823 replies to this topic

[bigtonyicu]

bigtonyicu, you know your shit, Mg S flash... What ratio and how fine does the Mg have to be, I have ribbon which I was going to file would that be sufficient? Also could boric acid be used as a buffer like the KNO3 Al S mix or is this not safe to use at all?

OK lets star with Safety... NO FLASH IS SAFE!!!, some are safer than other, but none a safe!!! Let’s keep in mind that Flash is the only explosive (wave front is supersonic). Nitrate flashes are as safe as you can get and still maintain the supersonic shatter affect required by salutes.

Ok not that that's out of the way...

Magnesium is much more reactive then aluminum and the formula I have for mag/nitrate flash is 50:50 mix, personally aluminum is easier to find, much cheaper. I don't have my Chem. book handy but even at twice the reactivity of Al, 70 micron if still too coarse, and I can't see how you could make it any finer with a file, for best results I'd use Micron grain sand paper (http://www.leevalley...amp;cat=1,43072) the only problem is aluminum has the bad habit of blocking sand paper, normally it would be wet sanded to prevent clogging.





As for boric acid I've never seen ANY Flash using Boric acid so I'd have to try it. But by reasoning, sulfur is normally added to increase the sensitivity and hence increase the combustion rate so adding boric acid would reduce the rate and with a mix of coarse metal powder and boric acid, I'm afraid you'd move back to subsonic combustion *DO NOT add SULFUR TO A MAGNESIUM/NITRATE FLASH EVEN IF BORIC ACID INCLUDED the combustion velocity would keep increasing and once supersonic you don’t need anything faster, sulfur mixed the increase reactivity of Magnesium could react with moisture in the air to createà MgSO4 (magnesium sulfate)+heat (you could get a case of spontaneous combustion of a an explosive), and that’s definitely not a risk worth taking.



My advice, if you can’t buy -10Micron aluminum is to sand an aluminum block with the above sand paper and use a standard 50:20:30 (KNO3:Al:S) flash mix, I’d stay away from Mg flash till you have A LOT of experience with flashes. You could make a machine to sand Al under water (http://gamekeeper.de...ng_machine.html). I’ve heard of a few machines like that and the results were acceptable.

That’s my 2 cents worth lol

Edited by bigtonyicu, 16 July 2008 - 04:31 AM.

[banga]

OK lets star with Safety... NO FLASH IS SAFE!!!, some are safer then other, but none a safe!!! let's keep in mind that Flash is the only explosive (vawe front is supersonic). Nitrate flash are as safe as your can get and still maintain the supersonic shatter affect require

I realize flash is not safe, the Al I have is not suitable for flash and I was considering using the Mg S flash mix but I take it that by not answering how to make that mix, it's not useful and too dangerous.

[bigtonyicu]

I realize flash is not safe, the Al I have is not suitable for flash and I was considering using the Mg S flash mix but I take it that by not answering how to make that mix, it's not useful and too dangerous.

sorry I posted before I was done,... got back and see the full post

[banga]

sorry I posted before I was done,... got back and see the full post

Thanks mate sounds good, the Al I have is already super fine you couldn't see one grain with the naked eye, I don't know how many micron it is because it's not included on the label. I've discussed this previously with 'Seymour' apparently it's not fine enough. Mg ribbon is very easy for me to get hold of, so I might try a small amount of the KNO3 Mg 50/50 mix you mentioned, albeit in as fine a flake form as I can get from filing it...

KNO3 S Al mix I did before made cool glitter nice and bright but too slow for flash it must be the Al...

Thanks heaps.

Edited by banga, 16 July 2008 - 05:19 AM.

[seymour]

A fast correction; but a huge one, that's not 10 times finer, 10 times per dimension (in other words 10x10x10) your aluminum is 1000 times finer

and also 1000 the surface area; so 1000 the reaction rate (not really because thermodynamic laws slow that down significantly, realistically it's something in the order of 600x the reaction rate).

Bigtonyicu, I must say I am impressed, it did not even occur to me to consider the most important thing, surface area!

