633 replies to this topic

[Phoenix]

Stuart:
Was this Shimizu's Tiger Tail with 6% dextrin? When using this composition, I have the same problem with the full amount of binder. You probably remember the discussion a while back. Whatever the cause, whether it was because the charcoal particles stayed bound after it had burnt, or because the stars became driven in, using only 4% dextrin solved the problem every time. I have had no problems with the stars breaking up. However, I usually ball mill the composition as fine as meal, so the smaller amount of dextrin has no problem binding it. With larger particle of charcoal the stars may be a bit weak. (Fortunatly, it looks better ball milled anyway, IMHO)

Maxman:
My guess is that the composition will light fine after it is made into stars, and work much better after the alterations BigG suggests. If you are looking for a bright white star, this one is fairly simple (and well known - its been posted here before):

Potassium Nitrate..........50
Sulphur..........................30
Aluminium......................20
Binder...........................+5
(Boric Acid.....................+1)

This composition makes a bright golden white. I think a true silver is probably reserved for barium nitrate or potassium perchlorate compositions, but this one is pleasing enough. For a binder I have used NC laquer (this was just added until the composition was cuttable, and was not exactly 5%) and dextrin (this was 5%). It will need an intermediate prime. In my experience, BP just burnt off, leaving it unignited.

The boric acid is probably a good idea, but I have made small batches of these without it. If you do, dry them carefully somewhere where they won't do any damage if they do ignite (like on a concrete slab outside).

[maxman]

Thanks for the info Phoenix.
I have just made some of the stars that Big G suggested using AL and boric acid instead of the Fe/Ti. The powder seems to burn very nice, so hope the stars will too. I'll let you know next week when they're dry.

Yes I was looking for a bright white star using Al. Will my 200 mesh be OK for the comp you mentioned? I see that it is mentioned as flash #5 at http://huizen.dds.nl...B.html#chapter6 I suppose it depends on the Al used as to if it is flash or white star dose it?

Will just adding excess Al to meal with boric acid also not produce a whiteish star?

Is there only a chance of spontaneous ignition when they are damp or wet? or can this happen when they are dry too? Does this apply to Zinc spreader/granite too?

Thanks. (count the question marks hehe)

[Stuart]

Thanks Phoneix, I did use 6% Dextrin so I will try 4% and ball mill it.

Stuart

[Phoenix]

I use the same Al whether it is flash or stars, the difference is that if it is flash it is a loose powder and heavily confined, whereas if it is a star it is unconfined and consolidated into a lump (so it burns from the surface inwards, rather than all igniting at once). With my homemade (at a guess, somewhere in the 100-200 mesh range, flake shaped) Al it is a very slow flash powder. Your 200 mesh powder should work well for stars, although something like German dark might be a bit too fine.

Adding aluminium to meal will make a white star of sorts. It will probably be something of a metal streamer star, but should look good.

Aluminium and nitrates are somewhat prone to reacting with eachother when damp, but this is mainly when they are exposed to alkaline conditions. That is why most Al/NO3 compositions include boric acid(you probably already knew this). With boric acid, the composition is unlikely to ignite spntaneously. If you don't have any, you can _probably_ get away without it, but yes, there is an elevated chance they will ignite when damp. Fortunatly, in the Al/NO3 reaction, ammonia is one of the products, and of course this has a very noticable smell. If you start to smell it, you should ditch the stars in a bucket of water, or just get away. If you do make these without boric acid, just do a small quantity, and as I said, be sure to dry them somewhere that won't burn. Finally, I have heard that sperical Al suffers much less from this reaction than does flake or granular.

I think this reaction is a problem mainly with damp stars, so once they are dry they are unlikely to ignite even without boric acid. Can anyone confirm this?

AFAIK, zinc containing stars are quite dangerous to dampen with water, but I haven't used zinc.

