Hi, John Hess from Filmmaker IQ.com and in today’s lab we’re going to create air
powered blood squibs.
Bloody gunshot wounds in film are a relatively recent thing.
Hollywood’s Production code prevented showing blood splatter on screen during the studio era.
It wasn’t until 1955 when director Andrzej Wajda employed explosive blood squibs in his
Polish film Pokolenie.
Technically the term “squib” refers to an explosive device which resembles a miniature
stick of dynamite only with much less explosive power.
Squibs have been used in many applications in various industries - not just in entertainment.
When used to simulate a bullet wound, the squib is worn on the body between a protective
metal plate and blood packet.
When detonated the squib has enough energy to rip a hole in the costume, send blood flying
everywhere and even give the actor wearing the squib a little punch to react to.
Now that kind of squib requires a pyrotechnic license and depending on your location, a
special effects permits.
Frankly, that’s not something I feel comfortable handling myself nor would I recommend anyone
in my audience attempt it without seeking proper professional training.
In place of explosives we’ll use compressed air.
Even though they aren’t real squibs, the industry still refers to this technique as
squibs or sometimes air squibs.
Although it’s much safer than explosive squibs, compressed air can still be dangerous
- as little as 12 pounds per square inch (82 kPa) can blow an eye out - air bubbles in
your bloodstream from compressed air can do all kinds of damage, not to mention we’re
basically using compressed air to shoot fake blood all over the place and that can be potentially dangerous.
But as long as you treat the equipment and your cast and crew with respect, you should
be relatively safe.
Let’s dive right into making our squibs.
To deliver the blood for our gunshot wound we’ll start with some clear vinyl tubing.
After experimenting with different sizes I discovered that 3/8th inch inner diameter
tubing is a good size for this project.
Any smaller and you don’t have much room for the blood.
Any larger and we have trouble finding the right hardware to connect to our compressed air.
For those of you in metric land, you’ll have to find similar sized pieces as most
of the bits we talk about will be using imperial units.
Start off with about 6-8 feet of tubing of this 3/8ths inch tubing.
You’ll need at least that much to wrap around your talent and get out of sight.
On one end of the tubing we’ll use a 3/8th inch barb to a 1/8th NPT connection which
will connect to a trigger for our air compressor - more on that in a bit.
You’ll want to secure the barb using a hose clamp otherwise it’s possible you hose will
slip off when fired and that’s not good.
On the other end of this tube I’ll inject some hot glue to act as a plug - about a half
an inch of glue will do it.
Now it’s time to cut the hole for the blood to come out.
Using a box cutter, cut down about a third of the way through the tube just below the
hot glue plug.
Then I’ll make a second cut this time at an angle.
The result is like the hole in a recorder or pipe organ.
Now we will make a mounting plate which will mount to our actor’s shirt.
Take about 3 inches of gaffers tape and lay it on your table.
Press the tube with hole facing down onto this tape.
Take another piece of tape, this time slightly longer and apply it on top of the hose and
cover up the exposed tape.
What you should have a flat surface where the hole in your tube was - take your knife
and cut away the tape from the hole.
Now apply strips of velcro to both sides of this platform we created.
Use the harder hook side as this will get covered in blood and the plastic hooks will
survive reuse better than the fuzzy loop side.
With that our delivery system is ready to go.
There are several ways to create and store the compressed air we’ll use for our wound
- from some experimentation I’ve found that you need between 20 and 30 PSI for this effect to work
A lot of DIY filmmaking tutorials out there use a manual bug and weed sprayers compressor.
You pump up and down about 100 times and you’re ready to fire.
20 to 30 PSI isn’t that much so these will work but honestly, I prefer something with
a little more control.
For single use blasts you could use a hand held CO2 bike tire inflator.
I got this one on Amazon for $15 which is loaded with a CO2 cannister which you can
order online or from a sporting goods store that sells paintball equipment.
When freshly installed, a CO2 cannister will deliver well over 30 PSI, so if you do go
this route, give the inflator about 4 or 5 quick puffs before you fire it off with blood
delivery system.
These CO2 canisters can be purchased in bulk for about a buck each.
