Start with the material
The best abrasive depends on what you are sanding. Wood is soft and fibrous, metal is hard and heats up, paint and finishes tend to clog, and drywall compound produces fine dust and is easily damaged. Matching the abrasive to the material matters more than any other single choice. For the meaning of grit numbers themselves, see the separate discussion of sandpaper grit; this article focuses on what the paper is made of and how it is backed.
Wood
Aluminum oxide is a dependable all-around choice for bare wood, on both hand sheets and machine discs. Garnet works well for hand sanding fine furniture parts because it produces a clean scratch pattern, though it wears out faster. For heavy removal on a belt sander, zirconia or ceramic belts last longer under pressure. Resinous woods can clog paper quickly, and an open coat product helps there.
Wood benefits from sanding along the grain in the final steps. Most softwoods and some hardwoods respond well to a final grit in the 150 to 220 range, though preferences vary by finish.
Metal
Metal needs an abrasive that stays sharp without breaking down too quickly. Aluminum oxide on a cloth backing is common for general metal work, and silicon carbide wet-or-dry paper suits smoothing, rust removal and polishing at higher grits, often with water or light oil when the product allows. Zirconia belts and discs handle heavy removal in tough metals. Use a grit appropriate to the job: coarse for rust and weld cleanup, finer for finishing.
Metal sanding creates sparks and hot particles in some cases, so keep flammable materials and sanding dust from wood well away, wear eye protection, and avoid loose clothing near spinning tools. Cleaning up after sanding is part of the job. Dust from some metals and coatings is harmful, so use a respirator rated for the material and read the safety information that applies.
Paint and old finishes
Paint clogs paper fast, so open coat aluminum oxide is a common choice. Use the lightest grit that works: heavy sanding of paint can gouge the wood beneath. For flat surfaces, a random orbital sander with medium paper is typical. On curved surfaces, flexible foam-backed sanding pads fit better than flat sheets.
Old paint, especially on homes built before modern lead regulations, may contain lead. Do not dry sand unknown old paint without researching safe testing and containment methods. Chemical strippers or other methods may be more suitable in some cases, and wood finishing guidance often notes how the existing coating affects what comes next.
Drywall
Drywall joint compound is soft and dusty, so it needs light cutting rather than aggressive grits. Common choices are sanding screens (mesh coated with abrasive) and specialized drywall sanding sponges. Screens resist clogging and let dust pass through, and sponges help with edges and corners. Medium to fine grits, often between 100 and 220 depending on the stage, are typical, but check manufacturer directions. Pole sanders extend your reach for walls and ceilings.
The dust is very fine and can irritate lungs and eyes, so wear a respirator or mask rated for fine particles, plus goggles. Learning how drywall mud behaves as it dries helps you avoid oversanding, since it is easier to sand a little more than to repair a gouge in the paper facing.
Backing types
Abrasive grains sit on a backing, and the backing affects flexibility, strength and tear resistance.
- Paper: economical and common. Lighter paper is flexible for hand work; heavier paper holds up better on machines.
- Cloth: strong and flexible. It is common on belts, flap discs and metalworking abrasives.
- Film: a smooth plastic backing that gives consistent scratch patterns, often used for fine finishing and discs.
- Foam: padded sponges and blocks that conform to curves and profiles.
- Mesh: open weave that resists clogging and allows dust to pass through, used for drywall and some machine discs.
- Non-woven pads: fibrous pads that scuff rather than cut, useful for smoothing finishes and cleaning metal.
Hand sanding versus machine sanding
Hand sanding is best for delicate work, curves, edges, between coats and anywhere control matters. Wrap the paper around a block for flat surfaces so that you do not sand soft grain deeper than hard grain. Machine sanding saves time on large areas, but you need discs or sheets cut to fit your tool. Check the pad size, hole pattern and attachment type: hook-and-loop discs swap quickly, while adhesive-backed discs stick and are harder to remove. Belt sanders need belts of the correct size and direction arrow.
A machine does not make sandpaper last forever. Overheating can glaze or melt the abrasive’s bonding. Let tools run at the speeds the manufacturer recommends, and ease up on pressure.
Wet or dry use
Some papers, labeled wet-or-dry, use waterproof bonding so they can be used with water to carry away particles and reduce clogging. This is common with silicon carbide on finishes, plastics and metal. Do not use wet sanding with electric tools unless the tool is designed for it, since water and electricity are a dangerous mix.
A practical way to decide
Ask three questions: what is the material, how much needs to come off, and am I using a machine or my hands? Then pick an abrasive that suits the material, a backing that suits the method, and a grit that suits the amount of removal. If in doubt, start with a less aggressive option on a hidden test area, because you can always sand more but cannot put material back.
Wear eye protection and a suitable dust mask or respirator, and unplug power tools before changing abrasives.