mix for the moon: 3/4 portland, 1/4 lime I left out the sand and had some flaking on the back of the piece. It was a sand cast. It didn't dry for days. In fact their are racoon footprints on the obverse side.
my usual mix is 3 parts portland, 2 parts sand, 1 part lime (for faster setting) and I usually add some structural support such as rebar or screening. On the moon, nothing.
regarding long-neck woman: the temp was so cold, around 30 degrees, that my hands were freezing out, and the mix was freezing before I could attach it to the sculpture. I tried using a teakettle of hot water for the mix. It was setting up in my hand. I have heard that is what the cement companies do...heat the water for the winter pours.