Always follow the recommended powder water ratio’s and measure both the powder and water accurately. Always add the powder to the water:

• If too much water is added the mould will be weaker. This can create flashing on casting
• If not enough water is added the slurry will be thicker.

This has 2 effects –

1. 1) It will not be able to release the bubbles efficiently so bubbles may form on the surface of the casting
2. 2) The slurry will set faster leading to flashing. This effect will be explained in more detail later.