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.
Introductory Observations on the Architectural Designs (XII), and Writings on Architecture (XIII).