Detergents and soaps are two of the most common cleaning and stain removing agents you will come across and many people think that they are the same thing, but actually there are distinct differences with different types preferable for different situations.
What’s the Difference?
Soap and detergents are similar in that they are both ‘surfactants’ or ‘surface-active agents’ which reduces the surface-tension of water and effectively allows it to “wash better”. Soap and detergents are also similar in that they perform the same function – that of lifting dirt and grease and cleaning. However, soap is made of natural materials, whilst detergents are synthetic, created during the Second World War when the oils and fats needed to make soap became very scarce. In general, as soaps are a more natural product and less harmful they are used to clean the body, whilst detergents are used in laundry, dishwashing and other household areas. However, detergents are fast superseding soaps in many areas, due to their ease of production and adaptability. Many cleaning agents nowadays are also a mix of soaps and detergents.
Soap
Soap is made when fats and oils (from plants and animals) are combined with an alkali (eg. lye) in a chemical reaction. Depending on the alkali used, soaps can be made in the hard ‘bar’ form, or the soft ‘liquid’ form which is popular nowadays in many public services. As well as being less harsh on the skin, soap is also kinder on the environment as it is made of biodegradable materials and does not cause pollution in the lakes and rivers. It is also not as toxic to wildlife and plants.
Most commercial soaps eliminate the glycerine at the end of the production process, which deprives the skin of the natural, moisturising glycerine and generally leaves the skin feeling dry. Thus, for the best soaps to use on skin, look for those which have not had the glycerine removed – usually these are ‘superfatted’ soaps or soaps made from an excess of fat. Hand-made soaps are usually in this category. In addition, avoid soaps that contain the additive sodium laureth sulphate as research has shown that this is very harsh on the skin. Soaps in which emollients such as jojoba oil or shea butter are added during production are also better for the skin. You can also find soaps made exclusively from vegetable oil (usually olive oil) called castile soap, which is one of the most basic, natural soaps. It can be slow to lather but produces rich, creamy suds which are gentle and mild enough for sensitive skin (although castile soap is not recommended for hair).
Unfortunately, soap does have one very big drawback, particularly in areas of hard water, in that it reacts with the minerals in water to form an insoluble film or ‘soap scum’, which can clog drains and pipes, and stick to clothing, turning them grey, as well as leave a residue. In addition, the soap does not rinse out as well and so causes a build-up on clothes over a period of time, causing the fabric to deteriorate, as well as leaving an odour. Lastly, it deteriorates faster in storage and its cleaning power decreases over time. Thus, for all these reasons, detergent is preferable to soap for use in the laundry and other household cleaning chores.
Sugar soap, which is an industrial cleaning material commonly used in painting preparation and general outdoor surface cleaning, is not actually a soap at all and does not contain any sugar either. It is made of a mixture of alkaline salts and can also contain abrasives.
Detergents
Detergents are made in a very similar process to soap, but using synthetic chemicals – one of which is propylene, a waste-product from the petroleum industry. Because they react less with minerals in water and are more powerful, they are ideal for use in the washing machine. In addition, they can be specially designed for specific cleaning tasks and for use in different types of machines (eg, front-loading washing machines should only use a low-suds detergent). They can contain abrasives to scour, chemicals to modify the pH of water and acids for descaling or caustics to destroy dirt. For areas of hard water, they can include water softeners to combat the effects of calcium deposits.
Many modern detergents claim to have “active oxygen” or oxidants – these help in bleaching and in the destruction of dirt. Others are specially formulated with enzymes to digest proteins, fats and carbohydrates, particularly effective on food and other organic stains – these are called biological detergents and are very popular. Their powers mean that they are effective even in warm or cold water, which is both energy-saving and kinder on fabrics. However, some people dislike them as they are believed to cause skin allergies. (NOTE: biological detergents must never be used on delicate natural fabrics like silk and wool).
For laundry, it is good to look for a detergent that is phosphate-free or low in phosphates, articifical fragrances and dyes, as these are skin irritants. Similarly, it is better to have the choice of adding fabric softener separately, rather than one that is combined with the detergent.
However, while detergents are better for practical purposes, they are terrible for environmental ones. They are incredibly toxic to fish and wildlife and contribute significantly to pollution. You can counteract this, however, by choosing detergents made from biodegradable ingredients, such as can be found in health food or environmentally-friendly shops. In addition, these detergents are made from renewable materials, instead of petroleum-based ingredients and with natural essential oil fragrance and no dyes.