Sandpaper

Last updated
Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine)) Schleifpapier verschiedene Sorten.jpg
Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine))

Sandpaper, also known as coated abrasive or emery paper, is a type of material that consists of sheets of paper or cloth with an abrasive substance glued to one face. [1]

Contents

There are many varieties of sandpaper, with variations in the paper or backing, the material used for the grit, grit size, and the bond. It is common to use the name of the abrasive when describing the paper, e.g. "aluminium oxide cloth" or "silicon carbide paper".

Sandpaper is produced in a range of grit sizes and is used to remove material from surfaces, whether to make them smoother (for example, in painting and wood finishing), to remove a layer of material (such as old paint), or sometimes to make the surface rougher (for example, as a preparation for gluing).

History

The first recorded instance of sandpaper was in 13th-century China when crushed shells, seeds, and sand were bonded to parchment using natural gum. [2] [3]

Shark skin (placoid scales) has also been used as an abrasive, and the rough scales of coelacanths are used for the same purpose by the natives of Comoros. [4] Boiled and dried, the rough horsetail plant is used in Japan as a traditional polishing material, finer than sandpaper.

Cheap sandpaper was often passed off as glass paper; Stalker and Parker cautioned against it in A Treatise of Japaning and Varnishing published in 1688. [5]

Glass paper was manufactured in London in 1833 by John Oakey, whose company had developed new adhesive techniques and processes, enabling mass production. Glass frit has sharp-edged particles and cuts well whereas sand grains are smoothed down and do not work well as an abrasive.

In the United States, a major development in the history of coated abrasives was the work of Henry Hudson Barton. After emigrating from England in 1846, Barton married into a Philadelphia sandpaper manufacturing family. Drawing on his knowledge of gem minerals, he began experimenting with Adirondack garnet as an abrasive. Barton went on to establish mining operations at Gore Mountain (New York), in 1878, creating what became the world’s oldest continuously operating garnet mine. Garnet from Barton Mines was widely adopted in coated abrasives and further developments in sandpaper and remains a significant abrasive mineral today. [6]

Backing

320 grit silicon carbide sandpaper, with close-up view SCSandpaper.jpg
320 grit silicon carbide sandpaper, with close-up view

Depending on the desired application, different backing materials may be used for sandpaper. Some are more flexible, allowing sandpaper to follow irregular contours, while others are thicker and more suitable for heavy use.

Paper is the cheapest and the most used backing for coated abrasives, hence the common name "sandpaper". Paper backing comes in five weight categories: "A", "C", "D", "E" and "F", with A being the lightest and F the heaviest. For heavy-duty applications, such as disks for electric sanders, the paper may be reinforced with extra cloth fibers, resin or other additives. [7] [8] : 23–24 

In addition to paper, the most often use backing materials for coated abrasives are cloth (natural or synthetic), PET film and vulcanized fibre. [8] : 22 

Cloth backing typically comes in weights "J", "X" and "Y", from lightest to heaviest. Some manufacturers use additional weight designators, like "F", "JF" or "XF" for variants with extra flexibility or "YY" for an even heavier option. [9] [10] Cloth is preferred for its high durability, and used in applications such as sanding belts. [8] : 25 

PET film and vulcanized fibre are other high durability options. Film is also chosen for a very even thickness across the sheet, which yields a clean sand pattern. It comes in weights from 1 to 7. [8] : 26  Fibre is a thick and extremely strong backing, generally only used for sanding disks. [7] [10]

Wet/dry paper

Paper backing may be coated in a layer of a waterproof material, such as latex. Those types of sandpaper, called "wet/dry" [10] or "wet and dry", allow the use of a water-based lubricant, which is required for some applications. [8] : 24  Wet/dry paper was invented by 3M in 1921 and sold under the brand name "Wetordry". [11]

Wet/dry sandpaper is more effective when used wet, because the water washes particles away from the grinding surface and reduces clogging. [12]

Abrasive coating

The backing is coated in abrasive particles using an adhesive. Different parameters of the coating, such as the particle composition, size, or used adhesive can be changed to produce sandpaper suitable for different purposes.

