Using my 30w fiber laser and a 110mm lens I was able to get an okay dark mark on sterling by using med-high power, low speed, tight line spacing and peak khz. The BETTER way of getting a nice black mark on silver was to do a deep engrave then use liver of sulfur on the engraving, let it sit for a several minutes, rinse and use a fine grit sand paper to lightly sand off the tarnish from the areas i didnt want discolored. The liver of sulfur causes the silver to oxidize and turn dark but its hard to keep contained inside only the engraved areas so youll have to do so,e light cleanup on the parts you want to keep silver but it isnt too bad.
