Probably too late but it is equally quantities of water to the mould powder (pot B, 1pot for babies, 3 pots for over ones) and for the casting stone powder it is: water - up to the mark on pot b to five scoops of the powder (times by three for over ones)
HTH

The mould mixture set too quick when I did it so it was rubbish for me but my sister did some really good ones.

It's a powder that you mix with water (can't remember how much!!) to make a latex mould, which you put a dc's hand or foot into and it sets after 2 mins, then you take out the hand,(or foot) and fill the hole with plaster of paris and you have a little tiny cast of a baby's hand or foot. Looks great, if I could only work out what the ratio of mixing is

What is magic custard?

we bought some of this some years ago, and used it to cast ds2's foot, but although we have enough left for dd, I can't find the instructions!!! does anyone have any?