Hi there Brendan,

Like a lot of areas in brewing, it's very hard to find good experimental data on something like this. Instead, often a theory gets proposed and this spreads, like wildfire, as fact. For example, we often hear that most of the conversion in a mash occurs within the first 20 minutes. There's some truth to this but it is very misleading when expressed like that. Also, who knows what other things happen in a mash apart from plain conversion? We sometimes hear the same thing said about iodine tests and I have no idea where that myth originated.

There's a thread that has just been started here on this very subject. Any time I have done this exercise, I have always seen an increase in gravity over mash time. So, take a few measurements on your next brew and see how you go. Also, the more of us that try experiments like this and record the results no matter what they are, the better.

I've never done an overnight mash and have only read bits and pieces on it, some negative and some positive, so I am no help to you there at all . From a practical point of view (not a chemistry one), I'd be worried, with my set-up about how much heat I would lose overnight and the time and labour I would have to spend returning the mash to that heat so I don't think I would personally gain much. Others though, don't experience this heat loss with their equipment.

One stage I went through when starting AG was trying to get the brew done as fast as possible. It only lasted a few brews but I do remember this obsession with time well . Maybe we all go through it? Now I just start a bit earlier and always do 90 min mashes and boils. It's a lot more relaxing and easier that way unless you start drinking too early which can lead to pistification (being pissed and mystified at the same time). Eg, "Where's my fermentor tap gone? It was here a minute ago." Pistification can quickly add 3 hours to any brew day.


PP