Another Cyanotype Fail

I know eventually I'm going to get this, but whew... By get this, I mean successfully bleaching and then toning a Cyanotype.

I know this can work, because it worked on an exposure test before I started exposing negatives. I bleached the exposure test in a mild sodium carbonate solution and then toned it in a ferrous sulfate solution. Almost instantly, the remnants of blue in the bleached image turned a beautiful greenish black. But I've been unable to duplicate the effect with an actual exposure of a negative.

My only thought is that I didn't over expose the negatives enough, so I'll try longer exposures on the next batch, hopefully tonight or tomorrow.

Meanwhile, here's the latest failure. The bleaching certainly worked, the toning not so much.

I also plan to try toning in Tannin as soon as that arrives.