7 replies to this topic

[Sparky]

Hi all,

I just made my second ever batch of dragons eggs with Bismuth Trioxide as the base and they are rubbish!

Strangely my first test batch were made using extremely low mesh size magnalium (350) and aluminium (dark) and I think I used parlon instead of nitrocellulose lacquer as I was in a hurry to test and didn't think the binder would make much difference.

This second batch was made to the exact formula and assuming I haven't made a mistake when calculating up with the ratios (very possible as I was trying to use up a last pot of Bismuth).

Bismuth trioxide Dragon eggsBismuth trioxideor Bismuth subcarbonate75Magnalium(-200 mesh)15Copper (II) oxide (black)10Aluminium(atomized, -200 mesh)+5Nitrocellulose lacquer10%

My first test batch are awesome, a single grain is firecracker loud. This second batch appear anaemic in colour, are softer and barely crackle at all. They are about as hard to light as the first batch. The second batrch burn with a lot of yellow smoke too.

Not sure how I could go about rescuing the formula. I was going to try adding a little extra copper oxide or magnalium to start.

Any ideas what I may have done wrong.

[PyroSkitz]

OK first things first , using nitrocellulose lacquer is what makes the start go into the smoulder phase, this is what it allows it to build up a bubble of carbon dioxide to make the "bang", it will also make your crackles rock solid, the yellow smoke.... possibly got a high chlorine content from your parlon, DONT BREATH IT IN!! its my only advice so far, but check out pyroguide.com for its micro star advice, use nitrocellulose lacquer next time!! its available on eBay or you can make your own

[digger]

OK first things first , using nitrocellulose lacquer is what makes the start go into the smoulder phase, this is what it allows it to build up a bubble of carbon dioxide to make the "bang", it will also make your crackles rock solid, the yellow smoke.... possibly got a high chlorine content from your parlon, DONT BREATH IT IN!! its my only advice so far, but check out pyroguide.com for its micro star advice, use nitrocellulose lacquer next time!! its available on eBay or you can make your own

Patience grasshopper, re-read sparkys post

Also be aware that paint grade and ping pong ball nitrocellulose has other plasticising additives that affect burning charachteristics. There are sources for nitrocellulose laquer that don't contain all of the additives

PyroSkitz what makes you think that it is a bubble of CO2 that makes it go bang? I always thought it was a clasical thermite redox reaction that smouldered until the activation energy level was reached.

Edited by digger, 04 April 2012 - 11:53 AM.

[digger]

P.S. maybe try a formula without the aluminium such as 75 bismuth trioxide 15 MgAl 100mesh 10 copper oxide. The MgAl seems a little too fine.

Edited by digger, 04 April 2012 - 12:04 PM.

[Sparky]

Hi Digger,

Thanks for the advice...

I've just learnt a very important lesson in keeping the details of the formula you make even if you think you are experimenting with something that will be sub-standard.

My initial batch are awesome and I can't remember for the life off me what I used. I broadly based it on the formula on Pyro guide but I'm sure I was missing nitrocellulose lacquer as I had yet to make it my self! I think I used parlon as a binder as it was quick and easy. Not sure though.

If I had used any aluminium at the time it would have been German dark.

Dammit!!!

Could my problems in my latest batch be down to the nitrocellulose lacquer being home made?

[seymour]

OK first things first , using nitrocellulose lacquer is what makes the start go into the smoulder phase, this is what it allows it to build up a bubble of carbon dioxide to make the "bang",

I've heard what you're saying and similar things about the role of NC in crackle quite a lot, and I'm quite unconvinced. While I cannot say what the role of NC in crackle is, largely as an extension of the fact that we have very little information on what happens in the reaction at all, I do know that whatever NC does do, other than it's binding properties, is quite unimportant.

I have made dragon eggs with a range of formulas using Nitrocellulose, Double Base and Dextrin as binders, and know of many more binders being used successfully, Red gum, Sparky using Parlon, and so on. I have not noticed any change in performance based on binder (unless you increase the % of NC to higher levels).

