"Ven de cold air strike the cups," said Mr. Kleesman, "then the slag are formed."
"Oh, what is slag?" cried Rob.
"All that are bad go into the slag," said Mr. Kleesman.
Then he put on a pair of thick gloves, and a hat on his head, and went close up to the fiery oven door, and took out the cups, and emptied them into little hollow places in a sheet of zinc. The instant the hot metal touched the cool zinc, it spread out into a fiery red rose.
"Oh, how lovely!" cried Nelly.
"By jingo!" said Rob.
Even while they were speaking, the bright red rose turned dark,—hardened,—and there lay three shining buttons, flat and round. Their rims looked like dark glass; and in their centres was a bright, silvery spot.
Mr. Kleesman took a hammer and pounded off all this dark, shining rim. Then he pounded the little silvery buttons which were left into the right shape to fit into some tiny little clay cups he had there. They were shaped like a flower-pot, but only about an inch high.
"Now these must bake one-half hour again," he said; and put them into the oven. Pretty soon he opened the oven-door to let the cold air in again, as he had done before. That would make all the lead go off, he said: it would melt into the little cups, and leave nothing but the pure silver behind.
"Now vatch! vatch!" he said to Nelly. "In von minute you shall see a flash in de cups, like lightning, just one second: it are de last of de lead driven avay; den all is done."