Not just for driveways or sidewalks anymore, concrete has become a staple product for lawn decorations. Statues, fountains, stepping stones and benches are only a few of the many uses that have become popular in recent years. Of course, making your own versions can be much less expensive than buying the products already made, and it allows you to customise your decor with your own unique style. For those who haven’t found, or don’t want to find, their inner sculptor, making these beautiful items means learning how to cast concrete moulds.
- Skill level:
Things you need
- Concrete mix
- Container for mixing concrete
- Concrete mould
- Release agent
- Cling film
- Shaded table
- Empty juice can
Prepare the mould. Coat the concrete mould with a releasing agent. This is an essential step. You can use a purchased releasing agent that is made specifically for casting moulds, or you can use cheaper alternatives that are available around your home, like light vegetable oil. You need to coat the entire inside surface of the mould and then wipe away any excess. There should be a barely visible, very light coat. If you forget to use a releasing agent, then you will not be able to get the concrete out of the mould with everything still intact. If you leave too much of the releasing agent in the mould, then you will get bubbles on the surface.
Measure the concrete. Follow the directions on the package to measure out the amount of dry concrete mix that you will need for the size of project that you will be doing. If you are going to use powdered colourant in your cement and you want an even colour, mix the colourant into the dry concrete mix.
Mix the concrete. If you are using liquid colourant, add it to the mixing water before adding the water to the concrete mix. Begin adding water to the dry concrete mix, stirring constantly. You want a stiff mix, but you don’t want it to be so dry that it crumbles. If your mix gets thin enough to flow like pancake batter, add more dry concrete mix to thicken it.
Pour the mould. Use the empty juice can to scoop the concrete into the mould. Fill the mould to the top, and then bounce the mould up and down. Bouncing the mould helps compact the concrete, forcing excess moisture to the top and pushing out air. This prevents bubbles in the dried concrete.
Cure the concrete. Place the filled mould on a flat table or level surface. The table should be out of the way, and needs to be out of direct sunlight. Cover the mould with cling film. This protects the concrete and keeps foreign objects from getting into it. It also allows the concrete to dry from the inside outward, a curing process that is essential for long-lasting concrete. Allow the concrete to remain untouched for at least 24 hours.
After allowing the concrete to dry and cure for at least 24 hours, flip the mould over so the mould is now facing upward. Grasp the edges of the mould and lift it off the concrete. If the mould sticks, press gently in the middle and each of the corners to loosen the mould.
Tips and warnings
- • If you are planning to seal the concrete, cover it in cling film after removing it from the mould. Place it in a shady area and allow it to cure for one to two more weeks before sealing.
- • For a 12-inch square tile mould, a 1,360ml juice can full of concrete will fill the mould to 1/2 inch. It’s an easy way to get a consistent measurement.
- • Do not use motor oil or diesel oil fuel as a release agent. While this method was once widely accepted, it is now considered bad for the environment because of the potential for the release agent to get on the ground or in the groundwater.
- • Do not force dry the concrete. Force drying weakens the concrete.