I got this from Mike Blue.
If you want to know for sure that a piece of steel is as soft as it can be, you have to anneal it before working on it. That way you can save yourself time and effort, since you cannot know how the steel was treated before it came to you.
You have to heat the steel till it is red hot and demagnetised completely. You can check this with a magnet.
At that point you immerse it in something that acts as a perfect insulator. Wood ash is a perfect material for this. Then leave it to cool off over at least 24 hours.
Be careful: wood ash is a perfect insulator. If you stick your hands in the ash after 24 hours, there is a real chance of burning your fingers really bad because the steel will still be hot enough to burn you.
Some practical points: you need a pair of tongs or vice grips so that you can remove the steel from the fire to check the temperature, and place it back if needed.
I was already firing the steel when I discovered this practical problem. Also, since I was abusing my smallish bbq for this, putting the big piece of steel back underneath the coals was a bit of a problem.
So I decided to simply stoke it as hot as possible, and then extinguish the flames by pouring a bucket of ash over the coals.
This was a partial sucess. Since I did not have a bandsaw, I simply used a hacksaw to cut off a strip of metal lengthwise for my first project (a Japanese style cutting knife for my mother).
As I was sawing I discovered that the part that had been in the core of the fire was noticably harder than that part outside of the core, which was also the part I could peek at through a hole between the coals.
Cutting all the way through took a lot of time and effort.
The nice thing about doing things by hand though (at least the first couple of times) is that it really teaches me a lot about the metal that I would never learn if I used power tools, because I simply wouldn't notice.
