I thought I had it all worked out there, didn't I? Ho ho ho. Luckily I have Mr Willis to help me, because otherwise I'd still be ignorant...
It turns out that in addition to ALL the other mistakes I made last week printing this damned edition, I used too much chalk when dusting the plate just before printing. The chalk has mixed with the ink and set hard on the plate. I thought I'd cleaned the plate off successfully every couple of pulls and didn't worry about the 'blackness' still in the etched lines because in my (apparently limited!) experience the lines often 'go black', but it turns out the lovely aquatint I put into the lines is clogged with a baked-on mixture of ink and chalk.
I'm currently experimenting with various solvents to see which one will break down the mixture so that I can clean the plate off properly and start again! And I've put some tonic water in the freezer to cool down so that when I've finished my nightly taxi service, in a few minutes, I can have a large gin and tonic, because I feel like a twit. I'm saving the chocolate I mentioned until a bit later on... when hopefully I'll have a clean plate.
The nice thing about Willis is that although he always gives me a quizzical look when pointing out my mistakes, he manages not to be a patronising bastard about it, for which I am very grateful. It means I only feel slightly smaller. Anyway, Willis is about to embark on a fun-packed trip to the USA and UK, where he'll combine putting work into an exhibition that has been conceived of by Julian Schnabel with not one, but two, artists' residencies, so good luck to Willis and let's hope that I don't muck anything else up while he's away!