We’ve always wanted to make an action movie with an array of cool prop weapons. All it took was some silicone, some special resin, and a fog machine.
The glass bottles that are smashed over people’s heads in movies aren’t really glass. If you were to actually hit someone with a glass bottle, it could cause brain damage, don’t do it. This breakable material is a specific type of resin that Smooth-On sells called Smash Plastic. The trick is to make a mold of your object, pour in some mixed Smash Plastic, and turn your mold so the liquid resin coats the inside. We used this materials to make bottles and an axe head. There are specialized tints available for the Smash Plastic, but be very careful, you need a tiny dot of ink to keep the translucent natured of colored glass.
We used a silicone for the molds with a very low shure hardness so that the brittle bottles don’t break when de-molded. It is also recommended to pre-heat your silicone molds before adding the Smash Plastic to help reduce the cure time. You want about 1/8″ (3 mm) layer all around for your bottle to be firm enough to handle, but brittle enough to smash!
We wanted to make a crowbar that you could either hit some with or bend like Superman. I decided to make a two-part mold to capture all sides of the round bar and the curvy neck. A two-part mold involves making a boundary box filled half-way with sulfur-free molding clay. Most modeling clays have sulfur in them and won’t allow the silicone to cure, ruining your mold. Then you press the crowbar or other item into the clay, trying to match up and existing seem lines in the object. You should, at this point, add some indentions into the clay with the ends of tools, pencils, nuts, or whatever can make some registration points in the final silicone.
Next, spray some mold-release onto the part and clay base and pour on some silicone. Once cured, flip the mold over and remove all of the clay. Don’t remove the object, just the clay. Put the embedded object back in the mold box and liberally spray it with mold release or coat it with Vaseline jelly. This second pour of silicone should entomb the object, but allow the two parts to separate. After a pour spout is added to the top, you can pour in the casting material.
To create the bendable crowbar, we used flexible urethan rubber with a metal armature wire inside it. This wire provides some strength, but it can easily be bent into position. To make the crowbar look like black metal, I used a technique called cold casting. This involves dusting the inside of the mold with a metallic powder and then pouring in the urethane. The cured object will look just like, and have the metallic properties, of the dusted powder.
I had the idea of making a cinder block that I could throw at someone and they wouldn’t get hurt. To do this, we found some expanding foam from Alumilite. The foam expands 3-5 times the volume of the mold and self-skins, which means it forms a flexible outer layer that encloses the foam. To begin, I made a silicone mold of an actual cinder block using A LOT of silicone. After breaking the block out of the mold, I mixed up the expanding foam parts and poured it into the cavity. It was super cool watching it fill up the mold. One way to ensure a complete block is to cap the open mold with a sheet of wood and leave a small opening. Once the foam spews out of the opening and starts to slow down, slide the sheet over the opening and cut the foam. After removing it from the mold, you’re left with a perfect replica cinder block that is super bouncy and fun!
Super Fun Action Props!
This was a super fun project to make. I hope you watch the entire video because we made a short action film at the end using the props that we made! Furthermore, all of these products are available to anyone. We used products from Smooth-On and Alumilite to make these props. You can totally makes any or all of these props for your short films.
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- SawStop cabinet saw
- Dewalt 20v drill driver combo
- Countersink drill bits
- Pancake compressor/nail gun combo
- Shop Fox Hanging Air Filter
- 2HP Dust Collector
- 1 Micron bag
- 90˚ corner clamp (4 pack)
- Box Cutters (for eva foam)
Finishes & adhesives I like: