How long would you soak oak cubes? I was thinking maybe 7-10 days....4 oz. oak cubes in 12oz bourbon.
I would boil them before soaking the. Removes some dust, and removes some of the really raw tannins that I think taste like crap in a beer. After that- soak them however long you want.. I'd age in the beer for probably no less than 3 weeks, but depends on beer, depends on what the user is looking for. If you are trying to get some legit barrel aged flavor.. gonna be a while.
My thoughts on using booze in brewing: The first thing I ever did was make vanilla extract. I used crappy vodka and crappy vanilla beans. I got crappy vanilla extract. I added exceptionally good vanilla beans, and I'm finally happy with my vanilla extract (4 years later). Shit goes in, shit comes out. I've never boiled cubes before ^^^, and would agree that there's some grit to oak that can be scrubbed. My method? Give it time. I'm not really experienced with oak, but I've noticed that a lot of vanilla nodes come out of oak after aging them for 6+ months in a decent bourbon. Maybe boiling can get you want you want in less time. For me, I bought a few oz of cubes and chips. I threw them both in decent bourbon and I used about half so far. The rest continue to age and I'm certain I'll be happy with the results the next time I oak a Barleywine or RIS. Any time you want to oak a beer properly, you're already a patient brewer. Buy a few extra oz of cubes and let them sit on $15 of booze and PLEASE report back.
I normally will start soaking the cubes in good bourbon on brew day. I let those sit in a jar while the beer is fermenting and in primary for about 3-4 weeks. When I transfer to the secondary is when I pour the entire oak/bourbon mixture into the bottom and rack my beer on top of that. I got a lot of good oak on a barleywine, but I had to let the beer sit on the 3 oz. of cubes for about 3 months.