40 replies to this topic

[The Swedish Scientist]

A coating of BP, or some other pyrogen, on the outside of the graphite/NC layer is needed for reliable ignition.

OH FOR CRYING OUT LOUD!!!!

Simply add some Ti to your second layer of lNC (low-nitrated cellulose, ping pong balls) for sparks, and if necessary, use BRINK'S E-MATCH, which means that you make the slurry from graphite, potassium nitrate, Ti spunges and lNC. Just remember, whenever you use metal in an e-match, coat it with a neutral layer of lNC to keep it from comming into contact with sulphur.

[fishy1]

HEY!!! It isn't safe, it contains aluminium and magnesium, combining theese metals with sulphur, and they will get very angry... or at least rather sensitive to friction, as the sulphur will catalyse the metal's oxidation reaction. NEVER combine sulphur with metals if you want to be safe.

A) Pyrotechnics is never truly safe.
B) Aluminium is used with sulphur very commonly (BP style rockets or fountains with Al powder). It may be more sensitive, but you can still ram it.
C) I can't think of a comp ATMO that uses magnesium and sulphur, but plenty of stars are primed with BP, and some of them contain magnesium.

Edited by fishy1, 13 June 2006 - 09:14 PM.

[Mumbles]

There are a few in the greenman comp database that contain Mg and S. Some strobe stars.

[BrightStar]

I received a packet of ODA 50 guage match heads yesterday and made up some ematches to test. I could do with some advice please...



The first layer of pyrogen was BP meal + 10% dextrin, dampened with 25% IPA in water. Once dried, the second layer was added, similar to Alan Yates' forumla - 65% potassium perc, 20% red gum, 10% airfloat charcoal, 5% fine magnalium bound in NC lacquer. A final outer coat of NC lacquer alone was added for protection.

Continuity was tested - 1.4 to 1.9 ohms in each case. They were fired from a 1.5V AA battery for approx 1 amp current. Out of the 4, only 2 fired - the others just made a quiet 'tick' noise as the bridge wire snapped with no visible damage. It appears that the BP layer did not ignite. Videos of those that worked here:

Ematch test fire (Divx avi, 1026 KB)

Ematch test igniting visco (Divx avi, 1318 KB)

The leaflet with the match heads recommends using a minute amount of chlorate 'Dark Flash' for the prime, followed by H3/NC or BP/NC. I have neither the chems nor the desire to make 'Dark Flash', but with such a tiny bridge wire, can the ODA heads be made to work reliably without it ???

Edited by BrightStar, 07 November 2006 - 11:59 AM.

[Richard H]

I think you will need something more sensitive than BP for your prime. In commercial matches they use Lead Mononitrorescorcinate I believe. Indeed this is not something we should consider attempting ourselves.

Just be careful when working with the sensitive primes based on chlorates.

[delta_echo]

I have had great success with 50:50 Potassium Chlorate/Antimony trisulfide bound in ping-pong NC laquer. Reliably ignites with a standard 9 volt with almost no delay. I hate to say it, but I don't know the wire gauge of the nichrome as I bought so much of it so long ago. Pretty thin, though. I've used these with a 300 ft. 12 gauge cord with no problem as well. The power source in this case was a 12V car battery, however! I've lit off about 250 of these with only one failure (later found out to be a broken bridgewire), so as long as you pre-test them, you shouldn't have any failures.

As has already been mentioned, this mix contains a chlorate and a sensitizer/fuel, so care must be taken. Bound in laquer, however, seems to desensitize the mix from pressure and friction.

[BrightStar]

I think you will need something more sensitive than BP for your prime.

Thanks Richard (and delta), the potassium chlorate / antimony trisulfide / NC lacquer Dark Flash looks to be the way to go, though I promised myself never to have chlorates in the workshop so the matches will have to be made somewhere else.

If anyone has an alternative solution, it would be great to hear it.

It was a bit frustrating to finally have a reliable electrical circuit with the ODA heads, only to find my pyrogens didn't measure up... especially since BP ignites at 300 - 400 centigrade and the nichrome is is melting at ~1400... such is life

Edited by BrightStar, 07 November 2006 - 05:14 PM.

[Frozentech]

Thanks Richard (and delta), the potassium chlorate / antimony trisulfide / NC lacquer Dark Flash looks to be the way to go, though I promised myself never to have chlorates in the workshop so the matches will have to be made somewhere else.

If anyone has an alternative solution, it would be great to hear it.

It was a bit frustrating to finally have a reliable electrical circuit with the ODA heads, only to find my pyrogens didn't measure up... especially since BP ignites at 300 - 400 centigrade and the nichrome is is melting at ~1400... such is life

I use the same primer, got it from a Skylighter newsletter along with directions for use. I was using the same 'chip' match heads as you until recently, I decided to shell out a little more money and bought some of the prewired ones from Skylighter, with the plastic shrouds.

I've fired them through 500 foot of twinlead 22 gauge as a test, using my 18VDC box ( 4 each 9 VDC batteries in series/parallel to up the current since I shoot in cold temps ) with no problems. I do like the nice sustained flame you got from your ematch there, that lasts longer than mine, which go with a decided *pop* and burst of flame for only 1 second. I might do a 2nd layer of bp/nc slurry and see if that lengthens my burn times. Hasn't been a factor yet since I only ignite QM with them (so far ).

[pyrotrev]

I think you will need something more sensitive than BP for your prime. In commercial matches they use Lead Mononitrorescorcinate I believe. Indeed this is not something we should consider attempting ourselves.

I've been told other formulations use azide/perchlorate mixes. Thanks Rich though for suggesting to me why lead resorcylate is a controlled substance!

Just be careful when working with the sensitive primes based on chlorates.

Would there be any mileage in a standard perchlorate flash mix perhaps?? still nasty stuff, but when mixed wet (in a NC laquer - tiny quantity only!!!!!!) it has to be safer than anything with chlorate, particularly given perc flash's reluctance to explode when in a solid form.

[BrightStar]

Well, being in a stubborn frame of mind this week, I tried a second batch using the same 2 layers as mentioned above. This time, the BP was the finest I could make, with only 3% dextrin milled in and dipped in several thin layers to ensure good contact. Surely 1400C melting nichrome would ignite this!

The results were at least consistent:



The matches all popped with 1A current, but the BP just shattered the outer pyrogen, so there was almost no flame at all

So guys, if anyone in the UK is feeling generous and could trade or barter a very small amount of potassium chlorate and antimony trisulfide, please feel free to PM me and state your terms! I'm determined to make these things work...

Edited by BrightStar, 13 November 2006 - 08:22 PM.

[BrightStar]

Apologies for the double post - but we have progress here

A UKPS friend kindly sent me some samples of potassium chlorate and antimony sulfide. I mixed a 5g batch of dark flash prime, using a minimal amount of 5% NC lacquer in acetone to bind, keeping it 'wet' at all times. This mix was used to coat the tips of the ODA heads. Once dried, they were coated liberally with a second layer of BP meal + 5% magnalium bound with 5% NC, dried over night. A final layer of thin NC lacquer alone was applied to protect them.

This method has worked 100% reliably, giving instant ignition from a 1.5V AA battery. I have had the matches ignite sparklers, visco and test devices with no problems. The cost is about 10p each (re-using the lead wires), so they present an expedient option for igniting garden Cat 3 shows.

I burnt the remainder of the dark flash slurry (still wet with acetone) to safely dispose of it and it vanished in a huge jet of white flame. This stuff is not safe to store, must not be allowed to dry out and full PPE must be used when handling. But it does work for very well for the tips of the matches...

Edited by BrightStar, 14 December 2006 - 09:33 PM.