Vine on copper : fail

I already told you about the beginning of my first try in engraving a plate of copper. Here are the next steps with, at first, the plate after a few weeks in contact with vinegar.

Everything was going well, I decided to remove the varnish and then washed the palte with water and soap to remove the last traces of white spirit. And suddenly, no oxyd any more :-(

No more blue, no more green, evrything disappeared in the cleaning :-((

We still can see the pattern but that's at all the result I counted on. Just have to do it again...