Hello
You people experience problems of the modern world. There is maybe some advantage living in a country full of problems like Israel, however, where they still use some old ways of doing things like, for instance, slaking lime for plastering in pit like in the good old days. Restoration of old ruins (Romans and others) is national task hear and I get for free good sand of any kind, ground tile of different size, volcanic tuff etc from the official Department of Restoration. Sand is most important for the structure of the surface and for the "feel" of the brush and I like to experiment with it, in fact I look for a fat, a little "yellowy", definitely not blank white mortar and for that try all kinds of sands, usually by obtaining it from different suppliers, trying it first, and in case it works, check it in the labratory. My next exp. is trying the sand of the mediterranean sea which originaly come from the Nile, looks of ideal texure and might feet (against all odds) the strict demands of purity.