Cassandra Stark, age 12, of Lynn, Mass., for her question:
WHO WERE THE FIRST TO USE BLEACHING?
Bleaching is the process of turning cloth and yarn white by removing the natural coloring. The ancient Egyptians, Babylonians and Hebrews were the first to use bleaching.
From ancient days until the 1700s, bleaching was done by spreading wet cloth on the ground and leaving it exposed to sunlight until it turned white. People believed that this process strengthened the fiber and made the cloth last longer.
Dutch weavers of the 1700s discovered that potash lye would bleach cloth. They dipped the cloth in lye several times and then soaked it in buttermilk. After this, they washed the cloth and spread it on the ground to whiten.
Fabric bleached in the dye and sun method was given the name holland or hollands.
A desirable quality of linen which weavers spread on plots of grass came to be known as lawn. The Scots and Irish still bleach their fabrics by spreading them on plots of grass. People call this process crofting, from the old English word croft, meaning a small tract of meadowland.
In industrial bleaching today, cloth is washed, boiled and soaked before being dipped in chemicals. Manufacturers usually use hydrogen peroxide or sodium hypochlorite to bleach cotton and linen cloth.
The material is usually soaked in a chemical bleaching bin for two to 12 hours. The length of soaking depends on the texture of the cloth and the strength of the bleaching chemical.
A solution of sulfuric acid washes the chemical out of the material before the cloth is dried. This solution prevents the bleaching chemicals from harming the fabric.
Wool and silk is bleached with hydrogen peroxide or sulfurous acid. These goods may also be bleached by exposing the wet cloth to fumes of burning sulfur.
In the bleaching method using fumes, the sulfur combines with the coloring in the material to form a colorless compound. This process does not destroy the original coloring matter. The color will reappear in a yellowish shade if the material is washed with a soap containing potash.
Surfuric acid is used to remove the color from feathers and straw.
Chlorine bleaches wood pulp and the rags from which paper is made.
Other materials which are sometimes bleached include beeswax, hair, ivory, oils and sponges.
Chlorine dissolved in water produces both hydrochloric and hypochlorous acid. The solution is used as a bleach and disinfectant. Chlorine also replaces bromine and iodine from their salts.