24 replies to this topic

[Pretty green flames]

I've got a formula that calls for -325mesh Bright aluminium (which is coated with stearin), now the binder is supposed to be dextrin, 5% of it. I've tried it and the finished stars are really crumbly, you can crush one with no problem.

I'm guessing that the stearin somehow inhibits the dextrin. Which binder is reccomended for stars that have a high content of stearin coated aluminium?

Thanks

[digger]

I've got a formula that calls for -325mesh Bright aluminium (which is coated with stearin), now the binder is supposed to be dextrin, 5% of it. I've tried it and the finished stars are really crumbly, you can crush one with no problem.

I'm guessing that the stearin somehow inhibits the dextrin. Which binder is recommended for stars that have a high content of stearin coated aluminium?

Thanks

mmmm Interesting one. I assume that you are doing an electric streamer or similar. I have done some of these comps with stearine coated bright ali. I milled the bp based components with the dextrin then added the ali. They dried absolutely rock hard.

How are you forming the stars?

[Pretty green flames]

mmmm Interesting one. I assume that you are doing an electric streamer or similar. I have done some of these comps with stearine coated bright ali. I milled the bp based components with the dextrin then added the ali. They dried absolutely rock hard.

How are you forming the stars?

I've cut them into 10mm cubes, they are dry and still, the dextrin seemed to have no effect, i really can't think of any other reason except the heavy coat of stearin.

Here's the formula if anyone is interested

Potassium nitrate..........................55
Aluminum (Bright flake).................15
Boric acid......................................2
Fine charcoal.................................10
Dextrin..........................................5

[karlfoxman]

I seem to remember making some streamer stars/comets and I used bright aluminium coated. The binder I used was gum arabic and they set rock solid! Might be worth a try PGF.

[AdmiralDonSnider]

Maybe SGRS also works. The cohesive power is much larger than that of dextrin.

[Pretty green flames]

Thanks for your help guys, will give Gum arabic a try, how much did you use Karl, 1:1 sub. for dextrine or as a solution with which you dampen the mix (5parts GA to 40 parts Water)?

SGRS is a little hard to come by, so gum arabic is the next best thing I would say.

[richard2]

Hi

I seem to remember a post on rec.pyrotechnics by Mike Swisher regarding the use of wheat paste as a binder in compositions with fairly high levels of bright flake and also discussion of problems binding such compositions. It may be worth having a search over there.


Regards


Rich

[seymour]

Pretty Green Flames, I always use Gum Arabic for my stars with water as a solvent, and have use 1:1 to the binder on formulas (Dextrin, SGRS, whatever) and it always works fine. I would not recommend using a Gum Arabic solution however, unless you are prepaired to let the Gum Arabic dissolve for quite some time. In my experience, adding the powder to water results in a significant portion of the binder forming a tacky lump of paste that sticks to the sides of the container, or the stirrer and necessitates leaving it to stand for a day or so. This is not good when you have prepared 3kg Tigertail which you are all amped to get down and dirty and cut.

[AdmiralDonSnider]

Just for safety I would look out if there are any chlorates in the comp (dk your formula), as the use of gum arabic is generally recommended with gunpowder or nitrate type comps only, due to possible acid formation during fermentation.

[Pretty green flames]

Ok, i've made some stars with Gum arabic and today they're dry, they are rock solid, thanks for the suggestion Karl.

But having worked in a pharmaceutical company I remembered that they use gelatine as a binder in granular forms. So I gave it a try.

A 100g batch of the above formula was prepared (with no binder added), then 3g of Gelatine were disolved in water, 1 part of gelatine to 4 parts water, to disolve, place the gelatine in a glass container and pour the calculated ammount of water onto it, let it set for about 1-2hours, then gently heat on a hot plate, not to a boil, the gelatine will disolve and you will be left with a clear yellowish solution.

Mix this to the raw composition, add water as you need to suit your needs (i was cutting so a little bit more water was needed).

The stars set ROCK HARD!

The burn rate, hardly effected.

Give it a try, I was pleasantly surprised.

[BrightStar]

PGF: What do these stars look like in the sky?

It's the simplest formula I've seen for a nitrate silver streamer - it almost seems to be missing a few parts sulfur or antimony trisulfide. Where did you find it?

Edited by BrightStar, 23 May 2008 - 08:25 AM.

[Pretty green flames]

PGF: What do these stars look like in the sky?

To be honest, I haven't had the opportunity to test them, I plan on doing so in the near future, hopefully this weekend. I'll be sure to film them in action and post the vid's here.

It's the simplest formula I've seen for a nitrate silver streamer - it almost seems to be missing a few parts sulfur or antimony trisulfide. Where did you find it?

The lack of Sulphur worries me a bit (higher ignition temperature due to the lack of it), I hope they'll light fairly easily or atleast from a simple prime like green mix + Aluminium. I've found it on Visser's site, under effect stars, Silver Shower star #3.

[Pretty green flames]

BrightStar, I didn't forget, I tested a couple this evening as promised.

Here it is, a 45mm mine, 25g of stars and 8g of lift, the stars were 10mm cuts. To make sure they light I primed them with a thin layer of greenmix + 10% Aluminium (200mesh atomized) which seeemed to light them with no problem.




PGF

[pudi.dk]

Where do you have the formula from, and what is it called?

[Pretty green flames]

It's called Silver shower star No.3 on Wouter Visser's site.

Here's the formula:
Potassium nitrate..........................55
Aluminum (Bright flake).................15 (Althoug it says any grade of aluminim, I was told that bright flake would work best, quite cheap aswell)
Boric acid......................................2
Fine charcoal.................................10
Dextrin..........................................5 (I don't use dextrin, the dextrine is replaced by 3.5g of gelatine per 100g of composition)

Note: The geltaine is added as a solution, so it is not incorporated dry in the mix.