Liquid flow is a type of photography that uses a property in physics called emulsion. An emulsion is a mixture of two liquids that ordinarily do not combine, such as oil and water. Think of an oil-and-vinegar salad dressing. When shaken, the two liquids will form a temporary emulsion. After a short time, however, the two will separate back out into layers. Many medicines and paint are other examples of emulsions. When you see the direction, "Shake well before using," you know you are dealing with an emulsion. In this photography example I am using an emulsion between water and colored half and half, which makes these cloud-type formations when the milk is injected into the water. The half and half in water is a permanent emulsion, because if the mixture is left to sit it will not separate back out over time.
Diffusion is another contributing factor in this picture. As you can see in the bottom of the photograph, where it starts, the stream is much smaller than it is later in the stream.
Diffusion is another contributing factor in this picture. As you can see in the bottom of the photograph, where it starts, the stream is much smaller than it is later in the stream.