29 replies to this topic

[Valec]

I had a look at some patents today and found one by Nico-Pyrotechnik that concerns crackling mixtures using sodium thiosulfate instead of lead or bismut oxides.
In my opinion, this would be a great replacement as sodium thiosulfate is neither toxic nor expensive.
The mixtures given are the following:

Basic mixture:
60 Na2S2O3
34 Mg (160-400?m)
6 S

Improved mixture I:
57 Na2S2O3
19 Mg (160-400?m)
8.6 Mg (250-600?m)
13.3 S
1.9 CaO
3 binder

Improved mixture II:
53.3 Na2S2O3
19 Mg (160-400?m)
7.6 Al (250-600?m)
15.2 S
1.9 CaO
2.9 binder

It is said that the larger Mg particles give louder crackles while the fine Mg is said to ingnite earlier and give brighter flashes.
The CaO should stabilise the mixture.

The mixes are manufactured into stars with a size of 2-4mm. The amount of water should be such that the thiosulfate becomes a dihydrate, which will enhance the effect over the completely dry thiosulfate. If too much water is used, it will become the 5-hydrate which would destroy the effect.


I would like to try it out, but at the moment I have no access to my chemicals, so I thought someone else might have a try. Sounds like a non-toxic and cheap alternative for me.

If you need more information you can have a look at the patent under www.depatisnet.de, number DE 196 14 007 C2 (German ). If you have precise questions, I could also look if the information is in the patent for you.

Edited by Valec, 20 March 2006 - 10:40 AM.

[Richard H]

Very interesting!

[Mumbles]

Very interesting. I am at college, but first time I get home I plan to try it out. I lack CaO however. If it is just a stabiliser I will leave it out, as they will not be sitting long. Ca(OH)2 could be use most likely though. The water from hydration of the Sodium Thiosulfate would react with the CaO, or water from the air. Does it mention anything about the binder, like which is used. NC is generally used to my knowledge, but I have seen older formulas using dextrin. With the Mg I would much prefer to use non-aqueous binders.

For those noticing that Sodium Thiosulfate is photographic hypo, be aware it is already in the pentahydrate state and will need to be dried. This material borders on the same price I get my Lead Tetroxide for, so if it works as well, the lead is being retired. The few dollars more a pound would be worth it. As much as I would like to use less toxic materials like Bismuth Trioxide, it is $20 a pound. The subcarbonate is more reasonable, but the effect is not as good.

I may also test with Magnalium, and finer Mg(-200 mesh). I may also test with a few different binders.

[Valec]

There is no explicite answer regarding the binder.
The patent mentions several ways to bind the stars:

1) The effect would be ideal if you use dry thiosulfate and add enough water to the mixture so that you'll get something like a dihydrate.
If the thiosulfate is finely powdered (<160?m) it should work as a binder itself (compare the first formula).

2) You might also use a binder which is soluble in water or an non-aqueous binder. Both are reported to have a tendency of reducing the effect.

3) If you use water, you should use some kind of buffer. It does not have to be CaO, all alkaline earth metal oxides or hydroxides should work;
It's just important to have something so that the pH is alkaline.
In this case, there should be no problem with Mg-water-reactions, there should be no temperature rise on drying.

Edited by Valec, 12 September 2005 - 09:04 AM.

[paul]

A kilo is 7.35€, so this would be great, if it works. Never heard of it before though.

1) The effect would be ideal if you use dry thiosulfate and add enough water to the mixture so that you'll get something like a dihydrate.
If the thiosulfate is finely powdered (<160?m) it should work as a binder itself (compare the first formula).

I think the first formula only works for cut-stars. Because it should be quite hard to get the right ammount of water when rolling them.

But I wonder if these really would get hard or even "dry".

A little calculation:

For a "dihydrated form [Na2S2O3 * 2H2O]" of the dry thiosulfate we would need about 36g water per 158g of dry Na2S2O3. For the 60g in mixture 1 it would be ca. 13,7g water.

Edited by paul, 12 September 2005 - 12:00 PM.

[Yugen-biki]

This sounds very interesting!

You can find more info here:

http://depatisnet.dpma.de/ Make a "falmily search" and type in 196 14 007 and chose DE and C2.

You'll need the NaS2O3*H2O for it to work as I read the text.

Edited by Yugen-biki, 13 September 2005 - 02:45 PM.

[alany]

I wonder if persulfates would behave in a similar manner...

[paul]

Alany, persulfates are used for etching. I think it will corrode the metals very fast under heat-generation if water comes to this mix.

