What Are the Types of Sandpaper for Painting?

Here are the four types of sandpaper for painting:

1. Garnet Sandpaper: Garnet paper is made of natural garnet backed with a paper or cloth. It is used for sanding uneven and grainy wooden surfaces. It is widely used due to its friability, which means its garnet wears out and smooths the surface with sharp edges.
2. Aluminum Oxide: Aluminium oxide sandpaper is made up of aluminium oxide grains. They are strong and durable compared to garnet sandpaper. Aluminium oxide removes the rust buildups on metal, debris on plastic, and bumps on wood. Like garnet sandpaper, it also has self-sharpening properties. 
3. Silicon Carbide: Silicon carbide, also called carborundum, uses Sic grains to remove dirt and debris from metal, wood, and steel substrates. It is sharp and strong enough to cut fingers. It is used to remove the old paint and clear the substrate. 
4. Ceramic Sandpaper: Ceramic sandpaper is sharp and strong compared to other sandpapers. It is made up of even ceramic grains that leave a smooth finish without any scratch marks behind. Ceramic sandpaper is best for heavy and deep sanding due to its self-sharpening properties. They are available in different grit sizes to achieve the smoothest and finest results.

How Do Sandpaper Grit Numbers Affect Painting Results?

Here are the five ranges of sandpaper grit numbers that affect painting results:

1. Coarse Grit (40–60): Coarse grit is made up of sharp and small grains. Sandpaper with 40 to 60 grit numbers is strong and can cut in seconds. They are used to smooth the welding buildups, old paint, and highly uneven wood surfaces. It is not recommended to use coarse grit and then switch to extra fine grit, as it leaves scratches on the substrate. 
2. Medium Grit (80–120): Medium grit is less sharp than coarse grit and more than fine grit sandpaper. They are used to remove the roughness after applying coarse grit. Medium-grit sandpaper is used between coarse and fine grits to scuff paint surfaces. 
3. Fine Grit (150–180): Fine grits are used to prepare the surface before varnish and sealers. They leave minimal scratches and smooth the surface.
4. Very Fine Grit (220–320): Very fine grit sandpapers are used to activate the surface when filling dents and stains. They are used on glossy substrates to maintain their shiny surface. 
5. Extra Fine Grit (400 and above): Extra fine sandpaper with 400 and above grit numbers is used to buff the metal surfaces. It is used to achieve a crystal clear and mirror-like look. Extra fine grit is also utilized in wet sanding to minimize sanding residues.

What are the Types of Sanders and Their Uses

There are four types of sanders used to sand the substrates:

1. Random orbit sander: Random orbit sander, also called palm sander, is an equipment used to sand the substrate. It is not as sharp as coarse grits but contains sandpaper with medium grits. It is named after its circular motion on the surface. Unlike the orbit sander that moves only in circles, the random orbit sander moves back and forth, too. They cannot be used to smooth the corners due to the round shape. Hold the tools in hand and let the machine do the rest of the work. Applying too much pressure on the handle increases the chances of scratches on the substrate.
2. Belt sander: A belt sander is a battery-powered tool used to flatten uneven and bumpy surfaces. It is highly aggressive compared to random orbits. Use a belt sander with coarse grit and random orbit to achieve a medium grit finish. These sanders contain a vacuum system to carry the sanding residues.
3. Detail sander: The detail sander is used to access the hard-to-reach areas of the random orbit sander. It is small in size and fits everywhere. It sands the cabinet, frames, and other detailing zones.
4. Hand sanding: Hand sanding is the widely adopted practice when homeowners do DIY paint projects. They fold the sandpaper in three or four layers to make it thick or use a sanding block. This technique is cost-effective but time-consuming than battery-powered sanders.

How to Choose the Right Sandpaper

Here are eight tips to choose the right sandpaper:

1. Surface Material: Assess the surface material and the type of the project. Use coarse grit (40–60) when painting the surface from scratch and medium grit when covering stains or filling dents. Use 120–150 fine-grit sandpaper when working on drywall and medium-grit sandpaper for metal buildups. Coarse to extra fine grit sandpaper is recommended for uneven and granny wooden surfaces. Use 220-grit sandpaper for plastic and 120 for fiberglass. 
2. Project Phase: Understand the progression and phase of the project before sanding the substrate. Look for the medium grits when starting and the extra fine grit for a mirror-like look.
3. Manual vs Power Sanding: Manual sanding is time-consuming and causes injury. Power sanding speeds up the work and carries out the work in an even pattern.
4. Paint Type: Prioritize extra fine or fine-grit sandpapers for water-based and oil-based paints between coats.
5. Surface Condition: Identify the condition of the surface before sanding. Don’t rub too aggressively on previously painted surfaces, as they need light sanding. 
6. Area Size: Assess the area size before investing in sandpaper. Use electric ones for heavy and industrial projects and sanding blocks for DIY.
7. Desired Finish: Avoid using coarse grits for sensitive surfaces. Look for the fine grits to achieve a glossy and shiny substrate.
8. Budget & Efficiency: Reusable sanding paper with a foam base is used to reduce the repeated money wastage. Sandpaper with paper cloth backing lasts longer compared to paper ones.

What are the Techniques for Sanding Before Painting

Here are the three techniques of sanding before painting:

1. Dry Sanding: Dry sanding is an aggressive and sharp form of sanding the substrate. They produce friction, heat, and noise when rubbed on the metal or wood surface. Dry sanding is suitable for highly uneven surfaces and welding buildups. 
2. Wet Sanding: The wet sanding technique is used to achieve a smooth metal or steel surface. Water is used as a lubricant, which reduces friction and heat. It provides finer and smoother results.
3. Block or Sponge Sanding: Block sanding contains a thin sandpaper over the wooden block, and sponge sanding is the thick, sponge-like material. These techniques evenly distribute the weight on the substrate. Sanding blocks can be reused, and they protect hands from direct contact with grit. 

How to Care for Sandpaper and Sanding Tools

Clean the sandpaper after sanding the substrate. Tap off the loose dirt first, and then dip in the solvent or water to remove paint. Make sure to spread them under pressure to avoid curly corners. Check the sharpness of grits after sanding and replace them if needed. Avoid using a blend of aluminium oxide and ceramic grit sandpaper, as they have uneven patterns that lead to scratches. Clean the power sanders against a shoe sole to remove dirt. Rinse and then let it dry in the air. Store the sanding tools carefully after wrapping them in microfiber.