This will teach you how to make a katana, or any other crucible steel weapon

Step 1: Step 1: Introduction to Crucible Steel

What is crucible steel? Crucible steel is a carbon steel made in medieval Far East/Middle East. It was almost pure steel, as the forges that made it were highly efficient. These forges had a small opening for excess heat to escape, a larger opening for extra oxygen to fuel it. This steel is special due to having minute amounts of slag, impurities in the steel, and being tempered, strengthening it more. The steel Is made in a crucible, a vessel that contains iron, carbon source, and sand to absorb impurities. The vessel was sealed and heated to at least 3,000 degrees Fahrenheit. This was so the impurities would melt away.

Step 2: Step 2: Forging the Blade

Now that you know what crucible steel is and how to make it, make crucible steel with varying degrees of carbon, to make three types of crucible steel, softer steel at the back of the sword, half and half heart-steel, and diamond-hard blade steel. Heat these to soften them, and pound them together and form a long bar. This bar should be about 4 feet, 10 inches. Leave the heart and blade steel out of the last 10.5 inches. That will form the hilt and edge less bottom portion of the blade.

Step 3: Step 3: Taking Shape

There are 2 ways to make the blade take shape. Heat it up and hammer it to a very sharp edge, or use a grindstone made of a material with a Moh's scale number of 10 or higher. Moh's scale determines how hard a substance is. Knife sharpeners are 10 or higher oftentimes. I have no idea which is faster, this takes a long time. Be sure to make the blade curved, without the curve it is more like an elongated ninjaken.

Step 4: Step 4: Tempering

Before tempering, be sure to engrave if you are going to. When that is done, temper have blade. Get the metal to a dull orange, then take it out of the flame and cool it rapidly. Use anything from water to blood, but not acid of any kind. If you hear a metallic pop or ping, you messed up and have to start over.

Step 5: Step 5: Polish

This is more necessary than thought, as it not only makes the blade pretty. Be sure to use a variety of stones, with finer grains as you go. Do not rush, this is a delicate job. When finished, feel free to put the katana in a showcase, on your wall, or whatever, except for illegal stuff.