16 replies to this topic

[StevenRS]

I have a large Van Graff Generator, capable of producing static electricity with voltages exceeding 100,000 volts. Very low amperage though). I have tested a few compounds for static sensitivity, and here is what I found:

Bp- nothing. couldn't get it to light
Flash-21 out of 25 attempts. Scary.
KNO3/SU- surprisingly, 3 out of 25 times
Armstrong's- didn't need to do this, but just felt like it. 25 out of 25 (duh)

Any ideas on what I should test? I'm open to requests. Don't have that many chemicals, though.

[portfire]

I find this quite interesting,iv not seen anyone here do tests like this.Maybe you could do more BP tests to see if it will ignite

Edited by portfire, 06 April 2007 - 05:46 PM.

[pudi.dk]

Try a few variations o' flash if possible.

For example

KNO3+
Al
Mg
(s)

KClO4+
Al (atomized, german dark, indian blackhead etc.)
Mg

[BrightStar]

Steven,

This is a very interesting and potentially important thread - thanks for posting it.

My requests would be for the compositions I know to be sensitive, but find myself having to use on rare occasions:

70/30 perc / dark Al standard flash
50/50 potassium chlorate / antimony trisulfide dark flash e-match primer
70/30 perc / Na benzoate (each 100 mesh) whistle mix

I had read before that BP was insensitive to static - perhaps this is because of the conductive carbon content?

It would be interesting to estimate the energy you are applying per spark. If you have the dimensions of the dome of your generator, I can dig out the text books for the capacitance, which will get us within an order of magnitude.

Detail of your experiment method would be good. Does one single spark count as one test?

Keep up the good work!

Edited by BrightStar, 06 April 2007 - 09:38 PM.

[pyromaniac303]

I use an ESD simulator at work, which would be perfect for testing this. It has adjustable capacitance and resistance ouput probes, though it cost a few thousand £s and I doubt they would take kindly to me bringing any of the above comps in to work, and possibly damaging it.

The standard ESD model I use for a human to an object is 2000 ohms, 330 or 150 picofarads, however reading other websites out there they specify various other models you can use. The voltages usually are around 15kV maximum, however I can test up to 25kV.

If you could get hold of some extremely high voltage capacitors, and high voltage resistors you could easily construct a simple ESD simulator using you van de graaf generator, though it would be more useful to measure and control the voltage. This site maybe useful for some ideas : Amazing1.com

[StevenRS]

I will try the flash variations, but I don't have any E-match comp, or those chemicals, is it the same as the commercial kind? ( I have some of those).
I will post the updated list every time I post, if there is enough new results.

I was really hoping someone else could also do this, as I have VERY limited supplies.(I have to make my own potassium perchlorate). I might have to cannibalize commercial fireworks if we are absolutely sure the comp used, and I could test that.

My test- I place very small amount of comp on a piece of Al foil on the 12"dome, flattened to eliminate corona discharge, and repeatedly spark with a wire with a rounded off point attached to the lower terminal.

dragon eggs- 12-25 (new) (cannibalized)
Whistle- 7-25 (new) (cannibalized)
Bp- nothing. couldn't get it to light, 0-25. Did tests on various ratios, granulations, still 0%
Flash-21-25
- Mg-24-25
- kno3-17-25
KNO3/SU-3-25
Armstrong's-25-25

Edited by StevenRS, 07 April 2007 - 05:08 AM.

[king pyro]

I consider it a bit dengerous so I would suggest you to take enough safety precautions. I dont know why bp did not ignite. I would like to know the exact answer. BTW I apreciate(I think the spelling's wrong) your effort of trying to find answers yourself. And I heard that a van de graff generator is very rare to find. How do you have it?

[TzaRocket]

You can buy one online(lol) or you could built one yourself.And the black powder dosen't ignite from spark because it not pressed like in a firework engine,beside you need flame or temperature to ignite Bp(static doesnt work,but if it would work i would be all fried now because I made my meal black powder in a coffe grinder,for numeros times and it never ignits).

[StevenRS]

I got my generator off the internet a few years back, I think you can buy them now from United Nuclear, and for safety, I use a face shield and very small amounts of compounds, dots about 5mm across.

