27 replies to this topic

[Vic]

Dragon egg core stars
Are Crackling Microstars used as a core for stars an effect worth pursuing? I don’t seem to be able find a video of this effect but I’m not sure what I’m looking for. I’m thinking of a blue star from "Chemistry of the Elements" which is formulated as follows

Ammonium perchlorate 48
Hexamine 14
Copper oxychloride 12
Copper sulfate 6
Gum arabic 1
Dextrin 6

With a Crackling core of by “Larry Stevens”

Lead Tetraoxide 10
Copper (II) Oxide 7
Magnalium, granular -200 mesh 4
Potassium Nitrate 1.5
Sulfur 1
Bound together with N.C


Further questions are…

Will the cores need priming?
Will the stars need priming?
Will there be any incompatibility problems?

Any input would be much appreciated.
Regards,
Vic.

[pyrotrev]

Yes, they are worth pursuing, an excellent effect, especially if you add some fine-ish flake titanium into the crackle mix, anyone who has seen the Yung Feng "chrysanthemum with crackling balls" shells will concur I;m sure. However you have a couple of chemical incompatibilities between your 2 mixes: 1) AP + KNO3 = ammonium nitrate = hygroscopic = mush. 2) AP + magnalium (unless dichromate passivated) = magnesium perchlorate = hygroscopic + heat generation, not good.

[Vic]

Yes, they are worth pursuing, an excellent effect, especially if you add some fine-ish flake titanium into the crackle mix, anyone who has seen the Yung Feng "chrysanthemum with crackling balls" shells will concur I;m sure. However you have a couple of chemical incompatibilities between your 2 mixes: 1) AP + KNO3 = ammonium nitrate = hygroscopic = mush. 2) AP + magnalium (unless dichromate passivated) = magnesium perchlorate = hygroscopic + heat generation, not good.

Thankyou for your reply, if my cores are bound with NC and the stars with dextrin does this limit the crossover incompatablity

[pyrotrev]

Potentially yes, particularly in damp climates. For one thing NC isn't the best waterproof coating, and then of course particles on the surface may have "thin spots" where the edges of e.g. crystals poke through the coating. For your purpose the problem isn't insoluble, if you use a crackle mix with no KNO3 and aluminium instead of magnalium then problem will go away. Alternatively use a KClO4 based colour composition for the outer layer.

Edited by pyrotrev, 13 October 2008 - 05:37 PM.

[Vic]

I don’t know of a crackle mix that doesn’t use magnalium. I could go the way of a flash core such as Shimizu brilliant core as this maybe the way to go, though this has own incompatibilities resulting in the need of Boric Acid
Vic

[spanner]

One thing with using eggs as cores, is that there are relatively few of them to give effect- one per star, obviously not that many.

[Vic]

The cores are cut about 1/8 square, somewhat large but they flash and crack on average five times. Would this core be best suited to a cake rather than an aerial effect or should I break them down and use them as a matrix in a pumped mix? Or would that blow the stars?
Vic

[pyrotrev]

I don’t know of a crackle mix that doesn’t use magnalium. I could go the way of a flash core such as Shimizu brilliant core as this maybe the way to go, though this has own incompatibilities resulting in the need of Boric Acid
Vic

I believe Shimizu quotes one with just fine aluminium flakein one of his papers, but I don't have the mix. Otherwise it's dichromate passivating the magnalium or using a a KClO4 colour comp.

[Vic]

I don’t think I will go the Potassium Dichromate way as it seems it’s pretty nasty stuff with a whole load of safety issues involved. I don’t have a chemistry background though I’m learning so I put Dichromate high on my one to ten risk assessment. But how about linseed oil?

Vic

[digger]

I don’t think I will go the Potassium Dichromate way as it seems it’s pretty nasty stuff with a whole load of safety issues involved. I don’t have a chemistry background though I’m learning so I put Dichromate high on my one to ten risk assessment. But how about linseed oil?

Vic

I agree dichromate should be high up on the nasties list, however with the proper PPE one should not be scared of it there are plenty of other nasties that we use. It is certainly far easier to use than linseed oil. It has solved a few problems for me in some of my experiments.

[Vic]

I agree dichromate should be high up on the nasties list, however with the proper PPE one should not be scared of it there are plenty of other nasties that we use. It is certainly far easier to use than linseed oil. It has solved a few problems for me in some of my experiments.

As I am using magnalium which has been bought already in the form of magnalium, can I treat it as a whole with the Dichromate in order to “get at” the magnesium?

Thanks for all the help so far,
Vic.

[digger]

As I am using magnalium which has been bought already in the form of magnalium, can I treat it as a whole with the Dichromate in order to “get at” the magnesium?

Thanks for all the help so far,
Vic.

Yep the only way to do it is to passivate the the whole lot. The idea is to create a passive oxide layer on the surface of the metal, all you are trying to do is create a layer which is not prone to attack.

Are you a member of passfire? If so just look at the article on dichromate treating magnesium and do the same with your magnalium. If you are not a member I can PM you a procedure if you want.

D

[Vic]

Yes I am member of Passfire a great place for information
Thanks Vic

[spanner]

Are you a member of passfire? If so just look at the article on dichromate treating magnesium and do the same with your magnalium.

I would be interested in the procedure, but I'm not a member there. Could you be persuaded to show it here?

All I have done to treat my magnesium is soak with cold 10% W/W potassium dichromate in deionised water for two hours, drain then air dry. I don't recall exactly where this procedure came from, possibly rec.pyro.

[Mumbles]

Have you guys never heard of barrier primes? The dragon eggs need a prime anyway. THere's no way that organic colored star is going to do the job on it's own, plus there are the incompatibilites mentioned before. While we're on the subject of formulas, try to get better ones. The copper sulfate in the blue will likely cause problems with hygroscopicity and burn speed. There are plenty of formulas out there using just Cu oxychloride.

BTW, if you use a coarser MgAl, you will get less crackles per cube. 60 mesh is usually what I use, and I get 1 crack per unit. I don't think it will cause a problem. They all will go off at slightly different times, so it will probably just be a little more sustained effect.

I've never seen dragon eggs using only Al, but I have seen a few with a mix. I have no idea what purpose the Al serves though.

Edited by Mumbles, 19 October 2008 - 01:04 AM.