Steve,
I have gone to Bill's ratio. Yes, almost 6:1 water. I did one etch with it lastnite at 5 seconds and it stripped the blue off very quickly. I'm getting ready to do it again in a few minutes after having rusted 3 times and gotten a decent deep blue. I recall Oscar mentioning that he sometimes blued several passes to one etch.

Currently, the solution Bill proposed is about 6% as near as I can figure. The RS MSDS on the web says it's between 32% to 45%, so I swagged at 40. But if this etch produces little contrast, I'm going to dilute further.