Homeowner’s Guide to Sandpaper

Using the right sandpaper can make all the difference in a woodworking, painting, or finishing project; but choosing between the many different types of sandpaper that are available can be a challenge. Here are some tips on how to choose the best sandpaper for your next project.

Read on to find out more about sandpaper.

Sandpaper Basics

Sandpaper consists of an abrasive material bonded to a paper or fabric backing. When selecting sandpaper for your project, you need to decide between the different abrasives, a range of grit sizes, and various types of backing.

The sandpaper you select will depend on the material you’re sanding and what you’re trying to accomplish.

Sandpaper Abrasives

There are several different types of abrasives used for sandpaper, including:

• Aluminum Oxide: This abrasive is the most common all-purpose sandpaper material for home or workshop use. Aluminum oxide sandpaper is economical and suitable for most materials – including wood, metal, paint, plastic, and fiberglass. One advantage of aluminum oxide is that it’s friable, meaning the particles fracture to expose new sharp edges as you sand, which makes the sandpaper last longer.
• Garnet: An inexpensive sandpaper abrasive, garnet is used mainly on wood. Garnet is a natural material that grinds down smooth with use. This allows garnet sandpaper to produce a velvety surface in fine woodworking projects, though it also tends to wear out rather quickly.

• Silicon Carbide: This synthetic abrasive is gray or black in color and often backed with a waterproof material for use in wet sanding. Since it’s harder than many other abrasives, silicon carbide is mainly used for sanding hard materials – such as metal, plastic, or fiberglass – as well as sanding between coats of paint or finish. It’s generally not used for sanding wood, except on wood floor sanding machines.
• Ceramic: A very hard abrasive, ceramic is generally used for removing large quantities of wood, such as with a belt sander. Ceramic sandpaper generally doesn’t produce a very smooth surface.
• Emery: Used for sanding, polishing, or removing rust from metal. Emery usually has a cloth backing to make it more durable and flexible.

Sandpaper Grits

Once you’ve decided which kind of abrasive you need, the next step is to choose the right grit. Sandpaper grits are graded according to the size of the abrasive particles, with lower numbers for larger particles and higher numbers for smaller particles.

You can find the grit size on the package label and printed on the back of each sheet of sandpaper. Grit is generally classified as follows:

• Coarse: Grits less than 60. Coarse grit sandpapers are used for removing material rapidly, such as when shaping corners or stripping paint.

• Medium: Grits ranging from 80-120. Medium grit sandpapers are used to smooth rough surfaces, remove scratches, and prepare surfaces for paint or finish.
• Fine: Grits ranging from 150-220. Fine grit sandpapers are used for final smoothing of surfaces before application of finish, or for sanding between coats of finish.
• Superfine: Grits above 220. Superfine grit sandpapers are used to smooth or polish surfaces between coats of finish.

When sanding, start with the lowest grit required, then work your way through successively finer grits, with each finer grit used to remove the scratches created by the grit before. For example:

• When stripping and refinishing a piece of wood furniture, you might start with 60 grit sandpaper to remove the old finish, then work your way through 80, 120, 180, and finally 220 to smooth the wood.
• To sand a piece of new unfinished furniture, you could begin with 120 grit sandpaper and work up to 220.
• For sanding between coats of finish, you would use 220 grit or higher sandpaper.

Sandpaper Backing

The backing on sandpaper can be made from various materials and come in different thicknesses:

• Backing Material: Most sandpaper has a paper or cloth backing. Paper backing is less expensive while cloth backing is more durable.
• Backing Grade: Backing materials are graded by weight. Paper backings are given alphabetical letter grades from A (thin) through F (thick). Cloth backings are graded J (thin) or X (thick). The grade of the backing material is printed on the back of the sandpaper. In most cases, the manufacturer chooses a grade of backing that corresponds with the grit, so it’ll hold up (or be flexible) for the job, with coarser grits on heavy backing and fine grits on thin backing. However, you may find that economy packs of paper are cheaper because they have a lighter weight backing.

Sandpaper Glue and Coatings

• Bonding Material: While many sandpapers are bonded to the backing with hide glue, others use special waterproof glue or heat-resistant adhesives.
• Open vs. Closed Coat: Sandpaper may be either closed or open coat. Sandpaper with a closed coat is completely covered with grit while open coat sandpaper has small gaps between the particles of grit. While closed coat sandpaper gives a smoother finish, it tends to clog. The gaps between the particles in the open coat allow dust to collect to prevent the paper from clogging.

Further Information

• Power Sanders 101 (article)
• How to Sand Round Objects (video)
• Using File Folders to Organize Sandpaper (video)
• Tips for Using Sandpaper on an Oscillating Finishing Sander (video)