They crack if they are often melted again and thicken and burn, so that even if a salmon is made, the tin becomes thick at the bottom if it is not stirred often during casting. It is better for casting to melt some lead and some tin and to renew it each time. The antimony makes them breakable, the iced tin makes them whiter. Pewterers mix a pound of iced tin with a quintal of fine tin and two and a half or three pounds of red, mild cauldron copper, which is better than latten. There is fine and mild tin and sour tin. Pewterers cast the sour as grills to sell it better. They go better and more cleanly in stone moulds than in copper molds because copper is fat and draws the mild tin when heated. Or when casting a large work, three quarts of lead with one pound of mild tin produces a very liquid mixture which is appropriate for casting and is as shiny as a mirror. Laxunge glass lightens them. All things that lighten metals a lot and remove their thickness and natural density and make them as liquid as water make them appropriate for casting because their thickness stops them from flowing. The mild tin is more even than the sour tin, which is whiter and seems to have been polished like a mirror.