How to Cast Resin Model Car Bodies

By Gary Powl

Things Needed

  • Sculpture of car body
  • Polyester casting resin mix
  • Silicone rubber mold-making mix
  • Spray-on mold release
  • Non-hardening model clay
  • Disposable paintbrushes
  • Foam board
  • Mixing buckets and cups
  • Glue
  • Packing or duct tape
  • Stir sticks
  • Talcum baby powder
  • Rubber bands
  • Latex gloves
  • Surgical mask
Protect hands and eyes when casting resin model car bodies.

Hobbyists who choose to create their own model kits of cars can produce dozens of copies on their own, in resin. They design the model and sculpt it themselves, or hire someone to do it for them. Then, using readily available mixes and tools, they make the models, which they can keep for themselves, give away or sell. Beginners should gain experience by casting solid resin car bodies, which begins with selecting a well-ventilated workspace and making a one-part mold.

Make a mold

Cut a square of foam board large enough to rest the car body on, with about two inches of open space on all sides.

Glue the sculpture to the foam board, bottom side down. Check for gaps between the bottom of the sculpture and the foam board. If you find any, fill them with modeling clay. Smooth out the clay.

Cut a long strip of foam board, about an inch and a half taller than the car body. Shape the strip into a square large enough to stand around the sculpture, leaving about an inch of space between the car body and the square. Tape the square at the corner, top to bottom, on both sides of the foam board to make the seal solid.

Glue the foam board square to the base around the car body, making sure the sculpture is at the center. What you end up with is a wall standing around the sculpture on the base, with an open top.

Spray the sculpture and mold wall with mold release according to the manufacturer’s instructions.

Put on gloves. Mix mold rubber in a bucket according to the instructions and pour a little over the car. Use the disposable paintbrush to spread the rubber over the car, making sure it gets into all tight spaces. Pour the rest of the rubber over the car.

Allow the rubber to cure, at least overnight. When the rubber feels dry and springy to the touch, it is ready.

Carefully tear off the mold wall. Peel the mold off the foam board base, using fingertips to first loosen and then pry the rubber. The sculpture may remain glued to the base, or it may come off with the mold. If the sculpture remains in the mold, again use fingertips to loosen and pry it out.

Clean clay or any other debris out of the mold.

Cast the car body

Sprinkle the interior of the mold with baby powder to create a fine coating. Blow off the excess.

Put on the rubber gloves and surgical mask. Mix the resin according to the manufacturer’s instructions.

Pour the resin into the mold. Use a disposable paintbrush to lightly but quickly work the liquid into detail areas and to dislodge air bubbles.

Allow the resin to thoroughly harden, at least 10 minutes and possibly much longer. Instructions will specify times.

Work your fingers around the edge of the casting to pry it loose from the mold, then pull out the casting.

Repeat the casting process as desired. A well-made mold can produce dozens of copies.

Tip

Make car body sculptures of clay, epoxy putty, wood, wax or almost any other sculpting material. Be sure the sculpture is dry before molding it. Seal the porous surface of wooden sculptures with lacquer.

The mold-making process often destroys sculptures. If this happens, set aside the first resin casting to use as a “mold master” in case you decide to make another mold of the car body.

This how-to is for beginning resin casters. More advanced casters can explore more complicated, expensive techniques, such as rotocasting, in which a hollow resin casting comes from spinning a special mold while the resin cures.

Warning

Always protect your lungs and skin from the resin mix and work in a well-ventilated area. Even odorless resin creates fumes that can be harmful over time.

Young children should not cast resin car bodies. Older children should be closely supervised.

Resin will ruin carpeting and other surfaces, so make sure to select your work area carefully.

About the Author

Gary Powl began his career as a professional journalist in 1989, serving as a copy editor, reporter, columnist and supervisor. He now works in a paleontology lab, molding and casting fossils, and runs his own molding/casting business. He has a Bachelor of Arts in English from Colorado State University.