Concrete planters are an extremely popular craft as they are cheap, fast, easy and there are a lot of shapes to try. The mix for these planters consists of 2 parts dry cement mix to 3 parts sand and water. As a general rule, the more cement mix you add, the paler the end result will be, so if you want a very light grey finish just add 3 parts each. Fill a plastic mixing bowl with the wet concrete mix and give it a good tap to bring any air bubbles to the surface. Then take a small round tupperware container and plunged it into the wet mix. The rest of the tutorial is here.