Rubber stars

[Foxfire87]

I have been trying to make red and green rubber cut stars following ned gorski formulas from sky lighter. First batch looked good but when my shells break only a few actually ignite. Took my time on next batch and really milled and screened it all, but they still seem hard to light, with a lighter anyways, when I put the stars on top a fuse or in a pile of coated rice hulls, they ignite, so do the first batch. So I'm not sure why they're not igniting when shell breaks? Can anyone point me in the right direction?...the second batch i also used finer magnalium thinking it should help it ignite and burn faster

[Foxfire87]

Forgot to ask, should a lighter held to the stars easily ignite them?...lighter takes a while to ignite

[Mumbles]

Are you priming the stars? This is typically a layer of comp on over the star which ignites easily and can burn pretty hot. Metallic fueled colored stars like you're making will effectively require some priming.

[Foxfire87]

Yes Iam doing a hot prime and a parlon black powder prime after that

[Arthur]

How do you cut the stars? If you roll out a sheet of comp then cut it, try dusting the table surface with prime, and dusting the top surface of the star mix with prime.

 

If the star formula permits, use a prime of BP ingredients and maybe add some silicon metal powder.

[Foxfire87]

I dont have any silicone powder at the moment, and it must be something stupid I'm missing or doing wrong, I dust both sides of patty with the hot until it no longer looks wet, then cut them, put them in a big tub, finish off the hot prime while swirling the stars, I wet with denatured alcohol after they're cut to pick up the prime, then same method for adding the parlon black powder prime. They look good and dusty when I'm done, rough outside surface. Then when its show time they dont work very good, this is all new to me so maybe with more tries they will get better. But I followed the instructions closely that were posted on sky lighter, I bought their red rubber screen sliced star kit, should they ignite easily when a lighter is held to them?...I completely line the inside of my 3 inch shells, fill with coated rice hulls, then it looks like only a handful are igniting.

[Foxfire87]

Is the shell breaking too hard?..I wrap my 3 inch 7 times with 1 inch tape, nice thud, loud break, but being new i dont know if this is too much maybe? Thanks for everyone's suggestions so far and input, and any more is greatly appreciated. Edited October 6, 2019 by Foxfire87

[pyrokid]

The Parlon content of the outer BP prime seems suspicious to me. Chlorine donors typically have some flame inhibiting properties. Stars have their highest velocity immediately after the break and it may be that they are being blown out while this poorly optimized outer prime layer is burning. I would move to replace the Parlon in your prime with red gum if you are binding with alcohol. Unless you have some aversion to water or the formula precludes its use, I would use an H₂O - dextrin system for the prime.

[Foxfire87]

No honestly this is just what the skylighter site calls the prime, there is no parlon in the prime though, I just thought it was called this because it's being used with a parlon star?. Sorry if I made it confusing but this was what I read so I call it "parlon black powder prime" because that is how they worded it

[Arthur]

Fast primes sometimes burn away before sufficient heat has been passed to the star. Clean burning primes usually burn to hot gasses that go away. Prime with bp ingredients and silicon (it's a metal used in powder form) burn slowly and the silicon forms silica as a fused droplet on the star which passes lots of heat easily.

[Mumbles]

There's a handful of skylighter rubber star tutorials. Do you have a link to the one you're following?

[davidh]

They should light when you simply show them the lighter. Your prime is bad.

[OldMarine]

I've shot dozens of shells with cut rubber stars with only BP prime with good effect.

These stars should light if you merely show them a photo of a flame.

I suspect you need to double check you chem quality and formula.

[dynomike1]

How hard are they to light with a torch?

[memo]

agree with old marine, if all is good, and a prime is used, maybe just maybe your breaking your shell too hard and blowing them blind.

[Mumbles]

I wouldn't be surprised if that's the cause or partly responsible. A thicker priming layer can often do the trick to cure that. The stars can allow down a bit more and stay out more easily. This is still a little strange though.

 

If you split a star in half, how thick would you say the priming layer is?

 

Firefox, for what it's worth your manufacture probably sounds fine. 7 layers is fairly reasonable for a 3" shell. It's all going to depend on the burst charge as well of course.

[Foxfire87]

https://www.skylighter.com/blogs/how-to-make-fireworks/screen-sliced-red-rubber-stars

Here's the link, not exactly sure how thick the prime would be but I have to hold a flame to them for about 15 seconds before they ignite. made a few batches since my last post and they seem hit or miss. Some work in shells, it mainly seems to be the red star that wont ignite from the shell burst. My other colors are lighting. But they all require me to hold a flame to them to ignite on the ground out of the shell

Edited October 26, 2019 by Foxfire87

[Foxfire87]

I'm making 3oz of hot, 3oz of the black powder prime, and the majority of both seem to stick to the stars, there's some left or stuck to the bottom of my tub but the stars themselves really seem to build up from time of cutting to finishing the primes. But the inconsistency of them is really frustrating and I'm just not sure what I'm doing wrong

[Foxfire87]

And all my chems have been ordered from fireworks cookbook, pyrochemsource, and skylighter

[Foxfire87]

I'm using acetone and denatured alcohol, could I be making them too wet? If I add silicon to the prime, should I eliminate the magnalium that the formula calls for? Or just add it in? These formulas call for nitrates instead of carbonates, would the carbonate formula be easier to ignite? Or as stated before, it seems to be more a problem with my prime.

[justvisiting]

When I make the 'rubber' stars, I use the Ziploc bag method and cut them with a knife. When I prime them, I take the dried, hard stars, and give them a quick dunk in water in a sieve, and turn them out into the powdered prime. The prime I use is 75-15-10 scratch mix (made with slow charcoal) +5% dextrin + 5% silicon +5% MgAl. I toss them in this prime, gently shake off the excess, and finish them in plain scratch mix- no dextrin. They take on quite a bit of prime. When properly dry, they are as hard as rocks. I've never had an ignition problem with any parlon-based star using this common priming method, originally developed by Gary Smith, the guy that invented screen-slicing. If the stars become damp in storage, it's easy to tell. The prime will be able to be flaked away without too much effort, leaving a bare star. Leaving such stars out in the sun will return them to the original hardness. I don't use any denatured alcohol. It's not necessary when using the bag method. Somewhere around here I wrote quite a bit about the bag method- I think.

[Foxfire87]

Thank you for the info, I will give this a try with my next batch and see if I can get better results

[justvisiting]