A DIY Foam Gun

Written by robert boumis
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A DIY Foam Gun
A realistic, yet soft, prop gun is not hard to make. (pistol's muzzle image by AGphotographer from Fotolia.com)

Foam weapons are extremely useful in making films. This effect is even used in big-budget films like the remake of "Casino Royal" or the recent adaptation of "Sherlock Holmes" staring Robert Downey Jr. It is also an inexpensive trick, allowing independent filmmakers to replicate this practical effect. At the same time, using foam props adds a considerable degree of safety to action scenes. Creating a DIY foam gun is not particularly challenging and within the reach of most amateurs.

Skill level:

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Things you need

  • Two realistic toy pistols
  • Modelling clay (non-sulphur based)
  • Two wooden dowels
  • Metal ruler
  • Mold-release
  • Platinum silicon mix
  • Disposable mixing jugs and stir rods
  • Art scalpel (X-acto knife)
  • Expanding foam
  • Spray paint

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  1. 1

    Seal any gaps in the toy pistol with modelling clay. Plug the barrel (if there is a hole there; some cheap toys will not have one) and fill the trigger-guard completely with clay.

  2. 2

    Create a open-top box out of hot glue and acrylic. The box must be large enough to accommodate the toy pistol with about an inch to spare on any side and at least two inches on the vertical side. The toy pistol will fit into the box with the barrel pointed downward.

  3. 3

    Glue two dowels onto the back of the handle. These will be used to suspend the toy pistol into the mould. Attach the other end of the dowels to a metal ruler.

  4. 4

    Apply mould release to the pistol, the dowels and the sides of the mould-box.

  5. 5

    Place the metal ruler across the open side of the box so that the toy pistol hangs into the mould-box without touching the sides.

  6. 6

    Mix the components of your platinum silicon, then pour slowly into the mould box. A slow pour will prevent bubbles. Fill until the pistol is completely covered with at least an inch of liquid silicon on each side.

  7. 7

    Wait for the silicon to dry per the manufacturer's instructions. Once the silicon is dry, remove the pistol and the silicon from the mould-box.

  8. 8

    Starting from the dowels, cut along the sides of the mould until the toy pistol can be freed from the mould using an art scalpel. The side-cuts should follow a wave pattern to help fit the mould back together when moulding. Do not cut further down than is necessary to free the toy pistol. Clean any remaining clay from the mould and apply a fresh coat of mould release.

  9. 9

    Place the mould (without the toy pistol) back into the mould box. Mix a batch of expanding foam silicon and pour this into the dowel-holes. Use enough that the expanding foam expands back out through the dowel-holes.

  10. 10

    Remove the foam pistol from the mould as you did with the original toy pistol. Using your art scalpel, cut away "flashing" (extra foam that expanded through the cracks) and clear the trigger-guard. Spray-paint both the foam pistol and the second toy pistol to match.

  11. 11

    When filming a foam gun, cut rapidly between shots of a realistic prop pistol (the second toy pistol painted to look like a real firearm) and the foam replica. Only use shots of the replica when it is in motion.

Tips and warnings

  • This method works best for pistols and knives. Larger props will not work as well.
  • Never use any prop gun in public. It can be mistaken for a real one.
  • Use caution and work in a well-ventilated area when working with resins, foams and liquid silicon.
  • Use care when using sharp tools.

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