This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
One-half of the piece-mould is placed on the table, that is to say, one of the copes, with all its pieces, and the mould is wetted with water in order to prevent the wax from adhering to it; the workman then, with his thumb, presses wax into all the hollows of the mould: this is an operation of considerable delicacy. The wax, which must be very pure and malleable, is affected by the weather, working more easily in summer than in winter; the most suitable quality for average temperature is composed of 1 lb. of yellow wax, 6.2 lb. of mutton fat, 0.1 lb. of white pitch, melted together and coloured a deep red with alkanet. The wax pressed into the mould should be 1/12 in. thick. When all the hollows of the first cope have had wax of the requisite thickness pressed into them, the same process is applied to the second cope; the two copes, on being united, form a complete mould; they are then tied together with strong cords, and the joints of the copes are smeared with clay so that the mould should be watertight. In the meantime another description of wax of harder consistency, composed of 1 lb. of yellow wax, 1 lb. of resin, and 1/4 lb. of Venetian turpentine, has been melted in a cauldron and allowed to stand on the fire until the froth has subsided.
The wax, being ready, is left to cool to 140° or 158° F. (60° or 70° C), when it is poured into the mould, which it fills, and is allowed to remain there for 40 seconds; the liquid wax is then poured out of the mould into a bucket prepared to receive it. On examining the interior it will be found that the soft wax which was pressed into the mould has received throughout a coating of strong wax 1/8 to 1/6 in. in thickness, making an entire thickness of about 1/4 in., which will be the thickness of the bronze when cast.