114 replies to this topic

[Creepin_pyro]

For an 'off white' very pale green, something along the lines of this, from Blesser:

Barium nitrate? 53
Magnalium, 100 mesh 12
Sulfur 17
Hexachlorobenzene 13
Dextrin 5

This kind of formula seems to be the 'standard' strobe mix in commercial items, and is often reffered to as a white strobe, even though it's not. A true white strobe would use Potassium Sulphate and Ammonium Perchlorate. The best, most vibrant strobes are made with Ammonium Perchlorate, Magnesium, and Sulphates and require Dichromate treated Mg. You can also make a nice pink strobe by substituting Strontium Nitrate in the above formula - I posted a tweaked version here a while back.

Have a look here:

http://www.thegreenm...s.html#Strobe I

And if you want to play with blue strobes, here:

http://www.skylighte...cle.asp?Item=79

Have fun and stay green!

[Bluehawk]

Is your formula for a strobe pot or for stars? Seems I read somewhere that strobe stars do not function well on the ground so am looking for those formulas and colors that will function when pressed into short squat tubes about .75-1 inch ID or so.
I do have ammonium perchlorate and MG as well as Magnalium so formulas containing those would be helpful also.

[karlfoxman]

Creepin:- I made up a batch of the pink strbe lastnight, 50g. They have been pumped into 1/4" stars, hoping to add them to the pistil of my maltese 5" beraq shell. I will post the results. As a loose powder it did not seem to strobe, once they are dry I will test again from a star gun or mine. I dont fancy making the barium nitrate version because i hate the stuff and get quite worried when using it. Thanks for the fromula though. If it works I will send you a vid of the shelll!

[Creepin_pyro]

I take it you're talking about the formula in the link below, not the above comp modified?:

http://www.ukrocketr...indpost&p=13329

It seems odd that they didn't strobe on the ground... either way, I'd be very interested to hear how they perform for you. Make sure you use a good prime - something like Veline's or the 'veline style' from passfire. Looking forward to seeing your beraq very much!

I'm going to revisit this pink strobe as soon as I can, and continue with the tweaking - I lost my notes on it which I am now kicking myself for doing... I'm looking forward to putting my knowledge learnt in the pyro chemistry course to good use in formula development, especially strobes. Haven't had the time to get back to this, but that will hopefully change soon ; )

Bluehawk, the formula I gave was for a star, and I wasn't aware that using it as a ground device would affect it too adversly, except mabye the strobing freq... I would suggest trying it out, seeing how it performs, and if it isn't looking good, let us know what the problem is and I could advice how to sort it out. I don't know of any strobe formulas specifically for use on the ground (apart from a few exotic blue ones), but I've heard the Shimizu set of formulas work wonderfully. They can be found on the PFP...

[karlfoxman]

It was the modded formula I used, the only problem I may have is I used parlon. I know this produces a fair bit of ash. So the next test will either use less or saran resin instead. With regards to prime I shall use my standard hot prime method of 50:50 star formula and black powder. Then a layer of black powder. I used this on my moddifed Velne orange 1" comets for the sun and planets shell. They light easily from the star gun. Im looking forward to see how the perform in the beraq shell.

[Bluehawk]

Thanks Creepin...I'll keep you posted...may take awhile. There was a time when I could make a batch of almost anything and when it was dry go outside and test it (stars...1 pound rocket motors...even 3-inch daylight shells) but after my divorce and moving into a new place where the laws are highly restrictive I cant hardly make a sparkler w/o a nosey neighbor wanting to know what I'm doing.
In the strobe formula you posted is there a substitute for Hexachlorobenzene? Seems thats one chem I dont have in my inventory.
On PFP I noticed Dr Shimizu uses dichromate to protect the magnesium but I wonder why since the binder is nitrocellulose...any thoughts on the matter? Why not Vaseline or boiled linseed oil or why not just coat the Mg with the NC and then add in the other ingredients to make a strobe pot?

Edited by Bluehawk, 29 July 2006 - 05:16 AM.

[pyrotrev]

If you're using magnesium with AP as the oxidiser you have to use dichromate or molybdate passivation to protect the Mg. AP seems to unfortunately be fairly unique in that linseed oil or other waterproofing methods just don't protect it enough. Using a non-aqueous binder is further protection, likely to be important if you're keeping your stars for any time in a non-dry environment.

[Valec]

If you're using magnesium with AP as the oxidiser you have to use dichromate or molybdate passivation to protect the Mg. AP seems to unfortunately be fairly unique in that linseed oil or other waterproofing methods just don't protect it enough. Using a non-aqueous binder is further protection, likely to be important if you're keeping your stars for any time in a non-dry environment.

Could you give any details concerning the molybdate passivation? There already was a thread some time ago, but all the information was just a few lines which was found in a Shimizu book.

[Mumbles]

I honestly haven't been able to find much about it either, other than you can passivate with it. No technical details on the process or what kind of reaction or coating it provides to protect the Mg. Due to the fact that Molybdenum is directly below chromium on the periodic table, I imagine it reacts very similarly. Find my post on here about the chemistry and surface reactions if you want to know more.

As far as processing, it would be exactly the same as dichromate, though more expensive. I would use the standard 5%. Ammonium Molybdenate is commonly used as a trace mineral componenet in fertilizers. They sell it on it's own, but if I remember, it is fairly pricy. Perhaps someone knows of a better source. All the sources I know of are in the US, so that doesn't help you all much.

[Yugen-biki]

I have read about the Mg coating in Pyrotechnica. I don't remember how exatly it was done, but I remember that it was complicated and not as good as K2Cr2O7.

[pyrotrev]

The molybdate/vanadate coating process is described in Pyrotechnica XVI (Aug 1995) apparently - anyone got a copy?. Ammonium molybdate is available in the UK from lab suppliers (expensive), and there's a place in Wales that was selling it in larger amounts, though I never asked the price - AP/mag stars are next winters project!

[BrightStar]

Comrades, I need some help here please...

I have been working on making mini white strobe cones for the garden:



These contain about 15g of the following comp (from United Nuclear, but looks like Bleser White Strobe):

Barium Nitrate 51
Potassium nitrate 7
Sulfur 19
Magnalium 18
Dextrin 5

About 15g was dampened with 25% IPA in water and pressed into the thin-walled (4 layers of kraft) cone, dried for about 2 days. The magnalium was 10 micron flake (very fine).

Results here:

Mini strobe cone (divx avi, 2.8 MB)

Essentially it did strobe, but at ~15Hz rather than the 3-5Hz I was hoping for.

What did I do wrong? Was the magnalium too fine? Can I compensate? Did I over-wet / not dry it enough? How does the cone / pot size affect the flash rate? Would a stronger case help?

Edited by BrightStar, 24 September 2006 - 10:53 PM.

[karlfoxman]

If anything I would think its the size of the magnallium, this is what causes it to burn with vibrating flame. The finer it is the faster the strobe. Try getting larger magnallium to adjust the freq of the strobing.

Edited by karlfoxman, 25 September 2006 - 05:24 AM.

[Valec]

Yes, that's about the same way, the composition is burning with 325mesh MgAl. Seems to be way to fine, stars made with it are rather bright and sizzling white stars than strobe stars. Looks still nice, but for strobing I think about 100mesh would be better.

Edited by Valec, 25 September 2006 - 06:19 AM.

[Yugen-biki]

In my experiense the Barium nitrate and sulfur based strobe formulas are sometimes hard to get strobing properly. 150-300?m MgAl will probably make it strobe about the speed you like. I have managed to make stobe stars 1-5Hz with Mg this size, with ammonium perchlorate.