How to Cast a Concrete Statuary

Cast concrete makes beautiful statuary.

When casting concrete statuary there are two types of molds that can be used. A rigid mold is used if there are no undercuts. This means the wet concrete can be put in the mold and when it has hardened the mold can be pulled away without it getting hung up on the statue. For statuary that has undercuts, flexible molds must be used so when the statue is ready to be released, the mold can be pulled up and over the statue where there are undercuts.

Things You'll Need

• Rebar
• Hack saw
• Wire
• Weld machine
• Rubber or rigid statuary mold
• Mold bands or bungee cords
• Mold release, spray on
• Scoop
• Pail
• Rocks
• Gravel
• Sand
• Trough
• Garden hoe
• Water
• Rubber mallet
• Electric vibrator
• Towels

Instructions

1. Make an armature out of steel rebar. Rebar is used to strengthen cast concrete. Wire or weld the rebar to create the armature.

2. Spray the inside of the mold with a mold-releasing agent. This will keep the hardened concrete from sticking to the inside of the mold when it's time to release the statue from the mold.

3. Set the mold upside down. Suspend the armature in the center of mold's cavity. A cross piece of rebar at the base of the armature rests in the recessed mouth of the mold. Use mold bands or bungee cords to keep the two sides of the mold clamped tight together.

4. Mix up the concrete and scoop it into the mouth of the mold. Start by dry mixing 6 parts rock, 3 parts gravel and 2 parts sand together. Take four buckets of this mix and add one bucket of cement and mix together. The amount of water added to this dry mix should be 40 percent by weight. If the dry mix weighs 100 pounds, add 40 pounds of water (a gallon of water weighs about 8 pounds).

5. Strike the sides of the mold with a rubber mallet or use an electric vibrator to vibrate out any trapped air bubbles in the concrete. This will also make the concrete stronger as well.

6. Allow the concrete to harden in the mold for 24 hours.

7. Undo the mold straps and carefully pull, first one side of the mold away from the hard concrete statue and then pull the second side of the mold away. Go slowly so as not to tear any part of the rubber mold or to avoid cracking a rigid mold.

8. Allow the statue to sit and harden slowly for the first week. If the atmosphere is overly dry, drape the statue with damp towels to slow down the drying process.

Tips & Warnings

• If the surface of your freshly cast statue has a lot of little holes, called bug holes, you can fill them. Mix up a soupy mixture of cement and water. Put on rubber gloves and rub the slurry into the holes. Twenty minutes later wipe off the excess slurry with damp sponge.

• Concrete can be tinted using masonry stains. For vibrant colors use white cement. If you use the standard gray cement your masonry stains will produce muddier colors.

• A statue can also be stained after its been removed from the mold. Mix straight cement and stain with water and brush it on. Wipe the liquid stain off on the high spots of the statue to create an antique look.

• Wear work gloves when working with concrete. Its has lime in it which can burn your skin.

References

• Cartage: Cast Concrete
• Cob Gardens: Concrete Facts