Finally, if you make the bright white stars, be sure to prime them well. I used this composition as "finishes" for some Tiger Tail stars. I made 10g of the composition, and rolled millet with 9g of it. The stars were about 4 mm in diameter (since the millet was the core, I guess the flash was a "finish"). I then mixed the remainder with 1g of BP meal, and rolled that on. Finally, I rolled on the Tiger Tail composition. If you just wanted plain white stars, you could probably just use a final layer of meal. If you are planning on cutting them, then it might only be possible to use the 50:50 first layer prime. However, this should be OK, I think.

[alany]

The Al/Nitrate reaction isn't a huge deal with small quantities of composition at room temp. With a big tub of a 100 lb of comp the surface area/volume ratio doesn't let the heat out quick enough and the center can get up to dangerous temperatures, it may not ignite, it may just steam and ruin the composition.

Flake is definately more likely to have problems than spherical. Using hot water for the moistening can bring an immediate ammonia smell, so I always use room temperature water, and usually a 25% solution of alcohol anyway.

In my experence the Iron/Nitrate reaction is faster and more likely to cause problems.

For cores I've been pumping nitrate flash using a soda straw to get < 5 mm cylinders and then rolling them until they are spheres. It only takes a few minutes in the roller to round them off into pretty good spheroids. Once roughly round I add the step-priming, then roll over the bulk of the star. The result is a coreless star that rolls really quickly, because that damn first few mm takes forever compared to the rest of the star, and you don't need to deal with sticky cores and uneven growth.

I would imagine cubical cut stars would work just as well, if not better.

[BigG]

Stuart:
Was this Shimizu's Tiger Tail with 6% dextrin? When using this composition, I have the same problem with the full amount of binder. You probably remember the discussion a while back. Whatever the cause, whether it was because the charcoal particles stayed bound after it had burnt, or because the stars became driven in, using only 4% dextrin solved the problem every time. I have had no problems with the stars breaking up. However, I usually ball mill the composition as fine as meal, so the smaller amount of dextrin has no problem binding it. With larger particle of charcoal the stars may be a bit weak. (Fortunatly, it looks better ball milled anyway, IMHO)

Maxman:
My guess is that the composition will light fine after it is made into stars, and work much better after the alterations BigG suggests. If you are looking for a bright white star, this one is fairly simple (and well known - its been posted here before):

Potassium Nitrate..........50
Sulphur..........................30
Aluminium......................20
Binder...........................+5
(Boric Acid.....................+1)

This composition makes a bright golden white. I think a true silver is probably reserved for barium nitrate or potassium perchlorate compositions, but this one is pleasing enough. For a binder I have used NC laquer (this was just added until the composition was cuttable, and was not exactly 5%) and dextrin (this was 5%). It will need an intermediate prime. In my experience, BP just burnt off, leaving it unignited.

The boric acid is probably a good idea, but I have made small batches of these without it. If you do, dry them carefully somewhere where they won't do any damage if they do ignite (like on a concrete slab outside).

Note that today, true "white stars" are credited for the metallic addition of Magnesium, or the organic (more common) inclusion of antimony trisulphide. You can also use Antinomy Metal powder. Formulas containing KNO3, Sulphur, and Antinomy will burn with a brilliant white much better then the white posted in the quote.

For Example:

Davis:
KNO3: 62
Antinomy (III) sulphide: 17
Sulfur: 17
Dextrin: 3

Lancaster:
KNO3: 51
Sulfur: 18
GP: 15
Antinomy Metal: 10
C (+150 mesh): 3
Dextrin: 3

Working many years with white formulas that utilize KN03, S and C (with or without AL), I had to redefine my understanding of ?White? after using Devis formula.

Edited by BigG, 14 March 2004 - 08:05 AM.

[Rhodri]

For Example:

Davis:
KNO3: 62
Antinomy (III) sulphide: 17
Sulfur: 17
Dextrin: 3

This is one formula that I have found very useful. The beauty of this comp. is that it doesn't use C. This makes it very easy to make.

