Blind blown stars

[MadMat]

My NYE display was disappointing. I had a lot of blind blown stars in my shells (offhand I would say well over half were not ignited). I had this problem in my early shells and thought I had it corrected and this NYE the problem reared it's ugly head again. A list of the things I tried when working to correct the problem are:

1) I experimented with primes and now use "hot prime + silicon"

71% Perc

14% charcoal

9% red gum

5% MgAl

+8% T.W. silicon .

I bind this to the stars with straight alcohol.

I then usually add a second layer of BP/ 5% dextrin, bound to the star with straight water.

2) I also tried backing off on my burst charges a bit. I now use 65% fine granulated BP and 35% 70/30 flash (no sulfur). My present burst patterns are great, so maybe I still have room to back down the burst charge a bit more.

3) I made it a practice to "fill the gaps" between the stars with polverone. I usually ball mill my polverone for 30-40 min.s not just screen mix it.

 

I have had success after these experiments until NYE. One other thought I have had and am wondering if it's a sound idea; Maybe I need to paste up my shells a bit more to make them stronger, giving the stars maybe a few more milliseconds to get ignited?

The problem was mostly with my 2" shells. My 3" seemed to have a bit better performance.

I am open to any suggestions

Edited January 2, 2016 by MadMat

[mabuse00]

What stars did you use?

 

 

I bind this to the stars with straight alcohol.

What binder?

 

 

 

I then usually add a second layer of BP/ 5% dextrin, bound to the star with straight water.

And the perchlorate prime underneath is alcohol bound?

 

That might be the problem. The BP is likely the just flake of under mechanical stress during the break before it can ignite the perchlorate prime.

The layers need to mix with each other a little to adhere properly.

This is only possible if they use the same solvent, so that they merge with each other.

 

Also the step from straight BP to the perchlorate prime is a wide one (imho). If the layers can mix, so that a smooth transition from one layer to the next is possible, thats no problem.

 

If they cant, and the changeover is to abrupt, the outer layer might just burn off without igniting the inner one.

 

 

 

I now use 65% fine granulated BP and 35% 70/30 flash (no sulfur)

Depending on the pasting job on your shell and the quality of your BP, this should give a hell of a boom. It doesn't make ignition easier for sure, but I dont think it's the main problem here.

 

 

I like to use an alcohol based binder too - in my case it's PVB.

My solution is to use PVB in the star itself, the perchlorate hotprime and also (in a very small amount) in the outer BP prime.

Last step is pure green mix or low quality meal without any binder, onto the alcohol-wet stars.

Edited January 2, 2016 by mabuse00

[MadMat]

The binder for my first layer of prime is the red gum in the prime. Your suggestion does make sense. I imagine I could add red gum to the bp (I could figure the stoichiometry and replace some of the charcoal OR just simply add say 4% to the BP. That way I could use alcohol for both layers. And yes, when my shells burst, they make a very discernible "pop" (to say the least) but my spread pattern is nice and round (well great if I say so myself)

Edited January 2, 2016 by MadMat

[Arthur]

While 2" shells need the burst charge boosting, I'd be tempted to suggest less flash and more pasting paper. The casing should take milli seconds longer to burst due to extra paper and due to reduced flash content so the internal flame frond should have more time to ignite everything.

[MadMat]

Yeah that was my thought. One of the problems is, I use TP tubes for my 2" shells, as such, I am kind of limited with pasting if they are going to fit in my gun. I could paste more and then spike the shells with dental floss. I tried out dental floss once as an experiment and it worked pretty dam good! (if anyone tries this make sure you use the unwaxed variety of dental floss)

[Sparx88]

Yes you need to step prime but like they said, first the hot prime and while the stars are still wet coat with the final prime so they kinda melt together. If not, it's like peeling a hard boiled egg. This also can happen with the first layer of hot prime and the star comp if the stars are bone dry when applying. I have been told to wet the dry stars with what you bound them with, water, water alcohol, parlon (acetone) etc so they star to slime up then apply prime. May take a few minutes so keep them wet until.

[MadMat]

Oh yeah,

I used a variety of stars... A parlon bound red with metal fuel (The most blind blown stars). Shimizu green (better ignition rate than the red),

A blue (comp with copper carbonate ect same ignition rate as the green) and winokur #26 ( these had the best ignition rate)

[braddsn]

Mat, are you rolling your stars or cutting?

 

Here are a few suggestions in the order of importance... I have spent a great deal of time perfecting priming techniques, and have learned a lot along the way:

 

1) The thickness of prime is critical. Don't guess, you need to cut into the stars and observe the thickness while you are priming. IF you are priming with a hot prime first, with a final layer of bp, then use .5mm of hot prime, followed by 1mm of bp. (The final bp layer can contain silicon, DE, or a combination). I prefer ball-milled bp + silicon for the final layer. 90% of the problems I encountered in the past with blind stars always traced back to insufficient thickness of prime. Better to prime to thick rather than too little. If I was a betting man, my bet is that your prime is not thick enough.