Remember though that I only guessed that Banga's Aluminium dust is 70 micron, it could be anything from 20 micron to 100 micron, and may be spherical or granular, however the principal is the same.

Someone can correct me on this if I'm wrong, but off the top of my head your Bright Al is usual spherical or speroidial. The reason it's so Bright is because the surface is perfectly smooth due the technique use to produce it, it's normally produced by atomizing molten aluminum in an inert atmosphere (think of a highly modified paint gun for painting cars, bad example I know but the principal is the same), as it exits the nozzle the surface tension pull each drop into a smooth sphere which acts like a nice convex mirror reflecting light in every direction in other word "Bright", or more accurately "Reflective"

Bright Flake Aluminium is indeed flake, but it is quite coarse, maybe the same mesh as Banga's Auminium, which is made by the method you described.the reflectivity comes from the large sheets which reflect light easily. I believe it can also be used in body paint where the sheets lay flat against the skin giving the appearance of a single metallic being. Skylighter describes their bright flake as:

Aluminum, flake, bright

-325 mesh, coated, Eckart 1400ND, silver-gray flake powder.

Used in flitter, and white and silver color compositions. Sometimes used as a substitute for American Dark aluminum; can be used in "slow flash" burst charges.

Particle size breakdown:
-325 mesh -- 100%; Particle size range 5-28 micron

Coated with stearin.

Also could boric acid be used as a buffer like the KNO3 Al S mix or is this not safe to use at all?

Banga,

You obviously have an understanding of this hobbies dangers and are prepared to ask before mixing, which is the kind of thing that results in an old pyro missing no limbs.

The reaction between nitrates and Aluminium, which Boric aid is added to prevent, I understand to be as follows, (someone please correct my mistakes). Aluminium can reduce aqueous nitrates forming some Ammonia, which then reacts with the Aluminium. All this produces heat, which can build up to high enough temperatures for ignition to occur. Boric acid neutralises the Ammonia and prevents the reaction from completing. This reaction needs not only nitrates and aluminum, but also water. Using non aqueous binders will also avoid the problems to a large extent, though in my opinion that is a but of an extreme measure.

Boric acid is not the only mildly acidic substance which makes such mixtures safer, Gum Arabic is also used (in addition to being a superior binder). Ignition of such mixtures is much more likely when they are in bulk and/or when the Aluminium has a high uncoated surface area. While it is your choice weather you want to add boric acid to small batches of star compositions containing unreactive atomised Aluminium and nitrates, it is unlikely that they will cause a fire, and if they are going to, the smell of ammonia will give you a clear indication that it is time to ditch your batch of chemicals in a bucket of water, or take them outside.

Magnesium-sulfur flash does not become safer with the addition of Boric acid. However, Magnesium is corroded quite easily by sulfur, which means that it has a short shelf life, and magnesium makes compositions more dangerous than Aluminium.

We are not trying to make life hard for you, it's just that the authorities every ware are not so keen on people making flash (for fairly good reasons). This, and the lack of alternative uses for flash capable metals mean that they are not easy to obtain over the counter, if possible at all. I think you will only have success looking for flash capable metals through the armature firework network or on the internet, the latter at a higher risk than the former.

If you do continue with your hobby for long enough, it is almost certain that you will get anything you want, giving it enough time.

I wish you the best.

Ps, I personally chose to take my chances on a website which could have easily pocketed my money and forgotten about me. It is your choice as to whether you are willing to take this route, and the possible consequences.

[banga]

Bigtonyicu, I must say I am impressed, it did not even occur to me to consider the most important thing, surface area!

Remember though that I only guessed that Banga's Aluminium dust is 70 micron, it could be anything from 20 micron to 100 micron, and may be spherical or granular, however the principal is the same.




