Some of us less-patient DIYers chafe at all of the sanding steps involved in many projects. But though it can be tedious, proper sanding is a must. And you can’t just pluck any ol’ sandpaper off a home-center shelf and expect it to work for everything.
There’s a reason so many different products are available. Choosing the right ones for your project involves a variety of factors, including the material you’ll be sanding, whether it’s wet or dry and the results you hope to achieve. To help you whittle down your choices, we’ve compiled a brief primer explaining the differences among sanding products and their various applications.
Sandpaper is made up of small abrasive particles adhered to a backing. Each particle features a number of sharp edges, which slowly cut away the surface you are sanding.
A sanding product’s applications and performance depend on the shape, size and type of particles it contains. A few of the most common types used for DIY hand-sanding include:
• Aluminum oxide, a synthetic material that is useful for many general-purpose sanding tasks. Probably the most common, it can be used to sand wood, metal, plastic, fiberglass, painted surfaces and more. Its particles boast high friability, meaning they fragment when heat and pressure are applied. This continually creates new sharp edges and allows the sandpaper to last longer.
Multipurpose aluminum-oxide particles (shown on this 60-grit sandpaper) are synthetic, strong and highly friable, which makes them cut faster and last longer than most natural particles.
• Garnet, a natural material that is not friable. It features a finer scratch pattern, making it a good choice for final sanding on woodworking projects. It can also burnish a wood surface.
The natural garnet particles shown on this 100-grit sandpaper are commonly used for final sanding on woodworking projects, as they help create a smoother surface than synthetic particles.
• Silicon carbide, a friable synthetic material that is strong enough to sand hard materials such as metal, stone, concrete, plastic, glass and fiberglass. Its particles cut aggressively and are waterproof, making it suitable for both wet and dry sanding applications.
Silicon-carbide particles are harder than garnet and aluminum-oxide versions, making them useful for aggressive cutting applications such as hand sanding with a drywall screen (shown).
Another thing to consider when choosing sandpaper is grit, the number of abrasive particles in each square inch. The lower the grit, the larger the particles and the rougher the sandpaper; higher grits yield finer sandpapers.
Keep in mind that low-grit sandpapers will remove more material faster than high-grit versions. Low-grit sandpapers work well for stripping material or roughing up a surface before painting; high-grit sandpapers are suited for more delicate tasks, such as removing small blemishes on woodworking projects.
Sandpaper Grit Guide
Appropriate grits for different sanding tasks
GRIT - PURPOSE
40-80 - Stripping layers of material; roughing up a surface
100-120 - Smoothing small imperfections; leveling a surface
150-180 - Fine surface prep; final sanding before finishing
220-320 - Sanding between coats of finish; removing dust spots
400-plus - Final sanding of finish to remove luster or miniscule blemishes
The difference between open- and closed-coat sandpaper is the amount of space between abrasive particles. Open-coat sandpaper has more open space, which helps to prevent clogging, as it gives dust and debris room to filter out. It is typically used for sanding wood and other materials that produce a lot of dust. Closed-coat sandpaper has little or no space between particles, making it susceptible to clogs, but it’s useful for applications such as sanding metal and some wood finishes.
Going through the grits
Going through the grits is an
important process that applies to many hand-sanding projects but is most
frequently used in woodworking. It refers to starting with the
lowest-grit sandpaper needed for your project and working your way
through the progressive grits until you reach the desired finish. For
example, if you’re starting with milled lumber, begin sanding with a
medium-grit abrasive (between 100- and 120-grit), which will remove most
visible marks. Then work your way up to about 150-grit, which will
create a smooth look and feel. It’s usually not necessary to sand bare
wood with anything finer than 150-grit. Grits between 220 and 320 are
for sanding between coats of finish, and grits finer than 320 are for
polishing wood finishes.
Executive Editor Dan Cary, HANDY’s
resident woodworker, recommends lightly marking the surface of your
project with a pencil each time you change to a new grit and then
sanding until you can no longer see the mark. This will help make your
sanding uniform. HANDY Editor Larry Okrend also recommends shining light
on your work at a low oblique angle to highlight miniscule ridges that
are often overlooked on milled lumber. — JS
The type of backing has a big impact on a sanding product’s strength, flexibility and purpose. Sandpaper’s namesake backing, paper, is classified according to weight: “A” through “F”; “A” is the lightest and most flexible. Heavier-weight paper is usually found on lower-grit sandpapers, as they are used for more rugged applications. Paper is very versatile: It can be used for a wide variety of sanding applications, is flexible and can be cut to size.
Sponge and foam are also common backings. They are flexible, making them great for sanding uneven surfaces, and are often washable, so they can be reused. Sponge and foam also allow for a secure, more comfortable grip than standard paper. Other common backings include cloth, which provides added strength and flexibility, and screen, which is typically used for sanding drywall, as it minimizes clogs. Different types of backings are often combined for added strength and flexibility.
Many times, the sanding product’s backing has another backing, such as hook-and-loop fasteners or pressure-sensitive adhesive (PSA). These allow users to quickly secure sanding products to tools such as handles and extension poles without using clamps.
The type of particles, adhesive and backing all play a role in whether a sanding product is waterproof and suitable for wet sanding applications. Aluminum oxide or silicon carbide particles paired with non-water-soluble adhesives and most cloth, sponge or screen backings usually make for waterproof combinations, though you should double-check package labels to be sure.