AND, persulfates give, together with magnesium or dark alu. a very fast burning flash powder. Very small ammount of it (about 0,5-1g) flash with a decent *plop*

Edited by paul, 13 September 2005 - 11:38 AM.

[Valec]

Well, I had a try with 50g of Improved Mixture I now.
I took 45,0g of sodium thiosulfate pentahydrate and heated it with an ethanol burner.
It melted very fast and started to bubble, becoming a white and crumbly powder.
Actually I heated a bit too much and it seems like some of the thiosulfate has decomposed, as it became a bit yellow and smelt like SO2 was produced.
I powdered the thiosulfate and mixed with the mentioned components, only leaving out the CaO.
The mixture was then wetted with 6.5ml of water which did not cause a reaction with the magnesium (probably as it not a fine powder). The mixture warmed a bit, which I think is caused by hydration of the thiosulfate.

I then tried to press stars with the wet mixture, what was a bit difficult. The mixture seems to be nearly dry, but if you compress it, it holds together quite well. (I've still got some of it stuck in a small syringe).
So I produced about 6 pumped stars 15mm and one larger star. The seemed to be completely dry right after pressing, although I did not try to ignite them.

Increasingly, the mixture became difficult to press, probably because the hydration and crystalisation used up the water and stopped afterwards. So I wetted the rest of it with NC-laquer and made cut stars (which were holding together not very well) and dumped them in some meal.

At the moment, the rest of the stars dries ad waits for some tests. A few early tests showed that the mixture is difficult to ignite; I will give you some more information later the day.

Edited by Valec, 20 March 2006 - 10:54 AM.

[Valec]

So, I finally managed to ignite some of the mixture. It was a batch of about 5g, which had been wetted, but not pressed.
Several attempts to ignite it using meal and/or green mix failed. In the end, I used a layer of green mix on a tile, then the composition, then some green mix again and some very coarse magnesium powder.

The composition seems not to produce the typcial, sharp and very loud crackling of lead/bismut oxide compositions but a softer crackling with a huge amount of sparks and light output. The mixture didn't burn all at once. It burned more like a strobe composition. First the crackling and sputtering for a small time, then nothing, then the crackling again; this repeated for about two or three times all in all.

It does not actually seem a real replacement for the commen dragon eggs,
but nonetheless, it's an interesting effect, and I think further experimenting will pay. Probably it could be improved in sound performance (maybe using finer magnesium, or magnalium like in bismut/lead oxid compositions). Maybe it could also be developed into a replacement for the problematic APC-based strobe compositions.

I will have a few more tries with the pressed and cut stars in the following days...

[Steve]

I'm really dredging up old memories here, but there was this composition, which I think was this one:
Perc: 30
Red Gum:20
Al, atomized:10
Rust (Iron oxide):40
Which is on p152 of Principles and practice 3rd edition, as a spark composition without Nitrate and sulphur.
But if indeed this is the same one, I got a mild crackling effect, nothing as loud as microstars, but very distinct, and unexpect from the components.
If anyone else fancies trying out the composition I would be interested to hear if they get the same effect.

[alany]

It isn't really what I'd call a crackle, but it does sizzle a bit.

I rather like that composition, I think it has much promise as a sparkler. If anyone has the 4th edition, I'd love to know if that composition has been updated at all, especially usage information.

[Valec]

There is another problem with the star composition mentioned before: I had some of the bound stars waiting for being shot in the garage since the 20th.
By now, they have become extremely crumbly, falling into powder upon touching them.
Probably a problem of hygroscopy, maybe dry storing may help.

[FrankRizzo]

There is another problem with the star composition mentioned before: I had some of the bound stars waiting for being shot in the garage since the 20th.
By now, they have become extremely crumbly, falling into powder upon touching them.
Probably a problem of hygroscopy, maybe dry storing may help.

It's a problem with the decomposition of the magnalium in the presence of water. Star comp made with fine aluminum and nitrates bound with water w/out boric acid is known to have the same problem after sitting for a bit.

[quest]

sorry for posting in such an old topic but I think I got some information\question to add.

I bought sodium thiosulfate and tried the Improved mixture I.
In powder form it didn't light, I used Ca(OH)2 to replace CaO. when I wetted it a little to make cut stars it started foaming after some minutes and a smell of sulfur (I guess H2S) was coming out of it.
I will wait till it will be dry and try to light it again, but I'm quite sure it won't be very lightable.

Any observations? maybe any one had tried it too?