The Rockbridge Bloomery - Reports

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The Best Ore Roaster

Skip Williams

April 5, 2006

Ore roasting can be accomplished in many ways. The simplest way is to build a large wood fire on the ground or in a shallow pit and toss the ore on top. The problems with this are that it is near impossible to guarantee that everything gets well roasted and when you’re done you just have a pile of ore and ash that is difficult to separate.

We’ve designed an ore roaster that overcomes these difficulties and really cranks through the ore at 75 pounds an hour. Since we generally roast 500 pounds at a time, an afternoon’s work will suffice for four or five smelts.

Construction

The roaster is a large cauldron made from the cut off end of a propane tank. It is four or five feet across and slightly over a foot deep, it sits on a five foot by five foot piece of sheet metal. Several 5 inch diameter holes have been cut through the cauldron to allow air in and to allow the ash and roasted ore to fall out. The center of the cauldron is just dead air space which I have filled with an upturned metal can.

Loading the Roaster

The cauldron is first filled with small wood that will quickly burn to become a charcoal bed.  Over this, layers of large wood strips and 4x4 bolsters are stacked.

Photo - Darrell Markewitz breaking ore.

The raw ore is busted into fist sized pieces. 20 pounds of ore are added to each layer as the stack is built.

This stack is at least five feet tall and contains 250 lbs of ore. When all is ready, the fire is lit and we sit back for the first hour or two and wait for things to get really hot.

As the fire burns down the roasted ore and charcoal will fall into the cauldron and heat up to a bright orange color. 

We continue to add new wood and ore to the top of the stack as long as we like.

The roasted ore will fall through the holes in the cauldron every once in a while. Ore that has fallen on the sheet metal is visible in this picture.

The ore is scooped up and thrown directly into a container of water causing it to fracture and fragment into many small pieces. It is then shoveled onto a tarp where it will air dry for a couple of days.

We find that when we roast our locally available hydrated ores (limonite, goethite) this method produces a very friable product that is ready to go into the bloomery furnace. We also notice, while poking through the remains left in the cauldron, that we always make a little iron in our big campfire.  A good Omen for the coming smelt!
Skip Williams