In coffee shops and kitchens around the world, there are people striving to make the perfect espresso – and the mark of a good espresso? 

Well, it's the crema, of course. So, how do you achieve that beautiful, foamy texture that sits on top of an espresso?  

What is crema, and how is it made?

Crema is the tawny, brown-coloured foam that sits on top of a freshly pulled espresso.

The crema on an espresso reflects the quality of the brewing process – it's the holy grail for baristas everywhere. But how is it made? Can understanding the science behind it help you to improve your skills at pulling the perfect espresso?

It all started with Achille Gaggia who made the first crema when he began using a pressurised espresso machine to make coffee in the 1940s. Though it was a by-product of the machine, he turned this 'crema caffe naturale' into a unique selling point.

Coffee contains carbon dioxide and when it leaves the pressurised environment of an espresso machine, the CO₂ escapes as tiny bubbles. These bubbles then combine with the coffee bean oils to make the distinctive-looking crema on your espresso.

So, it stands to reason that a good crema can only be made with a good espresso machine? Not quite – the beans and the barista also have an important part to play.

Beans for a crema espresso gourmet

The first, and most important, rule of making the perfect crema is to use fresh beans.

Freshly roasted beans produce more crema, and that's because when coffee beans are left for too long, they start to lose their carbon dioxide content (degassing).

For a rich, velvety crema full of flavour, make sure you grind the beans just before you're about to brew your coffee. To achieve that sought-after Guinness effect, we recommend using a slightly darker roasted coffee bean.

Our espresso crema blend uses Arabica beans roasted in a traditional way over an open flame to give the coffee its distinctive Italian flavour. This roasting process allows us to roast the beans differently to release their natural oils without burning them.

Perfecting your shot of espresso

How well your espresso machine performs will affect the quality of the crema, but the brewing process is as much about the barista as it is the technology.

For the best crema, you're looking for an extraction time of between 25 and 30 seconds (for a single or double shot), and to get this right, you'll need to experiment with your grind size.

The coarseness of your coffee affects the brew time and while always adding the same amount of coffee each time we can use this rule of thumb:

• if your extraction time is too quick, try grinding your coffee more finely, but
• if your extraction time is too slow, your grind needs to be coarser

Our fair trade espresso beans can be ordered as a fine ground coffee to get the best brewing experience from your machine.

Check the pressure and temperature on your machine before you begin. Using a high pressure setting (8-9 bars) at a lower temperature will soften the bitter elements of your coffee. We've had success as low as 86°C with the machines in our showroom.

Getting the volume of hot water right is also important. We recommend one part ground espresso coffee to two parts brewed espresso (you can use a scale to measure this if you are really geeky e.g. 18g of ground coffee to 36g of brewed espresso).

What does the perfect crema look like?

A good crema should be foamy with a fine layer of bubbles that stretches across the cup and holds for at least two minutes. If it disappears too quickly, then your coffee wasn’t ground fresh enough or something has gone wrong in the brewing process.The top of a shot of espresso should be about a tenth of the whole cup. 

Some people skim off the crema on their espresso because they don't like the bitter taste, while others stir it into the rest of their coffee – but whether you like it or not, the perfect crema will continue to be the mark of a well-made espresso.