Well, totally off topic - I decided to test it with a small burger-sized cast iron frying pan. Not an oldie, a few year old, but has now gathered a good seasoning finish and lots of burnt nits around the edges and underneath. It was absolutely foul, hasn't been used for months.
Changed the cleaning solution to a much more concentrated one - not 400-1, more like 30-1. Set the temp to 80 degrees, waited for 9t to heat up, and then dumped the pan in and set it for 30 minutes. then let it sit for half an hour in the hot solution, which had changed from a nice transparent yellow to a colour pretty close to Massey Ferguson grey.
Took it out and rinsed it off - clean as a whistle. Cast iron doesn't sparkle, but if it could, this would have. It even stripped off the factory applies "seasoning", a baked on oil of some sort. it was just bare iron.
So I'll have to re-season it, which involves cooking lots of bacon in it and just cleaning it with hot water and salt (salt if it's really messy). That means I will have to eat all the bacon. such a cruel punishment, when all I did was clean it and restore it to if's natural state.