 

2) Make sure your stars are COMPLETELY dry. I let my stars air dry for a couple days, then put them in a 600W dehydrator for several hours. Personally, I weigh them throughout the process in the dehydrator, and when they stop losing weight, I know they are done. I am paranoid about moisture, it has caused me a lot of headache in the past.

 

3) Make sure the final bit of bp prime on the outside is applied with almost zero water. It needs to have a dry rough texture when finished.

 

4) Don't take the time to build a shell with a star that has not been tested out of a star gun!! Keep in mind, the star gun tells the tale EVERY time! When I finish drying a batch of stars, I take the star gun out and load it pretty heavy with lift bp (like a tablespoon), and take 4 stars and load it up. Then I shoot.... if ALL 4 stars light and look good, then I know they are primed right. If any less than 4 ignite, then more than likely something is wrong.

 

One thing to note: While proper pasting and proper use of booster can have an effect on ignition, I have found that most of the time it's not very critical. I have experimented with rediculous amounts of booster (6g in a 3" shell) and was still getting 100% ignition when the stars were primed properly. And the same goes for pasting. A well pasted shell will of course break better, and more symmetrical.. but has little bearing on whether the stars inside light or not.

 

Good luck!!

[MadMat]

Mat, are you rolling your stars or cutting?

 

Here are a few suggestions in the order of importance... I have spent a great deal of time perfecting priming techniques, and have learned a lot along the way:

 

1) The thickness of prime is critical. Don't guess, you need to cut into the stars and observe the thickness while you are priming. IF you are priming with a hot prime first, with a final layer of bp, then use .5mm of hot prime, followed by 1mm of bp. (The final bp layer can contain silicon, DE, or a combination). I prefer ball-milled bp + silicon for the final layer. 90% of the problems I encountered in the past with blind stars always traced back to insufficient thickness of prime. Better to prime to thick rather than too little. If I was a betting man, my bet is that your prime is not thick enough.

 

2) Make sure your stars are COMPLETELY dry. I let my stars air dry for a couple days, then put them in a 600W dehydrator for several hours. Personally, I weigh them throughout the process in the dehydrator, and when they stop losing weight, I know they are done. I am paranoid about moisture, it has caused me a lot of headache in the past.

 

3) Make sure the final bit of bp prime on the outside is applied with almost zero water. It needs to have a dry rough texture when finished.

 

4) Don't take the time to build a shell with a star that has not been tested out of a star gun!! Keep in mind, the star gun tells the tale EVERY time! When I finish drying a batch of stars, I take the star gun out and load it pretty heavy with lift bp (like a tablespoon), and take 4 stars and load it up. Then I shoot.... if ALL 4 stars light and look good, then I know they are primed right. If any less than 4 ignite, then more than likely something is wrong.

 

One thing to note: While proper pasting and proper use of booster can have an effect on ignition, I have found that most of the time it's not very critical. I have experimented with rediculous amounts of booster (6g in a 3" shell) and was still getting 100% ignition when the stars were primed properly. And the same goes for pasting. A well pasted shell will of course break better, and more symmetrical.. but has little bearing on whether the stars inside light or not.

 

Good luck!!

 

The funny thing is I ran some mines NYE with these same stars and got great ignition. This is one of the reasons I thought maybe making my shells stronger might help.

[Seymour]

Having stars work in mines but not shells is not unusual. The lift from a mine is typically much more gentle and so is less likely to throw the stars too fast that they go out at some point (some priming combinations only work if the stars are not traveling too fast, but with the silicon in there I consider it unlikely that the flame is blowing out like a candle) and also less likely to by physically damaged by the force.

 

Personally I doubt that with a 2" shell there is any issue of it not having time to light the stars. This is usually a problem with larger shells.

 

I am probably a bit too anti red gum as a binder, and I know people have used it in this way with a lot more success than me, but I wonder if it could be the problem. I've never found that it gives the same strength as Dextrin, Gum Arabic, Parlon or many other binders. I suggest you take what Brad said a bit further and cut a star in half, or rub it on concrete until you have half a star left. Once you've done this not only will prime thickness be obvious, but you can scratch the star and see if the red gum bound bit is much softer than the dextrin bound bit.

