How Are Cleaning Sponges Made?
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Sponges for cleaning have evolved from natural sponges harvested from the ocean to synthetics made from a variety of natural and man-made materials. The industry of harvesting natural sea sponges began before Roman times and was centered near Greece. The Mediterranean was the source for most natural sponges until the west coast of Florida became a harvesting center in the 20th century.
The man-made variety became popular soon after engineers from DuPont created the first synthetic sponge in 1942. DuPont held sway over the market from the 1940s until it sold its processing secrets to General Mills in 1952. Today approximately 80 percent of cleaning sponges in America are man-made. Cellulose wood fiber is the main material used to manufacture the common cleaning sponge we use today. The natural sponge market now consists largely of sponges used for personal hygiene and beauty applications.
Materials
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Man-made sponges are manufactured from three main materials. The chief ingredient is cellulose made from wood pulp. Sodium sulphate crystals are used to make the pores, or air pockets, and hemp fiber is added for strength. Chemicals for softening the cellulose and bleach for cleaning and whitening are also used.
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Manufacturing
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Sheets of cellulose fiber are soaked in chemicals to render them pliable and soft. The sheets, hemp fiber and sodium sulphate crystals are then placed in large rotating containers to blend the ingredients. When the mixture is thoroughly mixed in the rotating vats, it is poured into a mold and heated. The heat melts the sodium sulphate crystals, which flow to the bottom, where the liquid is removed. The pores or gaps left from the melted crystals form the familiar structure we see in finished sponges. The size of the crystals determines the size of the pores and the eventual use of the sponge. Large pores are used to make big sponges for washing cars, walls and floors, while finely perforated material can be sold for beauty and art applications.
The material, a hard block, next must be softened and cleaned. The blocks are first soaked in bleach to remove impurities and to ensure consistent coloring. Next, repeated soaking and rinsing in clean water completes the process, leaving the sponge material pliable and ready for drying and cutting.
Finishing
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The sponge material can now be cut and shaped. Many kitchen sponges have a scrubbing pad laminated onto them in this stage of the process, using polyurethane glue. The material is also tested for its tear resistance, color and overall quality before being packaged and shipped for individual distribution.
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