I f***ed up with priming. Is there a way to repair what I did?

[50AE]

I made a 500g batch of Ba(NO3)2/Al bronze silver comp and I primed it with BP +15% bronze Al and then straight BP. The problem is, the prime burns away fast and can't ignite the star. From 10 stars, only 3 ignited.

What can I do about it? Do I have to "throw" these stars? The prime layer is at least 2mm thick.

[al93535]

I have had problems with stars at work not igniting completely, usually another coat of prime solves the problem. Last week I had this problem at home, as was found from stargun testing. Another layer of prime worked excellent.

 

What ratio of metal is in your star? Was your BP prime milled?

 

I always advocate a screened prime, with 5% to 10% magnalium.

[50AE]

Yes, my meal is lift quality, very hot.

I will try not milled meal.

So you claim that my stars will ignite with the 2mm prime separating if I put another coating?

[pyrochris732]

I just made a 200g batch of prime from just green mix and 10% magnalium. i think it was mumbles that suggested green mix, but i dont remember.

 

I was also told that step priming solves these problems.

 

good luck, i had the same problem with organic blue stars.

[pyrogeorge]

Dont use very fine kno3 in your BP.try this.

[Mumbles]

Are they not lighting on the ground, or is this from a star gun? If it's in a star gun, the extra prime could help. If they're not lighting on the ground, then they're probably garbage now.

[50AE]

Yes, they don't ignite on the ground...

[dagabu]

Not so soon!! What liquid did you use to bind the stars originally? I made a batch of blue stars once and the would not light at all. I had to crush the prime off of them by placing them between two pieces of plywood (12" x 12") and crushing the BP. Almost all the BP came off and I used fence post prime and they all lit.

[al93535]

Mumbles is right, if they are not lighting on the ground then there isn't much you can do. Since you used milled hot BP its just flashing off the star without heating it. The stars that I re-prime use slow burning prime in the first place and they simply didn't get enough prime. Yours are a different story.

[psyco_1322]

If you cant get the prime to break off like dagabu did, there might be some final hope for them. You would have to get the prime layer very wet, to the point something else you be forced into it. Aluminum usually doesnt light very well with just bp, so a bp/Al prime might be a bad choice. If you had a fine Ti or magnalium, about 100-200mesh, that would work much better. If you can get the stars really wet on the outside using some water and alcohol, you could work into the outer layer some coarse Ti or magnalium, 60-100 mesh range would be good. Then maybe rolled them in some coarse bp for a spiky outside for better ignition. The metal will light up and give some hot spot to help light the stars. This should work "theoretically."

[Arthur]

Primes need to have a slaggy burn. Some have silicon metal which burns to globules of molten sand which ignite anything even after the flame has passed. Veline prime has wood meal to make slag as the rest of the hot comp burns, Fencepost prime uses diatomaceous earthto force a slaggy burn.

 

Basically a clean burn produces gas which carries away the heat, if there is molten slag then this holds the heat produced, close to the star, and passes fire more reliably.

[50AE]

So I guess this will serve me as a lesson for priming. Can you give me tips for the next time?

1. For a comp with high metal content, I should use green mix with coarse KNO3 and some metal powder, right? I don't have MgAl for now, maybe later. I have bright Al, atomized Al and zinc.

2. Is diatomaceous earth efficient enough if mixed with green mix? Can it be a hot prime?

Edited June 14, 2010 by 50AE

[dagabu]

I think we can all agree that a step prime was the prime of choice with silicon metal being the best option. Don't feel bad, I still have a 1000g of a very nice blue comp that will not light with any prime.

 

I will find something.... some day

[Cookieman]

So I guess this will serve me as a lesson for priming. Can you give me tips for the next time?

1. For a comp with high metal content, I should use green mix with coarse KNO3 and some metal powder, right? I don't have MgAl for now, maybe later. I have bright Al, atomized Al and zinc.

2. Is diatomaceous earth efficient enough if mixed with green mix? Can it be a hot prime?

 

 

Most stars with a high metal content I use BP meal with 5% -325 mesh Magnalium. If you don't have any MgAl this works really well for me.

 

Potassium perchlorate............................74

Red gum...............................................12

Hemp coal (or paulownia coal)................6

Aluminum (fine flake)...............................3

Potassium Dichromate.............................5

 

 

[Mumbles]

I've been under the impression that both diatomaceous earth and wood meal are in the primes to make the surface kind of fuzzy or rough, not to make slag. This helps to enhance ignition, not really increase flame/slag temperatures.

[marks265]

I've been under the impression that both diatomaceous earth and wood meal are in the primes to make the surface kind of fuzzy or rough, not to make slag. This helps to enhance ignition, not really increase flame/slag temperatures.

 

 

And to further this it is the silicon that makes the slag. I just picked up a box of DE to try the fence post prime. The DE should last about 20 liftimes!

 

Mark

[Bonny]

I've been under the impression that both diatomaceous earth and wood meal are in the primes to make the surface kind of fuzzy or rough, not to make slag. This helps to enhance ignition, not really increase flame/slag temperatures.

 

I 've always thought the same about the woodmeal, but as for the DE doesn't Gene on Passfire have some "explanation" as to its function?

 

And to further this it is the silicon that makes the slag. I just picked up a box of DE to try the fence post prime. The DE should last about 20 liftimes!

 

Mark

 

Had to get the big bag at a pool shop???

[Mumbles]

Oh yes, he has a theory behind the DE. Diatoms are the shells of microscopic algae with cell walls composed of silica. When they die, their cell walls remain. It's commonly used for filter media both in pools, and for other fine filtering. Besides being quite fine, and chemically inert, they also have microscopic holes in the shells. This enhances it's filtering ability. Gene seems to think that these microscopic holes draw in molten silicon dioxide via capillary action, and funnel and hold the molten material on the surface.

 

This has obviously never been proven. I think that it is a little more far fetched than simply being a rough surface, but you never know. For what it's worth, I've heard that wood meal in place of the DE works just as well. It's a pretty hot prime though, so it may just be a coincidence.

 

Mark, if you want to offload a couple of those lifetimes of DE, let me know. I've been wanted to try the prime, but don't want to get a whole bag given that I am going to have to take a 4-6 year pyro hiatus in about 4 months.

[dagabu]

...given that I am going to have to take a 4-6 year pyro hiatus in about 4 months.

 

What the heck??? Why are you doing that?

[Mumbles]

I'm off to become Dr. Mumbles. Given where I am moving to, manufacture wont really be an option.

[dagabu]

Awwwww Are you still going to bless us with your knowledge here?

[Mumbles]

Oh of course. I am going to try to still make it to WPAG shoots, but building will be a bit harder. We're getting into more on-site manufacture, so we'll see.

[dagabu]

Good! Ill see you on the 9th, I finally got the OK from the keeper of the calendar!!

[psyco_1322]

Here is a personal prime of mine. Numbers were converted to parts of 100. Just screen it together and coat on stars. Seems to light most things up well. I use fence post prime on some of the heavy metal colored stars.

 

SRI Prime

KNO3 - 64

Airfloat - 16

Sulfur - 9.6

D.E. - 5

Dextrin - 6.4