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Trouble, such as bleeding of patterned items or partial exudation of colors, is repeatedly found when garments are returned from dry cleaner's. Many are items that require laundering or washing in water,
cleaners are blamed for such trouble, undetected when handed over.
But then with tumble-dried items, somehow, bleeding rarely occurs.
In most cases, bleeding is caused when a chemical bonding breaks off between reactive dyestuff and cellulosic fiber, which is generally known as 'acid hydrolysis' among experts. In short, acid substances
resolve the bonding of dye and fiber and not the dye itself, thereby producing staining.
Often, it involves past exposure to the rain when being worn or hung up to dry. The rain, regarded as acidic nowadays, contains sources of air pollution such as sulfur dioxide, which in the air turns
into sulfuric acid, or nitrogen oxides that become nitric acid.
The acidity of a rain-soaked garment is not so extremely high, however, highly-concentrated acid substances are produced as it dries, causing acid hydrolysis on reactive-dyed items. Such hydrolysed
substances often have a tendency to migrate along with water in fiber, which is how bleeding occurs when garments are hung up to dry. As migration is conspicuously found in more easily-dried areas,
staining trouble becomes particularly marked.
Stains are often removed by washing in a solution of an anion activator, whereas cation activators make removal more difficult.
Tumble drying makes bleeding homogeneous, and therefore, less obvious.
(T.T.)
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