The Swedish Lancashire hearth consisted of a rectangular closed furnace with a chimney (8 metres high) at one end and a working arch in front of the hearth proper at the other.  Pig iron was charged through a door at the foot of the chimney and stacked on an iron-clad bridge so that it could be heated by the waste gases from the hearth.  The hearth was blown through a single water-cooled tuyere with pre-heated air.  The hearth consisted of a rectangular box of iron plates, the bottom plate being water-cooled.  Surplus slag was removed with a shovel between finings, but some was left to help the process.  Pig stacked on the bridge at the back of the hearth was then pulled forward with a hook and charcoal added.  The blast was then turned on and fining began.
When the pigs began to melt, rabelling began (as in the Walloon process) using two bars of iron one to stir the iron and the other to lift it back into the blast.  Periodically the tuyere had to be cleaned of matter adhering to it with a third bar.  Finally, the iron was gathered into a loop which was lifted out of the hearth with a heavier bar and tongs, and taken to the shingling hammer.
The process was more fuel-efficient and more productive than its predecessors.