Your color method will work, but requires a pretty even heat source to accomplish, which is why I recommended the oven. The kitchen stove oven will hot a consistant 500 and hold it with no problem. You can also control things better. After a couple of hours you can pull the blade out using an oven mit and hit it with a file. the file will probably skip. You can pullit out and check it evey 30 minutes until you feel the file just barely brab the metal. It is perfect at that point. You can never meintain that kind of control in the fire.
Tempering and quenching temp is really not as critical on these all around steels. Get it good and red or hot enough that a magnet will not stick and plop it in a good oil bath. That will make it brittle and allign the structure. The trip through the oven will draw the brittleness out. Time in the oven can gauge the brittleness but that takes trial and error on "found steels". Not enough time in the oven and it will be hard, and spark, but will probably break. Too much time in the oven and it will be back to its anneled state.
It is the same with the forge drawing process you discribe, only very quick with no room for error. A second too long or past the color and the temper is disrupted and the metal goes soft. Not hot or long enough and you have a blade resemvling a piece of glass. I have several knives I have tempered and drawn at the historic sites where the process you discribe is necessary. I like to place a big slab of metal in the fire and get it white hot, lay the spine of the blade on the white hot slab and watche the heat creep up the width of the blade. When the spine heats and the "Blue Line" starts creeping up the blade I remove the knife from the fire as the color line reaches the middle of the blade, whatching and hoping it disipears before it hits the edge. This gives you a soft spine and hard edge, if all goes perfect, the fire was perfect, and the color was actually what you thought you saw. Occasionally it actually works.
If I am making blades for others they usually go in the oven, just so I can say they are "right", will sharpen and will not break.
For fire steels you skip the annealing process. You want them hard, brittle and sparky. The concrete nails are very inconsistant.
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