Knife Tricks


This effect uses stage blood and fake skin. You can find the recipes to make your own stage blood here or fake skin here.


Knife tricks have been popular throughout the history of special effects in film and other mediums. They are often one of the few effects that can be done at little to no cost and still look real. Depending on your medium and use, you may actually require multiple knives that will do many things. All of these effects will require a toy knife of some sort, whether it's plastic or rubber - do NOT use a real knife, a wood knife, or anything else but a toy or rubber knife. Here are many of the knife tricks used throughout film and theatre.


Stabbing Knife


Often than not, most people think about the toy knife you can find in a dollar store in the gags section of the Toy aisle. This knife often comes with a retractable blade (also called a collapsible knife or blade) that when pushed against someone usually pushes into the handle - the blade must be pushed with force to make the sharp end disappear. This knife, or the effect itself, works wonders in a theatre setting but does not cut it in film. Film requires this effect to be more realistic - a retractable blade can still be used but something must be designed so the blade appears to push into someone. For that effect, a fake stab wound must be built. The best way to do this is to build a small mound of fake skin where the knife will go - it must be small enough so the person does not look like a demon is trying to get out but large enough some of the toy blade goes into it and even stays in the fake skin. Put a shirt on the person one size larger than their regular size (the bagginess hides their real stomach, should any of it bulge out) and cut a small slit in the shirt where the toy knife will go. If you wish to continue using a retractable blade knife, the blade must be sturdy enough to hold itself in the fake skin, which can be complicated if this effect is done standing up. Then the blade will push forward and hide the blade. The other way to do it in film if you do not need to show the knife entering a person's body in real time would be to show the part of the body to be stabbed, then off camera apply a knife stab prosthetic (which can be made using the busted vein technique but not using a toothpick and gluing a cut knife to the latex) where the fake skin would go and then shoot this shot. If you need the blade to go through the other side in real time, often the knife or sword is pushed along the waist on the opposite side the camera is filming, and if you need to pull it out, such effect is as easy as pulling the sword or knife in an out motion. If the effect just needs to show part of the blade out of the person's back, use the same prosthetic trick but for the blade. Remember, when using a retractable blade, the stab motion must be fast or else the effect will look fake.


Bleeding Knife


This effect depends, again, on its intended use. Are you doing an effect that requires someone cutting their finger or hand to make a blood pact, cutting into someone's shirt, or slicing into someone's limbs? You'll need three different effects. For the blood pact effect, on the back of the blade of a plastic knife, glue some thin fish tubing as close to the bottom of the blade as possible. You'd want to attach a blood-filled bulb of some sort (as in the ones you'll find in earwax cleaning kits) to the blade (and may need to cut a small square in the blade to place the bulb and rethread the tube to fit the bulb in the blade). The tube needs to extend clear up to the tip. To achieve this effect, push the tip of the knife into your finger or palm of the hand, enough to make a wrinkle but not enough to actually hurt you, squeeze the bulb, and watch the blood pour. Cutting into someone's shirt and causing the knife to bleed will require the same trick, and depending on your situation, the fake skin effect from the Stabbing Knife trick, only this time the fake skin should run up that person's chest as far as the knife will go, as well as the slit in the shirt. You'll stab the person with the fake knife and squeeze the bulb as you move the knife upwards. If you squeeze it just right as you pull it out of them the blood will splatter under their chin or on their clothes, heighteing the effect. For an even more heightened version of this, especially in effects requiring gangfights, you'll want to have another knife but with the tubing on the opposite side of the blade. After the person is stabbed with the first fake knife, twist the knife, understanding this cannot be done in a continuous shot - you'll have to stop and replace the knife with the other one, then slit their chest as you did with just one knife. You may also opt to use just a plain toy knife, with no rigged tubing, if you require this as one continuous shot. Finally, if the effect requires slicing into someone's limbs, wrists, etc., another knife will be required. This effect, depending on your use, may require a multi-purpose trick knife. I'll assume your effect will and give you an alternative if your effect does not. This effect is commonly seen at Universal Studios' Horror Makeup Show in Orlando, Florida, though I will give you another variation of it. Let's assume you want to create the effect of cutting someone and then the blade goes into the skin. You'll need a method to cause bleeding as you're "cutting" them and then a method to make the knife appear to go into the skin - an effect that can only be done continuously using visual imagery. You can continue to use the tubing technique, but this time you'd likely want two tubes with their own bulbs, one tube stretched to the end of the flat part of the blade (not up to the point) and the other end stopping in the middle of the blade. This will allow for more blood and more realism. This effect could also be achieved, though its success isn't always as guaranteed as the tubing, by gluing sponges at the base of the blood and filling the sponge with enough blood that the blood is soaked but not enough the blood flows on its own. To add the blade going into the skin, which this part should be done before adding the tubing or sponges, you'll likely have to take a toy knife, cut the handle in half (a box cutter should be the safest way to do it - do NOT use a real razor blade) and make sure some of the blade will fit the handle. If so, there needs to be slits in the handle the blade can slide through because this blade must be retractable. Near the end of the blade, cut a semi-circle in the blade, with a diameter equal to the person's arm who will be "cut." When slicing into the person, the knife should be pushed down more so it hooks onto the arm and the blade pulls out to reveal what appears to be a knife in someone's arm. Should finding a toy knife prove difficulty when the blade is larger than the handle, a fake handle may need to be made or the knife may need to be trimmed. And if you do not wish to slice the limb in one continuous shot, just cutting a semi-circle in the blade of another knife will do - there will be no need for a retractable blade. As an added help with tubing, you may wish to curve your tubes downward at the end the blood is supposed to flow in all effects but the blood pact one, since the tip of the knife will be doing the cutting there.


Slitting Wrists


Make or buy a prop knife. Use tubing and food coloring bottle, attach to end of tubing with stage blood. There should be fake skin on your skin, and the knife should slit through it.


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