But if you're going the route of making your own dark finish, here's a couple ideas. There are many methods out there, but I'm going to share two of them here.
This first one works on wires in silver and copper. I've never done this with brass filigree, though I think I will experiment with it in the near future. This tutorial was made by Szilviabead on DeviantArt.Com, please visit the original to see the creator's comments.
A hard boiled egg is certainly the lowest cost method I've ever seen. This next method will require that you spend a little money, but it's still a reasonably priced alternative.
You can purchase liver of sulfer in multiple forms, the simple version is to buy the gel, which you can find on Etsy.Com or here at FireMountainGems.Com This form of liver of sulfer is wonderful because you don't have to worry about mixing anything or equalizing the chemical when you're done.
These pictures are the step by step process of how the liver of sulfer gel works on copper wire, these are by Geisha Creations. She buffs the wire with steel wool when it's all done soaking in the liver of sulfer, to get the lovely shine and bring out some of the original color.
Please visit Geisha Creation's Facebook page where the original images are located, here.
Hope you find these tips on applying your own finishes useful!