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Old December 2nd, 2010, 01:48 AM   #1
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"goo gun" advice/no budget gun hit FX

Hi. I will be DPing, starting in January, it looks like, a short film involving some gunplay. We have several characters getting shot, and would like to have bullet hits/blood. My friend, the director, had planned to try out squibs but has abandoned that idea.

He has built a "goo gun", basically same idea as a paintball gun, potato gun, tshirt cannon. It is an air tank hooked up to a valve with a trigger release, which is then hooked up to a barrel made of a PVC pipe. You cram your ammo/goo/blood into the barrel, manually pump (we use a simple bike pump) the air tank up (I can only get it to 30 psi before it starts to become impossible to pump further), and use the trigger to fire.

The idea is that if the goo/blood hits the person fast enough, it appears to just "appear" there, like a bullet hit, instead of being shot onto them.

We have tested it with mostly lackluster results.

We need to have several pistol hits, and maybe a shotgun hit. So far, even with the tip of the barrel at four feet away from the subject (far enough to be outside of frame on an MCU of a character), we're still getting too much spread/spatter, instead of a concentrated area of impact.

Let me tell you what we/I have tried so far.

We started just simply pouring our "blood" into the barrel. . .corn syrup and food coloring with chunks of banana mixed in.

I have tried a new mixture he come up with that was based on mashed up avocados. a neighbor who knows guns/ballistics to some degree advised putting something behind the goo (i.e. first thing into the barrel, before the goo), like a cotton ball, facial pad, pineapple core, etc., to ensure that the air hits a solid surface at the same time. So far these devices have stuck to the goo all the way to impact, resulting in a splat with a cotton ball in the middle.

I tried my own idea which was wet and torn up toilet paper, which gave a more concentrated mass, and the cotton balls, etc., did not stick, but still flew too far.

Anyway. . .using this device, any ideas to make it better? I should mention that I haven't had anything long enough to tamp the mass of goo and cotton all the way down compactly, as the tamping devices I was given fall 3 or 4 inches short of the length of the barrel.

I've attached a hastily taken photo of this gun.

on the left is the long barrel. . .about 38". The green part is the valve, see the trigger (red) on the bottom, and the air tank with pressure gauge at the back.
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Old December 2nd, 2010, 10:17 AM   #2
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One method is to use a water balloon or similarly shaped latex container (red or white/flesh colored), fill with blood mix, tie shut with a bit of pressure, and then shoot with either an airgun or slingshot. In post, edit out the frame immediately before the hit (when the projectile will likely be visible).
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Old December 2nd, 2010, 10:22 AM   #3
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if you want accurate shot, you need accurate bullet.
Most of them are made of solidified jelly. you need to find a mold that is just big as the tube and make a jelly enveloppe, eventually filled with liquid or jelly.
So made, the jelly keep relative shape until hitting the target, while being soft enough to avoid injury or being as a visible bullet.
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Old December 5th, 2010, 06:28 PM   #4
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Both of these sound clever.

with the balloon---tail (open end of balloon) goes in the back of the barrel?

How does this mold thing work? Is this something one can do oneself or does it require special tools? I'm not clear on what you mean.
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Old December 6th, 2010, 01:04 AM   #5
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Neighbor suggested actual paintballs. Why not? Barrel is 1/2" PVC.

Any other ideas that are totally different from this goo gun idea? We're already aware of the idea of filling condoms with goo, cutting a slit in it, and using fishing line to pull the hole open at the right moment.

Others?
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Old December 6th, 2010, 03:17 AM   #6
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actual paintballs bullet (if received one already are painfull, the envellope is really hard).
fo rjelly , there is two types, the ard/dry one and the soft/wet one.
The hard/dry one is the same on can find in these little jelly teddy bear.
you can dissolve some in hot water and use a thin layer to build the bullet envellope)
Pro: you can keep them for a long time, con: they are a bit harder.

the 2nd type is made from real jelly (animal or vegetal) you can find under sheet or powder in almost any kitchen. You dissolve the product in hot water and then simply fill the mold.
Pro: probably easier to build, con: they dry very fast (amost 95% of the jello is water)

you can even make a mix of both , very liquid jello surrounded by a thinh layer of hard jello.

for the mold , you cand find a small plastic bullet (like the one you find is distributor in supermarket, a little ball that contains a toy), it is about 1 " dia.
you can make a mold with silicon, that will be easier to unmold.
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Old December 6th, 2010, 09:52 PM   #7
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Thanks.

I'll have to read that a few more times about the jelly mold thing but I think I understand.

Real paintballs were the next idea. Went to Academy and they didn't have anything smaller than a 500 count for $15, which I didn't feel like getting. that size was maybe a little small (1/2" PVC barrel opening is about 5/8", and the .50 cal paintballs looked to be not quite 1/2".)

I wonder if this is the wrong approach, then? Shooting the goo onto someone as opposed to finding a safe and convincing way to have it come FROM them. Seems like with the shooting eyes/face are always in danger, even if you padded the area for the hit (torso).
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Old December 8th, 2010, 08:12 AM   #8
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You might do a google search for DIY squibs.

Here is an example...

Go FX Yourself: DIY Gunshot Squib Effects - G4tv.com
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Old December 8th, 2010, 12:05 PM   #9
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thanks. i think were going to try the condom thing instead of goo gun.
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Old December 9th, 2010, 04:50 AM   #10
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There's plenty of safer, less experimental, and easier ways to simulate a gunshot wound than shooting someone with a paintball gun or jello.

Clever editing and camera angles can get you around the problem really well - for example, you have the persons chest already splattered with blood. When he is in the gunfight and has his firearm raised, it obscures his chest but as soon as he is hit he can throw his arms out to reveal the blood splatter. Similarly you can shoot from behind or over the shoulder, and as he is hit he swivels around to reveal his bloody chest.

You can also composite the initial impact in during post, once again using editing to quickly cut to another shot where he is covered in practical blood - that way the initial CG hit happens so quick and cuts away before anybody can see it is fake.
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Old December 9th, 2010, 05:47 PM   #11
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I think we may abandon the "shooting blood onto people" angle.

Some of the shots planned for this stuff are very specific, and I think my director wants to see the hits themselves, otherwise I am all in favor of these suggestions.

I will investigate the homemade squibs.
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Old December 30th, 2010, 10:15 PM   #12
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Have you ever heard of molecular gastronomy?
there is a technique for taking a liquid...almost any liquid...and a couple of easily available chemicals
(Calcium Chloride & Sodium Alginate) and effectively creating a gel capsule, with a flexible, edible surface and a liquid center. Google "gelification"

mixing your liquid ( in this case fake blood) with a small amount of sodium alginate creates a suspension. You then create another suspension using calcium chloride and water.

Pour your fake blood suspension into a mold...maybe an old 35mm film cannister?? then submerge it in the calcium chloride solution for a few seconds. what you'll get is a soft, gelatin like shell ( the longer you submerge it, the thicker the shell) with a liquid center.

I would bet that you could submerge the suspension for, say a minute or so, and get a nice squib...firm enough to propel with an air cannon, and still fragile enough to burst on impact. no wadding behind the squib, it should fly OK, and you won't hurt anyone with it...it's basically gelatin.

VERY important: this stuff is EDIBLE. It's used for cooking. I've made espresso caviar to serve on ice-cream, mango puffs, etc.It's very cool to play around with,, and might do the trick for a cheap squib.
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Old December 30th, 2010, 11:03 PM   #13
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Thanks, but I think we're going to go another way. . .the youtube video with the design where the blood shoots OUT from the wound seems safer and more precise. Talking about the design using the pump and flexible plastic hose.
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