recommend a good prime

[shagaKahn]

Been working on red, blue and purple stars with ammonium perchlorate and have heard that it's not safe/effective to use a BP prime.

 

Have heard Shimizu prime mentioned--but also someone recommended a straight mixture of potassium perchlorate and charcoal.

 

What do y'all recommend?

 

Thanx,

s

[Seymour]

Potassium nitrate reacts with Ammonium perchlorate to form Potassium perchlorate and Ammonium nitrate. The Ammonium nitrate created will kindly take moisture from the air, and store it in your star, making it wet, and unignitable.

 

Because of this, Potassium perchlorate primes are commonly used, though not the only option, as Sodium and Barium nitrate do not cause the same reaction, and using a perchlorate buffer layer, and binding with Nitrocellulose, it is possible to have a Potassium nitrate prime on an AP star without the reaction occurring.

 

Depending on what your star contains, it may need or not need a hotter prime. However, generally Ammonium perchlorate stars light quite easily. If the composition contains a metal fuel, you might want to add a similar quantity of a metal fuel to the prime to ensure ignition.

 

While AP compositions usually ignite very easily, many (though not all) formulations are also blown blind very easily, because the stars have little or no liquid phase of the burning, and the clean, gaseous flame can be more easily blown out.

 

One simple method of dealing with this, would be to roll a slow burning layer over the prime (such as the high charcoal mix you mentioned), to give the stars time to slow down a bit before the colour ignites.

 

Adding metal fuels, or a small quantity of lampblack or Charcoal, are some methods, built in to the formula to provide resistance to being blown blind. Others include the use of more suitable fuels (some of which have more resistance to air flow than others), or using a hybrid of Potassium and Ammonium perchlorate.

 

Finally, you can make pillbox stars using KP match (instead of black match).

 

AP stars are beautiful, but often require their own set of procedures to become effective.

 

While you may already be aware of the incompatibility between Chlorates and AP (as well as most other Ammonium salts), it is a very serious one, so I feel obliged to point this out.

[Miech]

I have used two primes for AP based stars.

 

75 Potassium perchlorate

12 Red gum

09 Charcoal

05 Dextrin (if required)

 

Or if it needs to be hotter:

 

75 Potassium perchlorate

12 Red Gum

05 Charcoal

04 Dark aluminium

05 Dextrin (if required)

 

Both need a meal layer or dusting to ignite properly. They can also be bound using the present red gum, which I actually prefer.

[TYRONEEZEKIEL]

I use the first formula Miech suggested. It ignites very well. It is slower burning than BP, so it will really ensure ignition. Ive never used the latter since I dont have dark Al.

[shagaKahn]

Thanx for the primer suggestions.

 

Admit that I built a small batch of stars before recalling that ammonium perch required a different prime. (Yes, I went ahead and primed them as usual with homemade BP).

 

Only reason I'd gone that way was that I had no Sr Nitrate and had heard that you could still get a deep red star with Sr Carbonate if you went to the ammonium perch.

 

Made a batch of red, blue and purple stars. Interestingly, the red does light OK (fired from a stargun) but the purple is iffy and not a single blue star has ignited out of the stargun. (That's when I remembered that BP prime doesn't work).

 

They all fire up fine when I hold a light to them on the ground--but that ain't how stars work.

 

So do I understand you correctly Miech when you say even after the stars are coated with your suggested prime that they still need a final prime of BP?

 

Have heard that you need to seal the original star with something like NC lacquer, so the nitrate from the final BP can't come in contact with the ammonium perchlorate.

 

Again, thanx for the primer tips.

[Mumbles]

With AP stars I usually go safe and use NC lacquer to apply both prime layers. I roll on a good KP type prime as posted above, and then prime it again with green meal. I let the stars dry in between coatings just to get a good shell and prevent any BP migration.

 

Oh, by the way, I use a 2% NC solution in acetone so I can spray it. Generally the prime has red gum in it too, so that helps in adhering the first layer.

[pauliship]

what about a hot prime using sodium nitrate meal powder and some iron oxide and atomized aluminum would that be acceptable for hard to light AP stars?   I have heard of this with potassium nitrate primes but not with sodium nitrate primes, also if any one has used the potassium nitrate version how much iron oxide and aluminum did you add to the prime?

[qwezxc12]

I usually use a bastardized version of KP-based Fencepost prime for my AP based stars:

 

65 KP

15 C

10 S

5 Diatomaceous Earth (pool filter material)

5 -325 Silicon

+4% redgum for binder

 

 

Roll and spray with alcohol.

When I make prime, I can make up the base mix, divide it, and one batch gets Potassium Nitrate for an oxidizer, the other KP. I always keep a tub topped up with prime, because I work in batches.

Edited June 15, 2010 by qwezxc12