Grassing is one of the oldest methods of

bleaching Bleach is the generic name for any chemical product that is used industrially or domestically to remove color from (i.e. to whiten) fabric or fiber (in a process called bleaching) or to disinfect after cleaning. It often refers specifically t ...

textile Textile is an Hyponymy and hypernymy, umbrella term that includes various Fiber, fiber-based materials, including fibers, yarns, Staple (textiles)#Filament fiber, filaments, Thread (yarn), threads, and different types of #Fabric, fabric. ...

goods. The grassing method has been long been used in Europe to bleach

linen Linen () is a textile made from the fibers of the flax plant. Linen is very strong and absorbent, and it dries faster than cotton. Because of these properties, linen is comfortable to wear in hot weather and is valued for use in garments. Lin ...

and

cotton Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...

based fabrics.

Method

The linens were laid out on the grass for over seven days after boiling with the ''lyes of ashes and rinsing''. The atmospheric

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

and the oxygen left by the grass provide the whitening action. The cloth becomes whiter day by day until it attains the full whiteness. It was a slow process, but safer for the subjected material. Chemical bleaching may harm the cloth, but in the grassing it hardly affects the cloth's strength.

Bleachfield

The

Bleachfield A bleachfield or bleaching green was an open area used for spreading cloth on the ground to be purified and whitened by the action of the sunlight. Bleaching fields were usually found in and around mill towns in Great Britain and were an integral ...

was an open area to spread cloth. It was a field near the watercourse used by a bleachery. Bleachfields were common in and around the

mill town A mill town, also known as factory town or mill village, is typically a settlement that developed around one or more List of types of mill#Manufacturing facilities, mills or factories, often cotton mills or factories producing textiles. Europe ...

s during the British Industrial Revolution

Chemical bleaching

With the discovery of

Chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

in the late 18th century, chemical bleaching took over from grassing, as it was quicker and could be done indoors.

Oxygen bleaching action

It is the

conjugated double bonds In physical organic chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represent ...

of the substrate that makes the substrate capable of absorbing visible light. The absorption of light makes the cloth look yellowish. Bleaching with oxygen removes the chromophoric sites and makes the cloths whiter. Oxygen is a degrading bleaching agent. Its bleaching action is based on ''destroying the phenolic groups and the carbon–carbon double bonds.''. A major source of chemical bleaching is

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

() that contains a

single bond In chemistry, a single bond is a chemical bond between two atoms involving two valence electrons. That is, the atoms share one pair of electrons where the bond forms. Therefore, a single bond is a type of covalent bond. When shared, each of th ...

, (–O–O–). When the bond breaks, it gives rise to very reactive oxygen specie, which is the active agent of the bleach. Around sixty percent of the world's hydrogen peroxide is used in chemical bleaching of textiles and wood pulp.

Gallery

File:Old_method_of_Bleaching_Figure_20_Appleton_1884.tif, Early method of bleaching cotton and linen goods on lawns File:Linen Bleach Green (8251136135).jpg, Linen Bleaching/ Grassing File:Bleekveld.jpg, ''Bleaching Ground'' File:Jan Brueghel (I) and Joos de Momper (II) - Market and washing place in Flanders.jpg, Market and washing place in Flanders File:Catalyst 2188.jpg, A bleach worker File:Bleaching vats for cloth in the piece. Silk industry, South Manchester, Conn., U.S.A (NYPL b11707678-G90F070 026F).tiff, Bleaching vats for cloth in the piece. File:EB1911 Bleaching - Fig. 4. —High Pressure Blow-through Kier.jpg, High Pressure Blow-through Kier

References