For some reason almost everyone uses, or recommends the use of NC. Perhaps some people have decided it is slightly louder. I cannot deny that it is my preference too, but other than the fact that NC is a rather nice binder, the reason why I have yet to discover, though I suspect tradition is a large part of this.

Could my problems in my latest batch be down to the nitrocellulose lacquer being home made?

Possibly if it's not sufficiently washed the acidity could have reacted with the MgAl, but other than that possibility I doubt it.

Of all the crackle mixes I've made, by favorite by far is 37.5% each of Bismuth trioxide and Copper oxide (black), 25% MgAl, and 4% binder (usually NC, as noted previously). With 60-100 mesh Mgal (50/50) I can cut them at up to a quarter inch cube and if ignited evenly, they appear to be entirely consumed in the blast. They punch fearsome holes in corrugated cardboard, but appear to be prone to only partially explode when primed (as in Dragon flowers).

With -100 mesh my experience is that they multipop fiercely, burning q

[seymour]

OK first things first , using nitrocellulose lacquer is what makes the start go into the smoulder phase, this is what it allows it to build up a bubble of carbon dioxide to make the "bang",

I've heard what you're saying and similar things about the role of NC in crackle quite a lot, and I'm quite unconvinced. While I cannot say what the role of NC in crackle is, largely as an extension of the fact that we have very little information on what happens in the reaction at all, I do know that whatever NC does do, other than it's binding properties, is quite unimportant.

I have made dragon eggs with a range of formulas using Nitrocellulose, Double Base and Dextrin as binders, and know of many more binders being used successfully, Red gum, Sparky using Parlon, and so on. I have not noticed any change in performance based on binder (unless you increase the % of NC to higher levels).

For some reason almost everyone uses, or recommends the use of NC. Perhaps some people have decided it is slightly louder. I cannot deny that it is my preference too, but other than the fact that NC is a rather nice binder, the reason why I have yet to discover, though I suspect tradition is a large part of this.

What we do know about crackle, is that after ignition a primary reaction occurs that is revealed by a red or gold 'wave' which sweeps the star, shortly followed by another reaction, the explosion.

I think that the primary reaction partially burns the MgAl (or perhaps just one of the two metals in it), generating an unstable chemical that in the semi liquid phase intimately mixes with the remaining reactive metal, and once the thermal buildup is sufficient an entirely different reaction is triggered, a detonation, or an explosion powerful enough to appear to be one.

Could my problems in my latest batch be down to the nitrocellulose lacquer being home made?

Possibly if it's not sufficiently washed the acidity could have reacted with the MgAl, but other than that possibility I doubt it.

Of all the crackle mixes I've made, by favorite by far, Created by David Trimmel, is 37.5% each of Bismuth trioxide and Copper oxide (black), 25% MgAl, and 4% binder (usually NC, as noted previously). With 60-100 mesh Mgal (50/50) I can cut them at up to a quarter inch cube and if ignited evenly, they appear to be entirely consumed in the blast. They punch fearsome holes in corrugated cardboard, but appear to be prone to only partially explode when primed (as in Dragon flowers).

With -100 mesh my experience is that they multipop fiercely, burning quickly to form a cloud of multitudes of pops, like crackle would sound in a hollywood movie. I know though that others have succeeded in getting this formula, or variants of it to go off in a single bang using even finer MgAl, so tune-ability seems extensive.

While many published formulas have very high Bismuth or Lead oxide contents, more closely matching the conventional stoichiometric balance of all components reacting in a straightforward process, I consider them less effective than those with an "excess" of MgAl (and often CuO).

[Sparky]

I'm going to try some of the alternative comps as you suggest.

I've also seen a lot written about the importance of the NC but I know for sure that my first batch did not use it and at the time I was using parlon for pretty much everything as I had loads and it was quick to dry and therefore test.