So just sharing the results of my experiment a few weeks ago. Very interesting. I decided to give Kvas a go. It's a drink made from left-over bread. Much how I imagine ale to be like a very long time ago. Anyway, this was not a scientific experiment, so you will have to forgive my lack of rigour with this. Everything is approximation. I didn't make notes. Doesn't seem to be in keeping with the spirit of this type of drink anyway. I had about loaf of left over bread crusts which I had frozen. I toasted them, ripped them up and put them in a BIAG bag in a small fermentor. I poured on boiling water and cold water hoping to hit 65c but never did. I think it got to 55c. I covered it and let it sit for an hour. I made no attempt to keep the temperature up. After an hour I took out the bag and left the wort (?)/ bread water in the FV. I waited for temp to drop to 20c and put in a splash of rehydrated saison yeast, not much at all. I also poured in some sugared warm water and 10g of saaz hops to add some flavour. I left it for a few weeks at ambient temps 18c-22c. I took the hops out after three days or so. The OG I think was 1.01. Bottled after 2-3 weeks and left it at ambient temps. Result is a really interesting slightly tangy, almost lemony and slightly sour effervescent drink. Not unlike lemonade, but without the sweetness. Not unpleasant at all, but not recognisably beer or ale. It was really, really easy. I was careful with sanitation but even so I am surprised there were no nasties spoiling the party. My guess is that the tangy, tart flavour is due to wild yeast picked up from the bread. And that the yeast killed off any nasties in the liquid (which is exactly why people drank ale instead of water in the middle ages). I think I am kidding myself to think this is like Olde Worlde ale, but who knows how far away it is? A worthwhile experiment in any case and may be an interesting way to culture wild yeast for sours etc... Thought I'd share this discovery as it seems a waste to keep this all to myself.