Colour changing stars

[psymon]

I am not sure if this is the best place to ask this. So here goes. This weekend I was at a concert and to finish off they had some really great fireworks. All mortar shells (probably around 6" and bigger judging by the spread and amount of stars). The question I wanted to ask was does anyone have any good formulas for colour changing stars?

The stars from the weekend were blue/white red/white and other colours. What I would like to know is does anyone have any method and compositions they could reccomend? I have all the usual equipment like star pumps and ball mill etc. or will i have to roll these stars? If this has already been asked then I apologise - I did search but found nothing.

[_DB_]

To make color changing stars you will have to roll them.

[d4j0n]

What about pumping them? A finished star pressed into a bigger pump with another composition. Or one comp on top of another for roman candles.

[hst45]

I agree with DB; rolled is the way to go. It's pretty easy once you get the hang of it, although it can be maddening trying to learn.

 

For a really fun effect try this: roll the core with a color comp, follow with a layer of delay, then finish the outer layers with a second color, or a flitter trail. The star starts with effect #1, seems to go out, then at the end gives a "wink" of color.

[justanotherpyro]

Thats a really cool idea hst45. The key to good color changers is making sure that when you roll the first comp that they stars are all really uniform in size. Otherwise you get a botchy looking color swap.

[optimus]

I don't think there are any star comps particularly suited to colour-changing stars, just think about which colours go well together. Don't have a white Mg/organic blue star because the eyes will just have adjusted to the Mg just as the blue lights, etc... A 'dark relay' comp which produces little/no light output is commonly used between layers of multi colour changing stars. It helps to create the illusion of all the stars changing at exactly the same time.

 

I saw a video of a Japanese shell where the colour change went in a wave from left to right. Would be annoying and time-consuming to make well, but it looked fantastic!

[zAZO9a]

ive heard that some japanese companies use cut stars as the core for a lot of teres..havent tried it yet though..

[Arthur]

It's one of the finer parts of the pyrotechnic art! Commercially the changing stars are rolled to one size in the last colour then rolled to the next (final) size in the first colour. I suppose that you could pump some small stars then insert them into some wet comp in a larger pump.

 

The evenness of the colour change is governed by the precision of the process.

 

Some colour orders look better than others according to your formulations, blues tend to appear pale (to white). You will end up with a lot of black (prime) balls that are different (colour order) so be very methodical.

Edited March 23, 2013 by Arthur

[laserkoi]

a palon star core works well ( red or green ) heavly primed with 2 step pinball ,then roll on a tt or spider over the top .

i just cut up some left over paron stars to about 5/6mm cube .then rolled a spider over the top to about 10mm . worked ok in a 4" shell . was not 100% unform but i was happy for my 1st attempt

[loaded4bear]

I tried rolling on top of nicely cut square cores as Shimizu suggests but the cores just slid inside my roller drum. Anybody know any tricks?

[dan999ification]

Wet them some more to break down the edges slightly, or roll them I'm a bucket first by hand just until they grab some comp.

What is your roller like? Slippery drum, slow?

 

Dan.

[TYRONEEZEKIEL]

Dan hit the nail on the head. I notice my cores to do a bunch of slipping at first. It is a matter of having proper amount of moisture on the cores. I operate my roller by hand, so it takes a very long time. I have learned quite a few miniscule details doing it this way.

[dan999ification]

I hand roll, it helps to move quickly at this stage.

Wet them agitate them and get some comp on fast, adding moisture incrimentally and waiting will see the cores suck it up leaving the surface dry, rounding the edges and getting that first bit of comp to stick is the hardest part.

If you move fast you also keep the moisture on the surface aiding drying times

 

Dan.

[dynomike1]

I agree with DB; rolled is the way to go. It's pretty easy once you get the hang of it, although it can be maddening trying to learn.

 

For a really fun effect try this: roll the core with a color comp, follow with a layer of delay, then finish the outer layers with a second color, or a flitter trail. The star starts with effect #1, seems to go out, then at the end gives a "wink" of color.

 

What would you use for a delay?

 

Can you roll Parlon color stares instead of cutting them?

