The Appeal of Upcycled Concrete
Empty egg cartons usually go straight into the recycling bin. But with a small bag of concrete mix, that cardboard tray transforms into a custom, textured planter for your patio or garden.
Concrete is cheap, durable, and highly versatile. Using household waste like an egg carton as a mold eliminates the need for expensive silicone templates.
The dimpled shape of the tray leaves a striking, geometric texture on the finished concrete. It looks like a high-end architectural piece, yet costs pennies to produce.
Gathering Your Materials
You only need a few basic supplies from a local home improvement store. Pick up a bag of standard ready-mix concrete or Portland cement.
You also need a standard 12-hole or 24-hole cardboard egg carton. Grab some cooking spray to act as a release agent.
Finally, find a smaller plastic container to act as the inner mold. This will create the hollow space for the soil and plant.
Preparing the Mold
Thoroughly coat the inside of the egg tray and the outside of your inner plastic container with cooking spray. This prevents the concrete from bonding permanently to the cardboard and plastic.
If your egg carton has holes in the bottom, seal them with a quick piece of duct tape on the outside. This keeps the wet mix from leaking out before it sets.
Place the egg tray on a flat, level surface. Cover your workstation with a drop cloth or old newspaper to catch any spills.
Mixing and Pouring the Cement
Mix the concrete in a bucket with water according to the manufacturer’s instructions. Aim for a consistency similar to thick pancake batter.
Pour the wet concrete directly into the egg tray, filling it about three-quarters of the way to the top.
Tap the sides of the tray gently but firmly against your work surface. This forces trapped air bubbles to rise and pop, ensuring a smooth, solid finish without structural weak points.
Forming the Planter Space
Press your smaller plastic container directly into the center of the wet concrete. This pushes the mix up the sides of the egg tray, forming the walls of your planter.
Place a heavy rock or a few large washers inside the plastic container to weigh it down. Without weight, the inner mold will naturally float up as the dense concrete settles.
Curing and Finishing Touches
Leave the project undisturbed for at least 24 to 48 hours. Concrete needs time to cure and harden properly.
Once the material is solid to the touch and light gray in color, pull out the inner plastic container. Carefully peel away the cardboard egg tray.
The moisture from the concrete usually softens the cardboard, making it easy to tear away in pieces. Use medium-grit sandpaper to smooth out any sharp edges along the top rim before adding soil and your favorite plant.
