How to clean a copper pan from black burned fat chemically? I have several copper pans which I use daily. I don’t have the time to always clean them. Now they have a thick crust of black burned fat. When I wash it with dish soda, nothing changes. And I don’t want to use abrasive mechanics (steel sponge), because I am afraid this will scratch the copper surface.

Is there a chemical trick to dissolve the black crust? What is that black crust chemically and why is it so strong?
The crust is a giant mess of hydrocarbons that have been burned, caramelized, and congealed into the surface of the pan. 

I would recommend that you try the steel sponge to get some of the crust off, you may find that as you start breaking into the top layers of crust that it will fall apart. Another strategy would be to put the pan in the oven to the highest heat that is safe for the cookware and this might cause the pan to expand enough to create cracks in the crust or release it from the micro-cracks that were already in the pan surface. As a last resort you will have to chisel it off slowly.