 

Finally, I think that you are having problems that practically everyone does, so if it makes you feel better, I think having blind stars is a rite of passage of sorts, and once you sort it out you will be fine. By the way, from what you are doing it sounds like you have a very good idea of what you are doing, and you are not far off perfectly performing stars

Edited January 4, 2016 by Seymour

[braddsn]

Man I have to agree with Seymour, and I should have also added, star ignition problems is something EVERYONE goes through at some point. It is a rite of passage for sure! And MAN it can create a headache!! Binding with redgum is something that I have no experience with.. I have however read a fair bit about it, and I have came across many posts where guys had problems when binding with redgum. I would suggest binding with dextrin maybe and see if things improve, (like Seymour said). Just make double sure that enough prime is on the star. If that prime burns off and the star is still travelling warp speed, there is a good chance it will blow out. When I spoke about the star gun test, keep in mind that I put a large amount of lift to really push the stars hard. My goal is to try and get as close to a shell break as I can. Obviously, it is still more gentle than a shell break, and does not 100% guarantee perfect ignition.. BUT, IF they DON'T light out of a star gun, don't even waste the time putting them into a shell without fixing the problem. It will save you some time when troubleshooting.

[Nessalco]

Yeah that was my thought. One of the problems is, I use TP tubes for my 2" shells, as such, I am kind of limited with pasting if they are going to fit in my gun.

 

Make a liner out of chipboard, glued to the inside of the TP tube. I usually skive (bevel) the ends of the liners so they overlap at least 1/4" when glued in place, without making a lump. I prefer to use PVA glues for this.

[Stef727]

The problem was mostly with my 2" shells. My 3" seemed to have a bit better performance.

I am open to any suggestions

 

The bigger the shell the more heat and pressure it accumulates before it explodes

[MadMat]

Thanks for all the suggestions guys. I guess I have some experimenting to do. I feel kind of foolish for not considering the problems with using different solvents/binders in layers myself. One of my best friends has been a custom car painter for years, and after doing some painting with him at home, I know all about the problems of layering incompatible paints (the exact same principal.)

As far as using dextrin instead of red gum, I'm all for that; I'm not a fan of working with red gum.

 

The problem with this "rite of passage" is that I thought I had already passed that point . But, NYE was the most shells I fired off at the same time since the fourth, so I guess.....

Edited January 4, 2016 by MadMat

[MadMat]

Also, thanks for the words of encouragement as well... it's nice to know I'm not a total dumass

Edited January 4, 2016 by MadMat

[dynomike1]

Well the problem with testing different chemicals without asking can get expensive. I use Fencepost + Bp W/silicon, never had a problem. Unless a shell breaks to quick, i mean doesn't hold together long enough for all the stares to lite.

[lloyd]

I've said this before, but I'll say it again: There are only a few things that cause blind stars.

 

1) The stars are simply too hard to ignite -- they may be wet, they may be made of "inignitum", or they may be just difficult to ignite. Hot primes help with the latter. Nothing helps the other two.

2) The stars may not be exposed to flame long enough to ignite. Better containment and a more 'gassy' burst usually helps.

3) The stars may be leaving the shell at such a high velocity (above their "critical velocity") that they blow out AFTER having been well-ignited. Reducing the burst strength, or layering a high critical velocity comp over the 'slower' one will rectify that.

 

You can easily evaluate and change all three issues.

 

Lloyd

[MadMat]

Well, I know for a fact the stars being wet is not the problem; my red stars (worst ignition rate) are parlon bound, hence no water to begin with. I think my priming technique is the problem. As far as stronger containment, The TP tubes are officially history, from now on I'm making my own shell casings for 2" (I made the 3" casings and had better ignition rates with them.) If better priming doesn't solve the problem, I will reduce my burst a bit further.

[Seymour]

 

 

The problem with this "rite of passage" is that I thought I had already passed that point . But, NYE was the most shells I fired off at the same time since the fourth, so I guess.....

 

 

At least for me, this rite of passage involved rather a few steps when for different reasons I had blind stars, spread over several years

[MadMat]

Well the problem with testing different chemicals without asking can get expensive. I use Fencepost + Bp W/silicon, never had a problem. Unless a shell breaks to quick, i mean doesn't hold together long enough for all the stares to lite.

 

Mike, My all-time favorite job I ever held was in R&D, so if I spend a little extra money experimenting, I'm doing something I love to do and it's worth it to me

[dynomike1]

 

Mike, My all-time favorite job I ever held was in R&D, so if I spend a little extra money experimenting, I'm doing something I love to do and it's worth it to me

EXCUSE ME

[MadMat]

I hope you took no offense Mike, I know you were simply trying to be helpful, but I do love R&D!

 

And to everyone, don't think for even a second I don't appreciate your advice; at the very least it gives direction to my experiments.

Edited January 7, 2016 by MadMat

[dynomike1]

None taken.