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Padding compound is an adhesive that is used to bind different types of notepads and other paper products. Its name comes from its ability to turn loose papers into coherent pads in which pages can be removed one at a time. There are usually two main types of compound, both of which are widely available commercially in most places. The first, which resembles a thick white glue, is typically known as “common” padding glue. It’s more or less designed for general use, and is suitable for most materials. The biggest exception is paper known specifically as “no carbon required”(NCR) paper; on these pages, NCR glue is the best adhesive to use. The application process is similar no matter the type in question: manufacturers typically stack the paper, compress it, then paint the adhesive on with a brush. Once everything is dried, the compression is removed and the paper should remain bound. One of the biggest advantages to both sorts of adhesive is its flexibility. People can rip off pages easily without impacting the integrity of those remaining. Padding adhesive can also sometimes be made at home, though do-it-yourself bindings may take a bit of practice and trial-and-error before getting good results.
Most padding compounds are used in industrial manufacturing settings where production is automated. Even when done individually, though, the process is usually about the same. The manufacturer usually first stacks the paper and compresses it in a padding clamp. It’s important that the pages are even and perfectly aligned in order to give crisp corners and edges. In most cases pages are placed on top of a cardboard or other thick backing, which adds durability as well as stability.
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 usually 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 if they’re being made in bulk, or at least trimmed at the glue line if they’ve been made individually.
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 professional-grade cutters 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. Smaller merchants can get a similar look with craft cutters or precise use of thin knives.
NCR glue usually takes a little more skill to apply. Carbonless paper typically consists of several multi-colored sheets of paper that have a few more specifications than more ordinary stock, and their main purpose is to allow users to make multiple copies of written notes at once. This sort of paper is very popular for written receipts and invoices, among other things. 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 warps, the paper is probably over-saturated with glue. Once the carbonless padding compound dries, the sets are ready for use. Sometimes trimming is necessary, but not always; this sort of glue tends to more readily grip the sides and often creates a smooth edge on its own.
One of the advantages to NCR glue is its durability. Most common padding glues 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 paper will remain stuck together until the sheets are peeled apart.
Padding compound is generally considered safe for all environments and users. 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.