Sekkaboku is the crayon molded to different shapes used in Japan to rub the images found on the metal of the sword. The shape is key. The original crayons that I bought were broad and tapered at the end to make a higher quality rubbing. The crayons need to be similar to sekkaboku, with a shape to make the rubbing easier and better. I believe that sekkaboku are made with compressed india ink. That might be a follow-up instructable.
Step 1: Tools to Make the Tool
2. Empty metal cans. (SomArtMama recommends pop cans with the tops cut off and crimped.)
3. An old pot.
4. Forms in an appropriate shape that the melted crayons can be poured into. (use your judgement.) I use seashells or different shaped tins. Make sure that the melted shape can be easily taken or popped out of the form.
You want a shape that will make rubbing easy and expertly done. The original sekkaboku that I used was a bell-shaped wedge. (picture). Literally a bell shape, like, a traditional bell with Japanese characters on it. So far I have round that a small tin of snus tobacco from Camel (picture) works will too. You want to be able to get the solid crayon out whole so figure it out.
5. A small razor or knife. This is used to make shaving of the crayon so it will melt more easily.
6. A camping stove with fuel.
8. New or old crayons that can be melted without burning or creating fumes.
Step 2: Melting and Pouring
Bring a shallow level of water to boil in pot on stove.
Break crayons into reasonable pieces and place in metal tin. To mix colors in a marbling way, you might melt colors in separate tins and then pour them together into the same mold.
Once the crayons have melted in the tins, find a safe way to pour them into the mold.
Step 3: Cooling the Shape
One step that I have tried is placing the shape in cold water. This cools it faster and my pull the crayon away from the mold.
Step 4: Pop It Out
Now find some good paper and hard image and see what art you can make from rubbings.