Sweat soldering is a simple process that can be used to create depth, texture or contrast to your work.
Solder is applied to the back of the piece that is going to be the top of the finished item. It is cleaned and positioned on the back plate and the complete piece is then reheated until the solder flows between the 2 pieces. The surfaces of course have to be flat and free of grease.
Here's a piece I have just completed.