Introduction: Easy CO2-powered Squib for Self-contained Blood and Gunshot Special Effects
Well, here's one solution: Using inexpensive, readily available off-the-shelf materials, you assemble an actor-operated, CO2 cartridge powered squib that can create a blood spray up to 12 feet away, and you do it for around $30. The project is saved! Here's how you do it.
NEW! Check out this great video from member timlogik showing the effect in use by Amber's Sweets, his Repo! The Genetic Opera live performance cast. Thanks, Tim!
Step 1: You Will Need:
One CO2 bike tire inflator *
One CO2 cartridge that fits your inflator
One Hose Barb air nozzle adaptor **
Three feet of 1/2" vinyl tubing
One push-fit splice connector for 1/2" vinyl tubing (optional) ***
One small hose clamp (optional, but recommended - not pictured)
Blu-tack or low-tack masking tape
a banana (not pictured)
Some fake blood
A hobby knife
A vise, or a set of locking pliers
A marinating needle or large hypodermic needle
* You want an inflator that has a trigger valve as opposed to a push-to-fill valve. Also, you want one that screws into the Schrader valve on the bike tire, and ideally one that can accept multiple sizes of CO2 cartridge with both threaded and non-threaded tops. Mine cost $20.00 at the local bike shop, but they can be found cheaper at places like Walmart, or online.
** Usually found in packages of pneumatic air nozzle accessories - about $3.00 at Lowe's
*** This is just to make loading the banana plugs easier. If you don't mind taking the tube off of the hose barb to reload, you can skip it.
Step 2: Start the Effect Tube
Cut off about three inches of the vinyl tubing and set it aside. Take the remaining long piece of vinyl tubing and squirt just a little dab of vinyl cement into the end of the tube, making sure to get cement all around the top 1/2" of the tube without any gaps. Don't worry if it drips a little further into the tubing. Place the cemented end of the tube into the jaws of a vise, a set of locking pliers or a C-clamp, and clamp tightly. Leave to cure for about 8 hours.
While you're waiting for the glue to dry, do the next few steps.
Step 3: Assemble the Power-Unit-to-Effect-Tube Interface
Wow, that almost sounds complicated.
Take the tire inflator in one hand. Take the hose barb in the other hand. Screw the hose barb into the threads on the tire inflator. It should screw in easily, as the hose barb should use the same threads as the inflator. That's it.
Step 4: Attach the Effect Tube Base
Take the short piece of tubing that you cut off in Step 1. Push one end of the tubing into the splice connector. Slide the other end of the tubing over the hose barb as far as it will go. It should fit pretty snugly.
Secure the tubing to the hose barb with a piece of duct tape.
OPTIONAL, BUT RECOMMENDED
Further secure the tubing to the hose barb by placing a small hose clamp over the tubing and tightening the hose clamp screw. This helps prevent the tubing from being blown off of the barb by the force of the CO2 when the squib is activated.
Step 5: Finish the Effect Tube
Once the vinyl glue has cured, remove the effect tube from the clamping device. The end of the tube should be flat and fused closed.
Using a hobby knife, carefully cut a small hole about 3/4" down from the fused section. The hole should be about 1/8" in diameter, and irregularly shaped in order to produce a spray of blood rather than a squirt. Unless you want a squirt, that is. In that case make the hole as perfectly round as you can. Maybe use a drill bit....
If, after testing your squib, you find that it sprays too far or too fine a mist, simply enlarge the hole with scissors or a hobby knife until you get the effect you want.
Once your hole is cut, push the other end of the tubing into the open end of the push-fit splice, and you're done with assembly.
Step 6: Load the Squib
First, power up the squib by inserting a CO2 cartridge* into the inflator. My inflator has a handle that unscrews from the valve assembly, so you just drop the CO2 into the handle and screw it back on. Your inflator may work differently. If your inflator has a safety, engage it before loading the CO2.
Then, remove the open end of the effect tube from the push-fit connector. Cut a slice of banana about 1/2" thick and shove the end of the tube into it, creating a banana plug. Push the effect tube back into the splice connector. The banana plug is to help keep the blood from getting into the valve and gumming up the works. It will get pulverized and blow out the hole when the effect is triggered.
Fill your marinating needle or large syringe with stage blood (if you need to make your own, I'm rather fond of this formula). Insert the needle into the small hole in the closed end of the tube, and fill the tube with blood. Wipe any excess blood off of the outside of the tube, and seal the hole with a small piece of Blu-Tac or masking tape. Use only enough to barely cover the hole to prevent leaking.
(TIP: If you need to camoflage the effect so that it is less noticeable under your actor's costume, use a white version of Blu-Tac, such as Handi-Tac. Then color the putty with a Sharpie to match the color of the costume.)
* A word about CO2 cartridges: A 16-gram threaded cartridge costs about $3.00 at the bike shop. A 12-gram unthreaded cartridge (the same one used in BB and paintball guns) costs about $0.50 at Walmart. You do the math. Get a tire inflator that can accept unthreaded 12-grams. Really.
Step 7: Put the Squib Onto the Actor
Simply tape the tube to the actor in the position you want the shot to be, with the hole facing outward away from the actor's body.
Run the trigger assembly through a hole into the actor's pocket, hang it in the actor's beltloop, or place it anywhere else that it will be concealed from the audience/camera but still accessible to the actor.
Put the actor's costume on over the effect tube and make a small slit in the costume directly over the Blu-Tac plug. The larger the slit, the more blood will fly through the air. The smaller the slit, the more blood will stay on the costume. You are now ready to trigger the effect.
Step 8: Triggering the Effect
(Sorry no pictures yet.) When the time comes, all the actor has to do is casually reach into his pocket (or wherever the trigger is), flip the safety off and squeeze a short burst on the trigger. Blood goes everywhere. The actor falls down and plays dead. Cut, print, and that's a wrap.
It only takes a very short burst to make the effect work. CO2 expands very energetically, and is stored at very high pressure. A little goes a long way.
Step 9: Credits and Comments
First of all, let me say that this entire project was inspired by Crosius' amazing Pneumatic Squib Tutorial, which I consider to be a superior design in practically every way. The CO2 squib came about as I was waiting for the parts I ordered to build 8 of Crosius' version to arrive in the mail, and I started thinking about how to duplicate the effect without any specialized parts, and for less money.
Due to minimum part order requirements for the miniature pneumatic parts, Crosius' design will cost about $120 to build the first one if you don't have any of the parts on hand already, which may not be within the budget of the small theatre or filmmaker. If you need 5 or 10 of them, the cost per unit drops to about $40 each, making the CO2 version not much of a cost savings at all.
Crosius' version is also more flexible (you can vary the pressure to vary the effect), more concealable (especially with a minor mod to the trigger assembly. See the Comments section of the Pneumatic Squib Tutorial for details), and daisy-chainable. If you need multiple squibs, build his design. It's just better.
On the other hand, if you only need one or two and are on a tight time or money budget, the CO2 squib may meet your needs just fine. Enjoy.
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