Slow burning color composition?

[PyroCube]

Hi all

 

I`ve made Buell Red and Formula Verde 2 stars so far.

But these are quite fast burning compositions, has anyone

a slow burning star mix ?

I want to make smaller stars so I can put more of them in a shell like this:

 

Unfortunately I havent got any PVC or Strontiumnitrate here, so I can`t make the

comp from the video.

 

 

Greets

[FREAKYDUTCHMEN]

Slower burning stars will look more dim than the regular color star compositions containing about 50% oxidizer (Buell red is an exception, containing 35% perchlorate) If you want a denser effect, make a 4 inch ;-)

 

I think this one burns quite slow because only srno3 was used as oxidizer, normally a couple percent of perchlorate is used to turn up the burn speed.

[mabuse00]

Any slow burning red I know depends on the nitrate.

 

Swapping parlon for PVC might slow it down a little. PVC is easy to get anywhere, even if you avoid pyrodealers.

 

The trick with Buell red is that the carbonate works as a weak oxidiser in combination with magnalium.

Thus you can also try to use less Perchlorate and more carbonate.

 

Coarser magnalium might also be worth a try if you have some.

[Potassiumchlorate]

I have just tested Buell in a star gun, but it's the deepest carbonate red I have seen, and it burns pretty slow.

[Seymour]

Slower burning stars will look more dim than the regular color star compositions containing about 50% oxidizer (Buell red is an exception, containing 35% perchlorate) If you want a denser effect, make a 4 inch ;-)

 

While they will be dimmer, not necessarily too dim to be attractive. Buell Red has a higher oxidiser content than it appears if you include the rather high strontium carbonate content as an oxidiser, which with the 14% or so MgAl, will be contributing significantly, as mabuse00 has pointed out.

 

I agree fully with the suggestion to build a 4"

 

Still, on the topic of burst density and burn speed of stars, a neat trick to get a high density of stars with good brightness and colour quality for the shell size, as well as a full sized burst, is to roll a thin layer of slow burning streamer over the hot prime, followed by a final BP prime. You do this with quite small coloured stars, so that when they do light up they are relatively brief, but because there is that delay (for a small shell, maybe a second) they are far out enough to be a respectable sized burst, though due to the number of the small stars, and the decent brightness and burn rate, the density and briliancy of the shell is not diminished by a big burst.

 

Yeah you do get a different effect to a straight peony, but I think it's just as lovely, and you have limited space in a shell. The delay I talk about could really be any Potassium nitrate and charcoal composition. The higher the charcoal content generally the slower. If it's got Ti or FeTi added it'll be really twinkly and sexy. I do not suggest C6, it's way too fast, and really, so is C8. Tigertail I would consider the fastest mix to fit the bill. I should add that if it's really slow it's also quite likely rather cool. I would not take it for granted that it will definitely light the hot prime.

 

I know all these layers can sound like a lot of work, but really to make a coloured star it's almost universally desired, usually required, to roll one prime layer. I'd say most of us use two steps a lot of the time to prime colours. So pretty much you have to do it anyway, so I suggest diving in and exploring the possibilities of making the small step from rolling on prime to all the possibilities of layers.

 

While particle size of all materials greatly changes burn rate, in the case of most compositions, spark producing substances being exceptions, I find it hard to recommend coarser materials in order to reduce burn speed. Generally a higher burn speed is a desired feature (bigger, brighter) along with a cleaner and more uniformly coloured flame, and easier ignition and resistance to blowing blind. Slowing it down is also going to make the other features less pronounced. At the extreme end, carbon in the flame can yellow and pollute it, because excessively large particle size prevents the fuel and oxidizer properly mixing in the reaction zone.

 

Having said that if you are using 400 mesh MgAl, you could slow it down easily by using 200 mesh without too adversely mucking up the colour. If you really do want to have a slower colour, personally I would tweak it with the organic fuels. You can have a wide variation in burn speed while maintaining a clean flame. Rosin is the slow resin that I have used to this effect.

 

On the topic of slower burning coloured compositions, Besides Strontium nitrate, Barium chlorate also has a reputation for being sluggish. So does Ammonium perchlorate, though I'm not full convinced on that. Half of me thinks people are often scared to mill it and thus use it coarse and judge it on that. Fair enough, it's not the safest thing to mill it seems, I'd rather not loiter by the mill. Shimizu did tests that showed that with some resins it burned faster than Potassium chlorate and perchlorate.