Sciencemadness Discussion Board - Photography of high explosives on glass

Photography of high explosives on glass

hkparker - 29-7-2011 at 23:52

Hey everyone!

I normally don't like working with high explosives because I don't think the fun is worth the danger, but I recently started a cool project with a friend. This is my second encounter with HE.

A friend of mine does really cool high speed photos of breaking glass. Photos that capture the moments where the cracks are running through the glass but haven't destroyed the whole thing yet (usually cups and plates). He usually drops the glass, or drops something heavy on the glass, but he wanted to do something more creative this time. HE came to mind.

Explosive of choice: Silver Acetylide. Our method was to make a light proof plywood box, 2'x2'x3' with a top we could pull off. A hole was drilled in the back and wires from a model rocket igniter were ran through. The camera was set up behind a plexi shield and controlled with a little processor outside the box. The shutter was opened for 6 seconds, in which time I would detonate the blast. The flash was set to trigger 8 miliseconds after it heard the bang.

The silver acetylide was added by taping it and an igniter to the bottom of the glass with aluminum tape.

Were not done yet, but things are going really well. There isnt much noise made by the explosive surprisingly, I'm using about 100-200mg.

I will be uploading a full video of the process when we are done, until then, <a target="tab" href="http://www.flickr.com/photos/whosdadog/5989069729/in/photostream/lightbox/">here is a link to out first really successful picture</a>.

quicksilver - 30-7-2011 at 07:05

High-speed photography of that level has several dependencies & I respect the man for giving it a try. One of the most challenging issues is lighting origin. If you notice he has placed his light from the front to rear during his sequence.
Front lighting is not ideal for that type of HS photography. However if he examines his work closely he will see the challenge - the origin often needs to come from the initiation itself (& a Polarized filter). To get the "feel" for lighting standards, it's often easier to begin with minute levels alone (no object being affected) and work with the only light available. Some say the lighting could original from behind/beneath; but that's very difficult. A few mg of flash powder can teach a great deal of the HS photography lighting demands. I have attempted this quite some years back and got some interesting effects.

EDIT: (1530)

Personally, I would be very interested in what techniques you try.
I didn't know you had a deeper interest in photography. I will try to hunt down some of mine & post them also. You will clearly see how I learned from my enthusiasm early on. My first ones looked much worse than yous.
IF you are using a camera w/ no ability for attachment of a polarized lens; experiment, as (IMO) it makes a real difference.
I cut ambient lighting & results got much better.
This can be another area where film is a blessing. (I tried both but it was a long while back and the digital I was using was low grade compared to today).
Another area I happen to enjoy is photo- micrograph of crystalline structure & there back-lighting can't be helped. The crystal defuses the light and color bleaches.

[Edited on 30-7-2011 by quicksilver]

whosdadog - 30-7-2011 at 19:30

I'm not sure what you mean by using flash powder. Are you saying use the flash powder as the light source to illuminate something breaking, or just take pictures of the flash powder? I'm not sure for what duration flash powder produces light is, but my flash only produces light for 31.25 µs (microseconds). If I used anything slower, the image would blur.

Also, what effect would the polarizing filter have on the photos? And there is no ambient light. The photos are taken in a light-tight box.

The rest of the photos are on here http://flic.kr/s/aHsjjEAvQp

hkparker - 30-7-2011 at 19:50

whosdadog = my friend (duh?). I will upload a video of our project later. Thank you for your input quicksilver.

EDIT:

Quote: Originally posted by quicksilver

I didn't know you had a deeper interest in photography.

I'm not really the photo guy to be honest, that's whosdadog. All of the equipment was his and he set it up, I'm just providing the explosives

<a target="tab" href="http://www.youtube.com/watch?v=MG1bXlutrWE">A video of our project</a>.

[Edited on 31-7-2011 by hkparker]

quicksilver - 31-7-2011 at 04:54

@hkparker : are you using an electrically triggered mechanism? I worked with that and what I wanted to do was to be able to adjust down past the trigger - that's quite a challenge.

@ whosdadog:
(As an example) "Shattered wine glass" appears to have the light approach from the front.. You have no other illumination source than the energetic? You're shooting in a darkened medium? It's a very interesting effect as the light appears to project ->to the subject.

You certainly can get light in the microseconds from flash & it's remarkably controllable for a setup. (There is no power feature to speak of but you get light so as to work on timing). The more complex feature is electrical ignition / timing. By working with it you can push the "shatter-shot" to the beginning or end of it's movement. I love this stuff.
Polarizing can yield both the elimination of "wash-out" in a close shot and interesting ideas such as star effects, etc.

EDIT:
I should have written an addendum to this but was hurried.
Common 70/30 flash is a bit slow. One needs to work with it to get enough light and speed of ignition to get the best photo. The particulate must be super fine; of single micron size (2-9 um) in all chemicals of the composition. There is better results with something that would lower the temp of ignition. Sulfur flour might be acceptable but there are better. A discussion in another thread on Boron may not have mentioned that it's often in a very small particulate. The use of the "SMD Ignitor" is fantastic for that application as it focuses the heat right where you need it and without excessive componentry development (such as cap discharge or high amp sources). The better shots I had gotten were in a "flat black" medium or something to cut ANY reflection.

