What it says in the title....
I have a project at work that may require very fine sand for a casting-esque process. I'm not actually pouring anything, I've got a variation on the V-process I'm using for some tooling to be used in composite manufacture.
Neither I, nor any of my colleagues, have every worked with casting before (as in actually working in a foundary) so we're a bit stumped on where to get it! Google ain't much help.