15 replies to this topic

[pyrochris732]

per 100 grams of "green mix" how much magnalium would you add to make it hotter for a prime? I would be using 325 mesh magnalium so would 10% be ok? I cant seem to find good info on how much to add. I also have 30/60 mesh MgAl but I think the finer stuff would be better, right?

Thanks a lot,

Chris

[Ventsi]

That should be plenty in there. Silicon is a better alternative but the stuff you have should be plenty hot.
What is it you're trying to light?

[pyrochris732]

certain types of stars, and to use as a prime on the tips of my time fuse and cross match

[Mumbles]

I generally start around 5 or 6% metal, but 10% should work too. The other thing you may want to try if stars are being difficult is step priming. I've been avoiding it for years, but it looks like I am going that direction. It is actually easier than the other priming I was doing. Fuse should be fine with just BP alone.

[al93535]

I add 5% of -325 mesh mgal to my prime to get it nice and hot.. seems to light just about everything for me.

[pyrochris732]

i just got some silicon. Is silicon better than Al or MgAl, and if so, why? Would the green mix with Si be a nice hot prime for colored stars?

[Mumbles]

The advantage that silicon has it that it's combustion product (silicon dioxide) remains liquid, and sticks to the star surface, which helps to enhance ignition. Green mix with silicon should light just about anything. You may have heard of fencepost prime. It's a slightly modified BP with silicon and diatomaceous earth. It will light most anything.

[swervedriver]

I just want to share that when I've added to much metal to primes, the primes themselves become more difficult to light. Specifically fence post and pinball primes with 10% metal. Silicon seems to be even more prone to this than fine MgAl or Al.

Anyone else have this experience too?

[TigerTail]

I have some questions regarding primes. Please excuse me if it has been discussed before; I tried searching but there are too many threads to be sure I looked all(err... looked all or looked at all?).

Firstly, does dextrin play any real role in primes? Does it really help to have a very hard layer of prime? I assume it maintains the rough surface created while priming so it doesn't just fall off and smoothen while handling the stars. Correct?

Are there any simple substitutes for diatomaceous earth?

I have read about MgAl or dark Al being added to primes. Can I use 325 mesh spherical Al?

What is the best prime out of green mix, slow BP, and fast BP? By personal experience, I have seen that slow BP ignites much more easily in a pile compared to green mix or fast BP, but it probably burns cooler than fast BP, and these both leave less slag than green mix.

Lastly, why are compositions like C6, C8 and TT not good enough for priming? I understand they burn cooler but they sure leave smouldering sparks.

[Mumbles]

Dextrin adheres the prime to the surface. Many other binders work as well. Without it, the prime may fall off as you mention, during handling. I'm not sure if it does anything to make a rough surface though.

I don't know of any direct substitutes for diatomaceous earth. It is quite cheap however, but I am sure it's not available everywhere. It may also be called Celite or a variety of other names. Perhaps search for it under a few of these other names. Wood meal, which is fine sawdust, has been used in other compositions to make the surface rather fuzzy. This may be a possibility to use.

Yes, atomized aluminum can work in primes.

My personal preference is for green mixed BP in primes. There is debate about this of course. Some think that a faster BP will burn hotter, and be less prone to blowing out and thus light stars easier. Others argue that the slower burn of green meal will allow more time for it to light and that the slag helps it light.

Some people do use various streamers as primes. I find C6 or spider formulas to work typically better than the others. It's almost impossible to blow them out or have them not light. They light things probably just as well if not better than meal, but also typically need to be milled to function properly. When you start watching a lot of pyro videos, you tend to notice over the years that there really are a lot more streamer to color shells than other varieties. When done properly they look very nice. However, they are also incredibly easy to get to work. Not necessarily work well (simultaneous color change), but still on a basic level function. This is because the streamer lights extremely easily, and then can light the color at a later time when the star has significantly slowed down. I still like them, but honestly do get kind of sick of always seeing them. I also feel it cheapens the effect somewhat knowing that it is a way around proper priming.

[Peret]

I am quite disillusioned with metal-fueled primes. I don't like the bright white flare and I had far too many stars that didn't ignite, particularly barium nitrate comps. The prime that works best for me is 20% meal powder, 40% KNO3 and 40% silicon, with a few percent extra dextrin. I've had no blinds at all since I switched, and the prime burns with very little light.

[Ralph]

I am quite disillusioned with metal-fueled primes. I don't like the bright white flare and I had far too many stars that didn't ignite, particularly barium nitrate comps. The prime that works best for me is 20% meal powder, 40% KNO3 and 40% silicon, with a few percent extra dextrin. I've had no blinds at all since I switched, and the prime burns with very little light.

I tend to use 5% Dark al (or Si my prime container usually ends up with a mix of both as I top it up when it gets low) and there is no bright white at all when it burns

[Givat]

I invented this prime to use in most of my non chlorate stars:
50% BP
50% MgAl flash (6 KNO3/5 MgAl/1 sulfur)

if you calculate it's 20% MgAl in the comp.

[oldguy]

I don't know of any direct substitutes for diatomaceous earth. It is quite cheap however, but I am sure it's not available everywhere. It may also be called Celite or a variety of other names. Perhaps search for it under a few of these other names.

Filter grade Diatomaceous earth can be found at about every large swimming pool supply place in the USA for about a $1 a pound in 25 or 50 lb bags.

Edited by oldguy, 25 August 2011 - 02:25 AM.

[oldguy]

The typical chemical composition of dried diatomaceous earth (DE) is 80 to 90% silica, with 2 to 4% alumina, 0.5 to 2% iron oxide & the remainder is multiple trace elements..

Sodium carbonate "soda" serves as a flux to lower the temperature at which the silica melts. Soda glass has a much lower melting temperature than pure silica, and has slightly higher elasticity.

Typically, manufactured glass contains around 15% sodium oxide, 70% silica and 9% lime. So, I am wondering what could be added (in proportion) along with DE in a prime type composition to lower the melting temperature of the DE, without disrupting or compromising the remainder of the prime composition?

Edited by oldguy, 25 August 2011 - 11:46 PM.

[Potassiumchlorate]

Theoretically silicon primes should ignite stars better than MgAl primes, but I'm not sure of this. I have trouble igniting my parlon bound stars even with silicon prime.

One really hot prime, that was invented for ammonium perchlorate stars but should work for other kinds of stars too, is Hardt Prime #6:

Potassium perchlorate 37
Charcoal, airfloat 30
Lead tetraoxide 22
Silicon 7
Dextrin 4

Not very environmental friendly, but it produces molten lead, which is heavy and sticks to the stars.

Edited by Potassiumchlorate, 06 November 2011 - 11:19 AM.