Grit materials

Most sandpaper in the past used flint as the abrasive material. However, flint particles are too soft for most kinds of sanding, so flint paper is now barely used. [13] [8] : 10 

Instead, most coated abrasives nowadays use synthetic grit material. The most commonly used one is aluminium oxide (commonly abbreviated as ALO). Aluminium oxide paper is strong, inexpensive and suitable for a wide variety of uses for both wood and metal. Ceramic materials such as alumina zirconia are a more premium alternative, offering superior sharpness and longevity for an expensive price. Silicon carbide is another common synthetic material. It is available in very fine grit sizes and is commonly used for wet sanding. [14] [15] [13] [8] : 11–15 

Some natural materials are also still in use. For example, emery is used for metal polishing, garnet is used for wood finishing, while crocus paper (made from iron oxide particles) is used for fine polishing of soft metals. [13] [15] [8] : 7–11 

Friable grits

Some abrasive materials are designed to have a property called friability. Under the influence of heat produced from sanding, friable materials fracture at a controlled rate to expose new sharp edges. This allows them to last much longer compared to non-friable grits, which get dull and lose their abrasive properties with use. [8] : 13 

Grit sizes

Grit sizes Liivapaber-karedusindeksid.jpg
Grit sizes

Grit size is the size of the abrasive particles attached to the sandpaper. Sandpaper comes in a variety of grit sizes, ranging from very coarse (≈2 mm) to ultrafine (<1 µm). Coarser grit materials simplify sanding of hard surfaces, but also make it easier to accidentally damage fine details.

Several standards have been established for grit size and permissible tolerances. The most prevalent standards are:

Some sandpapers may sometimes only use descriptive nomenclature such as "coarse", "medium" and "fine", without referring to any standard. Those names are not regulated in any way and may differ between manufacturers. [8] : 16–17 

Size filtration

To achieve a uniform grit size, the crushed particles of the abrasive material must be filtered by size. Coarse grit particles are passed through a series of successively finer test sieves, with each successive layer blocking finer and finer particles. Medium grit particles are usually separated with air classification, which uses air flows to separate particles by weight. For the finest particles, water classification based on sedimentation is used, in which the particles are separated based on how quickly they settle to the bottom of the liquid tank. [16] [8] : 17, 20 

Coating types

Sandpaper can be either closed coat or open coat. In closed coat sandpaper, approximately 90% to 95% of the surface is covered with abrasive grains. Closed coat sandpaper is good for hand sanding or working with harder materials. In comparison, 50% to 70% of the surface is covered with abrasive grains with open coat sandpaper. The separation between particles makes the sandpaper more flexible, which prevents the sandpaper from clogging. However, the gaps in grit coverage limits the sandpaper's ability to perform even polishing jobs. Open coat sandpaper is better for softer materials. [17] [18] [19] [8] : 27 

Adhesives

Different adhesives are used to bond the abrasive to the paper. Hide glue is still used, but this glue often cannot withstand the heat generated during machine sanding and is not waterproof. Waterproof sandpapers or wet/dry sandpapers use a resin bond and a waterproof backing. [18] [8] : 26–30 

Adhesives are commonly applied in two layers: the make-coat adhesive is applied before the abrasive coating and binds it to the backing, while the size-coat adhesive is applied after the coating to further fix it in place. [8] : 6–7, 28 

In traditional gravity coating process, a long ribbon of backing material sequentially receives the coating layers in the correct order. An alternative to that is electrostatic coating, which passes the adhesive-coated backing material and the grit particles through electric fields, causing the backing to receive negative charge and the grit to receive positive charge. This causes the particles to attract to the backing, sticking to the glue with higher strength than in gravity coating. [8] : 6–7 

Anti-loading coatings

Sandpaper may be "stearated" where a dry lubricant (usually zinc stearate) is loaded to the abrasive. Stearated papers are useful in sanding coats of finish and paint as the stearate "soap" prevents clogging and increases the useful life of the sandpaper. [13] [8] : 30 

Shapes and types

Assorted coated abrasives Assorted coated abrasives.JPG
Assorted coated abrasives

Sandpaper comes in a number of different shapes and sizes. The most typical shape is a 9 by 11 inches (23 by 28 cm) flat sheet, [8] : 89  but other variants include abrasive rolls, sponges, belts for belt sanders and disks for disc and orbit sanders. [8] : 32–38 

Quick-change disks

Examples of sanding discs using a quick-change mounting system Quick Change Disc.jpg
Examples of sanding discs using a quick-change mounting system

