PSU medieval Iron Smelt
 
 
Our Smelting day took about 8.5 hours in total.  We started warming the furnace about 10:30, switched to a blast-heated charcoal fuel a bit before 12:00, added the first charge of ore just before 12:30 and added the final ore about 5:30.  By 7:00, the remaining charcoal had burned down and we tore the furnace apart. (We had to wait for the whole bloom mass to cool overnight, though, before seeing what we had.
The Day of the Smelt
Warming the furnace with hardwood first
The charcoal has to be broken down into smaller pieces
Standing around contemplating the furnace... we did a lot of this
Once lit, it acted as a very nice chimney (no blast yet)
Charcoal gets added slowly
Wenda adds some ore, about 1 cupful at a time
As the blast increases, Nick feeds the fire
All guests get a chance to feed it - here Anthony pitches in
The furnace going full blast (that's where the idiom comes from)
It shoots out some sparks, but not dangerously
Sparks do fly, but they’re just fly ash (like sparklers)
At full blast, nearing the end of the day
Glow from inside the furnace appears through the wall near the tuyer
Adding charcoal at full blast
And a view inside the furnace