Call them sandpaper if you want. The industry calls them coated abrasives. The name doesn’t change the grit. It just changes how you buy them.
When you stand in front of that wall of sanding sheets at the hardware store, you’re looking at a complex system. It’s not just about rough or smooth. Four specific variables determine if your project succeeds or fails.
First, the abrasive mineral. This is the actual cutting material. Is it aluminum oxide? Silicon carbide? Garnet? The mineral dictates what surfaces it can handle.
Second, the grade. This is the coarseness. Grits range from 40, which shaves wood like a chainsaw, to 600, which polishes like a mirror. You need to match the grade to the stage of your work.
Third, the backing. Paper or cloth. Paper is brittle. It tears easily. Cloth is durable. It resists heat and flexes better on curves.
“There are four factors to consider when selecting any coated abrasive: the abrasive mineral, the grade, the backing, and the coating.”
Fourth, the coating. How much mineral sits on the surface? How is it attached? A heavy coat cuts fast but clogs. A light coat lasts longer but cuts slower.
Mix up these four factors and you’ll waste time. You’ll burn through sheets in minutes. Or leave deep scratches that show up under stain.
Know your mineral. Know your grit. Pick your backing. Check the coating. That’s the only way to sand right.
Why Your Sandpaper Choice Matters
Holding sandpaper in your hand feels natural for small spots, but wrapping it around a block keeps the pressure even. If you skip the block, you’ll likely end up with dips and valleys where you shouldn’t be.
The backing paper itself dictates how the tool behaves in your hand. Manufacturers use four specific weights to categorize this durability. A-weight paper is labeled “Finishing.” It’s the lightest option. Use it for delicate work that requires a gentle touch. C and D weights fall into the “Cabinet” category. They are built for heavier, more aggressive sanding. E-weight paper is the heavy lifter. It handles the toughest jobs without tearing apart under strain.
Open vs. Closed Coatings
The way mineral grains are applied to that backing changes everything.
Open coated abrasives space the grains out. They cover only part of the surface. This spacing allows dust and debris to escape rather than getting stuck. You want open coating for gummy softwoods. It also works best on soft metals. If you are stripping old paint, this is your go-to.
Closed coated abrasives cover the entire area. The grains are packed tight. This setup provides maximum cutting power. The trade-off is that these pads clog up fast. They get filled with dust and lose effectiveness quickly. Save closed coated paper for hard woods and metals where you need aggressive removal without the immediate mess of clogging.
Decoding the Grit Confusion
Three different grading systems exist, and they often contradict each other. Don’t get confused.
The simplified system uses words like coarse, medium, or fine. It’s vague but intuitive. The grit number is more precise. It refers to the count of mineral grains lined up end-to-end to equal one inch. Higher numbers mean smaller grains and smoother finishes.
Then there is the O-symbol system. These markings are essentially arbitrary. The coarsest rating is 4 1/2. The finest is 10/0. That is six zeros. It sounds ridiculous, but it indicates a fineness that approaches a mirror shine. Knowing which system your supplier uses will save you time at the hardware store.
Matching Grit to the Job
You need specific grits for specific tasks. Using the wrong one will either waste your time or ruin your surface.
Very Coarse (30-60 grit)
Start here only when you are removing heavy material. Think rust on rough metal or stripping layers of thick paint from wood. The grades range from 2 1/2 to 2 on the O-scale. Use flint, garnet, or silicon carbide.
Coarse (80-120 grit)
This is for rough sanding of new wood. It also works for removing paint from existing surfaces. The O-symbols here are 0 to 3/0. Aluminum oxide and silicon carbide are common choices. This grit prepares the surface for finer work.
Medium (150-180 grit)
Use this for general wood sanding. It smooths plaster. It also preps previously painted surfaces for new coats. The O-symbols are 4/0 to 5/0. This is a critical step. If you skip from coarse directly to fine, you leave scratches that will show through your finish.
Fine (220-280 grit)
This is for the final sanding of bare wood. It also smooths surfaces before you apply a top coat. The O-symbols range from 6/0 to 8/0. Use silicon carbide if you are doing dry sanding. It handles the heat and dust better.
Extra Fine (320-600+ grit)
Use this for high-gloss finishes like lacquer, varnish, or shellac. It is also essential for wet sanding. Silicon carbide is the standard here. These grades often lack an O-symbol designation. They produce a surface so smooth it feels like glass.
Picking the Right Abrasive Material
The chart lists flint, garnet, aluminum oxide, and silicon carbide. Each has a purpose.
Flint and garnet are traditional choices for wood. Aluminum oxide is durable and cuts faster. It lasts longer on hardwoods. Silicon carbide is the specialist. It is used dry or wet. If you are wet sanding, you need silicon carbide. It won’t disintegrate in water or oil. It creates a slurry that helps polish the surface.
Choosing the right abrasive isn’t just about smoothness. It’s about efficiency. Use the correct grit and backing for the material you are working on. Your finish will look professional. Your back won’t hurt as much.
Beyond Sandpaper
If sandpaper isn’t the right tool, look elsewhere. Steel wool has grades too. Co
