Sandpaper: How to find the right grit
For a clean, precise and easy finish when smoothing or polishing, nothing beats sandpaper. Which sandpaper is suitable for which job and how do you find the right grit? You’ll find all the tips in our big sandpaper guide!
What is sandpaper?
Sandpaper is a sheet of paper coated on one side with small, irregularly shaped abrasive grains. These grains scratch the surface of the workpiece during sanding, removing material. Depending on the size of the grains, the sandpaper provides coarse or fine removal with each stroke.
Since its invention, sandpaper has consisted of 4 layers:
- Backing material: a robust, tear-resistant material such as paper (for DIY projects and trade use) or fabric and vulcanised fibre (for industrial use).
- Base coat adhesive: a layer of glue or synthetic resin that holds the backing and abrasive grains together.
- Abrasive grains: the actual “tool”, consisting of aluminium oxide (corundum), silicon carbide or diamond.
- Top coat adhesive: a final layer of synthetic resin or glue to prevent the grains from wearing away. It is coloured differently to help identify the sandpaper grit.
Did you know?
Sandpaper is also known as emery paper, because in the past, the abrasive grains were made from natural sand or emery.
What is sandpaper used for?
Sandpaper is an essential accessory for many fine-tuning jobs and DIY projects. Among other things, you can use it to:
- Sand wood
- Polish metal
- Round off edges
- Deburr workpieces (remove sharp edges)
- Smooth plaster
This makes sandpaper just as indispensable for upcycling furniture as it is for renovating a wall or removing rust.
Depending on the task, you can use sandpaper both by hand and with sanding machines. As a rule of thumb: the more delicate and smaller the workpiece, the better it is to work by hand. For large surfaces, it's best to use a power tool.
Choosing the right sandpaper grit – Chart & tips
The most important factor when choosing sandpaper is the grit. This describes the size of the abrasive particles and therefore the fineness of the finish. The rule is: the higher the grit number, the finer the sanding; the lower the grit number, the coarser the sanding.
Sandpaper grit is standardised according to FEPA (Federation of European Producers of Abrasives). It always starts with a “P” followed by a number:
- P12 to P30: coarse
- P30 to P80: medium-coarse
- P80 to P180: fine
- Over P180: very fine
When sanding, you should always work your way from a coarse to a fine grit, which means you will need to use several types of sandpaper. For typical jobs, the recommendations are as follows:
Aufgabe | Empfohlene Körnung |
|---|---|
Wand schleifen per Hand (aus Stein oder Rigips) | P60 bis P80 |
Abschleifen von Parkettkleber oder Estrich | P24 bis P30 |
Alte Farbe oder Lack von Holz entfernen | P80 bis P240 |
Holz anschleifen vor Lackieren | P180 |
Holz glätten | P80 bis P280 |
Kratzer im Autolack entfernen | P3000 bis P5000 |
Metall polieren | P150 und feiner |
Metall entgraten | P60 und feiner |
INFO:
Pay attention to the grit coating!
The grit coating refers to how densely the abrasive grains are packed onto the sandpaper. There are three categories:
- Open coat: 50 to 70% of the surface
- Semi-open coat: 70 to 80% of the surface
- Closed coat: approximately 100% of the surface
The more open the coating, the less material is removed. An open coat is therefore ideal for materials that tend to clog, such as resinous softwoods or soft layers of paint. In contrast, you should use a closed coat for hard materials like ferrous metals, as very little material gets stuck between the grains. A semi-open coat is the all-rounder for hardwood, plastic and non-ferrous metals.
Questions & Answers about Sandpaper
Sandpaper should be changed when it removes noticeably less dust while sanding, or if the sanding surface feels smooth.
Some sanders feature a built-in dust extraction function to collect dust produced when sanding. This works via holes that are pre-punched into certain types of sandpaper.
When removing scratches from car paint, ultra-fine sandpaper is used to remove as little of the paintwork as possible.
For wet sanding, sandpaper with a synthetic resin bond is ideal. Vulcanised fibre and fabric backing also increase the durability of sandpaper when used in wet conditions.
Specially designed sanding belts are available for belt sanders, which are made to resist tearing during use.
