70 replies to this topic

[Greg T]

Could someone please tell me what the difference is between flake, atomised, fine, and coarse aluminium and what the different varieties are used for when making fireworks. How do they differ in performance?

I see Labpak sell the coarse and fine variety and that 'Alec Tiranti' sells the atomised variety.


Could you also tell me whether it is more adviseable to use coarse or fine iron filings (or does it depend on what you're using the iron filings for?).


Thanks,

Greg

[Richard H]

Aluminium comes in several kinds, which I'll try to explain to you. First there are flake powders, these are fine needle shaped particles of aluminium that are irregular in size.

Atomised powders are produced by forcing molten aluminium through an inert atmosphere, the result is a particle that is spherical in shape, and their size can be controlled precisely.

Flake powders are generally much more reactive owing to their increased relative surface area, and this makes them much more suited for use in fireworks applications. Flake aluminium is often used in the majority of flitter based effects, as well as in flash powders where extremely fine flake is used.

Atomised powders are less reactive, but still find use particularly in composite rocket motors and the popular glitter effect. When a type of aluminium is given in a particular formula, it is because the size and shape of the particles will produce certain desired characteristics. For example in flitter based effects you want bright long duration tails, so a medium-fine flake might be used. In a flash powder you want the composition to burn extremely quickly, so a very fine flake powder with a huge surface area is used.

In the glitter effect the atomised powders add to the delayed nature of the effect, as they do not react as readily with the air.

Granular aluminium is another kind, and is not very useful in fireworks.

With regard to iron fillings, or indeed any metal powder, the mesh size used is dictated by what you are trying to achieve. Long duration spark effects are suited to larger particles, while a much more fine and bushy effect can be achieved with finer particles. It is common to see a range of mesh sizes given in a formula, to improve the overall effect.

Hope this helps

[Greg T]

Thank you Richard. That was a very helpful summary!

Do you know what type of aluminium powders are sold by organisations such as labpak (I assume that they are more likely to be atomised than flake).

Thanks again,

Greg

[Richard H]

I would imagine atomised or granular.

[pyrotechnist]

Hi does Alec Tiranti sell to private individuals or companys? I have had run ins with these and they told me they can sell then they can't and am F***ed off with these people.

[Richard H]

Why don't you ask them?

[phildunford]

I've used Alec Tiranti and they deal with individuals, no problem.

However, I've found their aluminium powder no good for pyro in any way, shape or form!!

Don't know if there is some form of inhibiter in it, but formulas made with it don't seem to burn....

[Pyromaster2003]

However, I've found their aluminium powder no good for pyro in any way, shape or form!!

No good at all? I have had success with Tiranti's Aluminium powder in 12mmID rockets when added to a slow burning BP comp. Also i found that it works good in stars along with great silver fountains.

[RegimentalPyro]

Huh?
I've had no problem getting nice white sparks from Tiranti Al.

Flash made with it will not even begin to burn however - The particle size is FAR too large.

What effect are you trying to achieve?

[Jerronimo]

Yes, I to use alec tiranti aluminiumpowder works great.

Just try a simple 80/20 bp/al formula you should get acceptable results.

[firedust2004]

I bought 500g of aluminium powder form tiranti about a week ago. It arrived quickly and tiranti was very helpful, no problems at all. I didn't order through the website and sent the order by post after requesting the total by email. It came to ?9.30 for the 500g of Al and the postage cost. I have tried it in flash but it doesn't work at all. I made a very effective fountain by adding some of the Al powder to a batch of Chrysanthemum #6. I really liked the effect. There was a 2metre high plume of beautiful golden and silver sparks which lasted for about two seconds (more like a small mine) The fountain tube was only 50mm tall and 18mm wide.

[Jerronimo]

Offcource it doesn't work in flash,the alec tiranti powder is atomised, you need highly reactive flake aluminium for that.

A 80/20 mix of crys6/Al works very well in stars aswell, will post a video of a 3'' shell soon in the spherical shells thread.

[blueflame]

i have a 5 litre square metal can that is about 50% full of ali powder that i used some years back in the resin trade. so now i got this powder in a tin with no external label letting me know how fine it is! it looks as fine as cooking flour.i also wasted loads of it in thermo experiments years back, now i hope to put it to better use thanks to you guys .

[Arthur Brown]

Everything depends on the particle size. Some mesh screens woll allow you to determine the particle size you have, then processing will allow you to reduce the particle size. re-screen to fine the new particle size and size distribution.

Fine aluminium is extremely reactive - thats why we want it - so it is often coated during manufacture. Typical coatings include stearic acid - a hard wax - introduced during milling, and linseed oil - a drying oil - poured over the product, intimately mixed, and the surplus drained off, after milling. With Stearic acid a few percent by weight is added to the mill load, and milled together with the aluminium, the product can be screened and re-milled if appropriate. With the linseed oil the protective film is produced as the oil dries and hardens on the powder grains,and the grains may clump. The product may - due to clumping - give false results when screened, and CANNOT be re-milled without breaking the hardened coating..

All compositions depend for their effect on the particle sizes and size distribution. Some formulae only list ingredients by weight, others will have screen sizes for each component and a size distribution --- so much at 20 mesh and so much at 200 mesh. Reliable effects only occur when the variables are controlled.

True flake shaped particles (thin and flat) may have to be formed differently as milling tends to break flakes, passing through a very close set two roll mill to flatten out the spheroidal particles is an option probably while wet with linseed oil for lubrication and surface film formation. -- Carefull Two roll mills eat fingers unless very well protected.

[broadsword]

Is this powderthe stuff your buying.... Click Here

Edited by broadsword, 19 November 2004 - 12:06 PM.