To get this to work with my delivery system I had to buy a Tank Valve to 1/8th NPT converter
and a 1/8th to 1/8th female coupler to connect to the hose.
If I were doing this effect in a remote location, this is probably the propellent I would use.
But why stop there…
I’ve got this bigger tank air compressor lying around the shop.
It’s capable of 100 PSI which if far above what we want but it’s got some great added
features.
First - it’s got gauges so I be more precise with the pressure I’m using and secondly,
there is a pressure regulator so I can control exactly what kind of pressure I’m using.
Because I have a bigger tank I can use this four way pass to power up to four squibs if I wanted to.
On this four way pass I installed 1/4th quick connectors.
Make sure you seal your threads with thread tape or else they will leak.
To trigger the squib itself, I’ll use a blow-gun - the 1/4th male plug will screw
in on the big end of the blow gun and the 1/8th will connect to my blood delivery system.
So now when I’m ready to fire all I have to do is screw in the blow gun to the blood
delivery system and connect it up to this air compressor.
To fire, all I have to do is push the trigger.
Rigging the talent is the most difficult part of the setup.
To begin, have the talent wear some kind of undershirt - here I’m using red cause fake
blood won’t stain this color.
An undershirt does make this setup much easier.
First I have the talent put on a backbrace, this will help secure our Blood Delivery System.
Since I want the impact to be on the upper chest I’ll use elastic bands to further
secure the tubes.
You can use gaffer’s tape but I find that can lose it’s stickiness really quickly
once it’s mixed with blood and we really don’t want this to slip around.
Next we’ll tuck the tubes of the blood delivery system in the back away from the camera lens.
Now to work on the outer shirt.
Have the actor put on the outer shirt and locate where the bullet holes will go and
make a small vertical cut with a pair of scissors.
It helps if the scissors are prestained with blood as it reminds the talent of who’s
in charge.
This doesn’t need to be too big because we want about 10% of the blood to be trapped
by this outer shirt to create that bullet wound.
Now attach the loop side of the velcro tape to the side on your blood delivery system
and secure the system to the shit making sure the exit hole of the system matches the shirt.
This is crucial if we want that gush of blood.
Now it’s time to load up the system with fake blood -either store bought or make your own.
You want this fairly watery so it doesn’t get stuck in the tube.
Using a flavor injector syringe we need to put in about 90 CCs of fake blood - that’s
about 3 ounces if your syringe uses imperial - mine is metric.
If you want more of a misty hit you can go with less and slightly higher pressure but
I feel like if you’re going to do this effect, you might as well have a big bloody explosion.
A lot of other tutorials would muzzle load the blood, putting the syringe in the exit
hole and pushing in the blood that way - being that I am accident prone and I know I would
spill some on the costume, I prefer to load the blood breech side - where the hose connects
to the trigger.
Now this might be slightly bit messier on trigger parts but this way but I think if
you think if you clean things up afterwards you’ll be fine.
Replace the blow gun on to the hose and now we’re ready for the shot.
Since I have two squibs going on in this shot, I’ll set my compressor to between 40 and 60 PSI.
Because I have twice the tubing so therefor we need to have twice the pressure
Then let everyone on set know you are are arming the air compressor.
Make sure everything is secure and safe and in position before you insert quick connector.
Then count it down...
I hope I’ve given you some practical direction into how to achieve good results with air
compressed squibs.
Truth is any time you work with fake blood, things are going to be messy.
So lots of first time filmmakers tend to just do the effect once and call it good enough.
But my first test shots were pathetic - it took three serious tries and dissecting how
professional air powered squibs worked before I thought I was ready, and even then my first
live action result didn’t live up to my expectation so I organized a reshoot and finally
got something I thought I could work with.
In the end that I spilt a lot of blood and got a lot of weird looks from my neighbors.
Plan on making mistakes - just make as many of those mistakes during preproduction as
you can but be prepared to roll more than one take in case the effect doesn’t work
out the first time.
But most importantly you got to get out there and practice!
Give the air squib a go - it’s all part of the process to making something great.
I’m John Hess and I’ll see you at Filmmaker IQ.com