Max Nitsche-Niesky recommends the following in Neueste Erfindung.: Good coke is ground and mixed with coal-tar to a stiff dough and pressed into moulds made of iron and brass. After drying for a few days in a closed place, it is heated in a furnace where it is protected from the direct flames and burned, feebly at first, then strongly, the fire being gradually raised to white heat which is maintained for 6 or 8 hours. The fire is then permitted to slowly go down, and when perfectly cold the carbon is taken out of the furnace.