Something is telling me that a compound must have something electrically conductive in it to be very static sensitive, or it must have a very low ignition temp.

Because KNO3 surprised me so much I did it again, and the results were a little bit less, 2-25 (25 sparks)

Edited by StevenRS, 07 April 2007 - 07:28 PM.

[Frozentech]

I got my generator off the internet a few years back, I think you can buy them now from United Nuclear, and for safety, I use a face shield and very small amounts of compounds, dots about 5mm across.

Something is telling me that a compound must have something electrically conductive in it to be very static sensitive, or it must have a very low ignition temp.

Because KNO3 surprised me so much I did it again, and the results were a little bit less, 2-25 (25 sparks)

Do me a favor ? Try adding 6% moisture to your BP test sample and hitting it with the arc. I just want to confirm an old old US Bureau of Mines study that claimed 6% humid BP was the most sensitive to ignition by static discharge. Coincidently, many is the time I read of someone saying they add 6% H2O to BP in the ball mill. I use even less than that, just for pressing meal powder into pucks for corning.

[StevenRS]

Do me a favor ? Try adding 6% moisture to your BP test sample and hitting it with the arc. I just want to confirm an old old US Bureau of Mines study that claimed 6% humid BP was the most sensitive to ignition by static discharge.

Ok, I tried something new. I dispersed meal into the air, and sent ONE spark though the dusty air, and POOF! Fireball! So if Bp is in the air, it is drastically more sensitive to shock, 23-25.

Moist Bp did ignite, once, I'm guessing because the water was made conductive from the dissolved KNO3.1-25

Now one else has one of these!? Dang.. I was hoping someone with access to more chemicals could help...

In the meantime, I will continue to test the more common comps and variants.

Edited by StevenRS, 08 April 2007 - 01:24 AM.

[king pyro]

I got my generator off the internet a few years back, I think you can buy them now from United Nuclear, and for safety, I use a face shield and very small amounts of compounds, dots about 5mm across.

Something is telling me that a compound must have something electrically conductive in it to be very static sensitive, or it must have a very low ignition temp.

Because KNO3 surprised me so much I did it again, and the results were a little bit less, 2-25 (25 sparks)

OK

'COOL'

Edited by king pyro, 08 April 2007 - 10:43 AM.

[BrightStar]

Moist Bp did ignite, once, I'm guessing because the water was made conductive from the dissolved KNO3.1-25

Now one else has one of these!? Dang.. I was hoping someone with access to more chemicals could help...

Good call Frozentech... most interesting - maybe moisture makes BP more sensitive, but might also prevent the static building up when milling in the first place...

At 100,000 volts (seems a bit low by the way...) giving a 3.3cm spark length between smooth sufaces in dry air, your generator is storing approx. 0.1 Joules of energy in the 17 pico-farad 12" dome. This scales with the square of the voltage, so at the 500kV claimed for similar generators, it would be storing 2.5 Joules.

At lower voltages, 0.1 Joules is enough to fire a commercial e-match, so this is quite a jolt. I'd be wary that it might be the locally heated air in the spark that could be igniting the compositions, not the static discharge itself.

By comparrison, a human (150pF) walking across carpet can charge to 15kV, storing about 0.02 Joules.

Good stuff though...

[StevenRS]

Good call Frozentech... most interesting - maybe moisture makes BP more sensitive, but might also prevent the static building up when milling in the first place...

At 100,000 volts (seems a bit low by the way...) giving a 3.3cm spark length between smooth sufaces in dry air, your generator is storing approx. 0.1 Joules of energy in the 17 pico-farad 12" dome. This scales with the square of the voltage, so at the 500kV claimed for similar generators, it would be storing 2.5 Joules.

It did seem a bit low, I will try to verify that number, as it was from memory. Good guess, it is a 12" dome. EDIT: You were right, that is low, it is 250,000 volts. (still kinda wimpy)

No new tests today

Edited by StevenRS, 08 April 2007 - 03:28 PM.

[Wyvern]

hmm, this might be an opportune moment to dust off my tesla coil and do a few tests with that although it gives quite a bit more kick than a VDG does.

Edited by Wyvern, 08 April 2007 - 04:26 PM.