Sandpaper
Sandpaper is a form of Paper where an Abrasive material has been fixed to its surface; it is part of the "Coated abrasives" family of abrasive products. It is used to remove small amounts of material from surfaces, either to make them smoother (painting and Wood finishing), to remove a layer of material (e.g. old paint), or sometimes to make the surface rougher (e.g. as a preparation to gluing).
Types of sandpaper
There are countless varieties of sandpaper, with variations in the paper or backing, the material used for the grit, grit size, and the bond.Backing
In addition to paper, backing for sandpaper includes cloth (Cotton, Polyester, Rayon), Polyester film (Mylar), and "Fibre". Cloth backing is used for sanding discs and belts, while mylar is used with extremely fine grits. Fibre or vulcanized fibre is a strong backing material consisting of many layers of impregnated paper made from rags. The weight of the backing is usually designated by a letter. For paper, the letters range from A to F, with A being the lightest and F the heaviest. Letter nomenclature is different for cloth, with the weight of the backing being, from lightest to heaviest: J, X, Y , T and M.Material
Materials used for the abrading particles are:- Flint - no longer commonly used;
- Garnet - commonly used in Woodworking;
- Emery - commonly used to abrade or polish metal;
- Aluminium oxide - perhaps most common in widest variety of grits;
- Silicon carbide - used in microgrits, especially for wet-and-dry sandpaper;
- Alumina-zirconia - (an Aluminium oxide - Zirconium oxide alloy), used in very fine (microgrit) papers;
- chromium oxide - used in extremely fine micron grit (micrometre level) papers
As well, 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.
Bonds
Different adhesives are used to bond the abrasive to the paper. Hide glue is still used, but this paper is not waterproof. Waterproof or wet/dry sandpapers use a resin and a waterproof backing such as cloth.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.
Shapes
Sandpaper comes in a number of different shapes and sizes.- sheet - usually 9 by 11 inches, but other sizes may be available
- belt - usually cloth backed, comes in different sizes to fit different belt sanders.
- disk - made to fit different models of disc and random orbit sanders. May be perforated for some models of sanders. Attachment includes Pressure sensitive adhesive (PSA) and "hook-and-loop" (similar to Velcro).
- rolls
Grit sizes
Grit size refers to the size of the particles of abrading materials embedded in the sandpaper. A number of 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 Japan Industrial Standards Committee (JIS), the micron grade (generally used for very fine grits). The "ought" system was used in the past in the United States. Also, cheaper sandpapers sometimes are sold with nomenclature such as "Coarse", "Medium" and "Fine", but it is not clear what standards these names refer to.Grit size table
The following table, compiled from the references at the bottom, compares the CAMI and "P" designations with the average grit size in micrometres (µm).|
ISO/FEPA Grit designation |
CAMI Grit designation |
Average particle diameter (µm) | |
|
MACROGRITS | |||
|
Extra Coarse (Very fast removal of material) |
P12 |
|
1815 |
|
P16 |
|
1324 | |
|
P20 |
|
1000 | |
|
P24 |
|
764 | |
|
|
24 |
708 | |
|
P30 |
|
642 | |
|
|
30 |
632 | |
|
|
36 |
530 | |
|
P36 |
|
538 | |
|
Coarse (Rapid removal of material) |
P40 |
40 |
425 |
|
|
50 |
348 | |
|
P50 |
|
336 | |
|
Medium (sanding bare wood in preparation for finishing) |
|
60 |
265 |
|
P60 |
|
269 | |
|
P80 |
|
201 | |
|
|
80 |
190 | |
|
Fine (sanding bare wood in preparation for finishing) |
P100 |
|
162 |
|
|
100 |
140 | |
|
P120 |
|
125 | |
|
|
120 |
115 | |
|
Very Fine (final sanding of bare wood) |
P150 |
|
100 |
|
|
150 |
92 | |
|
P180 |
180 |
82 | |
|
P220 |
220 |
68 | |
|
MICROGRITS | |||
|
Very Fine (sanding finishes between coats) |
P240 |
|
58.5 |
|
|
240 |
53.0 | |
|
P280 |
|
52.2 | |
|
P320 |
|
46.2 | |
|
P360 |
|
40.5 | |
|
Extra fine |
|
320 |
36.0 |
|
P400 |
|
35.0 | |
|
P500 |
|
30.2 | |
|
|
360 |
28.0 | |
|
P600 |
|
25.8 | |
|
Super fine (final sanding of finishes) |
|
400 |
23.0 |
|
P800 |
|
21.8 | |
|
|
500 |
20.0 | |
|
P1000 |
|
18.3 | |
|
|
600 |
16.0 | |
|
P1200 |
|
15.3 | |
|
Ultra fine (final sanding of finishes) |
P1500 |
800 |
12.6 |
|
P2000 |
1000 |
10.3 | |
|
P2500 |
|
8.4 | |
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. Shark skin was used as a sandpaper. Sandpaper was originally known as glass paper, as it used particles of glass. Sandpaper has occasionally been used as a surface for Painting, as by Joan Miro. Sandpaper was even used as a musical instrument, in Leroy Anderson's Sandpaper Ballet.Sandpaper was patented in the United States on June 14 1834 by Isaac Fischer, Jr., of Springfield, Vermont.