Q. How does fermentation make the dough rise?
A. During fermentation, carbonic acid gas is evolved; but the sticky texture of the dough will not allow it to escape, so it forces up little bladders all over the dough.
Q. Why is dough placed before the fire?
A. 1st—Because the heat of the fire increases the fermentation: and
2ndly—It expands the gas which is confined in the little bladders; in consequence of which, the bladders are blown up larger, and the dough becomes lighter and more porous.
Q. Why is bread heavy, if the dough be removed from the fire?
A. Because the dough gets cold, and then the air in the bladders condenses,—the paste falls,—and the bread is close and heavy.
Q. Whence does the heat of fire arise?
A. The carbon of fuel (when heated) combines with the oxygen of the air, and produces carbonic acid gas: again, the hydrogen of the fuel combining with other portions of oxygen, condenses into water; by which chemical actions heat is evolved.