Bright Flake Aluminium is indeed flake, but it is quite coarse, maybe the same mesh as Banga's Auminium, which is made by the method you described.the reflectivity comes from the large sheets which reflect light easily. I believe it can also be used in body paint where the sheets lay flat against the skin giving the appearance of a single metallic being. Skylighter describes their bright flake as:





Banga,

You obviously have an understanding of this hobbies dangers and are prepared to ask before mixing, which is the kind of thing that results in an old pyro missing no limbs.

The reaction between nitrates and Aluminium, which Boric aid is added to prevent, I understand to be as follows, (someone please correct my mistakes). Aluminium can reduce aqueous nitrates forming some Ammonia, which then reacts with the Aluminium. All this produces heat, which can build up to high enough temperatures for ignition to occur. Boric acid neutralises the Ammonia and prevents the reaction from completing. This reaction needs not only nitrates and aluminum, but also water. Using non aqueous binders will also avoid the problems to a large extent, though in my opinion that is a but of an extreme measure.

Boric acid is not the only mildly acidic substance which makes such mixtures safer, Gum Arabic is also used (in addition to being a superior binder). Ignition of such mixtures is much more likely when they are in bulk and/or when the Aluminium has a high uncoated surface area. While it is your choice weather you want to add boric acid to small batches of star compositions containing unreactive atomised Aluminium and nitrates, it is unlikely that they will cause a fire, and if they are going to, the smell of ammonia will give you a clear indication that it is time to ditch your batch of chemicals in a bucket of water, or take them outside.

Magnesium-sulfur flash does not become safer with the addition of Boric acid. However, Magnesium is corroded quite easily by sulfur, which means that it has a short shelf life, and magnesium makes compositions more dangerous than Aluminium.

We are not trying to make life hard for you, it's just that the authorities every ware are not so keen on people making flash (for fairly good reasons). This, and the lack of alternative uses for flash capable metals mean that they are not easy to obtain over the counter, if possible at all. I think you will only have success looking for flash capable metals through the armature firework network or on the internet, the latter at a higher risk than the former.

If you do continue with your hobby for long enough, it is almost certain that you will get anything you want, giving it enough time.

I wish you the best.

Ps, I personally chose to take my chances on a website which could have easily pocketed my money and forgotten about me. It is your choice as to whether you are willing to take this route, and the possible consequences.

Symour, thanks very much, I think that the KNO3 S Al, very slow flash, will have to suffice for now, Mg ribbon is easy for me to get hold of and I might just experiment with a very very small quantity to satisfy my curiosity.

On a side note if possible, you think you could PM me and help me with colours, there's too many different formula's and I don't have access to all the required chemicals. If you can, that would be fantastic!

[banga]

Symour, thanks very much, I think that the KNO3 S Al, very slow flash, will have to suffice for now, Mg ribbon is easy for me to get hold of and I might just experiment with a very very small quantity to satisfy my curiosity.

On a side note if possible, you think you could PM me and help me with colours, there's too many different formula's and I don't have access to all the required chemicals. If you can, that would be fantastic!

Oh, given that you think using non aqueous binder is an extreme safety precaution, would it be possible to use a KNO3 S Al C mix to make stars? with dextrin as a binder + boric acid?

[pyromaniac303]

Dark aluminum on the other hand is formed by a mechanical process (impacting) the first several thousand impacts thins and forge harden thin sheets of aluminum (foil), the harden aluminum then cracks from subsequent impacts resulting in jagged rough edges that aren't smooth and hence do not reflect light, industrially it's normally produced with hammer mill or a stamp mill in an inert atmosphere (a ball mill will produce very fine particles but the running time is very long).

This is correct, but not the only reason for the darker shade of the fine aluminium. I remember reading that dark aluminium also contains a certain percentage of carbon, which somehow improves the burn rate. The aluminium foil layers are stacked and a carbon layer also added, these are then pressed and heated together, then stamp milled as described above.

Possibly improved flame propogation due to the improved ability to absorb infrared light/heat? Maybe somone can explain the reason for the inclusion of carbon.

Edited by pyromaniac303, 16 July 2008 - 11:19 AM.

