"Ah, you know something of glass-making then, my young man?"
"A little."
"The pots are, as you say, a great lottery. Sometimes one will be in constant use three months or longer, and do good service; on the other hand a pot may break the first time using and let all the melt into the furnace. Then we have a lively time, I can tell you, ladling it out, and taking care in the meantime that none of the other pots are upset."
Giusippe nodded appreciatively.
Many a day just such a catastrophe had occurred when he had been working; vividly he recalled how all the men had been forced to come to the rescue.
"Are the pots filled to the top with batch?" asked Mr. Cabot.
"Yes, we charge them pretty solid; but the raw material loses bulk in melting, so they have to be filled in as the melt settles. At the end of ten or twelve hours we have a refilling or topping out, as we call it; usually this is enough. The first fill must become fluid and its gases must escape before any more material is added; we also have to be sure when we put the pots in the furnace that the temperature is high enough to melt the batch immediately, or the glass will go bad."
"What do you use for fuel?"
"Crude oil. In the West they can get natural gas, and there they often melt the batch in tanks instead of pots. But we find crude oil quite satisfactory. You can readily understand that we cannot burn any fuel that gives off a waste product such as coal dust or cinders, because if we did such matter would get into the melt and speck the glass, causing it to be imperfect. Much of the work done by the earliest glass-makers was specked in this way, and in fact the genuineness of old glass is sometimes determined from these very imperfections."
"I see," Mr. Cabot nodded.