Back during my blacksmithing days, the coal was washed, slack separated and saved. All was usually done at the forge in a tray with weep holes to the ground. For welding fires, a mound of larger chunks was laid down and started to burn from the inside. Then shovel fulls of drained but still very wet slack was troweled onto the outside of the mound. It makes a gigantic smokey mess as the coal turns to coke. (In a shop where the smokestack draft is poor this can lead to gambling which happens first: burnt eyebrows or death by explosion when the gasses ignite. I usually met the fate of death by explosion.) But it forms a hard shell which reflects the heat to the welding zone and keeps the atmosphere inside reducing (not oxidizing). Thus, the slack created an optimum temporary oven for forge welding. As the fire burns away at the coked shell, the outside of the shell is tamped with the back of the shovel and more slack is troweled onto the outside. Tamping the shell consolidates the shell and knocks coke loose from the inside where it falls into the fire, now acting as fuel. The second layer of slack does not create billowing plumes of gas like the virgin layer. It cokes more slowly and the fire is now hot enough to burn the off the explosive gasses. Given enough slack, the fire can be kept going for many hours. Also, there are far less clinkers as the incombustibles are heavy and generally sink to the bottom of the tray which are easy to separate with the shovel. Slack is not used in general forging as it blows off without combusting or in the worse case with high volitales it does combust and while blowing off. That's when I do a vigorous RAIN dance to purge all the fire bees that are down the back of my shirt.
El Wet
Re: 483 Getting Ready=Chama Yard =Photos