
Sanding is an important step in achieving a smooth finish on your painting project. The right sandpaper grit will help you properly prepare surfaces like wood, metal, drywall, and laminate before and after applying paint. The type of sandpaper grit you need depends on the surface you're working on and the type of paint you're using. For example, if you're working with semi-gloss or high-gloss finishes, you'll need to sand between coats. On the other hand, if you're painting with a matte or eggshell finish, you can apply a second coat without sanding in between. It's also important to consider the condition of the surface you're painting. If there is peeling or bubbling paint, be sure to sand it down before your first coat. Additionally, the quality of the paint you use will determine if you need to sand between coats, as lower-quality paints tend to drip, run, bubble, and leave brush strokes.
Characteristics | Values |
---|---|
Sanding before colour coat | Recommended for bare substrates, especially wood, that have not been previously painted or stained |
Sandpaper grit range | 40-80 (coarse), 100-150 (medium), 180-220 (fine), 320-400 (extra fine) |
Sanding tools | Sanding sponge, sanding block, palm sander, orbital sander, belt sander, floor sander |
Sanding technique | Sand with the grain of the wood, not against it |
Sanding before colour coat on drywall | Not necessary |
Sanding before colour coat on wood | Recommended for heavy sanding or stripping; use 60-grit sandpaper |
Sanding before colour coat on metal | Recommended for rust removal; use 120-180 grit sandpaper |
What You'll Learn
Sanding is not always necessary
The quality of the paint is another factor. Lower-quality paints are more prone to dripping, running, bubbling, and visible brush strokes. Sanding between coats can help conceal these imperfections and enhance paint adhesion. However, it is important to note that excessive sanding can lead to removing all the paint, so caution is advised.
The material being painted is also a consideration. As a general rule, if the surface does not feel or look smooth after painting, sanding is recommended. Additionally, sanding is particularly important when working with bare wood that has not been previously painted or stained. It is also suggested for previously painted surfaces with peeling paint or damage, metal surfaces with rust, and areas where repairs have been made, such as fixing cracks and small holes in drywall.
The desired level of smoothness is another factor to consider. Sanding can help achieve a silky-smooth finish, which is often desired for kitchen cabinets, walls in well-lit areas, or projects requiring a shiny finish. However, for most drywall interior projects, minor imperfections and debris from the roller are typically unnoticeable, making sanding unnecessary.
Lastly, time constraints play a role in deciding whether to sand. Proper sanding can add significant time to a project, especially if multiple coats are required and adequate drying time is needed between coats. Therefore, it is essential to weigh the desired quality of the finished product against the time available for the project.
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Sanding is important for paint adhesion
Sanding is an important step in achieving a professional-looking paint job. It helps create a smooth surface by removing imperfections such as brush marks, drips, or uneven textures. While it is not always necessary for every painting project, it is highly recommended in certain scenarios, such as when working with bare wood or repairing drywall.
The process of sanding creates a slightly roughened texture on the surface, which enhances paint adhesion. This improved adhesion helps to prevent peeling, cracking, or flaking of the paint over time. By sanding, you are not just making the surface smoother but also cultivating a more adhesive area for the paint to stick to. This is especially important if you are using a high-gloss or semi-gloss paint, as imperfections can be more noticeable.
The right sandpaper grit is crucial for achieving optimal adhesion. Sandpaper comes in various grits, ranging from coarse to fine. The grit level refers to the coarseness of the sandpaper by way of particle size. Lower-grit sandpaper has larger particles and is rougher, making it suitable for initial sanding to remove more material quickly. Higher-grit sandpaper, with its smaller particles, is finer and is typically used to finish the process, providing a smooth finish.
For sanding before a colour coat, it is generally recommended to use fine-grit sandpaper, such as 220-grit or 320-grit. This helps to smooth out any imperfections without removing too much of the previous coat. It is important to remember that you should not oversand, as it can damage the underlying layers of paint. Additionally, always clean the surface thoroughly before sanding to ensure the strongest adhesion for your paint.
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Sanding tools
Sanding Blocks
Sanding blocks are a great option for smaller areas that need a lighter touch. They are designed to create a uniform surface that applies even pressure to your project. Sanding sponges with angled edges are perfect for getting into cracks and grooves, and can even be used on curved surfaces. Computer mouse-shaped sanding blocks are comfortable to hold and are perfect for breaking corners before painting or staining.
Random Orbital Sander
The random orbital sander is a powerful tool that will rapidly sand large, flat surfaces. It has circular sanding pads attached to specialty sandpaper, and sands in a random circular pattern to avoid ugly circles and squiggly lines. Some models have attachments that allow the sander to function as an edging sander, keeping the tool at a 90-degree angle to prevent rounding over corners.
Palm Sander
The palm sander, or sheet sander, has a square pad that vibrates or moves back and forth to remove wood from the surface. It is prone to leaving scratches and marks, so it is best used on rough wood.
