The blast furnace is a smithing activity. It takes a bit longer than regular smithing, but you use half the coal you would normally.
Steel = 1 coal + 1 iron ore
Mithril = 2 coal + mith ore
Adamant = 3 coal + 1 addy ore
Runite = 4 coal + 1 runite ore
For me personally, the save in cost makes up for the time lost in smelting this way, but I appreciate that many prefer speed over saving money.
Anyway, for those of you who want to know how to play, the official world is world 58. I do use this world, but sometimes I just rather solo. For the purposes of this guide, I am soloing on world 117, smelting Mithril. I am using the smelt and bank method
, however there are anvils within the blast furnace room, should you wish to smith while you are there. (Should you wish to smith items within the blast furnace, there is a shop (Jorzik's Armour Shop) who will buy some items from you. You should check however, in advance
, what he will buy and what prices you can get from him) I use the trapdoor at the Grand Exchange to travel to Keldagrim, and a duel ring to mobilizing armies then the spirit tree back to the Grand Exchange in order to bank. This is the fastest way I have found. Keldagrim bank is accessible, but is on the opposite side of the river, and is quite a walk.
In my inventory I have a hammer (to repair pipes, but also as a space holder) Cash (to unnote ores) Coal (for unnoting) and 25 mithril ores. i find 25 an easy number to work with, as you can unnote coal in batches of 50, making it a nice easy maths job!
This is what the blast furnace itself looks like. You will see the two traders, Ordan (who unnotes ores up to mithril) and Jorzik (the armour trader).
Firstly, place your ores on the top of the conveyor belt, which is up the long ramp.
Then, trade Ordan and unnote 50 of your own coal. Put this with your ores, on the conveyor belt.
Then the fun starts! Sit on the bicycle and pedal until your coal and ores fall into the furnace. This gives agility exp, but runs down your Run energy too. The conveyor belt can break in two places. If this happens, just click to fix it (with a hammer in your inventory).
Next, pick up the spade which spawns next to the boiler and click to shovel coke into the boiler.
The boiler itself has three different heats. You want to keep shovelling until it reaches the third colour, shown above. Then stop. It doesn't need to go any hotter, and won't.
Now, it is time to pump the handle. This gives strength exp. You have to be watchful however at this point. If you over pump the pressure will get too high and blow up, causing you damage! You can either have someone watch the temperature gauge for you, and tell you to stop when it hits green, or just watch for the splash as the hot bars go into the dispenser.
Sometimes, as you pump, a pipe somewhere will break. With a hammer in your inventory, simply repair it. If your bars are not yet done, go back to pumping and they soon will be.
Stop pumping as the bars splash into the dispenser.
Go to the water source, take the bucket spawn from the floor, and fill it with water.
Throw the water all over the orange glowing bars, to turn them a cool green. You can now click the bar dispenser, and take your bars!
All that is left to do now is either smith them, or bank and repeat!