Texas Two Step - Kinda

[Cosmic Charlie]

I want to try making an Russian Imperial Stout as a partial mash brewer. I used to mash in a 2 gallon cooler, but now I have a 3 gallon cooler. I think I'll steep the dark grains in the 2 gallon cooler and mash in the 3-gal. This would be the largest volume of water I would need to cool.

But I thought about steeping the dark grains a day or more in advance, then cool it and keep it in the fridge. I could then pour this in after the boil to help cool it down.

Any reason not to do this? Do the dark grains need to be boiled with the mini-mash (I thought leaving the dark grains out would help with hop utilization). If I need to sanitize the dark grains, I guess I could bring them to a boil after steeping, then cool/refrigerate.

[bub]

If you steep the grains that long you may get sourness from the free lacto, this is known as a sour mash and it may affect your flavor. Perhaps this is what you want, most likely it isn't.
BUB

[Cosmic Charlie]

D'oh! That's not what I wanted to hear. Let me make sure I've explained what I have in mind:

Combine dark grains and maybe crystal malts in 2 gallon cooler. Steep them at 150ish for 30 minutes or so. Batch sparge, and bring runnings up to a boil to sanatize (if I use 4 lbs of dark malt plus crystal in this RIS, I would have about 2 gallons of grain tea). I should be able to quickly cool this volume of liquid after the boil - so I would cool, then put it in gallon jugs and put them right in the fridge. Next day, use this to top off and help cool my 3 gallon concentrated (mini-mash with extract late), boiled wort.