Then I tried applying the strongest mixture to more prepared stitched Shibori pieces, soaking them in the soda/salt solution and then applying the dye with a syringe. They were, of course wet when the dye was applied, cold that explain the stronger colour -- not according to the module notes, instead the patterning should be softer. The colour too?
Zigzag Machine Stitched.
Cross-hatched Machine Stitching.
Wavy Vertical Lines Machine Stitched.
These three samples have the tonal range, movement and markings I had hoped for. I also feel, though I've yet to put it to the test, that I could recreate any tones within the sample range. Such a relief! Still more work to do, but this is better. Maybe it's my greater experience which is evident.