Doing a Session Beer with Used Grains

[upperNY01brewer]

I'm getting ready in the next half hr or so to do a Dunkel and I'd like to do a second batch with the grains to brew something which will fall under no real defined category. I'm going to add a few oz. of whatever I have laying around and some DME that I have as extra, and some hops and yeast.

My question is Im kinda looking at a time constraint being that its 4:30 pm right now and I'm looking at about 9:00 pm till I'm finished with the Dunkel and I'm not going to be brewing till near 1:00 am as much as I'd like to. Would it be OK to leave the grains in my mash tun over night till early tomorrow after noon till I'm able to brew up the second batch ? I'm thinking it will be ok with some water warmed to around 120 degrees or so.

Whats anyones opinion on this ?

 

[statseeker]

I think you're going to leave it too long if you leave it overnight. I think it'll turn out acidic or sour. Plus you might end up extracting tannins from the grain husks. That's my opinion though, I've never left it overnight.