To prevent de-carbonization for ordinary work, charcoal instead of coal is sometimes used; and where hardening is not done continuously, it is a good practice, because a few pieces of charcoal can be thrown upon the fire and be ready for use at a few minutes' notice. Charcoal should be used for the heating for the forging as well as for that for the hardening. Green coal should never be used for heating the steel for the hardening, even if it is for the forging process; because, while the steel is being well forged, its quality is maintained, but afterwards the deterioration due to heating is much more rapid. A coke suitable for heating to harden should be made and always kept on hand. To obtain such a coke, make a large fire of small soft coal well wetted and banked up upon the fire, and with a round bar make holes for the blast to come through. When the gas is burnt out of the interior coal, and the outside is well caked, it may be broken up with a bar, so that the gas may be burned out of the outside, and then the blast may be stopped and the coke placed away ready for use at a moment's notice. Good blacksmiths always keep a store of this coke for use in taking welding heats as well as for hardening processes.

It is desirable that the article be heated as quickly as possible, so as to avoid decarbonization as much as possible. If an article has a very weak part, it is necessary to avoid resting that part upon the coal or charcoal of the fire, otherwise the weight may bend it ; and in 3 heating long slender pieced they should bed evenly in the fire or furnace, or, when red - hot, the unsupported parts will sag. In taking such pieced from the fire, the object is to lift the edges vertically, so that the lifting shall not bend them; and this requires considerable skill, because it must be done quickly, or parts will get cooled and will warp, as well as not harden so much as the hotter parts.