Selecting the right grade of sandpaper for a specific task can often be confusing. There are multitude of grits to choose from as well as both open coated and cloase coated sandpaper. So which is the right sandpaper for your project?
Sandpaper is made by bonding grit (sand) to strong paper. The coarser the grit then the coarser the sandpaper. Coarse sandpaper presents many grit particle which have sharp edges and it is these that cut into the surface being sanded. Fine grade sandpaper uses finer particles of sand or mineral which present many more sharp edges which will cut into the surface that is being sanded. These cutting edges are much smaller than those presented by coarse grain sandpaper and therefore the sanding results are much smoother.
Another aspect of sandpaper design that needs to be considered is whether open coated and close coated is most appropriate. Open coated sandpaper has the abrasive grit distributed across the surface with gaps in between the grains. This means that there are fewer cutting edges in a given area but it also means that the paper will tend to clog less easily. Close coated sandpaper has less space between the abrasive grains which means there are more cutting edges in a given area. But this type of sandpaper will tend to clog more easily than open coated.
The abrasive minerals used in sandpapers tend to be sand (quartz), emery, aluminium oxide and silicon carbide. The bonding agent (glue) and paper used in sandpapers also varies. High grade industrial sandpapers use high quality, card-like paper and top quality bonding agents. Whereas cheap sandpaper uses far lower quality elements.
For further great information and advice on all aspects of sanding your should read the Abrasives for Sanding Wood post provided by Wood-Finishes-Direct.com.
So what type of sandpaper is best for your project? The short answer is - it depends on what you are doing. Regular sand based sandpaper is good enough for sanding timber, but doesn't have many sharp edges. Emery paper uses a mixture of corundum and magentite and is generally good on metals, for rust removal, paint removal and fine finishing. Aluminium oxide is popular on sanding discs used in electrical sanders. It's very tough and is highly suitable for steel, plaster, hard woods and even some forms of stone. Silicon carbide is a very hard and sharp abrasive that is suitable for paint removal, metals, hard woods, plastic and more.
Some sandpapers can be used wet or dry. Wetting sandpaper can help to reduce clogging and therefore maintain the sandpaper's usefulness for longer. It is generally a good idea to start with a coarse or medium coarse grit and then progressively work towards a finer grit for a smooth finish.
When sanding wood its best to sand along the grain rather than across it. When sanding metals or plastics a circular sanding motion is a good idea. Never apply excessive force when sanding, either by hand or with an electrical sanding tool. Doing so will cause the sandpaper to wear out prematurely and may damage the surface being sanded. And it's always a good idea to pause periodically to check for clogging. Clogged paper can often be cleaned with a light brush.
