foam

Foam is an object formed by trapping pockets of gas in a liquid or solid.
A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas. Soap foams are also known as suds.
Solid foams can be closed-cell or open-cell. In closed-cell foam, the gas forms discrete pockets, each completely surrounded by the solid material. In open-cell foam, gas pockets connect to each other. A bath sponge is an example of an open-cell foam: water easily flows through the entire structure, displacing the air. A camping mat is an example of a closed-cell foam: gas pockets are sealed from each other so the mat cannot soak up water.
Foams are examples of dispersed media. In general, gas is present, so it divides into gas bubbles of different sizes (i.e., the material is polydisperse)—separated by liquid regions that may form films, thinner and thinner when the liquid phase drains out of the system films. When the principal scale is small, i.e., for a very fine foam, this dispersed medium can be considered a type of colloid.
Foam can also refer to something that is analogous to foam, such as quantum foam, polyurethane foam (foam rubber), XPS foam, polystyrene, phenolic, or many other manufactured foams.

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  1. Morning Glory

    Recipe Asparagus with Egg Fried in Brown Butter & Miso Tarragon Foam

    Making foams is great fun and much easier than some other ‘modernist cooking’ techniques. You will need lecithin powder and a stick blender. I managed to find some white miso which was nearly white in colour (a lot are more yellow or browny beige than white). The brown butter adds a nutty...
  2. Morning Glory

    Recipe Parsley Foam

    To make this foam I used a stick blender but to make life easier you could use a 'cream siphon' which takes nitrous oxide chargers. You will also need powdered lecithin which is available from Amazon. Here I used the foam with asparagus, smoked salmon and lumpfish caviar. Ingredients (serves...
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