It has been 24 hours since I fed my revived sourdough and my heart is singing, because it's alive!
This is what it looked last night - sort of half-time:
Most definitely bubbles, not to mention that it had risen, though I forgot to mark the original level.
Today I opened the jar to get a smello-visual confirmation:
The book said that now it would be the same as at the end of Stage 4 and ready for use. Actually it is quite a bit runnier this time and I don't need to bake right now, so I've put it in the fridge and will feed it in 3 days as per the instructions. This amount seems fairly good and I'll see if I can maintain it without discarding any ferment. It's about half of what I originally ended up with for baking, thus I should be able to manage better and just do one loaf at a time, rather than four in a quick succession.
I noticed that it's quite obvious how big it got at one point - double volume at its peak. This is just before I put it in the fridge.
I've spent the last couple of days reading up on sourdough and keeping one going, it seems that it can be quite badly neglected, i. e. not fed for a month, while in the fridge and still have some life in it. Or it can be fed once or twice a week and go on forever. Either way, it should be "perked up" to be at the peak of it's abilities when baking. I'll give it a try when I bake next time and I'll also try to make a slightly harder dough next time so that it doesn't spill everywhere. Though that might have been due to over-proofing.
Talking to friends in Sweden, it seems to have become so very fashionable to bake with sourdough, that even the shops sell it, though when I looked, I couldn't find any and so didn't try it out, as I'd planned. Just as well, though, my Mum had outdone herself on lovely food as usual, thus no need for additional bread delights.