Can You Sand Wood Against the Grain?

Mill Marks

• Sanding against the grain is helpful when sanding coarse wood with coarse sandpaper. Sanding this way removes more wood from the surface in less time than sanding with the grain. Wood is sent through a planer to be cut into boards, but the planer's blades make marks in the wood that are more defined when the blade is dull. These mill marks are more pronounced when finish is applied to the wood, so they must be sanded off the board. The bumps are easier to remove when you sand against the grain of the wood because more friction is applied to the bumps this way.

Warped Wood

• Sanding is a necessary part of refinishing hardwood floors. Wood may warp over time, making the surface unlevel and the ends raised in some places. Cupping and crowning is apparent when you look at a board from one end. A cupped floor board has raised edges and a dip in the center; crowned boards are raised in the middle with lower ends. Sanding against the grain is done to flatten all three types of raises in floor boards so that the floor surface is level again. A lot of sanding is required to level boards, and sanding against the grain removes wood faster. After the floor is level, the boards are sanded with the grain to remove scratches.

Product Buildup

• Wood is protected or modified with a variety of products to help it last or improve its appearance. Lacquers are sticky substances, such as shellack and bitumen, used to protect wood against water damage. Paint and adhesives may also be added to improve the appearance of wood. If wood is to be properly restored, however, these products must be completely removed from wood. Sanding against wood's natural grain is more abrasive so these products can be removed much faster. Following the grain essentially grinds the products further into the grain, making the process much more time consuming.

With the Grain

• Sanding with the grain is the best course of action for the most part, especially if a smooth surface is desired. Sanding scratches the wood surface to remove wood a little at a time. These scratches are barely noticeable if they follow the natural lines of the wood. After sanding a board against the grain to remove the rough surface or level the surface, use the same coarse-grit paper to follow the grain, which removes the cross-grain scratches. Continue sanding the wood with the grain, using progressively finer-grit sandpaper until the wood is smooth. Sandpaper grits range from very coarse 30 grit to medium 60 grit and ultra-fine 180-grit sandpaper.