When you get the right materials in place and focused you can make a solar furnace that gets hot enough to melt steel. It has to do with mirrors focused toward the right angles of the sun and the size of the mirrors and adjusting the right focal points. All physics and mechanics come into play in the correct design.
In reality, you can make any size of solar furnace that you want or need for your particular use. If you want to burn toast you can build it one way and if you want to melt steel, you build it this way.
It doesn’t take many materials or time to build this solar furnace.
Make a powerfully hot solar furnace…