers of very poor farmers whose livelihoods are frequently in the
balance, a few very big businesses buying from them cheap and cutting
quality, a mass public that doesn't know much about coffee except that
it's a pick-me-up, and a group of enthusiastic drinkers and purveyors
who love coffee. As enthusiasts, it's incumbent on us to convey to
others how rewarding good coffee can be. If we don't understand the
coffee trade and its issues, and if we don't foster a wider appreciation
of good coffee, many farmers will suffer, some of the world's great
coffees may disappear, and we will all be the poorer for it.
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