Turning a foam cutout of a gun into a “real weapon” in just 15 minutes? I thought it was impossible before I saw this, too. Just keep reading and check out the video to see how foam can be turned into a real aluminum object. [Scroll Down For Video]

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Thanks to YouTuber Grant Thompson, better known as “The King of Random”, there’s a now a step-by-step guide.

You start by cutting some foam board into whatever weapon you want to create:

And with the help of a little science – it’s like magic, but without the lies – turn it into solid aluminum:


In some states, use of a replica gun in the commission of a crime, would constitute a weapon just as if it was a real firearm. In some stricter jurisdictions, the mere possession of a replica firearm is a crime and replicas are treated as weapons.

All it takes is a handful of melted soda cans, some play sand, a 5 gallon bucket, and the foam board.

The same technique can be used to make other “weapons”, like this sword:

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THe process is called ‘lost foam casting’ and here is an explanation of how it works from our friends at Wikipedia:

First, a pattern is made from polystyrene foam, which can be done by many different ways. For small volume runs the pattern can be hand cut or machined from a solid block of foam; if the geometry is simple enough it can even be cut using a hot-wire foam cutter. If the volume is large, then the pattern can be mass-produced by a process similar to injection molding.

Pre-expanded beads of polystyrene are injected into a preheated aluminum mold at low pressure. Steam is then applied to the polystyrene which causes it to expand more to fill the die. The final pattern is approximately 97.5% air and 2.5% polystyrene. Pre-made pouring basins, runners, and risers can be hot glued to the pattern to finish it.

Next, the foam cluster is coated with ceramic investment, also known as the refractory coating, via dipping, brushing, spraying or flow coating. This coating creates a barrier between the smooth foam surface and the coarse sand surface. Secondly it controls permeability, which allows the gas created by the vaporized foam pattern to escape through the coating and into the sand. Controlling permeability is a crucial step to avoid sand erosion.

Finally, it forms a barrier so that molten metal does not penetrate or cause sand erosion during pouring. After the coating dries, the cluster is placed into a flask and backed up with un-bonded sand. The sand is then compacted using a vibration table. Once compacted, the mold is ready to be poured. Automatic pouring is commonly used in LFC, as the pouring process is significantly more critical than in conventional foundry practice.

There is no bake-out phase, as for lost-wax. The melt is poured directly into the foam-filled mold, burning out the foam as it pours. As the foam is of low density, the waste gas produced by this is relatively small and can escape through mold permeability, as for the usual outgassing control.

Here is the video showing the full process:

About Hunter Roosevelt

Hunter's political beliefs are always evolving. Not really. He can be seen supporting whichever side has the hotter women so it's almost always the conservative side (have you seen the hippy chicks? Gross). When he's not writing he's celebrating the resurgence of his beloved Florida Gators and New York Mets.