Cezve is famous for the foam, or raghweh, produced during the brewing process. As the slurry temperature passes approximately 88°C (190°F), a thick layer of ragweh begins to form on the surface. The cell structure of raghweh tends to be a little larger than that of espresso crema. The volume of the slurry can nearly double in size after the formation of the raghweh, and after a cezve is decanted into a cup, the foam can be very persistent, sometimes remaining far longer on the surface of a beverage than espresso crema typically lasts.
Traditional cezve recipes usually allow the foam to rise to the top of the cezve. At the point that the foam begins to skirt the rim of the cezve, the brew is rapidly decanted into a cup — foam, grinds, and all — usually in a single pour.
Some baristas prefer to stop brewing their cezveler at a very low temperature. In certain parts of the world, such as Greece, it is customary to allow the slurry to rise up, remove it from the heat, and then, after a few seconds, return it to the heat. This process is often repeated three times before the coffee slurry is decanted into a cup.
In the following experiment, we aimed to find out how much of a difference the end temperature makes to the TDS of the final brew.
This experiment showed us that it is difficult to achieve a consistent TDS from one cezve batch to the next. We observed a clear correlation between increased TDS percents and a fine grind, but with some notable exceptions. For example, the mean TDS for the 87°C brews was higher than for the 90°C batches.