The absence of oil (or the significantly lower oil content compared to traditionally brewed coffee) makes the system more stable and the bubbles do not collapse with the same ease as in crema. Soon after the foam is created, a process of thickening takes place where water molecules are constantly pushed out of the frothy mixture. The water is pushed out due to drainage occurring due to pressure differentials along the foam septum. Higher viscosity will retard the phenomenon, and that is the reason that the addition of sugar will create a better foam. The phenomenon continues until bubbles come very close together and the foam almost solidifies. This process can take between 2 minutes to 10 minutes and depends strongly on the agitation process during mixing.
When the bubbles come closer together, they will slowly begin to coalesce and form larger bubbles. According to Laplace's equation, variation in bubble size, is in rapid collapse of the bubbles, because bubbles consume the greater the smaller the result. Hand mixers for smaller and more uniform-sized bubbles create. The smaller bubble size reduces the bubble pressure gradient and is much longer lasting foam.
The presence of oil (a hydrophobic substance) can be a more rapid collapsing process localized reduction of the foam elasticity, which for the production of a lighter foam having an average bubble diameter of more than 4 mm. This is the reason, it is not possible to achieve good frappe in many countries, unless a spray-dried coffee pot (in fact generally less expensive than freeze-dried instant coffee). The use of a hand mixer makes it possible to fine bubbles by the time that the foam can be increased. The best coffee frappe often associated with the smallest bubbles and foam thickness about 1.5 cm to 2 inches (30 mm to 50 mm).
The presence of oil (a hydrophobic substance) can be a more rapid collapsing process localized reduction of the foam elasticity, which for the production of a lighter foam having an average bubble diameter of more than 4 mm. This is the reason, it is not possible to achieve good frappe in many countries, unless a spray-dried coffee pot (in fact generally less expensive than freeze-dried instant coffee). The use of a hand mixer makes it possible to fine bubbles by the time that the foam can be increased. The best coffee frappe often associated with the smallest bubbles and foam thickness about 1.5 cm to 2 inches (30 mm to 50 mm).