The 'white' is very bright and I have found the 'intensity' to be on a par with Al comps.

Throughly recommend this one!

[Creepin_pyro]

OK......... Here is a star formula that I've put together. I was trying for an organic star with a deeper red than Veline's - which was slightly pink when I made it. Also, I wanted to reduce the burning rate, and use less of my precious Perc. So.... I shall begin.

"Creeper's Organic Red"

Strontium Nitrate 38
Potassium Perchlorate 40
Rosin 10
Red Gum 7
Dextrin 4
Chlorinated wax 3

Strontium Nitrate was clumpy 10 year old lab grade
Rosin (violin bow....) was ground to dust.
Red gum was screened.

I have not got round to making stars from this, but loose ground tests seem promising. It takes fire reasonably well, and gives a nice red - less pinky more post-box. Any thoughts on binding/priming these? - I thought pumped, 33% Propan-2-ol, and Veline's prime (great stuff )

[RegimentalPyro]

Lancaster:
KNO3: 51
Sulfur: 18
GP: 15
Antinomy Metal: 10
C (+150 mesh): 3
Dextrin: 3.

BigG - What's GP?

Is it a typo of BP, or does this mean something different

[pedantic I know but I like to check......]

[Richard H]

I don't have my book at hand, but I think maybe GP is a reference to gunpowder.

[RegimentalPyro]

Whup! - Whilst I saw Lancaster at the top, I forgot I could actually check the book!



You are quite right - "Meal Gunpowder" - Thanks RichardH! [and BigG ofcourse....]

[Phoenix]

Hi,

I know that sodium nitrate can be used to make good yellow stars, and I believe that it's hygroscopicity is not too much of a problem in the UK if it is thoroughly dried before use, then bound with a non-aqueous binder and used quickly, or stored in an airtight container. However, there are a couple of other things I would like to know:

- Can the non-aqueous binder be shellac?
- Can NaNO3 be used as the sole oxidiser in an organically fuelled composition?

I prefer to avoid solvents like acetone if I can, because of the cost, safety and environmental issues. Therefore shellac would be better than polystyrene etc (which I have seen quoted elsewhere), as I can use alcohol (which can be dried with magnesium sulphate, can't it?). The sodium nitrate comps in the PFP Database mostly use dextrin, but posts from the rec.pyrotechnics archive say not to wet with water.

Also, I have not found an organic formula using NaNO3 as the sole oxidiser. Most of the formulas I have seen use potassium perchlorate (which I ain't got) or potassium chlorate (which I would prefer to avoid, if possible) too. There was a reference on rec.pyrotechnics to a formula containing NaNO3 as the oxidiser and colouring agent, flour and a little charcoal as the fuel and polystyrene packing foam as a binder. However, the formula was not given, and as I said, I'd rather use a friendlier binding system.

Does anyone have a tried and tested yellow formula using just sodium nitrate and common fuels (shellac, flour, charcoal, sulphur etc) rather than magnesium, that doesn't suffer too badly from moisture problems? If not, a starting point I had considered was a meal powder white, but making the substitution of sodium for potassium nitrate. Thanks for any help.

Edited by Phoenix, 06 May 2004 - 08:02 PM.

[adamw]

You should be able to use Shellac, PVC etc as long as all the composition is coated well in the binder. Sodium Nitrate is a good oxisider and should be able to be used as the oxidiser in compositions but it is not used much because of its hydroscopicity like you said. It is used a lot in flares (with magnesium) so I should imagine it could be used in stars as well.

[lord_dranack]

as I can use alcohol (which can be dried with magnesium sulphate, can't it?).

I don't know if it can, but I just thought that if the magnesium sulfate used is epsom salt, that is already the trihydrate, and so may not work.

[Stuart]

You could try dehydrating the MgSO4 or you could get some Calcium Chloride. Its sold as a water absorber, you could find it at DIY stores I think, I get mine from a builders merchant.