Sandpaper

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Sheets of sandpaper with different grits (40, 80, 150, 240, 600).

Sandpaper or glasspaper[1] are generic names used for a type of coated abrasive that consists of a heavy paper with abrasive material attached to its surface. Despite the use of the names neither sand nor glass are now used in the manufacture of these products as they have been replaced by other abrasives. Sandpaper is produced in different grit sizes and is used to remove small amounts of material from surfaces, either 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[citation needed]).

History[edit]

The first recorded use of sandpaper was in 13th-century China when crushed shells, seeds, and sand were bonded to parchment using natural gum.[citation needed] Sandpaper was originally known as glass paper[citation needed], as it was coated with particles of glass rather than sand[citation needed]. Glass frit has sharp-edged particles and cuts well whereas sand grains are smoothed down and do not work well as an abrasive. Cheap counterfeit sandpaper was often passed off as true glass paper[citation needed]; Stalker and Parker cautioned against it in A Treatise of Japaning and Varnishing published in 1688.[2] Glass paper was manufactured in London by 1833 by John Oakey, whose company had developed new adhesive techniques and processes, enabling mass production. A process for making sandpaper was patented in the United States on June 14, 1834 by Isaac Fischer, Jr., of Springfield, Vermont. In 1921, 3M invented a sandpaper with a waterproof backing, known as Wet and dry[citation needed]. This allowed use with water[citation needed], which would serve as a lubricant[citation needed] to carry away particles that would otherwise clog the grit[citation needed]. Its first application was automotive paint refinishing.[3]

Shark skin has also been used used as an abrasive[citation needed] and the rough scales of the living fossil, Coelacanth are used for the same purpose by the natives of Comoros.[4] Boiled and dried, the rough horsetail is used in Japan as a traditional polishing material, finer than sandpaper.[citation needed]

Types[edit]

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

There are many varieties of sandpaper, with variations in the paper or backing, the material used for the grit, grit size, and the bond.

Backing[edit]

In addition to paper, backing for sandpaper includes cloth (cotton, polyester, rayon), PET film, and "fibre", or rubber. Cloth backing is used for sandpaper discs and belts, while mylar is used as backing for extremely fine grits. Fibre or vulcanized fibre is a strong backing material consisting of many layers of polymer impregnated paper. The weight of the backing is usually designated by a letter. For paper backings, the weight ratings range from "A" to "F," with A designating the lightest and F the heaviest. Letter nomenclature follows a different system for cloth backings, with the weight of the backing rated J, X, Y, T, and M, from lightest to heaviest. A flexible backing allows sandpaper to follow irregular contours of a workpiece; relatively inflexible backing is optimal for regular rounded or flat surfaces. Sandpaper backings may be glued to the paper or form a separate support structure for moving sandpaper, such as used in sanding belts and discs. Stronger paper or backing increases the ease of sanding wood. The harder the backing material, the faster the sanding, the faster the wear of the paper and the rougher the sanded surface.

Material[edit]

Materials used for the abrading particles are:

Sandpaper may be "stearated" where a dry lubricant 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.

The harder the grit material, the easier the sanding of surfaces like wood. The grit material for polishing granite slab must be harder than granite.

Later abrading surfaces include long-life stainless steel sanding discs.

Bonds[edit]

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 or wet/dry sandpapers use a resin bond and a waterproof backing.

Sandpapers can also be open coat, where the particles are separated from each other and the sandpaper is more flexible. This helps prevent clogging of the sandpaper. The wet and dry sandpaper is best[citation needed] used when wet.

Shapes[edit]

Sandpaper comes in a number of different shapes and sizes:

Grit sizes[edit]

Grit size refers to the size of the particles of abrading materials embedded in the sandpaper. Several different standards have been established for grit size. These standards establish not only the average grit size, but also the allowable variation from the average. The two most common are the United States CAMI (Coated Abrasive Manufacturers Institute, now part of the Unified Abrasives Manufacturers' Association) and the European FEPA (Federation of European Producers of Abrasives) "P" grade. The FEPA system is the same as the ISO 6344 standard. Other systems used in sandpaper include the Japanese Industrial Standards Committee (JIS), the micron grade (generally used for very fine grits). The "ought" system ({0, 00, 000, ...} aka {1/0, 2/0, 3/0, ...}) was used in the past in the US. Cheaper sandpapers sometimes use nomenclature such as "Coarse", "Medium" and "Fine", but it is unclear to what standards these names refer.

Grit size table[edit]

The following table, compiled from the references at the bottom, compares the CAMI and "P" designations with the average grit size in micrometres (µm).

Grit size table
ISO/FEPA Grit designationCAMI Grit designationAverage particle diameter (µm)
MACROGRITS
Extra Coarse (Very fast removal of material, hardwood flooring initial sanding)P12 1815
P16 1324
P20 1000
P24 764
 24708
P30 642
 30632
 36530
P36 538
Coarse (Rapid removal of material)P4040425
 50348
P50 336
Medium (sanding bare wood in preparation for finishing, for gentle removal of varnish, also used for skateboard grip tape) 60265
P60 269
P80 201
 80190
Fine (sanding bare wood in preparation for finishing, not suitable for removing varnish or paint from wood, use for cleaning plaster and water stain from wood)P100 162
 100140
P120 125
 120115
Very Fine (sanding of bare wood)P150 100
 15092
P18018082
P22022068
MICROGRITS
Very Fine (sanding finishes between coats)P240 58.5
 24053.0
P280 52.2
P320 46.2
P360 40.5
Extra fine, start polishing of wood 32036.0
P400 35.0
P500 30.2
 36028.0
P600 25.8
Super fine (final sanding of finishes, final sanding of wood) 40023.0
P800 21.8
 50020.0
P1000 18.3
 60016.0
P1200 15.3
Ultra fine (final sanding and polishing of thick finishes)P150080012.6
P2000100010.3
P2500 8.4

See also[edit]

References[edit]

  1. ^ E. M. Kirkpatrick, ed. (1983). Chambers 20th Century Dictionary. Edinburgh: W & R Chambers Ltd. p. 532. ISBN 0-550-10234-5. 
  2. ^ Stalker & Parker (1971) [1688]. A Treatise of Japaning and Varnishing. Tiranti. 
  3. ^ Jeffrey, Kirk (1989). "The Major Manufacturers: From Food and Forest Products to High Technology". In Clark, Clifford Edward. 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. 
  4. ^ Thomson, Keith Stewart (1992). Living Fossil: The Story of the Coelacanth. W. W. Norton & Company Limited. ISBN 978-0-393-30868-6. 

Further reading[edit]

External links[edit]