Here, just visible, the shadow of blackwork unpicked. I hadn't centered the pattern properly, didn't like the way it interacted with the edge, so out it came, leaving a trace of black fiber within the slightly larger holes. I am hoping the stitching will cover that little remnant.
I'm not happy with the way this one is centered either, so might have to find another square of fabric
This, on the other hand, has worked well - the difference in colour is down to the lighting
I'd forgotten what fun blackwork can be - the rhythm of the stitching so soothing, the patterns almost stitch themselves, and the back can look like cuneiform ...