Belt Sander
The belt sander is perfect for projects that need serious power sanding. It uses a sanding belt to smooth a rough surface and typically uses grits up to 120. Handheld belt sanders are ideal for flattening and smoothing wide surfaces, while benchtop belt sanders are better for sanding edges and uneven joints.
Detail Sander
The detail sander is a versatile tool that can sand flat surfaces and reach into tight places, making it perfect for cleaning trim, moulding and furniture legs.
Drum Sander
The drum sander is similar to the belt sander but you feed the wood into the tool. It is often a large, heavy, stationary tool used for sanding multiple pieces to the exact same thickness.
Other Tools
There are many other sanding tools available for specific jobs, including the oscillating spindle sander, disc sander, file sander, and drywall sander. For very small areas, you can glue sandpaper to a paint stirrer, or use a putty knife with sandpaper wrapped around it to reach into tight corners.
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Sanding tips
- Sanding is not always necessary for every painting project. However, it is highly recommended for bare substrates, especially wood, that have not been previously painted or stained, and previously painted surfaces with peeling paint or damage.
- When sanding, remember three words: clean, dry, dull. Always clean the surface and allow it to dry fully before sanding. The goal of sanding for most painting projects is to dull the surface, especially when working with a previously painted surface with a high-gloss coating.
- Choose the right grit level for your project. Sandpaper grit ranges from coarse to fine. For heavy sanding or stripping, use coarse 40-80 grit sandpaper. If you want to smooth the surface and remove minor imperfections, medium 100-150 grit sandpaper or higher is a better choice.
- For most DIY painting projects, a handheld sanding sponge or block is sufficient. If you want to work faster, consider using a palm or orbital sander.
- If you're sanding wood, always sand with the grain, not against it, to avoid causing unnecessary scratches or imperfections.
- Beware of over-sanding, especially with higher-grit sandpaper, as you could lose adhesion. Consider the type of paint you're using. If you're using a clear finish, sand down any imperfections and be sure not to scratch or damage the surface.
- Sanding is a best practice when using acrylic and alkyd paints, as well as stains.
- You can achieve a very smooth finish by lightly sanding between each coat of primer and paint using fine-grit sandpaper.
- When sanding softer materials, such as plywood or wood, using too coarse a sandpaper can cause significant marks. Always follow the instructions on the sandpaper packaging.
- Wet sanding makes surfaces smoother and is often used in polishing cars and other items. If you wet-sand the base coat, wash the vehicle with soap and water afterward.
- When preparing for a clear coat, do not scuff the base coat beforehand. The clear coat should be applied to a smooth, not rough, surface.
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Sanding between coats of paint
If you are using cheaper paints, you are more likely to encounter bubbles, drips, brush marks, and roller imperfections. These paints don't have the additives that help with a smooth finish like premium paints. If you are using such a paint, you may need to sand between coats if the paint doesn't "lay flat" or leaves brush marks. However, be careful not to overdo it, as trying to remove brush marks by sanding can remove all of the paint.
The material you are painting will also determine if sanding between coats is necessary. As a general rule, if the surface you just painted doesn't feel or look smooth, sand it!
If you do decide to sand between coats of paint, make sure your coats of paint are dry before you start. A minimum of 24 hours is recommended. This will likely extend your project out for a few days, so this is a good time to weigh speed and quality, as the more quality you require, the longer your project will take.
When sanding between coats of paint, you can sand the entire wall if you demand perfection, using a drywall sanding pole. Otherwise, just look for specific trouble spots (paint bubbles, chips, etc.) and only target those areas. This will help keep your project moving forward without sacrificing quality.
When sanding between coats of paint, use fine-grit sandpaper. Sandpaper with a grit level of 180 to 220+ is best for smoothing a surface between coats of paint. If you are sanding wood, always sand with the grain, not against it.
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Frequently asked questions
Medium to fine grit sandpaper (100-220) is best for drywall. Avoid anything below 100-grit to prevent damage to the drywall surface.
For heavy sanding or stripping, use coarse 60-grit sandpaper. For smoothing the surface and removing minor imperfections, use medium 120-grit or higher.
For metal surfaces, start with a coarse grit (40-80) to remove any old paint or scratches. Then, switch to a medium grit (100-150) to give the paint something to grip onto. Finish with a fine grit (180-220) for an ultra-smooth finish.
Sanding between coats of paint is generally beneficial, but it depends on the type of paint and surface you're working with. If you're painting over a glossy surface, like bathroom trim or kitchen cabinets, you'll need to sand between coats as paint doesn't adhere well to glossy surfaces. However, if you're using a matte or eggshell finish paint on a non-glossy surface, you can usually skip sanding between coats.
180-220 grit sandpaper is a good choice for sanding between coats of paint on most interior walls. If your project involves polishing, consider using a higher grit, such as 240 or above.