"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. "After the melt is in a fluid state it throws to the top, provided the heat is sufficient, many impurities such as bubbles and scum. These are, of course, skimmed off--a process called plaining. Afterward the hot material has to be cooled before it can be worked, and reduced from fluid to a thicker consistency. This we call _standing off_ or _fining_." "How long does it take to melt the batch and get it ready to use?" "About three days. We run a relay of furnaces--three of them--and plan so that a melt will be ready to be worked every other day; in that way we keep plenty of usable material on hand." "And then?" "Then we are ready to go ahead and blow it. We make nothing but the better grades of blown glass here; that is, no window glass or cheap pressed ware. Of course there are some patterns, such as fluted designs and their like, which cannot be entirely fashioned by the blower; therefore these are first blown as nearly the required size as possible and are then made into the desired form by shutting them inside iron moulds and squeezing them into the proper shape. You shall see it done later on." He now led them up to where a gatherer stood at one of the working-holes of the furnace. "This man," explained Mr. Wyman, "is collecting on his blow-pipe enough glass to make a pitcher. He uses his judgment as to the amount necessary, but so often has he estimated it that he seldom gets either too much or too little. He will next carry it to the blower, who will blow it into a long, pear-shaped cylinder the size he wants the pitcher to be."