[Edited on 31-7-2011 by quicksilver]

hkparker - 31-7-2011 at 10:34

Kinda. We are using model rocket igniters, which are really thin wires coated in an unknown pyro mix, and I'm not sure what sets of the silver acetylide because when I examine the igniter after the explosion it looks like most of the material on the igniter hasn't burned.

whosdadog - 31-7-2011 at 22:17

I understand that flash powder could work when I am using an explosive to destroy the items, but are you suggesting that I use flash powder when I am dropping or using a gun to destroy the items? I have no idea how I would ignite the flash powder using a projectile from a gun. Also, what other direction should the light be coming from? If I do it from the side, the item will cast a shadow on itself.

Bot0nist - 1-8-2011 at 03:31

Quote: Originally posted by hkparker

Kinda. We are using model rocket igniters, which are really thin wires coated in an unknown pyro mix, and I'm not sure what sets of the silver acetylide because when I examine the igniter after the explosion it looks like most of the material on the igniter hasn't burned.

I have noticed this as well on many occasions. It was always my belief that the primary is initiated as soon as the the bridge wire (that's coated in a low-temp pyro mix) starts to heat up from the resistance. It is my thinking that the silver acetylide is detonating and severing the connection to the igniter before it gets hot enough to burn the pyro composition. One would think the heat of the detonation would be sufficient to burn up the dipped ends, but in practice I often observe seemingly new looking igniters after initiation, albeit pretty bent up though.

Excellent project by the way! When you play with energetics, you do it with class.

[Edited on 1-8-2011 by Bot0nist]

quicksilver - 1-8-2011 at 06:39

Quote: Originally posted by whosdadog

I understand that flash powder could work when I am using an explosive to destroy the items, but are you suggesting that I use flash powder when I am dropping or using a gun to destroy the items? I have no idea how I would ignite the flash powder using a projectile from a gun. Also, what other direction should the light be coming from? If I do it from the side, the item will cast a shadow on itself.

I used SMD resisters at very low resistance and NC lacquer to coat them with a very hot flash; another small amount of flash was used for a "ping-pong" ball shot I photographed and I get the edges of the ball moving away cleanly. - came out very well for an armature. The ping pong ball was just delicate enough to balance the energy of the energetic so the picture came out nicely. The switching of both camera and ignitor were in unison.
Finding objects "in balance" with the the energy also appears to be a very rewarding thing.
Painting the whole of the "scene" flat-black is excellent becasue it reduces washout. Shadow does get sharp: yet it looks OK.

hkparker - 2-8-2011 at 00:50

Quote: Originally posted by Bot0nist

It was always my belief that the primary is initiated as soon as the the bridge wire (that's coated in a low-temp pyro mix) starts to heat up from the resistance. It is my thinking that the silver acetylide is detonating and severing the connection to the igniter before it gets hot enough to burn the pyro composition. One would think the heat of the detonation would be sufficient to burn up the dipped ends, but in practice I often observe seemingly new looking igniters after initiation, albeit pretty bent up though.

My thoughts/observations exactly

Quote: Originally posted by Bot0nist

Excellent project by the way! When you play with energetics, you do it with class.

thanks!

<img src="http://i1091.photobucket.com/albums/i387/Default1user/9186377.jpg" height="269" width="215" />

whosdadog - 2-8-2011 at 01:38

Quote: Originally posted by quicksilver

I think I understand. You use the NC coated resistor to generate enough heat to set off the explosive. What I'm still confused with is the switching of the camera and the ignitor simultaneously. Most SLR's have a shutter lag of 150ms, so if you use the same switch to trigger the camera and the detonation, the camera will trigger 150ms after the detonation has begun. In addition, if you are triggering the camera, rather than a flash, the fastest you could set the camera would be 1/4,000th, which in my experience would lead to blurring of the item in the photo. When I shoot I am shooting at 1/32,000th. I think you are using flash powder to expose the scene, as you mentioned in a previous post, but I am also confused on the delay with that. I used a delay of 10ms between detonation and flash, and I used a microprocessor for that. If you are using pure mechanical connections, I do not see how you could reliably time the gap between the detonation of the explosive and the ignition of the flash powder, and timing both of those around the 150ms delay the camera has.

quicksilver - 2-8-2011 at 05:53

There's an (fairly old fashioned) "frame grabber" that I use with digital that can also work with autofocus Cannon bodies. I have tried the one crafty mechanical method also & indeed, even modern SLR's have too much shutter lag. I'll find the URL for what I bought (it's still around).

watson.fawkes - 2-8-2011 at 07:46

Quote: Originally posted by whosdadog

I do not see how you could reliably time the gap between the detonation of the explosive and the ignition of the flash powder, and timing both of those around the 150ms delay the camera has.

It sounds like you need a custom initiation device with three outputs and programmable delays.

For a fine collection of photo's

The WiZard is In - 2-8-2011 at 09:11

of explosives (liquid) in glass I commend —

Melvin A Cook
The Science of Industrial Explosives
IRECO Chemicals 1974

Unfortunately short of the how it was done.

See also —

Melvin A Cook
The Science of High Explosives
Krieger 1958

Chapter 2 Modern Instrumentation and Methods