Why should sandpaper need 240 grit?

Sandpaper: the right grit

Buying the right grit sandpaper - tips for the various projects

On the back of sandpaper you will always find a number such as 80 or 240. This is the grain size used by the manufacturer how many abrasive grains are on a certain surface and how big the individual grains are. This information has a decisive influence on the sanding result, because the more densely a surface such as paper is sprinkled with fine abrasive grains, the smoother the surfaces that you work on with the abrasive.

However, in most cases it does not make sense to start straight away with fine paper. For example, you would have to work on a wooden surface that is still very rough with fine sandpaper for an extremely long time until the result is satisfactory. In addition, you would use a lot of sandpaper. As a rule, you therefore start with a low grain size and then sand the surfaces again with fine paper. Which grain sizes are optimal depends on the material and how it has already been treated. So here are some tips for choosing the right grit.

Still untreated solid wood

To make furniture and other solid wood products that you have built yourself nice and smooth, it is best to first sand the surfaces with 80-grit sandpaper. This paper is used to remove the roughest bumps. Then continue with 120 grit sandpaper and finally use 180 grit sandpaper. It makes the wooden surfaces absolutely smooth and is therefore an ideal preparation for the subsequent treatment with, for example, a varnish.

Note: When sanding solid wood, remember to work in the direction of the wood grain. A cut across the fiber would cause scratches. In addition, always remove the sanding dust from the surfaces while working.

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Wooden stairs

The steps are often damaged, especially on wooden stairs in older buildings. If you want to restore such a staircase, it is best to start with very coarse 24 or 36 grit sandpaper. It removes scratches and other signs of wear, so that you can then continue with 40 and 80 grit sandpaper. Use 120 grit sandpaper for fine sanding.

Grinding all the steps of a staircase by hand is quite a laborious affair. An orbital sander is therefore recommended for sanding the surfaces, with which you can quickly remove even major damage. A delta sander is ideal for sanding the corners because it tapers to a point at the front.

So that the wood of a staircase is well protected again after restoration, you should oil or paint the surfaces after sanding. The agent usually has to be applied twice, as the wood often feels a little rough after the first treatment. If this is the case for you, smooth the surfaces with 240-grit sandpaper or a sanding sponge and apply a second layer of oil or varnish.

Note: If you do not remove all residues of the agent with which the stairs were originally treated during sanding, it is best to use an oil again for a previously oiled staircase and a varnish again for a varnished staircase.

Floorboards and parquet

To sand a wooden floor, you can borrow a floor sanding machine from a hardware store or from a machine rental shop. You will also need smaller machines such as a delta sander for the corners. The optimal grain size of the sandpaper depends on the signs of use or the tenacity of the paint. If you want to remove a relatively large amount of material, start with grit 24, otherwise with grit 36 ​​or 60. 100 or 120 grit sandpaper is sufficient for fine sanding parquet and floorboards.

Windows and doors

Wooden windows and entrance doors made of wood are often painted with a varnish or a thick layer of glaze. If you only want to renew this protection so that the windows and doors look neat again, a light sanding is sufficient. In this case, smooth the surfaces with sandpaper with a grain size of 120 or 150. If your windows or doors are to be given a new coat of paint, you must first remove the old layer of varnish or glaze with coarse sandpaper or a stripper. You can find out how to do this in our guide to painting wooden windows - with a glaze or varnish.

Tip: When sanding a window frame, it can easily happen that you slip off with the sanding device or sanding block and scratch the glass. You should therefore stick masking tape to the pane along the frame.

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