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Woodworking demands various sandpaper grits to achieve different finishes. Guido Mieth / Getty ImagesApplying primer before painting is crucial as it protects the surface and enhances paint adhesion. The chemical properties of primer create a bonding layer, shielding the material from mold and sealing surface pores. Moreover, primer can conceal stains and ensure a longer-lasting paint job. Tinted primer even reduces the number of paint coats needed for a complete finish.
Whether you're priming porous materials like wood or smooth ones like metal, sanding the surface first is essential. Sanding removes the glossy top layer, allowing the primer to bond properly. Skipping the sanding step will result in the paint not adhering to the surface. Along with removing gloss, sandpaper helps fix imperfections and stains. Sanding also ensures a clean, smooth, and professional finish.
Choosing the right sandpaper grit size depends on the material you're prepping for priming. For instance, when sanding wood, begin with a coarse grit like 80-grit and gradually move to finer grits. Each time you switch to a higher grit, it helps eliminate the scratch marks from the previous sanding. When dealing with softer materials like plastic, you might want to start with a higher grit, such as 120, to avoid damaging the surface with deep scratches. For auto repair or metal surfaces, begin with 60-grit paper if you need to sand away rust and repair deep scars. Afterward, use 120-grit to remove rust stains or refine body filler. Just before applying primer to the metal, finish by smoothing the surface with 320-grit sandpaper.
