Got Grit? Sandpaper and Sanding Guide

Sanding is a step in many a DIY project or repair. So how do you know if you have the right sandpaper or tool for the job? Does it make a difference in what grit sandpaper you use? What does grit even mean? All these questions and more will be answered here for your reference and convenience.

What is Sandpaper?

Fine natural or synthetic particles are sifted and sorted prior to being bonded with adhesive to paper, sponge, or a cloth-like backing. Sandpaper is used for removing finishes, smoothing, or polishing woodwork and other surfaces. Available in a variety of grits, sandpaper can make all the difference for buffing out blemishes, smoothing patched areas, or refinishing surfaces.

In the United States, grit is based on a gradation scale set by the Coated Abrasive Manufacturers Institute (CAMI).

NOTE: If sandpaper is purchased online, it may be from a different country and have a different size or grit scale.

What Does Grit Mean?

Grit refers to the number of particles per square inch bonded to the backing. The lower the grit number, the coarser the sandpaper. Reversely, the higher the grit number, the finer the sandpaper. Most sandpaper products also have a label from extra coarse to super fine on the packaging, along with a description of what job that sandpaper is best suited for.

What Grit of Sandpaper Do I Need?

Extra Coarse (24-36 grit)

Best for removing paint and varnish. Only use on the toughest jobs (not on a veneered surface).

Coarse (40-50 grit)

Rough shaping of wood and removal of previous finishes. Deep sanding with surface roughness.

Medium (60-100 grit)

Can do some final shaping. Primarily sanding of rough wood and removal of planning marks.

Fine (120-220 grit)

Most common for home workshops. Great for shaping and removing a lot of material quickly. Will work for final sanding before finishing.

Very Fine (220-240 grit)

Works great for finishing; gives a nice, smooth finished surface.

Extra Fine-Super Fine (320-600 grit)

Gives you the smoothest finish. Perfect for polishing.

Tips for Sanding Success

Start low and work you way up to a higher numbered grit. Otherwise, the sandpaper will get clogged or filled with dust particles quickly and you’ll double your efforts.

Sand in the direction of the wood grain. Going against the grain will cause striations in your surface that will show up in your finish.

Let the grit do the work for you. The coarser grit will remove more material at a faster rate than a fine grit. Save the fine grit sandpaper for smoothing and finishing.

Run your hand over the surface to feel for rough patches your eyes may not have noticed.

Always wear eye, ear, and respiratory protection while sanding.

Types of Abrasives

Aluminum Oxide

Synthetic. Suited for sanding and polishing various types of metal and all types of hardwood.

Emery

sandpaper and sanding — Photo credit: Alibaba.com

Natural Grain. Often used to remove corrosion and/or for polishing steel and other metals. The edges can be too sharp for sanding wood.

Flint

Natural Grain. Durable and great for sanding off surface products such as old varnish or paint.

Garnet

sandpaper grit — Photo credit: Kramer Industries Inc.

Natural Grain. Slightly softer than flint or emery, so it may dull quickly when sanding metal. Best for fine sanding of wood.

Silicon Carbide

Synthetic. Most durable synthetic. Good for sanding a wide range of materials like plastic, metal, hardwoods, and softwoods.

Zirconia Alumina

Synthetic. Long lasting and good for grinding burrs on metal and initial sanding of rough wood. When sanding metal, the grit particles may become sharper and you will not need to switch sandpaper as often.

Types of Sanders

different types of sanding tools — Sponge sanders, sanding blocks and a palm power sander pictured.

Sanding Sponge

Just as it sounds, a spongy base with particles adhered to it. May be a rectangular prism, or a parallelepiped (a polyhedron with 6 faces which are all parallelograms). More ergonomic; material made to form to your hand. Will conform to curves in wood. Good for tight spaces. No reloading, may have different grits on different sides of the sponge for an all in one sanding tool. It is disposable, so once used up just toss it.

Sanding Block

A block where the sandpaper wraps around and is clamped down in some way to hold it in place. Reusable, just switch out the paper as needed. Best on large, flat surfaces and corners. Some sanding blocks are designed with handles for a more comfortable hold.

Power Sanders

Power sanders do the work for you as you move it along the surface.

BELT SANDER- Removes a lot of material in a short amount of time. A machine that rotates the circular piece of sandpaper in one continuous direction. You move the wood piece along the surface. Best on flat, open pieces without a lot of details, nooks, or crannies. There are some belt sanders that can be used to strip wood floors.

ORBITAL SANDER- Can change out the round pads. Can work on broad surfaces, sides and angles. Move sander along the surface or it can wear a circular design into the wood.

PALM POWER SANDER- Smallest of the power sander options. Best on hard to reach places that belt and orbital sanders can’t quite get to. Some styles use regular pieces of sandpaper, others require pre fabricated shaped pieces. May be round, square, or mouse shaped.

What is Wet Sanding?

Wet sanding is sanding done with some type of lubricant that aids in the removal of dust particles and causes a slurry that fills in any finish imperfections. Leaves a high gloss finish. Wet sanding is typically done after dry sanding to get an even finish. Dry sanding is mostly done to shape the surface while wet sanding is mostly done to remove the large scratches often left by dry sanding. Think of a car, this would be done on the finished surface before the clear coat.

Can Wet Sanding be Done on Painted Furniture?

Yes. It is just like normal sanding but with a liquid added as a lubricant. Water based paints would use a water solution and oil based paints would use mineral spirits.

Used to get a high gloss finish without the use of a sprayer. Best used when trying to achieve a lacquered look.

Check out Coastal Upcycling for a tutorial on wet sanding painted furniture. Here.