🟢 Why do sanding marks appear during repainting?
As with other defects, there are many reasons for sanding marks to appear. Knowing them in detail will allow you to anticipate possible errors.
1. Incorrect choice of sand grit size and orbit
The main cause of the appearance of sanding marks is related with an incorrect choice of the grit used for sanding the putty or filler. If you choose a coarser grit than what is recommended, it will cause a mark that is too deep to be levelled by the paint layer.
Follow the instructions provided in each product’s technical data sheet, where the grit size to be used will be specified.
In addition, choose an orbit size according to the type of paint coat you are going to sand. For example, for finish coats, use smaller orbits. When sanding the filler, the eccentric movement should exceed 5 mm.
It may be advisable to use a sanding guide for better control of the surface being sanded, thus avoiding the appearance of sanding marks.
2. Incorrect preparation of the intermediate coats
It is also important to follow a proper sanding technique, using the different sandpaper grits in a staggered way.
It is advisable to smoothen the sanded surfaces to enhance the paint coverage and levelling. This step will also result in better anchoring and performance of the final paint finish.
3. Not respecting the drying times
Observing the drying times established in the technical data sheet for the intermediate coats is essential.
Sandpaper marks become more noticeable as a result of the swelling of the intermediate coat products during application, and their subsequent shrinkage during the drying process.
4. Lack of layer thickness
Likewise, an insufficiently thick finish coat will prevent the full coverage and levelling of the marks and grooves produced during sanding, encouraging the appearance of sanding marks . Use the coat thickness recommended by the manufacturer.
How to fix sanding marks?
Once the part has dried, inspect and assess the size and scope of the sandpaper grooves.
27 авг 2024
