at left middle margin of folio 083v
To cast with a bellows furnace, cast the hottest you can. Do not place your bellows at the bottom around the base of the furnace, lest some coal should enter them. Place the bellows under the grate. It is wise to place your furnace in a place where there is wind so that the heat will grow better. It is necessary to stop carefully the doors of the furnace, that way only the bellows have an opening. At the end of the cast, you will blow slowly, as you did at the beginning.