Categories of Aluminum

This is a post by Mike Swisher on rec.pyrotechnics dated October 2001.  There are other nomenclatures out there now
but this is a good primer on the aluminums.  Some newer nomenclatures for Eckhart are 10890 (about like U.S. Bronze 809)
and 5413H (aka Eckhart Super which is called German Black and is similar to Indian and other black
aluminums - it is much more reactive than 10890 and much darker). 5413H is good for small reports and
bottom shots.  I like 10890 for slow flash, larger bottom shots and well spiked reports.

Broadly speaking there are two kinds of powdered aluminum - flake and atomized.

Atomized aluminums are made by forcing molten aluminum through an aperture.While in free fall the metal droplets cool and solidify into spherical or spheroidal shapes. Particle size and shape depend upon the size of the aperture and the atmosphere in which the droplets form (which may be air, or may be an inert gas). Particle sizes range from a few microns up through something resembling small shot. A typical grade used in fireworks, such as Reynolds No. 120, is in the 200-325 mesh range. Coarse atomized aluminum is sometimes called granular aluminum or "alluminio in granelli" (e.g. Reynolds No. 40) and this also has a use in specialized tremalon compositions of the "pampanino" type. Atomized grades are dense grey powders and relatively clean to handle.

Flake aluminums are typically made by ball milling atomized aluminum with a lubricant, often under an inert gas. Depending upon the particle size of the atomized aluminum chosen as a raw material, and the duration of the milling, the powders msy range in size from less than 400 mesh up through perhaps 12 mesh. All of these are very fluffy and dusty, with a great tendency to become "airborne" in handling. They also (except for the finest sizes) all have some metallic lustre. Flake grades may also be made by stamp milling aluminum foil with a lubricant, though this procedure is more common in Europe than in the United States. Stamp-milled powders tend to be denser than the ball milled
kinds.

U.S. Aluminum (formerly U.S. Bronze, formerly Valley Metallurgical) makes the following grades:

No. 809 - American dark pyro - greyish-silvery powder, -325 mesh
No. 808 - Light pyro - silvery powder, a finer bright grade, -200 mesh
No. 810 - Bright - a little coarser than 808, the classic varnish or paint
aluminum
No. 813 - Fine flitters, 30-80 mesh
No. 812 - Coarse flitters, 12-40 mesh

German black aluminum (Hummel "black head," so called because the head of the drum is painted black) is supposedly made by
stamp milling foil to which a quantity of carbon black is added. It is a dark grey powder (about the color of antimony sulphide), and relatively dense compared to other flake aluminums. German "Blue head" is intermediate between German black and U.S. No. 809, and can be approximated by a mixture of half-and-half German black and No. 809. German "Yellow head" is a bright grade. These were all still in Hummel's catalogue the last time I looked. An old timer told me there once was a "Red head" grade, intermediate between blue head and yellow head, that was good for tremalons. All of these are or were made either by Gloria or Eckhardt, I think.

I hope this helps.