8 replies to this topic

[Steelrat]

Hi all, im looking for compositions to create scale explosions on film,

Used so far:
FIRE BALLS simulate petrol explosions
Benzoyl peroxide (though a little nasty as its a bleaching agent)
Rubber dust
Naphthalene and black powder


Looking for quick burn faster the better with little smoke and a powder rather than a gas.

Any ideas welcome as there is hardly any information on the net referring to miniature pyros.

Edited by Steelrat, 12 September 2006 - 09:36 AM.

[BrightStar]

OK, a silly but fun starter:



Very simple - 3g of slow BP in a 1" tube, topped with 5g of a 50/50 mix of slow BP and coffee creamer (it will not work alone on this scale). Cover the top with a glued paper cap.

Video here (3gp mobile format, works with Quicktime):

Mini cremora pot

I'll post my mini-magnalium orange star mine when I have a moment - it would be great for an Andromeda style laser hit

[fishy1]

Hi all, im looking for compositions to create scale explosions on film,

Used so far:
FIRE BALLS simulate petrol explosions
Benzoyl peroxide (though a little nasty as its a bleaching agent)
Rubber dust
Naphthalene and black powder
Looking for quick burn faster the better with little smoke and a powder rather than a gas.

Any ideas welcome as there is hardly any information on the net referring to miniature pyros.

Virtually any flammable powder can be used in place of nap, flour, calf milk susbtitute are a few that come to mind. of course, you need BP to lift them.

[adamw]

Hehe I love a bit of Supermarionation!

Try something like xylene or even IPA (isopropyl alcohol). Propane would also make a nice smoke-less effect while being controlable and *fairly* safe but as you said you don't want a gas...

A good solution might be lycopodium (moss spore dust - yuk!)

[Steelrat]

thanks guys ill give some a go, as you will know fire effects are hard to scale right as many a thunderbirds explosion will show.. though it was thunderbirds that got me into pyros as a child... hehe.. but better just brush over that

ps ive used lycopodium, not bad but burns a little to slow. waiting to see Team america miniature Pyrotechnics, think its about 15 min long, if anyone has it or knows where to down load let me know please, also if you have any tech questions on large fireballs or HE pyros let me know and ill see what i can do to help

Edited by Steelrat, 13 September 2006 - 02:58 PM.

[BrightStar]

One nice trick that works for me on a miniature scale is a modification of an Xmas tree bulb ignitor. Just take one of the Xmas bulbs from a cheap string and carefully break off all of the glass down to the plastic base. With hot glue, attach a 20mm long length of drinking straw in its place, passing over the filament. Test for continuity before and after.

You can fill the drinking straw with about 0.7g of the composition of your choice and seal it with more glue. BP alone will give a flame and a puff on cue, BP with 25% fine aluminium burns for a couple of seconds shooting off sparks, BP with 5-10% fine aluminium will go BANG (surprised me when I first experienced it - the burning aluminium greatly raises the burn temperature and speeds up the BP). For more noise, wrap a few turns of electrical tape around the drinking straw to stengthen it. I'm sure many coloured flash comps (eg strontium nitrate and magnesium) could also be used (carefully...).

Be aware though that these will fire at very low current and so risk igniting prematurely with some continuity testers and firing panels.

[adamw]

RE: Xmas bulbs... it's easier and safer to use ignitors.

Steelrat: I have the Team America DVD and I think there is a 'making of' on it, but I'm not sure if it focuses specially on the scale pyro.

You might want to experiment with small quantities of your own composition. I have used redundant mixtures very sucessfully for large scale fireballs. Also, try smokless powder. You might have to contain it somehow so it gets to a decent pressure to combust properly and produce a fire ball (similar to a gun muzzle flash)

[BrightStar]

RE: Xmas bulbs... it's easier and safer to use ignitors.

Hi Adam, yup, ignitors are safer but might be expensive with dozens of cues on a model scale - I pay ?0.05 GBP per Xmas bulb and they do work with a variety of compositions. Out of interest, do you know how fast the camera has to be for Thunderbirds type effects?

To broaden the discussion a bit, I was recently asked to make a confetti cannon cartridge - in the end I just bought a couple of LeMaitre cartridges from Stage Electrics.... In testing my own version, BP worked, but the flame and smoke sunk it for indoor use. Should I try whistle, make sulfurless-bp, or try to get some Pyrodex (tricky in the UK...)???

Edited by BrightStar, 19 September 2006 - 06:51 PM.

[adamw]

As far as I know, the LeMaitre ones use BP...

Frame rate for the slow-mo effects is usually 120fps or faster (4 times faster than conventional UK video, or use 100fps for film which will be 4x25 (24)fps)

Unfortunately, those lovely slow-mo effects cost quite a lot of money - the cost of film using a cine camera (4x or more consumption to get the same lenth of time) and for video, the cost of the equipment it's self.