Aluminium concrete moulds are used to create multiple concrete castings of an object. Aluminium is an inexpensive mould-making material and with proper handling a single mould can be used to create thousands of exact replicas, making it useful for a large variety of projects. Whether you're creating stepping stones for walkways or decorative garden statues, using an aluminium mould requires that you do little more than mix and pour the concrete.
Prepare the aluminium moulds for the concrete by spraying the surface of the mould with a release agent. Create a release agent by combining 473ml. alcohol with 59.1ml. castor oil. Place the mix in a spray bottle and lightly cover the aluminium mould.
Place the mould onto a flat surface stable enough to hold the weight of the mould with the concrete.
Mix the concrete in a large bucket according to the concrete manufacturer's instructions, using a drill fitted with a paddle bit. Alter the mix according to the detail work of the moulded part. Use less sand and more cement when smaller details are required in the part. Mix the concrete to the consistency of pancake batter for ease of pouring into the mould. Add colourant during the mixing process if coloured concrete is desired.
Pour the concrete into the prepared mould, beginning at a corner of the mould and pouring a layer 1/2 inch thick to cover the bottom of the mould. Gently tap the sides of the mould to force any air bubbles to rise to the top of the layer of concrete. Add the remaining concrete, filling the mould completely. Tap the mould again to release any air bubbles from the poured concrete. Allow the concrete to set within the mould for 48 hours.
Remove the concrete from the mould by placing a piece of plywood atop the mould and then upending it. Slide the mould from the concrete and then allow it to complete setting for about seven days before use.
Dry your concrete at a temperature of about 21.1 degrees C for best results.