First, go out and find your ore. Start out with something high quality that you know without a doubt what it is, even if you have to buy it. Keeps the variables down. Crush it into pieces no bigger than a pea. Dust is ok.
Get your charcoal gathered up. I think we used 70Lbs. Anyhow, just figure out how much the furnace will hold, then add to that the amount of ore you want to run plus 10lbs. Break it up into lumps that are roughly 8 to 10% the size of the furnace diameter. That will help alleviate what's known as the "wall effect" where furnace gasses escape through the gaps created by too large a fuel lump diameter. It will also prevent your ore from prematurely falling into the furnace hearth, where temperatures aren't really suitable for reduction.
For the furnace preheat, I start with gas. I did the last one starting with a little 1/2 sidarm venturi and gradually stepped it up to the bigger 3/4". The idea is to not thermally shock it. That's the problem with a gas preheat, but I was quite happy using this setup. I also like to put a lid on it for this.
Once you get the furnace nice and hot, add your solid fuel and put your blower on it. Also, you want your tuyer set at a 15 degree angle. It helps to cover it with some hard refractory so your iron doesn't weld to it in the furnace(ask me how I know) as you want it to extend an inch or so into the chamber.
When the furnace burns down enough, add the first charge. It can be anywhere from 3 to 5 to 15 pounds, the smaller the furnace, the smaller the charge; the fuel:ore ratio is 1:1 by weight. You can also add some crushed calcium of some sort as flux if you feel like it. Check and clear the tuyer periodically. You want a pretty high temp at tuyer level, about 3000f.
Tap slag out of the bottom every so often so you don't freeze the furnace up. Feel free to recharge the slag, you'll get a higher return on your ore. You can also charge hammer scale.
Rinse and repeat 'till you either run out of stuff to burn, freeze it up or otherwise reach the capacity of your furnace.
Oh, I recommend setting a grill on the top during the burndown for a cookout.
Forging the Bloom
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