[bigtonyicu]

This is correct, but not the only reason for the darker shade of the fine aluminium. I remember reading that dark aluminium also contains a certain percentage of carbon, which somehow improves the burn rate. The aluminium foil layers are stacked and a carbon layer also added, these are then pressed and heated together, then stamp milled as described above.

Possibly improved flame propogation due to the improved ability to absorb infrared light/heat? Maybe somone can explain the reason for the inclusion of carbon.

Well you guys are in luck, I happen to have some Eckart #5413-H on hand and full access to a matarial analasys lab, including a Gas phase Chromatographe. time to go buy a cup of coffee to my friends and let him work his magic.

i should have the break down by the end of the week

[minalth]

Well you guys are in luck, I happen to have some Eckart #5413-H on hand and full access to a matarial analasys lab, including a Gas phase Chromatographe. time to go buy a cup of coffee to my friends and let him work his magic.

i should have the break down by the end of the week

<holds his breath>

[portfire]

Well you guys are in luck, I happen to have some Eckart #5413-H on hand and full access to a matarial analasys lab, including a Gas phase Chromatographe. time to go buy a cup of coffee to my friends and let him work his magic.

i should have the break down by the end of the week

Eckart #5413-Super H German dark is the powder I have. I can remember reading somewhere how it is produced, but seem to remember it was a Carbon-Foil-Carbon sandwitch, then then above process.

I can say though that my 8micron Bright flake, is certainly in flake form and not spherical. This Al is like airfloat, you can see it twinkling in the air as the light hits it. This leads me to your point about spherical Al reflecting more light. Lets say you had a large shinny Al ball and shone light at it, the observer would only see a small proportion of the light been reflected back, the rest would be refracted. Now if you did the same with a flat piece of Al the same size as the outer dimensions of the ball, more light would be reflected back.

Anyway, looking forward to the results on the Eckart.

[bigtonyicu]

Lets say you had a large shinny Al ball and shone light at it, the observer would only see a small proportion of the light been reflected back, the rest would be refracted. Now if you did the same with a flat piece of Al the same size as the outer dimensions of the ball, more light would be reflected back.

That's not 100% true, flat surface will reflect directed light back in the opposite direction angle at which it's exposed to (ex: light shinning on a mirror at 20 degree from the right = (output) 20 degrees to the left) think of looking in a mirror, the only time flat surfaces reflect light directly back to the source is when the light source is perpendicular to the light source (ex. you'll only see your self if you are standing perpendicular to the mirror. a sphere, (more precisely a hemisphere since the light is only exposed to half of it) on the other hand, scatters light in every direction highly increasing the likely hood of some being directed at your eye.

(I'm not saying there's no such thing a Bright flakes, but scientifically, if a flake and a sphere have both same surface finish, the light reflected by the sphere is Omni directional and will be bright in all direction while flake will be highly localized brightness making it look very bright in very specific areas but as a whole darker from any given vantage point.)

In the case of eckart it seems to be a pigment added to make it dark, not a light reflection property (I should have the results on the analysis tomorrow afternoon) I agree with pyromaniac303 that it's more then likely to absorb IR energy.

I'm going to see if I can also get electron microscope images of the eckart dark, I wish I had some bright here so I can so we could compare.

[portfire]

aahhh, I see. Well you really know your stuff, so I'm backing down but I still have Bright flake though

[bigtonyicu]

aahhh, I see. Well you really know your stuff, so I'm backing down but I still have Bright flake though

I'm a Mech. Eng. with a PHD in aerospace propulsion so this kind of stuff is right up my alley, now if they only gave firework formulas in all those Chem. books they might actually come in handy

[bigtonyicu]

Good news my guys in the lap had a very slow day and they owed me a few favours so Quess what I have... results a day early

Eckart #5413-H

(here's the link to the image http://www.box.net/s...20994:177587674 )

I have yet to ask them what thier opinion with regards to the source off everyting else, but that's a star... as soon as I hear more I'll get back to you.

Edited by bigtonyicu, 16 July 2008 - 06:40 PM.