Damascene is an ancient technique of applying a metal overlay to a base metal for decoration. Someplace between inlay and metal leaf it has traditionally been done with gold and silver, but any two metals can be used as long and the overlay metal is softer than the base metal. Here I have used lead (diamond) and yellow brass (square) on mild steel base (these are only my first two attempts).
Damascene is accomplished by the mechanical application of a thin sheet of annealed metal to the surface of a harder metal base with a burred texture. The technique requires simple chisels capable of cutting into the metal base. The chisels and setting tools are fashioned of tool steel shaped, polished, hardened and tempered in the traditional manner.
Sharp chasing chisels and planishing tool. Chisels are made from 1/4in square 1075 high carbon steel; forged, ground, tempered, and polished. Planishing tool I forged from a large broken Allen wrench and also highly polished.
First step of Damascene is metal prep. Both pieces have to be clean and free of oxidation, oils, etc. The overlay material has to be thin (max .005 inch. To make your own cut a piece of 20g material of your choice 1 inch square and roll it through a jeweler roller until it is 8 to 12 inches long), fully annealed, and etched/pickled clean. Not only is the burr texture locking the two pieces together mechanically, it is also greatly increasing the surface area of the two allowing them to cold fuse together - this will only happen if both pieces are very clean. Once both pieces are clean transfer the design to the base metal. Avoid using pencil or other marking devices that can contaminate the surface. I am using marker.
Start by outlining the design. Grip the chisel as if you are holding a pencil with your off hand and drag the edge along your design while tapping with a small hammer. Go around the outline twice; first with the chisel held at a 90 degree angle to the base, then again with the chisel tipped at a 70 degree angle with your hand toward the inside of the design. You want to create a lifted under-cut bur all the way around the design. For curved lines use a smaller chisel that fits the radius. This step finalizes the outline of the overlay so care is needed.
After the outline is lifted the area inside the design or background needs to be burred. This is done in a crosshatch pattern to open as much surface area as possible. The chisel needs to be sharp and highly polished so the resulting cuts are also sharp and clean. Again the chisel is held like a pencil and 90 degrees to the base. But instead of dragging, the chisel is held slightly above the surface and bounced with each rap of the hammer leaving a uniform course of parallel cuts perpendicular to the movement of travel. Above you see my first set of parallel cuts in two courses.
Turn the chisel 90 degrees and repeat.
Now a 45 degree angle and repeat
The other 45 and repeat. The final burred background is crosshatched from all four directions. At this point I went back and re-lifted my outline but I don't think it was a good idea (more on this later)
Now the Damascene can begin. Again the overlay metal has to be thin (around .005 of an inch or thinner), full soft annealed, and clean. This piece of yellow brass began as 30 gauge (.010 of an inch) so I cut out a 1 inch square, folded it half with a piece of paper in between and rolled it until it was again 1 inch square. This effectively reduced the thickness by about half and created two pieces of 1 inch square overlay material. I annealed these and pickled in a 50/50 mix of hydrogen peroxide and phosphoric acid (can also use 50/50 peroxide and vinegar for brass) for about 5 minutes to get rid of all the fire scale. The side that had the paper came out a little dirty so I have it facing up.
Much like metal leaf, the overlay does not need to be cut to shape (what a relief!). With tweezers (watch out for hand oils on your clean metal), simply lay it over the design and the next step, planishing, will both lock it in place and trim it to size. Start in the center of the design with the polished planishing tool and a hammer and work out to the edges in concentric circles. As the overlay is driven into the surface the thin metal will stretch, so be sure it is locked in place before moving outward as coming back later may cause wrinkles.
Once the extra overlay metal cleanly falls away from the design the Damascene is complete. As you can see I still have a bit of a raised outline, I believe caused by lifting it too much after crosshatching the background... Further practice and this should lay flat and be a smooth surface.
For further reading here is the Ganoksin article where I learned this from. https://www.ganoksin.com/article/contemporary-applications-area-inlay/