{{Short description|Abrasive material used for smoothing softer materials}} {{Redirect|Sanding|the fish known as sanding|Pseudaphritis urvillii}} {{good article}}
thumb|upright=1.35|alt=Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine))|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 ''(grit)'' glued to one face.<ref>{{Citation | last = Hill | first = Ray | title = PS guide to sandpaper and other coated abrasives | journal = Popular Science | volume = 211 | issue = 1 | page = 106 | date = July 1977 | url = https://books.google.com/books?id=LAEAAAAAMBAJ&pg=PA106 |issn=0161-7370}}.</ref>
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 ==
Since the ancient days, civilizations around the world used abrasive materials like fish scales<ref>{{Cite book|url=https://books.google.com/books?id=Ex2Nr3lLzM0C&pg=PA60|title=Living Fossil: The Story of the Coelacanth|first=Keith Stewart|last=Thomson|publisher=W. W. Norton & Company Limited|year=1992|isbn=978-0-393-30868-6|url-status=live|archive-url=https://web.archive.org/web/20140627025033/http://books.google.com/books?id=Ex2Nr3lLzM0C&pg=PA60|archive-date=2014-06-27}}</ref> or marble dust.<ref name="mcmillen">{{Cite journal |last=McMillen |first=Loring |date=2025 |title=Sandpaper |url=https://www.proquest.com/docview/3301683514 |journal=The Chronicle of the Early American Industries Association, Inc. |volume=78 |issue=1/2 |pages=31-33 |issn=0012-8147 |via=ProQuest}}</ref> The first recorded mention of a coated abrasive resembling modern-day sandpaper comes from 13th-century China, where crushed shells, seeds, and sand were bonded to parchment using natural gum.<ref>{{cite journal |last1=Casey |first1=Don |title=Know How: Sandpapers and Sanding |journal=Sail Magazine |date=May 3, 2016 |url=https://www.sailmagazine.com/diy/know-sandpapers-sanding |access-date=1 February 2019 |archive-date=2 February 2019 |archive-url=https://web.archive.org/web/20190202041839/https://www.sailmagazine.com/diy/know-sandpapers-sanding |url-status=live }}</ref><ref>{{Citation | last = Parker | first = Jerry | title = How to choose the right coated abrasive | journal = Popular Science | volume = 180 | issue = 4 | page = 159 | date = April 1962 | url = https://books.google.com/books?id=LCEDAAAAMBAJ&pg=PA159 |issn=0161-7370}}.</ref> Modern coated abrasive technology developed throughout the industrial revolution, with inventors across the UK and USA refining the manufacturing process and trying new coating materials.<ref name="mcmillen" />
== Backing ==
thumb|alt=320 grit silicon carbide sandpaper, with close-up view|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.<ref name="mt_backing">{{Cite book |last=Institute |first=Coated Abrasives Manufacturers' |title=Coated abrasives: modern tool of industry. |date=1958 |publisher=McGraw-Hill |edition=1st |location=New York |pages=16–19 |ol=6249647M }}</ref><ref name="woodsanding">{{Cite book |last=Nagyszalanczy |first=Sandor |title=The wood sanding book: a guide to abrasives, machines, and methods |pages=1–39 |date=1997 |publisher=Taunton Press |isbn=978-1-56158-175-7 |location=Newtown, CT}}</ref>{{rp|pp=23-24}}
In addition to paper, the most often used backing materials for coated abrasives are cloth (natural or synthetic), PET film, and vulcanized fibre.<ref name="woodsanding"/>{{rp|p=22}}
Cloth backing typically comes in weights "J", "X" and "Y", from lightest to heaviest. Additional weight designators also exist, like "JF" or "XF" for variants with extra flexibility or "YY" for an even heavier option.<ref>{{Cite web |title=Coated abrasives basics |url=https://www.klingspor.com/coated-abrasives-basics |access-date=2026-04-19 |website=KLINGSPOR Abrasives |language=en-US}}</ref><ref name="coxon_back">{{Cite web |title=Abrasive Backing Materials |url=https://www.coxontool.com/index.php/References/AbrasiveBackings |archive-url=https://web.archive.org/web/20250420221805/https://www.coxontool.com/index.php/References/AbrasiveBackings |archive-date=2025-04-20 |access-date=2026-01-18 |website=www.coxontool.com |url-status=live}}</ref> Cloth is preferred for its high durability, and used in applications such as sanding belts.<ref name="woodsanding"/>{{rp|p=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.<ref name="woodsanding"/>{{rp|p=26}} Fibre is a thick and extremely strong backing, generally only used for sanding disks.<ref name="mt_backing"/><ref name="coxon_back"/>
