This mix was from lime (calce viva) that i slaked myself. Lime is made by burning limestone to form quick lime (calcium oxide) and then slaking the quicklime with water (forming calcium hydroxide). This leaves you with lime putty – you may want to read up on slaking lime by doing an online search. The Lime putty is mixed with sieved river sand as the salts from beach sand will ‘bloom’ staining your fresco and weakening your intonaco. I mixed in this case with a garden hoe and by hand- its always best to mix by hand. Some books will say 50 percent sand to 50 percent lime, however mixing intonaco cannot be learned well from a book or video, Its best to learn in person from someone who knows and then experiment a little to see what may happen with small changes such as different sands, different ages of lime putty and different proportions. Intonaco is the last application of the malta on the wall after the Rinzaffo and Arriccio and is the layer that fresco is painted ‘into’ , unless you use an ‘intonachino’ ….another discussion. The application of Intonaco becomes easier each time you do it, like many things in life practice makes almost perfect.