How Sandpaper is Made

  • 01 of 10

    How Sandpaper is Made

    Printing the grit size and type on the back of sandpaper
    Printing the grit size and type on the back of sandpaper. (c) 2009 Chris Baylor licensed to, Inc.

    The first step to making any sandpaper product is to print the backer on the back of the paper. On sheets of sandpaper, this is where the grit and type of paper are noted. As can be seen in the image above, this is done on very large rolls of paper (roughly four-feet wide), even though the printing may eventually be covered by backing such as a hook-and-loop attachment for power sanders.

    An interesting side note: In 1994, Ali Industries began building a huge sandpaper manufacturing machine (that they affectionately call "The Maker"). Printing the backing is the initial step performed by The Maker. The first paper that came off of this manufacturing line was a batch of 320-grit garnet sandpaper in 1997. A number of the upcoming steps will show parts of The Maker.

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  • 02 of 10

    Adding the Grit to be Applied

    A hopper full of the raw sandpaper abrasive
    The raw sanding grit to be used on sandpaper. (c) 2009 Chris Baylor licensed to, Inc.

    The grit to be applied to the sandpaper is poured from bags (that are purchased from outside sources) into a hopper.

    There are various types of grit used in different types of sandpaper. For instance, many hand sandpapers are made using garnet or aluminum oxide, while many abrasive papers used for power sanders are manufactured using black zirconium (which is basically the same material that cubic zirconium faux-diamonds are made from).

    Surprisingly, this sand grit in the hopper feels far smoother than it does on the sandpaper. The above picture is of some 120-grit abrasive, but it literally feels almost silky in the raw form.

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  • 03 of 10

    Applying Resin to the Sandpaper

    Adding resin to the sandpaper
    Adding resin to the sandpaper. (c) 2009 Chris Baylor licensed to, Inc.

    In order to add the grit to the paper, a resin must first be applied to the paper. The printed paper is fed through a vat containing the chosen resin in the image above.

    There are a few different resins that are used in the manufacturing of sandpaper, but the two main types are urea resins, used for hand sandpapers, and phenolic resins for power sanding. Phenolic resins hold up much better to the heat generated by power sanding.

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  • 04 of 10

    Adding the Grit to the Sandpaper

    Grit as it is applied to the sandpaper
    Grit being embedded into resin on the sandpaper. (c) 2009 Chris Baylor licensed to, Inc.

    With the resin applied, the paper is ready for the grit to be applied. This is probably the most interesting and critical step of how sandpaper is made. One might expect that the grit is simply sprinkled evenly onto the paper, but in actuality, it is a bit more high tech.

    The grit is sprinkled onto a conveyor belt that is electrostatically-charged, which in turn gives the grit a static charge. As the conveyor moves along, the resin-coated paper is brought down across a roller about two inches above the conveyor. Because of the difference in the static charges, the grit literally leaps upward onto the resin-coated paper. More impressively, because the heaviest part of each uniquely-shaped grain carries a stronger charge, the thickest part of each grain is embedded into the resin, leaving the sharpest edge of each grain exposed.

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  • 05 of 10

    Drying the Resin

    Drying the resin in the oven
    Drying the resin. (c) 2009 Chris Baylor licensed to, Inc.

    After the grit is applied to the paper, the entire roll is run through a huge oven. The long strip of paper is literally draped over a series of arms (see the image above) that will slowly carry the freshly-created sandpaper through a long oven. The temperature in this oven is closely monitored, and the draped paper is taken down one side of the oven, then back up the opposite side. The entire drying process takes less than an hour to dry the resin and bond the grit to the paper.

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  • 06 of 10

    Adding a Second Coat of Resin

    Adding a second resin coat to the sandpaper
    Adding a second coat of resin to the sandpaper. (c) 2009 Chris Baylor licensed to, Inc.

    After the sandpaper has dried in the oven, the second coat of resin is applied and then dried. By adding a second coat of resin to the paper, the grit is coated with resin, which will give it a much longer life when in use than would occur without the second coat of resin.

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  • 07 of 10

    Flexing the Sandpaper

    Flexing the sandpaper
    Flexing the sandpaper. (c) 2009 Chris Baylor licensed to, Inc.

    Once the sandpaper has had a second coat of resin applied and dried, the entire roll is next run through a machine called a flexer (see the image above). This is basically a series of rollers designed to loosen up the resins a bit without removing the grit from the paper. The result is much more pliable sandpaper.

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  • 08 of 10

    Applying the Backing

    Applying a fabric backing
    Applying a fabric backing. (c) 2009 Chris Baylor licensed to, Inc.

    After flexing the sandpaper, the final manufacturing step before cutting and packaging is to apply any required backer to the sandpaper. For instance, many random orbit sanders utilize a hook-and-loop fastening system. It is during this step that the fabric backing for the hook-and-loop fastener would be applied to the sandpaper.

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  • 09 of 10

    Printing the Packaging

    Printing the Gator Finishing Packaging
    Printing the Gator Finishing Packaging. (c) 2009 Chris Baylor licensed to, Inc.

    Before the finished sandpaper can be packaged and prepared for the retail shelves, the packaging must be prepared. Ali Industries does nearly all of their packaging in house. They can print, cut fold and glue nearly all of the packaging that their customers require.

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  • 10 of 10

    Cutting and Packaging

    Cutting random orbit sanding disks
    Cutting stacks of random orbit sanding disks. (c) 2009 Chris Baylor licensed to, Inc.

    The final step in how sandpaper is made is cutting and packaging.

    Once the finished four-foot wide roll of sandpaper is completed, it is delivered to a cutting machine where the end product is cut and packaged. In the picture above, random orbit sanding disks are cut and packaged. The cutting machine will actually accommodate a number of rolls at one time, making packaging easier. For instance, if a finished package contains five random orbit disks of varying grits, the cutting machine operator would install five rolls of the required grits onto the machine, and the five sheets would roll off into the machine stacked on top of one another to be cut all at once. This makes it easy for the operator to simply remove stacks of five disks at a time, as seen above.

    In the case of other products, such as belt sander belts, there are additional steps to be taken. However, for most products that don't require additional manufacturing, the process is similar. Add the prescribed number of rolls to the cutter, run through the cutter and remove stacks from the back side, placing them into finished packages and into boxes for shipment.