XI. The Notes on Sculpture: 740.
740.
OF LUTING THE FURNACE WITHIN.
The furnace must be luted before you put the metal in it, with earth from Valenza, and over that with ashes.
OF RESTORING THE METAL WHEN IT IS BECOMING COOL.
When you see that the bronze is congealing take some willow-wood cut in small chips and make up the fire with it.
THE CAUSE OF ITS CURDLING.
I say that the cause of this congealing often proceeds from too much fire, or from ill-dried wood.
TO KNOW THE CONDITION OF THE FIRE.
You may know when the fire is good and fit for your purpose by a clear flame,
and if you see the tips of the flames dull and ending in much smoke do not trust it, and particularly when the flux metal is almost fluid.
OF ALLOYING THE METAL.
Metal for guns must invariably be made with 6 or even 8 per cent, that is 6 of tin to one hundred of copper, for the less you put in, the stronger will the gun be.
WHEN THE TIN SHOULD BE ADDED TO THE COPPER.
The tin should be put in with the copper when the copper is reduced to a fluid.
HOW TO HASTEN THE MELTING.
You can hasten the melting when 2/3ds of the copper is fluid; you can then, with a stick of chestnut-wood, repeatedly stir what of copper remains entire amidst what is melted.