=== 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"<ref name="coxon_back"/> or "wet and dry", allow the use of a water-based lubricant, which is required for some applications.<ref name="woodsanding"/>{{rp|p=24}} Wet/dry paper was invented by Francis Gurney Okie, an ink maker from Philadelphia. He was hired by 3M to work on his ideas, and in 1921 the company released the final product under the brand name "Wetordry".<ref>{{Cite book |last=Fort |first=Tom |url=https://www.google.com/books/edition/Rivets_Trivets_and_Galvanised_Buckets/nSN0EAAAQBAJ |title=Rivets, Trivets and Galvanised Buckets: Life in the village hardware shop |date=2023-05-11 |publisher=Headline |isbn=978-1-4722-9197-4 |language=en}}</ref><ref>{{Cite book|chapter-url=https://books.google.com/books?id=NxNlGsE7EVwC&pg=PA234|title=Minnesota in a Century of Change: The State and Its People Since 1900|first=Kirk|last=Jeffrey|editor-first=Clifford Edward|editor-last=Clark|publisher=Minnesota Historical Society Press|year=1989|isbn=978-0-87351-238-1|page=234|chapter=The Major Manufacturers: From Food and Forest Products to High Technology|url-status=live|archive-url=https://web.archive.org/web/20140627122427/http://books.google.com/books?id=NxNlGsE7EVwC&pg=PA234|archive-date=2014-06-27}}</ref>
Wet/dry sandpaper is more effective when used wet, because the water washes particles away from the grinding surface and reduces clogging.<ref>{{cite book |last1=Stack |first1=Jim |title=Box by box |date=2006 |publisher=Popular Woodworking Books |location=Cincinnati, Ohio |isbn=1558709436}}</ref>
== 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.<ref name="coxon_grit">{{Cite web |title=Abrasive Grains |url=https://www.coxontool.com/index.php/References/AbrasiveGrains |access-date=2026-02-06 |archive-url=https://web.archive.org/web/20260130094256/https://www.coxontool.com/index.php/References/AbrasiveGrains |archive-date=2026-01-30 |url-status=live |website=www.coxontool.com}}</ref><ref name="woodsanding"/>{{rp|p=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.<ref>{{Cite web |last=Abrasives |first=Red Label |title=Abrasives 101|url=https://www.redlabelabrasives.com/pages/sandpaper-buying-guide |access-date=2025-09-14 |archive-url=https://web.archive.org/web/20250914163527/https://www.redlabelabrasives.com/pages/sandpaper-buying-guide?srsltid=AfmBOooVjSCdp0W5g5bNSC_23WdPQWFj1id4TszZX-Te5BSQ0XU-5Mlm|archive-date=14 September 2025|website=Red Label Abrasives |language=en}}</ref><ref name="prefabr">{{Cite web |title=What are the different types of abrasive grain? |url=https://www.preferredabrasives.com/faq/different-types-abrasive-grain/ |access-date=2025-09-14 |website=Preferred Abrasives |language=en-US |archive-date=2018-01-25 |archive-url=https://web.archive.org/web/20180125015458/https://www.preferredabrasives.com/faq/different-types-abrasive-grain/ |url-status=live }}</ref><ref name="coxon_grit"/><ref name="woodsanding"/>{{rp|pp=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.<ref name="coxon_grit"/><ref name="prefabr"/><ref name="woodsanding"/>{{rp|pp=7-11}}
==== Friable grits ====
Abrasive materials can 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.<ref name="woodsanding"/>{{rp|p=13}}
=== Grit sizes ===
thumb|alt=Sheets of sandpaper with different grit sizes|Sheets of sandpaper with different grit sizes (200 (bottom){{en dash}}40 (top))
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).<ref name="uama">{{Cite web |url=https://uama.org/abrasives-101/ |access-date=2026-04-19 |website=Unified Abrasives Manufacturers’ Association|title=Abrasives 101|url-status=live}}</ref><ref name="woodsanding" />{{rp|pp=16-17}} Coarser grit materials simplify sanding of hard surfaces, but also make it easier to accidentally damage fine details.<ref>{{Cite web |date=2025-04-03 |title=Want to Know Which Sandpaper to Use for Your Project? This Guide Can Help. |url=https://www.popularmechanics.com/home/a64273047/sandpaper-grit-guide/ |access-date=2026-04-19 |website=Popular Mechanics |language=en-US}}</ref><ref>{{Cite web |title=The Nitty-Gritty of Sandpaper |url=https://www.woodmagazine.com/wood-supplies/sanding-abrasives/the-nitty-gritty-of-sandpaper/ |access-date=2026-04-19 |website=Wood Magazine}}</ref>
Several standards have been established for grit size, permissible tolerances and filtration method. The most prevalent standards are:<ref name="uama" /><ref name="woodsanding" />{{rp|pp=16-17}}
* The ANSI grade, also known as the CAMI (Coated Abrasive Manufacturers Institute) grade. Used in the United States. * The FEPA (Federation of European Producers of Abrasives) grade, also called the P Grade. Used in Europe. The ISO 6344 standard is based on this scale.<ref>{{Cite journal |date=1997-09-10 |title=Commission Decision of 4 December 1996 declaring a concentration to be incompatible with the common market and the functioning of the EEA Agreement |url=https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=OJ:L:1997:247:TOC |journal=Official Journal of the European Communities |volume=40 |issue=L 247 |pages=23}}</ref> * The JIS grade, mostly used in Japan and other Asian countries. * Micron grading, which specifies the exact size of particles in microns. Mostly used for extra fine grits (60-0.1μm).
