Crema Diagnostics & Achiving Espresso Perfection

The presence of crema, the foam on your espresso, means you are in the ballpark within range of having the variables of temperature, grind, pressure, tamping, etc. under control. But how do you achive ‘Espresso Perfection’?

Crema is a part of the espresso. Espresso is not meant to be all crema, nor should it have less than 1/10th crema. Crema is part of the visual lure of espresso, the aromatics, the mouthfeel, the flavour and long-lasting aftertaste or espresso. In its technical definition, crema is gas bubbles suspended in a liquid film, that has high “surface tension” between the water molecules.

Crema should be compact and persistent: it should last 2 minutes before the suspended water molecules drain, the entrapped gas is released and the liquid underneath shows through.

The chart on the following page will assist in finding out symptoms that appear in crema and help you achieve espresso perfection. Treating one cause can sometimes reveal another problem.

The problems you cannot see:

Bad taste! Bitterness in espresso is a popular complaint. Before you blame the coffee, you need to make sure the machine is clean. A very bad, acrid bitterness results from machines/coffee handles that are dirty. A thorough cleaning of a neglected machine can be a considerable undertaking.

When the machine is clean, you should be able to do a dry-run with no coffee in the portafilter (meaning, run hot water into the cup through the coffee handle) … then let the water cool and taste it. If it tastes good, your machine should be clean.

Crema Diagnostics:

ISSUE	PROBLEM	SOLUTION	PICTURE
Is the crema a very light tan/yellow colour? Did the extraction take under 15 seconds? (Note, light crema can also indicate low water temperature).	Under Extraction	Increase extraction time by grinding coffee finer or tamping harder to increase extraction time. Did you use enough coffee? Check the weight of the coffee in the basket. Check water temperature. Was the machine, the group, the coffee handle all warmed up properly? Did the coffee rest long enough to degas?
Does the espresso have a very light tan dot in the middle of extremely dark crema colour? Did it take: take 7-10 seconds for the first drops of espresso to appear? come out in drops, never becoming a stream? take over 30 seconds?	Over	Grind to be coarser, back off on the pressure when you tamp the coffee. Did you use too much coffee? The range is 7 to 11 grams per single espresso.
Did the espresso have great crema colour, then visibly drop 1/4 inch or more in the cup as it sat for the first 1 minute? Was the surface of the espresso marked by very large, unstable bubbles in the crema? Is the crema pale?	Fast extraction, or light roast too.	This might be a combination of short extraction and lighter roast. Keep in mind you get a less persistent crema if you use robusta in your blend therefore you have more crema perhaps but it fades sooner.
Does the crema have a rich dark colour of tightly compacted foam? And/or does it have darker striations producing a “tiger skin” effect?	None! You have achived Espresso Perfection.	This is how I like my espresso to look. However, remember espresso is a matter of taste. When you see dark speckling over substantial amounts of crema, tightly compacted and persistent crema, with perhaps a lighter swiggle in the middle from the last drops of the shot … You can anticipate something good.
Does the espresso have a thin crema with large oil globules? Did it take a really long time to produce 1 oz of liquid? Did it come out of the coffee handle one drop at a time?	WAY Over extracted	Grind coarser, back off on the pressure when you tamp the coffee. Did you use too much coffee? The range is 7 to 11 grams per single espresso.
Does the espresso have grit in the cup after you finish?	Grind too fine