Screen or mesh size

In the language of the sandblaster the size of the blasting grit is referred to as the mesh or screen size.   The screen number is the number of equal size holes in a 1" square screen.  The larger the number, the more holes and therefore the smaller each hole is.  The lower the number the coarser the media.  Please note that the screen material takes up space so a #4, which has 4 holes per square inch is not 1/4" in size.  It is actually about 3/16" or 1/16" less then 1/4".

The size of a particle of blasting grit is the number given to the smallest screen it will pass through.  In other words if something passes through a #30 screen but stops at the #25 screen it is known as a #30.

In blasting you want to have a mix of sizes to give the best cleaning and profile so you normally see sizes like 20/40.  This means that most of what is in the mix is a #30 with part of it finer, up to a #40 and some of it coarser, down to a #20.

The terms fine, medium or coarse or the numbers 0, 00, 000 or 2, 3 or 4 given out by some manufacturers are not what you want to use to compare sizes between two companies.  One companies fine can be someone else's medium.

For your information:

• Regular ground coffee is approximately a 16/40 mesh.
• Sugar is about a 50/80 mesh.
• Table salt around a 30/80 mesh.
• Fine ground black pepper is a 30/50 mesh.

The following is a friendly comparison chart of National Bureau of Standards (NBS) screen sizes used in the blasting industry

*Close to, but not exact in every case!