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How to Make Rocks for Model Railroads

Varied and interesting scenery is the key to an attractive model railroad layout. Rocky outcrops and boulders are a visually striking element of this type of scenery. There are several different ways of producing rocks for your model railroad scenery. You can purchase premade rocks from a model store, or carve them out of insulation foam. Another method is to cast rocks from a modeling compound such as gypsum plaster. Rocks made using this method are light, durable and inexpensive, and you can reuse the molds to make as many as you need.

Things You'll Need

Rock mold
Water
Dish soap
Toothbrush
Spray bottle
Plaster
Large bowl or bucket
Mixing stick
Sandpaper or file
Acrylic paints and brushes
Matte varnish

Instructions

- 1
  Prepare the mold. You can buy rock molds at hobby shops, or make your own using latex mold material. Rinse the mold in water, then clean it with a mixture of water and dish soap. Use a toothbrush to scrub out hard-to-reach areas and edges. This is particularly important on molds you've used before, because particles of plaster may cause air bubbles. Spray the mold with water from a spray bottle, then shake it to dislodge the droplets.
- 2
  Mix plaster and water in a large bowl or bucket. Pour the plaster in first, then add water until you have reached the ratio indicated on the packaging, which varies depending on the type of plaster. Stir the plaster with a mixing stick until the consistency is smooth and even.
- 3
  Dislodge air bubbles in the mixing bucket or bowl by tapping the sides firmly.
- 4
  Pour the plaster mixture into the mold. It's important to do this promptly after mixing, because the plaster begins to set as soon as it is mixed with water.
- 5
  Vibrate the molds gently to release air bubbles. You can tap the sides of the molds or gently but firmly shake the table or work surface they're resting on.
- 6
  Allow the plaster time to harden. This period varies depending on the type of plaster, but is usually around 20 minutes.
- 7
  Remove the completed casting from the mold. Clean up any rough spots with sandpaper or a file.
- 8
  Paint the casting with acrylic paints. Use a mid-brown or gray color, then highlight the edges with a lighter shade of the same hue. Put a small amount of paint on your brush's head, then wipe most of it off. Brush lightly over raised areas with the remaining amount. The paint will highlight the raised areas, giving the rock a more natural appearance.
- 9
  Protect your rock by applying a coat of matte varnish.

Model Railroads