Sandpaper or sanding paper: types, types, grain size

Recommendation points

• Choosing the grain. From removing old paint to sanding glass products
• Pros and cons of different foundations
• Types and methods of applying abrasive
• Each abrasive has its own tasks
• Homemade sanding sheets according to old recipes

Having understood the technology for the production of sandpaper, you can easily find the right sheet. It is conventionally divided into three groups: coarse-grained, medium-grained and close to zero for finishing. There are other subtleties, without taking into account which, you can spoil the material or abrasive..

Choosing the grain. From removing old paint to sanding glass products

There is a marking on the back of the sandpaper, but it may differ depending on the manufacturer and year. It is better to buy it by examining it personally, and not trust inexperienced people or ordering it on the Internet. If this is not possible, rely on a combination of indicators, not numbers. As one and the same grain size can be indicated by three different markings: P 800-21.8, 400-23 and J 700-21. In the table we will indicate all the options.

Table No. 1. Marking of grain size

In all situations, choose at least three variations and start with the finest graininess and end with the finest.

Processing options by material:

• glass, plastic, and stone use wet sanding methods, so choose sheets that are moisture resistant. If there are chips, start with 3 thousand microns, for light scratches from 1500 microns. Then go to 1000 or 600 microns and finish with 100 or 30 microns. To create gloss, GOI paste is used. On lenses, lenses or screens, more gentle compounds;
• wood and plaster surfaces – it is better to choose finer grades so as not to leave deep scratches. You can start from 1 thousand microns and finish from 30 and below;
• iron – polished in different sizes, depending on the tasks. To give the desired shape, take the coarsest fractions from 4890 microns and finish with zeroes. As a rule, 4–5 intermediate options are used. Coarse abrasives for soft metals like gold and tin cannot be used;
• surface painted with water-based paint – finish sanding with sandpaper with a grain size close to zero. Otherwise, she will show all the minor scratches.

Be careful not to confuse type and microns. If the marking shows from F4 to F22, this is coarse sandpaper, but its grain size is measured only in microns and is equal to from 4890 to 885 microns. When choosing, it is better to call the grain size, 1 μm = 0.001 mm.

Pros and cons of different foundations

Some foundations are not suitable for use in a humid environment, others are elastic and wrap around curls well, there is a particularly strong base or, conversely, soft on thin paper and inexpensive.

The most common basics:

• paper – inexpensive, do not stretch and there are all types of grain, but they are not strong enough. It can be waterproof, but in these properties it is inferior to fabric;
• fabric – elasticity is their main plus and minus. On the one hand, the base easily takes the shape of any product, on the other hand, the abrasive crumbles under strong stretching. Durable and moisture resistant, but expensive;
• fiber – more often made for discs, but irreplaceable when processing stone. It is used for very hard materials;
• combined – layers of fabric and paper are glued together and an abrasive is applied to the base. Has the advantages of paper and cloth, but has a high price.

The base also has its own markings, which can be seen on the article or on the back. The values ​​can be seen in the table.

Table No. 2. Marking of bases

Types and methods of applying abrasive

When choosing, pay attention to the type of application, some of them are more suitable for products with a fragile surface, others for grinding hard material.

Table No. 3. Marking of the type of application

Coating by application method:

• by open filling – 60% of the area is covered. Thanks to the voids, it is suitable for crumbling material, chips and gypsum are poured through them. This skin is less likely to clog;
• closed filling – the abrasive covers the web by 100%. They are chosen for metal processing, since when used on a soft surface, it quickly clogs;
• mechanical method – less uniform application due to the use of gravity. The particles fall on different sides;
• using electrostatics – the “sharpest” emery layers are created. The impact on each particle of an electrostatic field turns them with a point in one direction.

The abrasive is glued to the surface with resins and glue. Some are waterproof or antistatic.

Each abrasive has its own tasks

A soft abrasive will not help when processing glass or stone, but a very hard one will make deep grooves in plastic or putty. Usually the sharpest materials are used for rough peeling or shaping, and soft materials are used for leveling and smoothing..

Most often you can find such materials:

• diamond is the most durable and sharpest material, but expensive;
• garnet – harder than aluminum oxide, but wears out faster. Most often used for wood;
• quartz – known as “glass skin” due to its frequent use in optics and ceramics;
• aluminum oxide (emery) – with strong friction, it is renewed due to chips that form new facets;
• silicon carbide – the sharpest and most affordable, replaces diamond grit in terms of properties. Used for metal, ceramics and paint stripping;
• electrocorundum – differs from aluminum oxide by greater strength, since it is alloyed with titanium, aluminum or chromium.

If it is impossible to identify the material externally, be guided by the letter marking.

Table No. 4. Marking of abrasive

Homemade sanding sheets according to old recipes

The first sandpaper appeared not in 1833, but thousands of years ago. Coastal residents used shark skin or boiled glue on fish scales. Further, they smeared pieces of leather or cloth with it and sprinkled it with sand. Craftsmen living far from the coast extracted glue from animal bones and veins or used tree resin.

To change the effect on the treated surface, the craftsmen made several versions of the canvas. On some of the sheets there was a crumb of precious stones, on others there was sand, and on the third there were ground shells or plant seeds. For processing large stones or objects, metal plates were created, on the hot surface of which an abrasive was applied.

Modern sheets are produced with the same type of marking accepted all over the world. Old sandpaper inherited or purchased on the construction market can differ greatly from the accepted standards, so focus on the appearance better, this will help to avoid mistakes.