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There’s nothing more frustrating than finishing up a paint project and seeing the paint you carefully applied peeling or lifting off of the surface.
If you’re looking for a smooth application with maximum adhesion, you need to remember to prepare the surface by using the correct type of sandpaper before applying primer.
But with so many different types of sandpaper, from extra coarse to extra fine, how do you know which grit to use?
What Grit Sandpaper for Primer Before Paint?
Before using primer, you’ll want to use 320 grit sandpaper to get a smooth finish and proper adhesion, but that can change depending on the material you’re sanding.
The material you want to paint matters when deciding on grit. You’ll want to make sure you’re using the right tool for the job, so understanding the basics of sandpaper is a must.
Sandpaper comes in different grits, grades, and types. You choose the grit depending on the job you need to complete. The coarser the grit, the rougher the result.
When you’re ready to select what grit sandpaper for primer before paint, think smooth. The smoother the wood, the less likely you will see streaks, imperfections, and rough areas. Rough wood requires a lower grit number sandpaper.
Most paints and varnishes will suggest what grit sandpaper to use in the application instructions. So be sure to thoroughly read all instructions before applying primer.
What is Sandpaper Grit?
Grit is the particles bonded on sandpaper used to rough up or polish a surface depending on the size. The larger the particle, the coarser the sandpaper.
Grit can range from 30 to 7000, though the most common sandpaper grits range from 60 to 330.
The grit number represents the number of particles used, and coarse sandpaper has fewer and larger particles. In contrast, fine sandpaper has more but smaller particles.
Usually, during the process of sanding, you start with larger grit sandpaper to strip away old paint or shape wood and then move progressively to a smaller grit.
Sanding each layer using a finer grit each time produces a very smooth and even service.
What is Sandpaper Grade?
Sandpaper grade simply puts ranges of grit into larger categories as follows:
- Coarse (30-60)
- Medium (80-120)
- Fine (150-180)
- Very Fine (220-240)
- Extra Fine (280-320)
- Super Fine (360 and above
Types of Sandpaper
There are two types of sandpaper: natural and synthetic, each with its own use.
Flint, Emery, and Garnet are natural grains, while Zirconia Alumina, Aluminium Oxide, and Silicon Carbide are synthetic grains.
Here’s how they are best used:
- Flint: Use a flint grain to remove old paint or varnish or clean old products off of wood before applying a new coat of paint.
- Emery: Too sharp for use on wood, Emery cleans up and polishes metals. Use this type of sandpaper to remove corrosion from metal.
- Garnet: A soft grain sandpaper best used on wood. Metal wears this type of sandpaper out too quickly.
- Zirconia Alumina: This particular particle is used to rough up sand wood or metal. It’s super durable and can last a long time.
- Aluminum Oxide: Used on metal and hardwood, Aluminum Oxide is another tough synthetic grain. It’s the most common type of synthetic grain used today.
- Silicon Carbide: This versatile grain can be used on metal, wood, plastic, and many other materials. It’s long-lasting and durable.
Hand Sanding vs Power Sanding
Some people prefer to hand sand their projects. Sanding by hand can keep the mess down significantly, but it also is a much slower process.
Sanding with power tools, on the other hand, is faster, requiring less physical effort.
Common Types of Handheld Power Sanders
- Orbital sander: Orbital sanders spin the sandpaper in small circular directions, assuring that no path is taken twice the same. It leaves a smooth finish and works exceptionally well.
- Belt sander: Belt sanders are used for leveling large areas like tables or desktops. They are mighty and can leave marks on the surface if not used correctly by a skilled operator.
- Disk sander: This sander is used for the same type of projects as a belt sander, but its circular and open design can sand edges the flat belt sander cannot reach.
- Finishing sander: When you’re looking for a smooth finish for your project, it’s time to reach for a finishing sander. It will give your project the perfect polished finish.
You can also use a tool like an angle grinder to sand.
There are a lot of considerations when selecting what grit sandpaper to use for primer before paint and lots of ways to get that smooth finish you want.
Choosing the correct grit will make a world of difference in your final product and keep your projects looking polished and professional.