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goo oozing out of a stab wound

Hello friends, 

I am doing fx makeup for a gory short film called "Corpse Bong." These punk kids dig up the corpse of their old friend Steve and turn his corpse into a bong for smoking marijuana. In one shot they stab the bong slide into the corpse's stomach, and green goo oozes out of the corpse's stomach and into the bong slide.

Any suggestions on how to achieve this? I'm thinking I will have some kind of plastic bag that is full of green goo and it will be just underneath a latex stomach skin. When the bong slide stabs through the skin and into the bag, the goo will ooze out of the bag and into the bong slide. I don't know if there will be enough pressure in the bag to make this happen. I also don't know if it will be hard to get the bong slide to to smoothly cut through thin latex. 

I may have one person holding the bag so that once the bong slide stabs into it, if there is not enough pressure to make the goo ooze out on its own, someone can squeeze the bag to force the goo out. I'll have to figure out a safe way to do that though.

I guess I would want to use some kind of syringe to pump the goo out for this effect, but its hard because the hole is being created in the shot, so I don't know how to place the syringe in the right spot ahead of time. 

I will be doing a test of this in the next week, but I wanted to post here asking for suggestions on materials, methods, or relevant SWSCA tutorials. 

Things I expect to learn from testing:
- how thick/thin does the stomach skin need to be for the bong slide to slice through it? 
- does the bong slide need to be sharpened to slice through the skin? 
- what is the best kind of bag to use for the goo? Can I use a simple ziplock bag and put duct tape over the zipper so it doesn't open from the pressure of the slide stabbing in?
- how thick does the goo need to be? 
- will the goo have a hard time traveling from the bag out of the stomach skin? Will it get trapped between the bag and stomach skin? I guess not, cuz it's traveling through the slide's hollow interior. 

Thank you for all!
-BenG


Comments

  • Chris EllerbyChris Ellerby Los Angeles Admin
    My first suggestion would be to use the magic of editing and cover the effect in 2 shots.   One shot of the puncturing, and a second showing the fluid being pumped into the apparatus.  (perhaps a wider shot of the stabbing, then a closeup of the fluid gag)  This gives you absolute control over each stage of the effect, allowing for many takes without expensive prop duplicates and reset times.

    You could have a pressurized container of fluid under the skin that gets punctured, but the challenge there is having a good enough seal around the puncture and enough pressure to get the fluid to exit at the right speed (not too fast or too slow). That approach is one I would avoid because there are too many variables that are out of your control that could prevent reliably repeating the effect multiple times on camera.  Physics and fluid dynamics are hard to wrangle on set when you want a very specific result.  Sometimes you have to cheat a bit.

    By handling it in 2 shots you can hook up a syringe and get the right volume and speed of fluid to match the energy you are going for.

    You could also do it in reverse.  Start with the filled apparatus in the stomach, let the fluid drain, then pull it out while ramping the motion so it looks like the appropriate speed/force was used to make the puncture.  To help sell that effect you can push in slightly before pulling out to help simulate an impact with enough force to press the stomach in.   The challenge there is that some fluid may remain on the edges of the apparatus as it drains, which could give away the effect.  To address that you could adjust fluid viscosity.  You would also want to time the draining of the fluid so it starts slow, then speeds up, so it looks like a burst of fluid that slows as pressure drops.  The puncture point may also be visible in the reverse gag, so you would want to film it from an angle where that spot is not visible or obscured by the performer's hand coming in.

    If you really want to do it all in one shot I would suggest first figuring out a skin material that you can puncture and get a good enough seal to allow fluid to exist and fill the apparatus.  You also need to have this be resettable, because gags like this often take quite a few takes to get just right.  I would suggest having some kind of insert skin that you can remove and replace for every shot.  A material like gelatin is inexpensive, easy to penetrate, would provide a good seal, and can be colored to look just like human skin.  But what material you pick is also based on the character design of the body you are using and its state of decomposition. 

    Next you would want to try and add some supports inside the stomach to help provide enough resistance to allow the piercing.  Rigid foam could work, as you want a little give.

    I would actually try having a socket just under the skin that the apparatus seats into, and have that hooked up to a tube that is fully primed (filled to the very edge) with fluid so it is ready to start pumping fluid right when the stabbing action occurs.  The other end of that tube could be connected to a large syringe or other hand operated pump.

    That socket could be designed a bit like a funnel, so it helps to guide the apparatus to the center if you are off by a bit.  Durability is key there, as you'll want multiple 

    Then just paint a small mole on the skin where the target point is, and have the actor aim for that.

    You could also pre-score that area so it would puncture easier, and hopefully prevent a plug from being formed that could block the fluid.

    I would also suggest lubricating the apparatus with something like KY or vaseline so it punctures easily, and helps create a seal.

    /Chris


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