A milk watcher, milk saver, pot watcher, pot minder, milk guard, or boil over preventer is a

cooking utensil A kitchen utensil is a small hand held tool used for food preparation. Common kitchen tasks include cutting food items to size, heating food on an open fire or on a stove, baking, grinding, mixing, blending, and measuring; different utensils a ...

placed at the bottom of a pot to prevent the foaming boil-over of liquids by collecting small bubbles of steam into one large bubble.

Description

A milk watcher is a disk with a raised rim notched on one side (see images). Some milk savers are designed so they can be used with the obverse or reverse side facing up and appear to have two notches. The interior of the disk slants upward toward the notched side, creating a space just behind the notch where water vapor can collect. Water vapor trapped under the Milk Saver causes the notched side to rise up, releasing the water vapor and making a rattling noise.

Explanation

Normally, boiling water does not boil over. When fats, starches, and some other substances are present in boiling water, for example by adding milk or pasta, boiling over can occur. A film forms on the surface of the boiling liquid; for example, cream can boil over as

milk fat Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain. Composition Butterfat is mainly composed of triglycerides. Each triglyceride contains three fatty acids. Butt ...

separates from the milk. The increased viscosity of the liquid causes the

steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization ...

bubbles to form

foam Foams are materials 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 reg ...

trapped under the film, pushing the film up and over the lip of the pot, boiling over. A milk watcher disrupts this process by collecting small bubbles of steam into one large bubble and releasing it in a manner which may puncture the surface film. The device also rattles when boiling occurs, alerting the cook who may then lower the heat setting of the stove. By circulating fluid around the bottom of the pot the device may also prevent material from being deposited and eventually burned on the pot's bottom.

History

The milk watcher was invented by I. F. Ivankovitser in 1921; a patent was obtained in 1929. It was reinvented by Vincent Hartley in 1938.History of Hartley Botanic
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References

External links

{{Kitchen tools Food preparation utensils Milk 20th-century inventions Products introduced in 1921