Once the fire is burning, add the tree branches at random until the container is full. When the fire is hot, and will not go out, place a large rock over the top of your container, leaving a 4 inch gap for smoke to escape and air to enter. Dense white smoke will be prominent during the charring process.
Step
3:
charcoal-image
4
When the smoke turns from white to blue, cut off all air by placing the rock firmly over the top of the container. After the burn finishes (2-3 hours) allow it to cool. After cooling for 24 hours, your charcoal is ready.
step
4: 
charcoal-image5
To
react these chemicals, we heat about half of the materials to 850˚C,
the melting point of the mixture, in a furnace. Once this is liquid, we add the rest of the materials. Keep the furnace hot overnight to insure
that all of the products have completely melted down. After the substance has cooled, pour it
into a wood mold, and let it cool .
You then have a pane of glass. 
glass-image
6 click to see larger image