Sandpaper

Did you know that both sandpaper and toothpaste use abrasives in their formulations? That’s right, toothpaste contains an abrasive mild enough to scrub off tarter without damaging tooth enamel. Did you also know that these days sandpaper manufacturers don’t actually use raw sand as an abrasive agent? Over the years, more specialized and durable abrasive agents like zirconium oxide, emery, garnet and diamond have replaced sand.

Sanpaper is useful for a range of chores from removing rust from metal and paint from wood, preparing wood surfaces for new coats of paint or stain, cleaning, planing uneven surfaces, to polishing gemstones.
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Types
Characteristics
Grit hardness
The equipment
Which sandpaper?
Sanding tips
Safety
Accessories

Types

Sanding can be performed either by hand or with a machine. Hand sanding is usually reserved for the smaller or more precise jobs, while power sanding is used for just about everything else. Power sanders vary in size from the smallest, palm-sized orbital sander for detail work, to large drum and belt sanders for the more important jobs.

Hand sanding

When it’s for a minor repair job or for restoring a delicate wood sculpture, hand sanding is the way to go. As long as the job is simple and short, a plain folded piece of sandpaper will often do the job but, when sanding minutes turn to hours, more efficient tools are in order.

Power sanding

Power sanders range from models that fit in the palm of your hand for work in restricted or convoluted spaces, to models designed to sand all the hardwood floors in a home, so matching the tool, and the paper, to the job can save time and money.

Characteristics

What is sandpaper?
Sandpaper is made of a flexible backing, an adhesive and a natural or synthetic abrasive referred to as the grit. The backing can be made of paper, cloth, fibre, etc. and is designated by the letters A to E (E is the thickest), with C and D being the most common. These backings are coated with various abrasive products that are carefully ground to precise sizes and, depending on the type, held onto the paper with water soluble or waterproof adhesive. Consumers usually employ sandpaper to sand wood, plaster, metal and it’s sold in sheets, pads, disks and belts of appropriate sizes.

Grit
Grit is the numeric term used to describe the number of grains per linear inch. Low grit numbers indicate coarser materials and high grit numbers finer materials, e.g. 60 = coarse grains and 220 = fine grains. It comes in natural forms such as emery, diamonds and corundum or in synthetic forms such as alumina (synthetic corundum), silicone carbide and zirconium oxide. Over the years, synthetic abrasives have come to replace most natural abrasives. With their “10” rating on the Mohs scale, natural and synthetic diamonds are the hardest of all commonly used abrasives.

Grit hardness

AbrasiveHardness ratingType
Natural diamond10Natural
Industrial diamond10Synthetic
Corundum9Natural
Alumina9Synthetic
Silicon carbide9Synthetic
Flint7Natural
Quartz7Natural
Talc1Natural
Grades
Although grade designations may vary from producer to producer, sandpaper can be classed into seven grades:
  • Extra coarse (16 – 40 grit):
    the roughest grade, used on very rough or damaged surfaces, deep scratches.
  • Coarse sandpaper (50 - 60 grit):
    for heavy material, deep scratches, paint, stain and varnish, stubborn stains or other imperfections.
  • Medium sandpaper (80 - 100 grit):
    is used on more fragile items like furniture and on minor imperfections and scratches.
  • Fine sandpaper (120 – 150 grit):
    the grade for final sanding prior to painting or staining and for cleaning wood surfaces.
  • Very fine (180 – 220 grit):
    mainly used between coats of stain or sealer and for final sanding.
  • Extra fine (280 - 320 grit):
    sanding between finishing coats.
  • Super fine (360 - 600 grit):
    final surface sanding.

There’s a wide range of sandpaper shapes and sizes, but for minor, all-purpose jobs look for 9 x 11 inch sheets (229 x 279 mm).
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