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Padding compound is an adhesive that is used to bind different types of notepads and forms. Some padding compound consists of thick white glue that is known as common padding glue. Another type of padding compound is used on No Carbon Required (NCR) paper, where the compound is known as NCR glue. Manufacturers typically apply the adhesive to the edges of the paper; once the adhesive dries, the edges stick together to form a pad of paper.
To apply the adhesive to the edges of the paper, a manufacturer usually paints the padding compound on with a brush. The manufacturer usually first stacks the paper and compresses it in a padding clamp. With the paper compressed, the glue is then brushed on in a thin, even layer. The adhesive usually goes on white and each pad typically requires two coats. When the adhesive dries, it changes color from white to clear. Once the entire surface is clear, the compound typically is dry and the pads are ready to be cut to size.
Because most padding adhesive peels off easily, manufacturers try to cut the pad without tearing the glue. To accomplish this, they position the pads on the cutter so that the blade slices through the dried glue before slicing through the paper. If the blade cuts into the paper before the glue, it might drag the glue away from the paper and ruin the pad.
NCR glue usually takes a little more skill to apply. Carbonless paper typically consists of several multi-colored sheets of paper. The sets usually include a top white sheet, a middle yellow sheet, and a bottom pink sheet. Manufactures typically stack 500 sets at a time into a padding clamp. The sets of paper contain a chemical that allows the compound to adhere to the paper instead of to each individual sheet.
Manufacturers then use a paint brush to apply the NCR glue. The glue is watery and goes on clear while the NCR paper soaks it in. During the process, the paper might wrinkle due to the soaking process. Manufacturers typically allow the paper to wrinkle a little bit, but if the paper fuzzes up or wrinkles too much, it indicates the paper is over-saturated with glue. Once the carbonless padding compound dries, the sets are ready for use.
Padding compound is generally considered safe to use. Although it is not recommended to eat, if children come into contact with it, it usually will not poison them. If a parent is concerned about his or her child's safety, it is generally recommended that he or she consult with a physician.
Common padding glue will become brittle over time. When the adhesive becomes brittle, the pages will peel apart easily and the spine of the pad could crack. NCR compound does not crack over time — once the adhesive dries, the NCR paper will remain stuck together until the sheets are peeled apart.