78 replies to this topic

[scientific.pyrotechnics]

I had considered that. I also considered the low self-ignition temperature being within reach of friction generated heat. Lactic acid isn't strong enough to protonate the chlorate to chloric acid, which is what causes all the issues from the generation of Chlorine dioxide, so I don't know how reliable that is. Then again it only takes a minute amount to increase sensitivity, but I have a hard time believing a weaker acid, probably present in smaller amounts would cause it to become more sensitive than sulfur/chlorate.

Any Acid even organic such as Ascorbic or Tartaric acid will make extreme sensetive mixtures with Chlorates

If sulfur was totaly free from H2SO4 mixing Chlorates with it should be fine, i can't explain the problem with Sulfides though

[seymour]

I think Mumbles is referring to acid-free Sulfur.

[50AE]

Any Acid even organic such as Ascorbic or Tartaric acid will make extreme sensetive mixtures with Chlorates

If sulfur was totaly free from H2SO4 mixing Chlorates with it should be fine, i can't explain the problem with Sulfides though

Well, I have a small batch of very pure lab grade sulfur (99.95%) and I've tried to get an acidic pH by putting some in water and stirring, but I didn't succeed.
But it's still very sensitive. You maybe can handle chlorate mixtures with it with caution, but you should always watch out.

[BrightStar]

Furthermore, how do you execute step priming? I´m really curious how this is done best

If you're rolling stars it's easy. Make up a simple BP prime (I'd use a mixture of scratch mix green meal and milled meal powder). Roll up your (non-chlorate) colour stars. Make a mixture of 50/50 colour comp and prime and roll this on, then add a layer of BP prime only. You can let the stars dry between prime layers (I do, just for neatness) but it's not really necessary. Some people advocate more of a graded transition - say 75/25 colour/prime, 50/50, 25/75, 0/100 for very hard-to-light stuff.

For dried pumped stars, a nice method is to spray them with gum arabic solution and just hand roll in the prime.

[AdmiralDonSnider]

If you're rolling stars it's easy. Make up a simple BP prime (I'd use a mixture of scratch mix green meal and milled meal powder). Roll up your (non-chlorate) colour stars. Make a mixture of 50/50 colour comp and prime and roll this on, then add a layer of BP prime only. You can let the stars dry between prime layers (I do, just for neatness) but it's not really necessary. Some people advocate more of a graded transition - say 75/25 colour/prime, 50/50, 25/75, 0/100 for very hard-to-light stuff.

For dried pumped stars, a nice method is to spray them with gum arabic solution and just hand roll in the prime.

Well, I´m using cut stars most of the time. Doing so I consider it very inexpedient to wet already dried stars again to add a second layer of prime. Shimizu mentions that priming stars is not easy once they´re dry, as the solvent will be absorbed very rapidly and they´ll quickly go out of shape. He says that speed is essential.

However, wouldn´t it be nicer to make a slurry for the first stage and then dust the still wet stars with the dry second stage prime. Just wondered how you do it - in case you are not using round stars - method a, b or c?

[digger]

Well, I´m using cut stars most of the time. Doing so I consider it very inexpedient to wet already dried stars again to add a second layer of prime. Shimizu mentions that priming stars is not easy once they´re dry, as the solvent will be absorbed very rapidly and they´ll quickly go out of shape. He says that speed is essential.

However, wouldn´t it be nicer to make a slurry for the first stage and then dust the still wet stars with the dry second stage prime. Just wondered how you do it - in case you are not using round stars - method a, b or c?

Yes this is more difficult with cut stars but I have primed pumped cylinders and cut stars in a star roller without any problems, however I mainly only use round stars these days.

My method for step priming is to chuck the stars in the star roller when dry give them a quick wetting with whatever solvent is appropriate for the binder in the prime add a mix of 50% prime and 50% composition, re-wet, add etc more until I have a layer about 1/2mm thick then I add a top coat of the 100% prime then maybe a a very small amount of meal in a similar fashion without drying in between.

I have had to go even further on a couple of stars and use a first layer of 75% comp 25% prime, second layer 50/50, third 25/75 and forth 100% prime. However after investigation on these particular stars it was found the problem was when they were blasted out of the shell they were being blown out (showed up when I looked at the video frame by frame). So it was more a problem with the composition than the prime. The extra thick prime gave them time to slow down enough so they were not blown out.

Edited by digger, 02 July 2009 - 05:49 PM.

[scientific.pyrotechnics]

I think Mumbles is referring to acid-free Sulfur.

Acid free Sulfur is like Oxide free Peroxides. dosent exist so far i know

[sir steve]

Thanks. That´s some useful information and sounds like good news. However, I´ve got two more questions. You say you step prime e.g. Independence Red: What compositions do you use for the layers?

