Cleanliness

Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and the habit of achieving and maintaining that state. Cleanliness is often achieved through cleaning. Cleanliness is a good quality, as indicated by the aphorism:

"Cleanliness is next to Godliness",[1] and may be regarded as contributing to other ideals such as 'health' and 'beauty'.

In emphasizing an ongoing procedure or set of habits for the purpose of maintenance and prevention, the concept of cleanliness differs from purity, which is a physical, moral, or ritual state of freedom from pollutants. Whereas purity is usually a quality of an individual or substance, cleanliness has a social dimension, or implies a system of interactions.[2] "Cleanliness," observed Jacob Burckhardt, "is indispensable to our modern notion of social perfection."[3] A household or workplace may be said to exhibit cleanliness, but not ordinarily purity; cleanliness also would be a characteristic of the people who maintain cleanness or prevent dirtying.

On a practical level, cleanliness is thus related to hygiene and disease prevention. Washing is one way of achieving physical cleanliness, usually with water and often some kind of soap or detergent. Cleaning procedures are of the utmost importance in many forms of manufacturing.

As an assertion of Moral superiority or respectability, cleanliness has played a role in establishing cultural values in relation to social class, humanitarianism, and cultural imperialism.[4]

Cleanliness is linked with proper hygiene. A person who is said to be clean usually depicts cleanliness.

Hygiene
Main article: Hygiene

Since the germ theory of disease, cleanliness has come to mean an effort to remove germs and other hazardous materials. A reaction to an excessive desire for a germ-free environment began to occur around 1989, when David Strachan put forth the "hygiene hypothesis" in the British Medical Journal. In essence, this hypothesis holds that environmental microbes play a useful role in developing the immune system; the fewer germs people are exposed to in early childhood, the more likely they are to experience health problems in childhood and as adults. The valuation of cleanliness, therefore, has a social and cultural dimension beyond the requirements of hygiene for practical purposes.

Industry
In industry, certain processes such as those related to integrated circuit manufacturing, require conditions of exceptional cleanliness which are achieved by working in clean rooms. Cleanliness is essential to successful electroplating, since molecular layers of oil can prevent adhesion of the coating. The industry has developed specialised techniques for parts cleaning, as well as tests for cleanliness. The most commonly used tests rely on the wetting behaviour of a clean hydrophilic metal surface. Cleanliness is also important to vacuum systems to reduce outgassing. Cleanliness is also crucial for semiconductor manufacturing.