Sandpapers and Glasspapers
By: The Working Man


Sandpaper is a general term used to describe any abrasive
paper with grit on one side that is designed to be used to
smooth a surface. Originally sandpaper was paper with actual
sand on one side to be used as an abrasive, and isn't
available anymore.

Most of what is termed sandpaper these days has one of these
abrasives on one side:

- Aluminum Oxide
- Garnet
- Glass
- Silicon Carbide
- Other specialist sandpaper Grit

Sandpaper or glasspaper is a term used to describe all forms
of adhesive papers. Each type of grit has different uses and
characteristics. That is what makes them suitable for
particular jobs. If you know what each abrasive is used for
then you can select the right or type of sandpaper for your project.

To explain how a piece of sandpaper or glasspaper is made:
grit is attached to a backing sheet using an adhesive. The
type of adhesive, grit and backing sheet used all have an
effect on how that particular sandpaper will perform and is
supposed to be used.

There are many different sizes of grit available for each of
the different grit materials used. The size of the grit is
given a number that represents the number of holes per
linear inch in a sieve screen.

The grit size can range from forty to over four hundred.
Good quality sandpaper will have grit that is the same size
all over the backing sheet.

The size of the grit determines the grade that is used to
classify the sandpaper:

Grit size (grade)
40-60 (coarse)
80-100 (medium coarse)
120-150 (medium)
180-220 (fine)
240 upwards (very fine)

On the backing sheet the grit size is marked and sometimes
even the grade is marked. If you are in doubt as to what you
need for the job at hand, the clerk at your local hardware
or home supply store should be able to advise you.


Choosing the Right Sandpapers and Glasspapers for the Job

More often than not the sandpaper you will buy is "closed
coat," which means that the entire paper is covered with
grit. Closed coat sandpaper cuts faster but clogs faster
than open coat. "Open coat" refers to paper with only fifty
or seventy percent of the backing sheet covered. Most often
only a specialist supplier will stock open coat sandpaper.

Backing Sheet Materials:

- Ordinary Paper
- Waterproof Paper
- Cloth

Ordinary paper is the usual backing used for sandpaper. It
is cheap and effective, and the brand, price and intended
use of the sandpaper you buy will determine the quality of
the paper backing used. Sandpaper for use with electric
sanders usually has a good thick quality paper backing
sheet.

Waterproof paper is needed if the sandpaper is going to be
used with a lubricant. The back of this type of paper is
usually glossy and darker than regular paper.

Cloth is used when a high degree of flexibility is needed
when sanding an object with sandpaper.

The backing adhesive used to stick the grit to the paper is
usually soluble, but it will be waterproof if you are using
waterproof paper. Water soluble sandpaper is most commonly
used and this works just fine for most applications. The wet
and dry sandpapers and other sandpapers designed to work
with lubricants use waterproof adhesive.

It is important, no matter what type of adhesive is used,
that the bond between the grit and the backing sheet is
strong so that excess separation doesn't occur when in use.
The sandpapers for use with electric sanders usually have
the strongest grit to paper bond versus sandpaper for hand
use.


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