Furthermore, how do you execute step priming? I´m really curious how this is done best; assume there are several possibilities:

a.) Spray the stars and shake in dry first stage prime. Let dry. Spray again and roll in second stage prime.
b.) Make a slurry (Toro-like) from the first stage prime and coat the dry stars by rolling them in the slurry. Roll in second stage prime while first layer is still wet.
c.) Spray the stars and shake them in first stage prime. Shake in 2nd stage prime immediately. Don´t know if that really gives good results but some people argue in works.

Thank you for your help!



Why use a colored or brocade prime? The effect will be very short lived, or am I wrong?

However, that brocade style prime sounds interesting. What kind of stars is it used for?

The green is not used as colour it is just cheap and hot, The silver brockade makes a very
beautiful star. All depends on The charcoal and the Al powder. A fast pine charcoal meal powder with cut aluminium 300 mesh.
A 5mm electric green or red core rolled up to 10mm is realy nice.


Another very effective prime for chlorate stars is KClO3 52, KNO3, mixed charcoal 40.

Steve

[starseeker]

Both expensive and unnecessary. And I don't see why you put sugar in there.

For perchlorates and nitrates a basic BP formula with 10-15% Magnalium will light most stuff, and 10-15% silicon will light basicly anything. And chlorate stars light easily anyway, a couple layers of sulfurless BP with some metal should light them with no problems.

Do you then roll a layer of b.p over the top or just use the one layer of prime ?

[sir steve]

I will take back my green prime. The reason we use it is there is normally some hanging around.
This breaks my own rule "don't store loose powders" The rule is loose powder make into stars ,Stars when drymake into fireworks. I was not having a personal go at scientifcpyro but a general dig at over complicated formulas.one 19th century recipe calls for an alcoholics urine. I will save a fortune on MEK. Steve

[Sambo]

Do you then roll a layer of b.p over the top or just use the one layer of prime ?

I've found the one layer of prime to be sufficient, I use 5% Si and 5% dark al in a lightly milled bp.
I wet the stars quite well before priming to get a good contact between the prime and star comp, for the last bit of prime I try to spray as little water on as possible to get a “fuzzy” look to the outside.

[Vic]

Quick fix primes containing Si and dark al sure save time and are reliable but step priming with meal and the star comp give more of transitional affect from the initial break although this happens within a split second but this maybe a important part of the original formulas effect.

[dr thrust]

So what ? Does the composition say to put sulfuric acid in ? This is off topic.

not really off topic i guess sulphur ( which may be present in another part of your device) could react with the wet hygroscopic chlorate /sugar mess and go off in your workshop whist your fast asleep, but i guess that's never happened before in the history of firework making... and that's why the industry still uses it.. not.
seriously, chlorate's in fireworks, old hat and whats the point?
old out of date shite!

Edited by chris m, 02 July 2009 - 11:57 PM.

[50AE]

not really off topic i guess sulphur ( which may be present in another part of your device) could react with the wet hygroscopic chlorate /sugar mess and go off in your workshop whist your fast asleep, but i guess that's never happened before in the history of firework making... and that's why the industry still uses it.. not.
seriously, chlorate's in fireworks, old hat and whats the point?
old out of date shite!

Stop inventing these ideas, did I say that I'll be putting sulfur in my device ? Damn !
You safety maniacs have nothing to do but to harass people using chlorates, while you don't even have any idea about them - their knowledge and their ideas.
If you have money to buy perchlorates, then good, best wishes for your pyro manufacture.
But when you don't like chlorates, just don't use them and that's all, because you say "old hat and what's the point". This doesn't mean everyone shouldn't use them.

From Fireworks, the Art Science and Technique by Takeo Shimizu :

When it was used for firework compositions,
high temperature flames which gave epoch-making beautiful colours of
fireworks, became easily obtainable. But it has been a matter of sincere
regret that potassium chlorate has often caused explosive accidents.
It would be ideal to reject this material from fireworks, but it is quite
difficult even at present, because no other oxidizer can surpass potassium
chlorate in burning speed, in ease of ignition or in noise making, using
the smallest amount of composition. The match head composition cannot be
made without it; it is also absolutely necessary for some dye smoke,
small crackers and various kinds of toy caps.

[digger]

I agree chlorates are great for many things. I have used them extensively in the past (and still do in certain comps).

My only concern in my main workshop is that is now contaminated with sulphur so I can't use it for chlorate comps so I have a small shed specifically for the purpose. Ultimately in the UK it is illegal to mix chlorate with sulphur.

I don't agree that perc is more expensive though. From a true chemical supplier perc is now cheaper than chlorate!