Mesh and Grain sizing

[shockie]

I thought I would post this here as it has some interesting information in it that all can use:

 

Mesh Sizes and Microns

We first ran this conversion table in our printed catalogs. But we still get questions concerning mesh sizes, micron conversion, etc. So here it is again.

What does mesh size mean? Figuring out mesh sizes is simple. All you do is count the number of openings in one inch of screen (in the United States, anyway.)

The number of openings is the mesh size.

So a 4 mesh screen means there are four little squares across one linear inch of screen.

A 100 mesh screen has 100 openings, and so on.

Note, therefore that as the number describing the mesh size increases, the size of the particles decreases.

Higher numbers = finer powder.

Mesh size is not a precise measurement of particle size.

Screens can be made with different thicknesses of wire.

The thicker the wires, the smaller the particle passing through that screen, and vice versa.

What do the minus ( - ) and plus ( + ) plus signs mean when describing mesh sizes?

Here’s a simple example of how they work. -200 mesh aluminum would mean that all particles will pass through a 200 mesh screen.

A +200 mesh aluminum means that all the particles are retained on a 200 mesh screen

How fine do screens get?

that depends on the wire thickness.

But the supplier of our screens does not offer any screens finer than 500 mesh.

If you think about it, the finer the weave, the closer the wires get together, eventually leaving no space between them at all.

So, beyond 325-400 mesh, we usually describe particle size in "microns."

What is a micron?

A micron is another measurement we use for measuring particle size.

A micron is one-millionth of a meter or one twenty-five thousandth of an inch.

1 micron = 1 micrometer.

This table is adapted from a post made by Ken Kosanke to the PML and previously published in a PGII Bulletin.

U.S. Standard * Space between wires

Sieve Mesh No. Inches Microns** Typical material

14 0.056 1400

28 0.028 700 Beach sand

60 0.0098 250 Fine sand

100 0.0059 150

200 0.0030 74 Portland cement

325 0.0017 44 Silt

400 0.0015 37 Plant Pollen

625 0.000787 20

(1200) 0.0005 12 Red Blood Cell

(1250) 0.000393 10

(2400) 0.0002 6

(4800) 0.0001 2 Cigarette smoke

* The mesh numbers in parentheses are too small to exist as actual screen sizes; they are estimated and included just for reference.

Size Does Matter: Finding the Right Black Powder

This was also lifted from our old printed catalog, but some folks do not know what "meal powder, 2FA, or 4FG" mean, so this should help.

Having a hard time finding the "right" size black powder or confused about it?

Black powder types and grain sizes are classified by the manufacturers by the numbers and letters shown below.

Most black powder sold in the US is either "sporting grade" ("G" powders), or "fireworks grade" ("A" powders), or "blasting grade" ("B" powders)

Professional fireworks manufacturers prefer the "A" series powders, but you are required to have an ATF license to buy them legally.

However you don't need an ATF license to purchase up to 50 lbs. of sporting grade (G) powders, which are chemically identical (go figure!).

Since the composition of the two types of powders is identical, you can, in fact, substitute G powder for A in your fireworks, if you understand the following:

back in Neanderthal times, the powder manufacturers created completely different grading schemes for each type of powder (ie. sporting vs. blasting powder).

Hence, 2FG powder is not the same size as 2FA. But using the table below you can see how to substitute G Grade powders for the harder-to-obtain A grades.

In the USA, gun stores will sell you Cannon Grade, 1FG, and 5FG powders as suitable substitutes respectively for the most commonly used 2FA (for lift and burst), 4FA (for lift and burst), and Meal D (for rice hulls and priming).

If you are making your own black powder, you can use this chart for approximate screen sizes for granulating powders to standard grain sizes. Black Powder Grades & Equivalent Sizes (in mm)

Sporting Grades (G) Grain Size (in mm) Fireworks Grades (A) Grain Size (in mm)

1FA 8.0-4.0

Cannon Grade 4.76-1.68 2FA 4.76-1.68

1FG 1.68-1.19 4FA 1.68-.84

2FG 1.19-.59

3FG .84-.29 5FA .84-.297

4FG .42-.15 7FA .42-.149

Meal D .42

5FG .149 Fine Meal .149

Extra Fine Meal

[shockie]

Here's a chart

[SeaMonkey]

Very handy convenient size reference! Many thanks!

 

According to some sources the Graphite coating of the Sporting (g) powders does make the grains

somewhat more difficult to ignite by spark than the uncoated Fireworks (A) powders.

 

Could that explain the reasoning for the difference in regulation?

[shockie]

Very handy convenient size reference! Many thanks!

 

According to some sources the Graphite coating of the Sporting (g) powders does make the grains

somewhat more difficult to ignite by spark than the uncoated Fireworks (A) powders.

 

Could that explain the reasoning for the difference in regulation?

 

I think you just answered your own question. The sporting powders with the graphite coating reduces sparking, hence explosions.....the (A) powder, not having the graphite coating a=can be more prone to spark and go boom

[SeaMonkey]

That does make sense.

 

Therefore, for those who make their own, it might be advantageous to tumble the grains with graphite powder

to achieve the light coating which alters "storage requirements."

 

Perhaps Graphite such as this.