Take a crusol that can contain a certain amount, as you wish to place roughly crushed borax into it. Place [the borax] at the bottom and then the gold on top of it. Arrange the coal in the forge in such a way that the wind of the bellow will blow above the crusol and no on its side as it would cool it down and would not heat it enough. Also, make sure it is three good fingers away from the wall of the forge so that it is quite surrounded by coal. Allow the crusol to anneal until it is quite red. Then, have your boy strongly blow the bellow with long pushes, as in this manner it heats it better. Meanwhile, once the gold will be melted, blow a small bellow above it. Because [otherwise] the gold would turn sour and would acquire some kind of coat. As long as there will be some swirling smoke as you blow this way, it means that it is not soft enough for the cast. Therefore, uncover the melting pot and without displacing it and without stopping the bellow, tilt it towards you so you may well see what is inside. Throw a ferue of borax in it and blow wind towards it with the small bellow in a jerky fashion. Should there be coal inside, blow a bit stronger to make them come out. And if the gold still smokes and swirls, add borax again and blow above it. Beware that it is still sour and not soft enough, it will show a coat when you blow it as if it had cooled down. By contrast, if it does not show this sign, it is soft enough. Then, blow strongly so that it [the gold] is quite heated and once you think it is hot enough, throw colour on top of it in the crusol and the colour should be composed as following: verdigris, saltpeter, sal ammoniac, and a bit of borax. And continue blowing with the small bellows, and the gold will turn shiny like
at left top margin of folio 135v
If you cast in gold some piece of important [dimensions], lute your mold with the same sand or put crocum on it.
at left top margin of folio 135v
If you wish to cast some large work, or of important [dimensions], create at the bottom or at an extremity of the forge a vented furnace where you may hold your mold in the sand so red.
at left middle margin of folio 135v
One may cast two or three pounds of gold.
a mirror. And once you will want to [start] casting, put a bit more colour in and let it rest a little, still blowing wind with both the small and the large bellows. Finally, place your mold quite red between the small molds or in a crusol full of sand quite hot and [start] casting. And once it will have stuck, you may, if you wish, throw it into water as gold does not get damaged like tin which breaks.
To melt gold bullion, there is no need to blow above [the crusol] with the small bellow.
For large works, the crusol made of sand has to be placed in a wind oven so that it is all red at the end of the furnace.
Gold, when exposed to wind or when forged becomes black. But a bit of aqua forte removes [the black] instantly.
If you have to forge a work made of gold on brass, as is done on small statues, put a lead sheet between the gold and the brass, and rather than anneal it and put it back in the fire, dip it in the aqua forte and it will be soft.
It is enough for the cast to be of the same thickness as the medal, that it from the middle of the cast, up to the medal. But if the medal is very thick, one should not thicken the cast as a result, because a thick cast never comes out well. It may be done large to embrace the medal as much as possible.