78 replies to this topic

[digger]

P.S.

Whilst the Veline prime is a nice hot prime, there is no need for such a complicated prime which has the nasty potassium dichromate in it. Simple BP/charcoal/Silicon primes are more than good enough for pretty much any app, and they are dark enough.

D

[Peret]

Seymour, the one I'm having most trouble with is Veline green. They always light but they're a bit slow starting, so the effect is a silver star changing to green at some height. It's not an unattractive effect, just not the one I'm looking for.

Brightstar, this is the first time I've tried these small mine stars so I just went at them the same way I make shell stars. The brightness of the prime was a surprise. They're a bit small for a multi layer prime, and anyway, I want them burning green immediately... Ok, maybe the first half intermediate stage would do it greenishly. I shall experiment.

Digger, I hear ya, but as long as one has the chemicals it's hardly any more trouble to use 6 or 7 ingredients than 4. I admit that adding dichromate is my least favorite part of the job, except for the bit about milling the crystals to fine powder, which is worse. That stuff goes everywhere.

[digger]

Digger, I hear ya, but as long as one has the chemicals it's hardly any more trouble to use 6 or 7 ingredients than 4. I admit that adding dichromate is my least favorite part of the job, except for the bit about milling the crystals to fine powder, which is worse. That stuff goes everywhere.

What can be easier than using some meal powder which you have to make anyway and just adding silicon? Fast, hot, and no colour. My main point was why use dichromate if it is not really required? minimise risk. I do use it but only when absolutely necessary.

How fine is your barium nitrate? as it is often supplied as free flow which is granular, which really needs milling? (I know granny and eggs)

Edited by digger, 14 May 2010 - 06:22 AM.

[seymour]

I definitely agree with both Digger and Brightstar.

Dichromate is a very useful chemical for coating Mg and MgAl for use with Ammonium perchlorate, but in other situations the benefits are minimal, and avoidable. If you want to add a catalyst to your prime, which in not neccisary, I would choose Iron oxide, Chrome oxide, Manganese dioxide and Copper oxide over Potassium dichromate.

Since you have the silicon, you may as well just use that with black powder. In fact, it is more effective, and probably less effort to simply use 'green mix', the black powder chenmicals simply screened together instead of ball milling. It does not burn as cleanly, and thus you get more dross sticking to the star.

If this fails you do not have a thick enough prime layer, or your star it unusually unignitable, and it's time to step prime.

[seymour]

I swear I only clicked 'post' once...

Edited by seymour, 15 May 2010 - 10:37 AM.

[BrightStar]

The Chinese seem to have no difficulty with colours that 'snap on' almost instantly even with a hard break. This leads to speculation that they must have a secret 'super prime', and we devise new mixes in the hope of finding it. Some (e.g. Fence Post Prime) are indeed pretty good, but not by any means infallible.

In reality I'm sure their trick is to combine the correct colour compositions with the right primes, traditional techniques and burst strengths for each device they make. Tested over many generations, they find an optimum combination. This of course is all just part of 'The Art'...

Edited by BrightStar, 14 May 2010 - 03:38 PM.

[digger]

The Chinese seem to have no difficulty with colours that 'snap on' almost instantly even with a hard break. This leads to speculation that they must have a secret 'super prime', and we devise new mixes in the hope of finding it. Some (e.g. Fence Post Prime) are indeed pretty good, but not by any means infallible.

In reality I'm sure their trick is to combine the correct colour compositions with the right primes, traditional techniques and burst strengths for each device they make. Tested over many generations, they find an optimum combination. This of course is all just part of 'The Art'...

They seam to use fast thin layers of prime from whaty I have seen

[BrightStar]

They seam to use fast thin layers of prime from what I have seen

A couple of Chinese 3" Green Peonies I filmed displayed the full colour only 200ms after burst, so it's probably a fairly thin and fast prime.

My point is that there's probably nothing exotic (and certainly nothing magical) about the prime used. The shells are made with the right star comp that's just easy enough to ignite, a prime that's just hot enough without being too slow, layers applied to just the right thickness, and a burst that's strong enough to be impressive without blowing everything blind.

It's this balancing act of many variables that forms the art.

[a_bab]

Actually most of the chinese shells are thought to be "overbroken" (boken too hard for my taste and not only). They really pack a bang, especially the 3" and 4". The stars are propelled really fast, but they burn fast too (usually 1-2 seconds). I would't wonder if there is some chlorate in these stars, since there were batches of chinese BM discovered to have chlorate in them (stepping hard on these would set them off).

The experience chinese have is theirs greatest plus for sure. I myself find the chinese items too "comercial", the maltese shells being my favorites (where art combines with love).

[Potassium chlorate]

Chlorate stars are wonderful, if you just avoid sulfur, sulfur compounds and ammonium compounds.

[Vic]

Priming can be as complicated as you want to make it or as I feel at times aesthetically necessary to the ignition of the star formula. When Shimizu says step prime I believe it's an important part of the visual effect intended, as in the subtleties of colour changing relays.

Needless to say if you are looking for near instant ignition and colour I would go the silicon route, but am I right in thinking that the silicon globules can still be blown off fast moving stars?

[Mumbles]

Ofca introduced some "negative" primes. Where they are oxygen deficient, and actually burn faster when propelling through the air. The compositions are pretty much spider star formulas. I bet you could add some metal to them if you're having issues still.

KNO3 - 15
C - 9
S - 2
Dex - 2

That is a pretty standard spider star, and very pretty on it's own in stars. It is normally ball milled, but I don't know about the primes.

Having struggled with priming for the last few years. I am rather convinced that the chinese shells have to use something similar. Something that is designed to burn at high speeds.

Edited by Mumbles, 14 May 2010 - 09:48 PM.

[Peret]

How fine is your barium nitrate? as it is often supplied as free flow which is granular, which really needs milling?

Milled to -325. I've had problems getting it - it's not that I can't buy it (I live in the USA), it's that many suppliers won't ship it, and picking it up is a long drive - like a round trip from London to Vienna. I either had to buy really expensive laboratory reagent, crystalline, or make do with carbonate. This year I found a new vendor who will ship, hallelujah, though he doesn't mill it until you order it so it takes an extra week. It does tend to get lumpy, but I just knead the lumps out in a plastic bag and then put it through 100 mesh. I bought some barium chlorate while I was at it, since it was available, but I haven't tried it yet.

I'll try a bp-silicon prime this weekend.

[a_bab]

Just mix up few grams of your barium chlorate with shellac, red gum, even dextrin in say 80:20 BC/fuel, light it and you'll grin the whole day.

[Potassium chlorate]

Barium chlorate is my absolute favourite. The absolutely best for green, especially Bengals, and the most ignitable in stars. Barium chlorate stars with Mg or MgAl don't really need priming. They catch fire very easily.