I have been casting aluminium for various projects for the last ten years, you could say that I have a fair amount of experience. I'm not so sure. I have always used greensand for my moulds, when I started I had no choice but to use sand from the beach and cat litter as a binding agent. I did this whilst living abroad and on returning to the UK I met with the availability of materials that I could have only previously dreamed of. Or so you would have thought. For the first four years all was fine but last winter my supply of greensand was flooded by the rain and I had to start again this year. Despite my best efforts I could not produce a decent mouldable sand. then I remembered a Youtube video I had watched on using lost foam casting. What a revelation! It made everything so much easier, and cheaper. If you are casting something simple that does not involve complex pattern making then lost foam is the way to go. The fumes and flames are a bit scary but it works and needs no special preparation of the sand!