So I ran out of the black scratchbords, but did find this small 4x4 claybord. I coated it with prussian blue watercolor ink and after letting it dry awhile, went ahead and started scratching. It doesn't respond in quite the same way -- the clay surface seems softer. This one will have to be coated with a clear protective coating to prevent smearing. It reminds me of the ocean. And may be part of a larger ensemble at some point in the future. This process makes the creative mind whirl.
Here's another artist who does scratchbord. She explains the process quite well if you care to peek: