Iron bacteria, the source of ore for the furnace
Pouring iron bacteria into porous pot
The water slowly seeps out of the pot leaving the iron rich paste inside
The congealed paste
I'm going to roast the ore to drive off any moisture and impurities to see if it improves the smelt
Wood is stacked over a pit in alternating layers
The damp ore is placed on top of the wood pile and a hole is made in the middle to put the fire
Fire by friction,
Once you get good with firesticks, it's easier to maintain than a bow drill or pump drill due to fewer parts (rope etc) which is why I don't use the other methods anymore.
The fire is placed in the pit of the ore pile so it burns back down the wood pile roasting the ore
Specks of red hot ore fall through the pile into the pit
This is done in the hut so the rain doesn't affect the process
A few hours later the coals and ore are stirred and separated
The ore is grey from the ash but reddish brown when crushed. Charcoal is picked out to be neat but could probably be left in with no ill effect to the smelt
Roasted ore and residual wood ash
The smelting set up, roasted ore, charcoal, furnace and blower
Preheat with wood for an hour
Fill to the top with charcoal
4 single handfuls of ore
air blast for about 5 minutes
From now on 3 double handfuls of charcoal and 2 single handfuls of ore
After less than an hour and 7 charges of ore the charcoal has burnt down to tuyere level
The next day the resulting mass is taken out through the top of the short furnace
It is very glassy suggesting a good smelt
It's slag with large high carbon iron droplets embedded in it (the grey spheres)
Crushing the slag to get the iron out
The first nugget of iron
It can be tested by striking lightly with a stone, slag shatters easily whereas iron doesn't
This is larger than typical nuggets from unroasted ore
Another large nugget
A lot more pieces of iron than from unroasted ore
Panning the slag to get more iron still
Overall 33g of iron from roasted ore (typically get 15 g from un roasted)
Preparing another batch of ore
Collecting snail shells to test as a source of lime flux in smelting
The idea is that lime reacts with silica in the ore making it more fluid so that the iron comes together more making larger pieces.
Lime should also take the place of iron chemically bound in the slag adding to a greater yield.
The shells are crushed to a powder
The shell lime is added to the ore prior to the smelt to reduce handling
I'm also trying a taller furnace so that all the charges are put in prior to starting. Less interruptions to blowing air will mean a hotter smelt.
Furnace is about a meter tall above the air entry
Preheat about an hour again
9 double handfuls charcoal
3 single handfuls ore/shell mix
All the materials are put in before blowing the air now so there are no interruptions during the smelt
7 charges in total
The smelt goes uninterrupted for about the same time as usual
The product needs to be taken from the door in the base of the furnace now as it is too tall to be taken from the top
The mass is jagged and not glassy like the last smelt
No iron is evident prior to crushing, this is not a good sign
A tiny iron prill
This is all that came from the smelt, adding shells was a bad idea
Compared to last smelt, adding shells greatly reduces efficiency. This is probably due to the ore already being basic. Increasing the PH made the slag less viscous
Discarding the lime ruined slag
I'll try re-smelting the original slag (no lime) and see if any more iron comes out
Re-forming the door
Hour preheat again
9 double handfuls of charcoal
3 single handfuls of slag
then fill the rest up with alternating layers: 3 double handfuls of charcoal and 3 single handfuls of slag
9 Charges in total
The product is better than the previous smelt
Iron is immediately visible in the slag (grey spheres)
A good yield considering this was from waste slag from old smelts
Roasted ore smelt on right: 33 g. Recycled slag smelt on left: about 20g
All the iron I currently have at the moment from various experiments