slow silver streamer without flake Al ?

[klachner]

Hello,

 

i want to roll color stars with a silver or golden tail (the golden wave effect like here: https://www.youtube.com/watch?v=OYNtcs1KWXk ). My problem is that i only find streamer compositions with flake aluminium, but i hate working with it because it flies everywhere if I move too fast, i cant imagine putting this into the star roller, my whole workshop would be covered in al flakes...

I also tried this comp before i found here somewhere:

Shimizu silver falls

41% KNO3
4% Sulfer
49% Aluminim (Best is bright aluminium, -325mesh coated stuff works excelent)
6% Dextrine

 

but i hadn´t bright flake aluminium, so i used 39% 325mesh atomized al and 10% <200μm coarse al granulate because i thought this coarse al could make some long lasting sparks. The composition didnt burn at all, so i added more kno3 and also pyro dark al and potassium perchlorate, until the mixture lights. Then i made cut stars and put them in a 3" shell, the result was really nice, not too fast burning but great silver tail. The problem is I dont know anymore what I exactly added to the shimizu comp to get it working :/ but it showed me that silver streamer are possible without flake al that would be much better to roll on color cores.

Some time later i ordered 45μm and 100μm flake al to try this silver shower composition: http://pyrodata.com/compositions/Silver-shower-star-1 I also made cut stars the same size as before and made a 3" shell with them. They also looked great but burned much faster, leaving a shorter tail than the modified shimizu stars before, so the effort needed for the flake al stars wasnt really worth it...

Does anyone know a silver streamer comp with atomized / granular al? or any ideas how much and what exactly could be added to an existing composition to get a slow burning star with long lasting tail, or maybe slow down the shimizu comp, not for rolling but silver palm shells?

The same problem is with the golden wave comps, the shimizu golden waves i found on pyrodata also use flake al, but i would love to roll them onto red cores... any suggestions for golden wave without flake al?

 

 

 

[lloyd]

The 'real secret' to any silver-tailed composition is an excess of aluminum, in order that UN-burnt Al be left behind as molten, ignited droplets behind the comet.

 

I can't give you a formula (for proprietary reasons), but I'd say that it's pretty safe to make Al/KNO3 compositions with just about any aluminum except GB or Indian black, and still get a good silver tail. I've even seen some made with the Indian Black, and they were fine. They can also be made with an excess of AL and KClO4.

 

Lloyd

[Mumbles]

Another trick for longer silver tails is to use an organic fuel in the mixture. Red gum is the most common, but other things like shellac or phenolic resin would have a decent chance of also working. Maybe charcoal and sulfur like if the formula you posted. The idea is that the oxidizer will consume the organic fuel first, thus leaving more aluminum to burn up in the tail, resulting in an elongation of the tail.

 

The formula you posted is for a waterfall type effect. I'm not overly surprised that it didn't burn with the major modifications. For a silver streamer star, the following will get you to a workable composition in short order. It's what I use for most everything.

 

Oxidizer - 58

Aluminum - 30

Organic fuel - 7

Dextrin - 5

 

For the oxidizer you can use potassium perchlorate or a blend of potassium perchlorate and potassium nitrate. I think some amount of perchlorate is helpful to get the tail color I like, probably at least 10-15 parts. All KNO3 doesn't have the same brilliance or appearance. For the metal you can use whatever you want. Blends of bright flake and dark flake or atomized Al look great and handle well. Mixing mesh sizes can be used to modulate the tail. I've never tried 100% atomized, but I'd be interested to know if it works. I would at least use a blend of meshes to get a varied effect like you did before. Flake aluminum can help with combustion and keeping the star going if that proves to be an issue. The slow surface area of atomized Al sometimes needs a little boost to get going.

 

Also BP (or BP components) with 5-20% metal also make bright streamers. The more metal the brighter they get. Low quantities are just sort of a brighter charcoal streamer, but the upper end they appear white or straw gold. Titanium is also useful and will appear white if good material.

 

You can turn the above formulas gold by incorporating sodium into the mixture. Sodium oxalate is my preferred source. Be wary of metal reactions though, as it can be pretty aggressive toward flake aluminums. Boric acid is recommended.

[Bigmark]

If you are using red gum do still need the dextrin Mumbles.

[Mumbles]

I wouldn't know as I have never tried. Red gum is kind of a shitty binder so I've never tried it on it's own. I always bind these types of stars with water, or with a thin wheat paste solution. This wheat paste helps to wet compositions containing considerable coated flake aluminums.

 

Despite popular conjecture, dextrin does have a fuel value so removing it would potentially partly undo some of the good that red gum is doing.

[Bigmark]

Thank you Mumbles

[Mumbles]

I will say that I have heard good things about phenolic resin though. It has a good reputation as a binder, and does have a slightly higher fuel value than red gum. If you replaced red gum 1:1, you could probably drop the dextrin without an issue. I don't know how it would behave in a composition like this, and actually don't know that I've ever heard of anyone trying. Alcohol should cut through some of the waxiness you get from using flake aluminums, but I don't know what sort of wet strength phenolic would have in combination with the Al. I suspect it'd probably be fine, but confirmation on that would be great.

 

If you want to try to bind these with red gum, you should try on a test batch. Just because I don't use it doesn't mean it wont work.

[klachner]

nice thank you mumbles, i will try your composition soon, do you think adding some mgal would also work? because i have more different sizes of mgal than al

the problem is i dont have sodium oxalate, but sodium nitrate, could it work with that some way?

 

and to the red gum as binder topic, i once tried using it as binder but even though the formula contained about 10% redgum they weren´t hard at all, i could crush them with my fingers easily... but they were still nice in a starmine