When using a plastic mold there are a few easy steps to take:
1. Lubricate and brush evenly the mold with a mold release agent such as a spray of butter or vegetable oil found at the grocery store.
2. Mix the concrete.
3. Add some concrete color at mixing, add a color or concrete stain later or leave the concrete its natural gray.
4. Pour the ready mix concrete into the molds and vibrate a bit to compact the concrete and release air bubbles. Tapping with the trowel in the process in a trembling manner is
also a good practice.
5. Let the filled molds sit for at least 24 hours.
For bigger compositions a couple of days wait won’t hurt.
6. Flip the molds and place the composition over something smaller. This will allow finger space at removal and also protect the edges by not placing them directly on rough hard surfaces. Gently remove the molds and handle the newly made concrete with care for the next few days since corner edges are fragile at this time.
7. A concrete sealer can protect weathering while leaving a mat or glossy finish.
Through a process called hydration, the cement and water harden and bind the aggregates into a rock like mass. This hardening process continues for years meaning that the concrete gets stronger as it gets older.