Can't help much but DC will do that . I etch with ac to get the depth then switch to dc to make it black.
Bass Ackwards.
DC Etches, AC Blackens...
Did you tape off the spare wire on the transformer, or ground it like the Crawford instructions state?
Do NOT ground it, tape it off.
Are you running 12v or 24v?
12v is better than 24v, 16v is better than both, but requires a doorbell transformer instead of the radio shack transformer.
Do you have the leads connected properly?
I don't care about colors, the Crawford plan has screwy colors.
Positive is the Blade, negative is the electrode.
What are you using for electrolyte?
Salt water works, sort of, but proper electrolyte is inexpensive and orders of magnitude better.
Same thing, better schematic found here.
http://www.knives.mlogiudice.com/knifeshop/etcher/