Testing star compositions.

[Bobosan]

Not sure which category this really should go but since I'm a forum noob, I'll post here.

 

Can you dry test a star formula before cutting, pumping or rolling and get a reasonable idea of what the final end result will be after binding with a solvent? By "dry test", I mean placing a small amount (<29gm) in a line or pile and igniting it to see color results.

 

Is it normal practice to completely finish the star formula by cutting, rolling or pumping before testing for color?

 

Say you have a comp that uses red gum and dextrin in the formula. If I'm thinking correctly, either one can be used as the primary binder depending on solvent used. Or maybe even both if the proper solvent mix is applied which reduces both binders.

 

Do the dissolved binders alter the final color from that of a dry tested composition?

[Seymour]

Can you dry test a star formula before cutting, pumping or rolling and get a reasonable idea of what the final end result will be after binding with a solvent? By "dry test", I mean placing a small amount (<29gm) in a line or pile and igniting it to see color results.

 

You can get a rough idea with some compositions, while others won't behave at all the same way. Slower burning charcoal based streamers and glitters are notable in that you often get no, or very few sparks or glittering spritzels falling off at all, and they have no distance to fall and show themselves. With faster burning streamers and colours you are likely to get a bit of an idea what it might be like, but it is limited. You might be surprised how much deterioration there is in some colours if lit in a pile as opposed to consolidated. Thus pressing the coloured mix in a tube is an improvement, though you are still ignoring the realities of flying through the air, which do have quite an effect.

 

You are also likely to be way too close to the burning sample. When you test star mixes, you want to be a distance back to get a more realistic, less overwhelming and washed out idea of how it is burning.

 

29g is way too much. Sure, if you can afford to burn that much up in a casual test it may be fun, but you will get a better idea of what a star looks like if you burn a gram or two.

 

Is it normal practice to completely finish the star formula by cutting, rolling or pumping before testing for color?

 

Yes and no. I usually burn bits and pieces from start to finish, to get some information, to 'clean up' and for fun. I doubt I am unusual in this regard. However, it is normal practice to hold back on judgement until stars have burned in the air.

 

Say you have a comp that uses red gum and dextrin in the formula. If I'm thinking correctly, either one can be used as the primary binder depending on solvent used.

 

Correct, though I will personally suggest dextrin over red gum as a binder. Nicer to work with, and I have had poor results with using Red Gum as a binder (not that this is everyones experience).

 

Or maybe even both if the proper solvent mix is applied which reduces both binders.

 

Not in this case. If you add water to a solvent you activate red gum with, it lowers the solubility of the resin in the solvent relatively quickly. The same applies to adding Red Gum solvents to water, and the effect this has on lowering dextrins solubility. If you try to meet in the middle, neither binders will work.

 

However with the range of binder used in pyrotechnics there are cases where what you are suggesting does work. For example you can use Parlon and Red gum as co-binders if you use Acetone (or other ketones), and you can use alcohol a co-solvent, though this is primarily to improve handling properties (lower stickeyness). I suggest you keep the mix ketone heavy to ensure the Parlon binds well, though if the Red Gum content is high enough to be a sole binder, it is of less importance.

 

Do the dissolved binders alter the final color from that of a dry tested composition?

 

Yes, a bit. So does the extra oxygen from the air it is flying through in the sky. The difference is usually small, but the complex mixes of lovely substances we play with can have unexpected changes in performance due to seemingly small tweaks, yet seem indistinguishable at other times when huge changes have been made.

[dan999ification]

some star comps will behave like flash powder i would'never ignite a pile of anything.

Make stars test stars, make more, unless you intend to invent your own formulae there should be no real need to test for colour, if it says red its red, i like to test stars with a bent neck to get a better idea of how they look.

 

Dan.

[AlexPyro66]

I make 1/4 thin walled tubes and put some composition inside light it and throw it in the air.

[dan999ification]

dangerous, try that with silver wave to name one and you may have a report very close to you.

The best and safest way to test is with a stargun.

 

Dan.

[Megabusa]

A stargun is the only way & it's very easy to make.

 

Some comps will burn on the ground & give an idea of how they perform, but some (charcoal streamers for example) just smoulder on the ground & don't perform until they are moving through the air.

 

I test comps (small amounts < 1g) throughout the star making process, mainly to see if it burns & I haven't made a stupid mistake when weighing / mixing.

 

A stargun also shows you if the star will ignite from the BP as in the actual situation. You can ignite all stars with a blow torch, but BP is not always hot enough to ignite some star comps.

[AlexPyro66]

Yes know what are you talking about silver wave is like slow flash?

[dan999ification]

yes, a 1/4 inch tube unplugged will not confine it enough but certainly possible with other comps and bigger tubes, i read of a chlorate magenta comp confining in a screwed up shhet of newspaper.

You would get sprayed with sparks at least.

 

Dan.

Edited December 6, 2012 by dan999ification

[Potassiumchlorate]

Yes know what are you talking about silver wave is like slow flash?

 

Lancaster Silver, for instance, that I have made two batches of this year:

 

Potassium chlorate 56

German Dark 19

Bright Al flakes 19

Dextrin/SGRS 6

 

As a loose powder it is in principle chlorate flash.

[Bobosan]

Thanks for all the good info fellas. I had a feeling that the ultimate test of a comp would be a star gun type of arrangement. Maybe I am wasting chems by making 28gm test batches but I don't burn the whole lot in a pile or line....just a gram or two. That leaves plenty of comp for further testing as completely finished stars which you all have suggested.

 

Haven't messed with any chlorate or metal bearing stars yet but I am aware of the increased risks involved. As to testing comps by packing in a tube and throwing, I'd probably burn myself someplace where the welding gloves and smock didn't cover. If not that, I'd slice my neck with the full face shield.

 

I started into this hobby because I was looking for a way to reload my 25mm flare rounds. I accomplished that but the more I read up on pyro and what can be done, the more I got interested. Hmmmmm......do you think it possible to safely use my flare pistol as a star test gun if remotely fired?

[dan999ification]

card tube, hdpe tube, capped copper pipe, used cake tubes.

30 grams of stars and 5 grams bp will make a nice mine from a 1.5-1.75 consumer mortar.

Its best to use things for the intended purpose, stars will leave residue in the flare gun and may ruin it, my mine mortars are covered in a mm of crud in places.

 

 

Dan.

[AlexPyro66]

I am not sure but the copper pipe isnt a litle dangerous?

[Potassiumchlorate]

Copper pipe is pretty safe, since it won't form any shrapnel in the very unusual case that a star would detonate. I once had some barium chlorate that obviously was something weird with; two stars detonated and both star guns were destroyed. Both were of copper. No shrapnel.

[AirCowPeacock]

Really, I would think copper would present a danger, allbeit less then cast iron, but still. I prefer cardboard for star testing, I can quick roll up a gun of whatever size is ideal out of gummed tape and have it ready in an hour while I'm waiting for my acetone bound stars to dry.

[dan999ification]

for stars it is fine, it does get hot though so best not to touch it or reload too quickly.

A well soldered joint is stronger than the pipe, they tend to behave a bit like hdpe when overloaded and mostly swell,bulge,split straight this takes thousands of psi of course its not going to happen with a few stars.

 

Dan.