A quick-change system is commonly used with disc-type coated abrasives. A plastic or metal hub is bonded to one of the faces, which is threaded. This then mates directly to the sander or angle grinder or to a mandrel that can be mounted in a sander, grinder, or drill. The advantage is that the disc can be quickly replaced when needed. Quick-change discs are available in sizes of about 50 millimetres (2.0 in) and larger. [20]

See also

References

  1. ↑ Hill, Ray (July 1977), "PS guide to sandpaper and other coated abrasives", Popular Science, 211 (1): 106, ISSN   0161-7370 .
  2. ↑ Casey, Don (May 3, 2016). "Know How: Sandpapers and Sanding". Sail Magazine. Archived from the original on 2 February 2019. Retrieved 1 February 2019.
  3. ↑ Parker, Jerry (April 1962), "How to choose the right coated abrasive", Popular Science, 180 (4): 159, ISSN   0161-7370 .
  4. ↑ Thomson, Keith Stewart (1992). Living Fossil: The Story of the Coelacanth. W. W. Norton & Company Limited. ISBN   978-0-393-30868-6. Archived from the original on 2014-06-27.
  5. ↑ Stalker, John; Parker, George (1971) [1688]. A Treatise of Japaning and Varnishing . London: Alec Tiranti. ISBN   978-0-85458-598-4. OCLC   1947744.
  6. ↑ Kelly, William M.; Hill, Mary Louise (1995). Garver, J.I.; Smith, J.A. (eds.). Geology and Mining History of Barton Mines Corporation, Gore Mountain Mine (PDF). Field Trips for the 67th Annual Meeting of the New York State Geological Association. Schenectady, NY: New York State Geological Survey / Union College. pp. 405–412.
  7. 1 2 Institute, Coated Abrasives Manufacturers' (1958). Coated abrasives: modern tool of industry (1st ed.). New York: McGraw-Hill. pp. 16–19. OL   6249647M.
  8. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Nagyszalanczy, Sandor (1997). The wood sanding book: a guide to abrasives, machines, and methods. Newtown, CT: Taunton Press. pp. 1–39. ISBN   978-1-56158-175-7.
  9. ↑ "What are the different types of backings used in coated abrasives?". preferredabrasives.com. Archived from the original on 2026-01-02.
  10. 1 2 3 "Abrasive Backing Materials". www.coxontool.com. Archived from the original on 2025-04-20. Retrieved 2026-01-18.
  11. ↑ Jeffrey, Kirk (1989). "The Major Manufacturers: From Food and Forest Products to High Technology". In Clark, Clifford Edward (ed.). Minnesota in a Century of Change: The State and Its People Since 1900. Minnesota Historical Society Press. p. 234. ISBN   978-0-87351-238-1. Archived from the original on 2014-06-27.
  12. ↑ Stack, Jim (2006). Box by box. Cincinnati, Ohio: Popular Woodworking Books. ISBN   1558709436.
  13. 1 2 3 4 "Abrasive Grains". www.coxontool.com. Archived from the original on 2026-01-30. Retrieved 2026-02-06.
  14. ↑ Abrasives, Red Label. "Abrasives 101". Red Label Abrasives. Archived from the original on 14 September 2025. Retrieved 2025-09-14.
  15. 1 2 "What are the different types of abrasive grain?". Preferred Abrasives. Archived from the original on 2018-01-25. Retrieved 2025-09-14.
  16. ↑ Linke, Barbara S. (2016). Life Cycle and Sustainability of Abrasive Tools. RWTHedition Ser. Cham: Springer International Publishing AG. pp. 46–50. ISBN   978-3-319-28345-6.
  17. ↑ Cahill, Caylena (2019-08-30). "Sandpaper "Coatings", Demystified". Uneeda. Archived from the original on 2026-01-15. Retrieved 2026-01-15.
  18. 1 2 "Sandpaper 101". www.sawdustmaking.com. Archived from the original on 2024-12-11. Retrieved 2026-01-15.
  19. ↑ "Sandpaper Buying Guide | Lowe's". www.lowes.com. Archived from the original on 2026-01-12. Retrieved 2026-01-15.
  20. ↑ Chitnis, Rohit (2024-10-09). "Quick Change Sanding Discs: When to Use Them and Why". Benchmark Abrasives. Archived from the original on 2025-09-08. Retrieved 2026-02-06.

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.