Edited March 30, 2013 by dynomike1

[mathiasxx94]

Dark comps. (low light-emitting compostions) is often used as a delay between the different stars. The use of it is a great way to surprise the audience. Aaw show is over... BAAM some red stars coming out of nowhere 2 seconds after the "main" star has burned up.. An example from Shimizu:

 

 

Dark relay

Potassium Nitrate.................................75

Charcoal Airfloat....................................8

Potassium Perchlorate...........................7

Antimony Trisulfide, Chinese needle......3

Red Gum................................................2

 

Keep in mind that the relay might not ignite the core: You may need to prime the core before rolling a layer of delay. An example would be:

 

Slow gold > Dark relay > BP + 7% Silicon > Emerald green

 

or maybe Tiger tail > Dark relay > BP + silicon > Flash core igniter > Flash core

 

 

 

"Can you roll Parlon color stares instead of cutting them?":

 

Are you thinking about using parlon as binder and roll with acetone? My experience is that it's hard to roll due to the sticky nature of parlon. If it's some dextrin in the formula you may want to just use water and some alcohol.

 

If you want to try some red stars i would take a look at these:

 

60% Strontium nitrate

15% MgAl ~250mesh

15% Parlon

10% Dextrin

 

You can bind with water, they roll easily, are easy to ignite, and gives an excellent red color. Good thing is that you can substitute strontium nitrate with barium nitrate to get a nice green colour, although this color is a bit more pale than the red one.

 

-Mathias

Edited March 30, 2013 by mathiasxx94

[pyrokid]

I have a quick question for you guys:

 

Is the use of SGRS critical when using the toro method? I want to make a toro composition out of a charcoal streamer and use it with cut color cores, but I'm concerned about viscosity issues and over wetting the toro.

[50AE]

I used the toro for a while. It took some practice for me, I used it mainly for priming first, because I was scared of wasting any good rolled stars. You have to make slurries of different thickness. I think it's more suited for large batch rolling. For small batches to 500-2kg of stars, I prefer the spray&dust technique.

 

As for color changing, use your imagination. Just keep in mind that it's advisable to start with a dimmer color and finish with with a brighter color. If done the other way around, the first comp will overlight and the final won't be so noticeable/nice.

[Mumbles]

The toro method isn't new. However any modern information on it is relatively scarce. Most can only really give you general information. If you're committed to it, a lot must be learned by trial and error.

[Algenco]

As Mumble said it's trial and error but quick to figure out.

Thin Toro works best for me, if it's too thick everything sticks together.

Think about it, it's not so different from wetting stars for the next layer.

With larger stars that need to be rolled and dried in stages, if you use the standard spray method the dry stars take a lot of water before they'll pick up comp, almost to the point of saturating the whole star again.

With "Toro" you apply a wet layer of comp that will pick up dry comp immediately

2:1 water comp is a good starting point for the slurry and stars need to be 1/4" or larger before swithing to "Toro"

It will build up stars quickly

[Mumbles]

If you look around, I made a rather lengthy post a while ago related to this subject. I use a toro-like method for priming stars. I generally like 1:1 solvent to composition. I also stir everything by hand, so I can get away with a thicker, stickier slurry. If I was using an actual powered star roller, I'd probably have to go thinner and in smaller increments. You just have to find what works for you and your setup.

 

Back to your original question. I have use a variety of binders including red gum, SGRS, and dextrin. With red gum I used isopropyl alcohol as the solvent. With SGRS I used just water. For dextrin, I mostly used gum arabic solution. SGRS works the best in my opinion. Red gum does dry faster which is nice for priming, but it doesn't give as robust of layers and is a little harder to work with IMO. Dextrin and gum arabic is similar to SGRS, and dries hard as a rock. If you can get it and want to experiment, I'd go with SGRS. As I said, I really only dealt with priming which is a far less exact or demanding application.

[dynomike1]

Thanks Mathis i'll try some.

[dynomike1]

I started with this formula.

Barium Nitrate 50

MgAl -250mesh 18

Parlon 15

Red gum 10

Dextrin 5

I rolled some stars 75-25% water/alcohol and the green worked fine. Then i rolled some of the green on top of some red stars now the green has turned kinda yellow. I wonder what happend.

[Mumbles]

Hard to say really. Red light plus green light does make yellow light. A changing relay might help, and does make the color change look more crisp.

[dynomike1]

I guess green on white wont work either without a relay. I rolled some green just now let me see how that works. I don't guess Barium nitrate goes bad does it?

[burningRNX]

Maybe some barium, or if you used it strontiumnitrate has gone in solution and migrated to the other layer? , I've had this before, If thats the case, dry the first core thoroughly, and roll on a thin layer (like 1 or 2 mm) of the next collor, and dry immediately, or even better, use forced drying, after that rol on thin layers of composition to the desired diameter. Edited July 15, 2013 by burningRNX