Using dark mirrows, or obsidian mirrows?

Is somebody here using Dark Mirrows for evocation? Or even obsidian mirrwos?
I have only expiriences with crystal balls, and can really recommend using them.
Here is my small store, where you can purchase different kinds of them:

I do. I do this as part of my build up to a full physical manifestation. I call whomever up in a black mirror and question them, write down the answers and verify them. It is kind of like using a series of phone interviews before I set an appointment to meet with the spirit. I use the time to see if the spirit is the one I want for the job.

You can make your own dark mirror with a picture frame and black paint. You can inscribe your own sigils on the back as well.