Under-extracted espresso has a pale colour with a thin layer of crema. Under-extracted espresso often flows very fast delivering 30ml of liquid in less than 25 seconds. Under-extracted espresso can have an acidic flavour with a lack of body.
The cups are cold
Cold cups cause the beautiful rich espresso to lose body very quickly
Store your cups on the cup warmer (where available) or pre-heat your cups with hot water before use.
Ground coffee is old/stale
Once coffee has been ground it begins to rapidly lose its flavour and aroma due to oxidisation.
Coffee should be ground fresh for each cup of coffee to ensure the best quality espresso. If you grind too much coffee, then discard this before you make the next cup. If you don't have a quality burr coffee grinder, then this should be the next thing on your shopping list.
Coffee grind is too course
Coffee that is not ground fine enough (too course) has insufficient contact with the water to fully exploit the coffee oil and flavour for quality espresso. Equally ground coffee that is too course will result to an extraction pressure that is too low.
Adjust your coffee grinder so that you achieve espresso extraction that meets the espresso extraction criteria.
Extraction pressure is too low
Insufficiant extraction pressure will not allow the oils in the coffee to be exploited for the correction creation of espresso crema.
Insufficient extraction pressure is due to not enough coffee being used, the grind of coffee not being fine enough, or insuffcient tamping pressure used to compress the coffee.
Water temperature is too cold
Water at the point of extraction (not in the cup) must be at least 88 degrees centigrade for correction exploitation of the coffee for successful development of espresso crema.
Wait for your esresso machine (inclduing the brewing group) to warm up to the correct temperature.
Coffee dose is too low
Using less than 6.5 grams will result in too low an extraction pressure and not enough coffee oil being available to make a single espresso.
Increase the dose of coffee to at least 7 grams per single shot of espresso.