Mesh

From PyroGuide

[edit] Mesh size

Mesh is a unit of particle size. Very often, the effect obtained with a specific pyrotechnic mixture depends not only on its chemical composition but also on the size and shape of the particles. In those cases, the particle size is specified in 'mesh' units, referring to the screen that is used to sieve the powder. For example, 80 mesh refers to a screen that has 80 holes per linear inch. The smaller the mesh number, the larger the particles. The larger the number, the finer the particle size. (A 10 mesh screen has 100 holes per square inch. 80 mesh screen has 6,400 holes per square inch.). When a narrow range of particle size is required, it may be specified as in the following example: -100 mesh + 40 mesh, meaning that the material is too large to fit through a 100 mesh screen, but small enough to pass through a 40 mesh screen.

The minus ( - ) and plus ( + ) signs mean that the particles of –200 mesh aluminum would pass through a 200 mesh screen and +200 mesh aluminum means that all the particles are retained on a 200 mesh screen. Generally anything smaller than 400 mesh is referred to as micron.

A micron is another measurement used for measuring particle size. A micron is one-millionth of a meter or one twenty-five thousandth of an inch.

[edit] Screen mesh numbers and relative opening size

Screen Size	Opening Size
mesh	inches	mm	microns
4	0.1874	4.760	4760
6	0.1260	3.200	3200
10	0.0787	2.000	2000
12	0.0629	1.600	1600
14	0.056	1.400	1400
16	0.0472	1.200	1200
20	0.0288	0.711	711
25	0.0284	0.710	710
28	0.0280	0.700	700
40	0.0165	0.420	420
60	0.0098	0.250	250
75	0.0077	0.196	196
80	0.0071	0.180	180
100	0.0060	0.152	152
120	0.0049	0.125	125
150	0.0041	0.105	105
180	0.0030	0.089	89
200	0.0028	0.074	74
270	0.0021	0.053	53
325	0.0017	0.044	44
400	0.0015	0.037	37
1200	0.0005	0.012	12
2400	0.0002	0.006	6
4800	0.0001	0.002	2