How To Sand Surfaces For Painting
Sanding is often a crucial step for ensuring that your surface is ready to be painted. If you don't have a properly sanded surface, paint may not adhere to certain items properly. You can oversand, undersand and often people underestimate its importance. But, you don't have to be a pro to sand a surface. You just need patience, some protective gear, and some elbow grease. Here's everything you need to know about sanding.
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How to sand surfaces during your paint job
Why Sand?
Sanding serves to remove imperfections on walls, ceilings, furniture, floors, etc. It is also used to roughen surfaces too glossy for paint or filling compound to adhere easily. Steel wool and sandpaper are the most commonly used abrasive materials for this purpose. Sanding can be performed by hand or with electric tools.
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Learn How to Sand
Why Sand?
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Tools and products for sanding
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Sanding wooden surfaces
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Sanding masonry
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Sanding previously painted surfaces
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Tools and products for sanding
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Steel wool
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Steel Wool
Why Sand?
Steel wool is used for cleaning, stripping and polishing metals, wood, etc. Types of steel, bronze and copper-based wool are good for surfaces exposed to water. You can use them to sand wood if you apply water-based or micro porous finishing products. Other types of steel wool leave traces that could imbed themselves in the wood and rust on contact with water.
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Varieties of Steel Wool
Why Sand?
The degree of roughness in steel wool range from extra-coarse (4) to extra-fine (0000). Very coarse wool (3) is used to smooth rough surfaces and remove varnish or paint during stripping. Coarse wool (2) is used to remove old paint and rust. When soaked with solvent, it easily removes grease and wax. Fine wool (0) is used to clean painted surfaces, trim and floors. Extra-fine wool (0000) is used to rubdown paint, varnish and shellac before applying a final coat. It also serves to polish surfaces and give them a satin finish.
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Sandpaper
Sandpaper consists of grains of aluminum oxide, emery, garnet, or silicon carbide glued to a backing. This backing may be paper, cloth, fibre, plastic or a combination of paper and cloth. The grains may be open or closed. Closed grains crush more easily during use. Sandpaper comes in sheets, belts and disks and in various grades of coarseness.
The coarseness of certain types of sandpaper is graded from 12 to 600. The higher the number, the smaller the grains. Other kinds of sandpaper come in three grades: coarse, medium and fine. The type of surface and its condition determine which grade should be used. Coarse paper is used to make rough surfaces smooth as quickly as possible. Finer paper is used to eliminate traces of the coarser grades. The following two charts present the main types of sandpaper and their different uses.
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Main types of sandpaper
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Different uses for sandpaper
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Use |
Coarseness |
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To remove old finishes |
60-80 |
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For bare wood |
80-120 |
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Plastic, ceramics, melamine, Formica, metal and stone |
100-150 |
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Between coats of paint |
120-220 |
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Before applying stain inside (water-based) |
180-220 |
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Before applying stain inside (solvent-based) |
120-220 |
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Before applying stain outside |
80 |
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Old stained or varnished wood that is still in good shape |
220 |
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Between coats of varnish |
220-320 |
Before you start sanding, make sure you are using the right sandpaper for the job by testing it on a hidden patch of the surface. Use a sanding block appropriate to the surface if you plan to sand by hand. The block helps you apply even pressure across the surface and so makes sanding easier. You can buy such a block or make one yourself with a properly sized piece of wood.
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Electric sanders
Why Sand?
Electric sanders are faster and often more effective than hand tools when doing a large quantity of work, but they also require more skill. These tools include belt sanders, vibrating sanders, disk sanders and floor sanders.
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Sanding wooden surfaces
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Sandpaper
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Sanding block
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Electric sanders
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Shop vacuum cleaner
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Protective goggles
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Filter mask
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1. Start with a coarse aluminum oxide or garnet sandpaper and end with a finer (80, 120, 180, 220) sandpaper.
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2. Sand with the grain to avoid ripping the wood fibres.
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3. Vacuum up the dust.
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Masonry sanding checklist
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Sandpaper
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Sanding block
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Electric sanders
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Dry white rag
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Shop vacuum cleaner
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Protective goggles
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Filter mask
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1. Start with a coarse silicon carbide sandpaper and end with a finer (100-150) sandpaper.
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2. Sand in a circular motion.
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3. Vacuum up dust.
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4. Wipe with a white, moist, lint-free rag. The moist rag removes any dust left by the vacuum cleaner. Soak rag in clean lukewarm water and wring out thoroughly before wiping to avoid leaving behind any moisture that could cause wood to swell.
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Sanding previously painted surfaces checklist:
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Sandpaper
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Sanding block
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Electric sanders
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Shop vacuum cleaner
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Protective goggles
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Filter mask
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High-pressure washer
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1. Start with a coarse silicon carbide sandpaper and conclude with a finer (80, 120, 180, 220) sandpaper.
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2. Rub surface in a circular motion, smoothing edges of the old paint job.
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3. Remove dust occasionally by vacuuming or striking the sandpaper on a hard surface. Replace sandpaper when it becomes encrusted.
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4. Fold sandpaper occasionally for a new sanding edge.
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5. Vacuum up dust.
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