Some sandpapers may 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.<ref name="woodsanding" />{{rp|pp=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.<ref>{{Cite book |last=Linke |first=Barbara S. |title=Life Cycle and Sustainability of Abrasive Tools |date=2016 |publisher=Springer International Publishing AG |isbn=978-3-319-28345-6 |series=RWTHedition Ser |location=Cham|pages=46-50}}</ref><ref name="woodsanding"/>{{rp|pp=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.<ref>{{Cite web |last=Cahill |first=Caylena |date=2019-08-30 |title=Sandpaper "Coatings", Demystified |url=https://www.sandpaper.com/articles/sandpaper-coatings-demystified/ |url-status=live |archive-url=https://web.archive.org/web/20260115161319/https://www.sandpaper.com/articles/sandpaper-coatings-demystified/ |archive-date=2026-01-15 |access-date=2026-01-15 |website=Uneeda |language=en-US}}</ref><ref name="sandpaper101">{{Cite web |title=Sandpaper 101 |url=https://www.sawdustmaking.com/Sandpaper/sandpaper.htm |url-status=live |archive-url=https://web.archive.org/web/20241211144106/http://www.sawdustmaking.com/Sandpaper/sandpaper.htm |archive-date=2024-12-11 |access-date=2026-01-15 |website=www.sawdustmaking.com}}</ref><ref>{{Cite web |title=Sandpaper Buying Guide {{!}} Lowe's |url=https://www.lowes.com/n/buying-guide/sandpaper-buying-guide |url-status=live |archive-url=https://web.archive.org/web/20260112054430/https://www.lowes.com/n/buying-guide/sandpaper-buying-guide |archive-date=2026-01-12 |access-date=2026-01-15 |website=www.lowes.com |language=en }}</ref><ref name="woodsanding"/>{{rp|p=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.<ref name="sandpaper101" /><ref name="woodsanding"/>{{rp|pp=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.<ref name="woodsanding"/>{{rp|pp=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.<ref name="woodsanding" />{{rp|pp=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.<ref name="coxon_grit"/><ref name="woodsanding" />{{rp|p=30}}
== Shapes and types ==
Sandpaper comes in a number of different shapes and sizes. The most typical shape is a {{convert|9|by|11|in|cm}} flat sheet,<ref name="woodsanding"/>{{rp|p=89}} but other variants include abrasive rolls, sponges, belts for belt sanders and disks for disc and orbit sanders.<ref name="woodsanding"/>{{rp|pp=32-38}}
== See also == * Grain size * Lapping film * Sanding block * Steel abrasive * ISO 6344
== References ==
{{reflist}}
== Further reading == * Dresdner, Michael (1992). ''The Woodfinishing Book''. Taunton Press. {{ISBN|1-56158-037-6}}. * Flexner, Bob (2005). [https://archive.org/details/isbn_9780762106219/mode/2up ''Understanding Wood Finishing: How to Select and Apply the Right Finish''] {{registration required}}, rev. and updated ed. Fox Chapel Publishing. {{ISBN|978-1-56523-548-9}} (hardcover), {{ISBN|978-1-56523-566-3}} (paperback).
== External links == {{commons category}}
* [http://www.fepa-abrasives.org Federation of European Producers of Abrasives] * [http://www.sizes.com/tools/sandpaper.htm sizes.com on sandpaper] * [http://www.fine-tools.com/G10019.htm Conversion Chart Abrasives - Grit Sizes] * [https://www.gritomatic.com/pages/grit-chart Grand Logarithmic Grit Chart]
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Category:Abrasives Category:Chinese inventions Category:Paper products Category:Surface finishing