What is commonly known as “bleach” is actually any chemical solution which can remove or lighten colour, through a process called oxidation.
Essentially what happens is that the bleach interferes with the chemical bonds within the chromophores – these are molecules within a stain or dye which absorb light at specific wavelengths and so “produce” colour. When these bonds are disturbed, it changes the optical properties of the molecule which makes them “colourless” and thus, we say that the stain has been removed or the dye faded. In actual fact, it is still there but we just can’t see it anymore. The sun itself has the same effect as high energy photos in sunlight, such as ultra violet rays, can also disrupt the bonds within the chromophores, leading to decolorisation – this is why things can fade when you leave them in the sun for too long.
Types of Bleaches
The most common bleaches are “chlorine bleaches” (such as a solution of sodium hypochlorite) and “oxygen bleaches” (such as hydrogen peroxide or compounds that release peroxides, such as sodium per carbonate). Another common product is ‘bleaching powder’ which is made of calcium hypochlorite.
However, many other chemicals can have bleaching properties therefore it is always worthwhile checking the ingredients list of any product you are using to make sure that you will not be unwittingly removing colour from your fabrics. Names to look out for are: sodium persulfate, sodium perphosphate, sodium persilicate, their ammonium, potassium and lithium analogs, calcium peroxide, zinc peroxide, sodium peroxide, carbamide peroxide, chlorine dioxide, bromate, and organic peroxides (e.g., benzoyl peroxide).
Bleaches and Stains
Because of their strong ability to remove colour, bleaches are of course very popular in the removal of stains although they do have to be used with great care and cannot be used on many fabrics. In particular, never use it on silk or wool or on anything delicate. It tends to be good for the treatment of white cottons and linens, especially if they have yellowed through use and time.
Washing them with bleach in hot water and then hanging in the sun afterwards to dry will usually do the trick. Be careful, however, about using bleaches on fabrics such as spandex, nylon, leather and of course, wool and cotton, as the bleach itself can cause permanent yellowing of these fabrics! In these cases, it may be better to use a specific stain removing product instead.
Always dilute bleach before it comes in contact with fabric (follow the instructions from the manufacturer). Chlorine bleach is the strongest form of bleach and comes in both powder and liquid form, although the latter is more popular. It is used a lot as a disinfectant because of its ability to kill bacteria and algae and other organisms (e.g., in swimming pools and even drinking water) and as a cleaning agent. However, for laundry purposes, oxygen bleach may be a better choice as it is milder and safer to use on more materials than chlorine bleach. It is a popular ingredient in carpet cleaners and laundry detergent. Bleach also oxidises food and other particles making them easier to remove from fabric.
Remember also that there are many household items that have mild bleaching properties and so can be tried on stains first before resorting to strong chemicals. These include white vinegar and lemon juice and drying the fabric afterwards in the sun will help the bleaching effect. However, you should still test for colour-fastness before using them.
Hazards of Bleach
Like all powerful chemicals, bleach is potentially very dangerous. Chlorine bleach, in particular, is very reactive. For example, it should never be mixed with ammonia (or even urine), as the chemical reaction triggered can produce poisonous fumes that can cause a severe respiratory reaction. In addition, chlorine can react with organic material to form trihalomethanes (a well-known one is chloroform) which are carcinogenic compounds.
Chlorine gas is also a respiratory irritant – it reacts with the moisture on the mucous membranes in the nose and throat and forms acids which burn the membranes. It can also burn the skin. In fact, a few deep breaths of pure chlorine gas can be fatal. Therefore, always wear protection (e.g. gloves, goggles and mask) when using chlorine, make sure the area is well-ventilated and limit your exposure to the shortest time possible.