Caking
Tendency of powder to form lumps or masses
Caking is a powder's tendency to form lumps or masses. The formation of lumps interferes with packaging, transport, flowability, and consumption. Usually caking is undesirable, but it is useful when pressing powdered substances into pills or briquettes. Granular materials can also be subject to caking, particularly those that are hygroscopic such as salt, sugar, and many chemical fertilizers. Anticaking agents are commonly added to control caking.
Caking properties must be considered when designing and constructing bulk material handling equipment. Powdered substances that need to be stored, and flow smoothly at some time in the future, are often pelletized or made into pills.
01Mechanism
Caking mechanisms depend on the nature of the material. Caking is a consequence of chemical reactions of grain surfaces. Often these reactions involve adsorption of water vapor or other gases. Crystalline solids often cake by formation of liquid bridge between microcrystals and subsequent fusion of a solid bridge. Amorphous materials can cake by glass transitions and changes in viscosity. Polymorphic phase transitions can also induce caking. The caking process can involve electrostatic attractions or the formation of weak chemical bonds between particles.
02Anticaking agents
Anticaking agents are chemical compounds that prevent caking. Some anticaking agents function by absorbing excess moisture or by coating particles and making them water-repellent. Calcium silicate (CaSiO3), a common anti-caking agent added to table salt, absorbs both water and oil. Anticaking agents are also used in non-food items such as road salt, fertilisers, cosmetics, synthetic detergents, and in manufacturing applications.
Sources and credits
This article is adapted from the Wikipedia article “Caking”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Calcium chloride CaCl2.jpg by No machine-readable author provided. Firetwister assumed (based on copyright claims)., CC BY-SA 3.0
- Charcoal Briquette.JPG by Vladsinger, CC BY-SA 3.0
Fathomly is not affiliated with or endorsed by the Wikimedia Foundation. Spotted a problem? Tell us.