I just brewed an imperial stout for my 8th batch. I don't really feel like a beginner any more but this situation has me a little puzzled. This was the first time I brewed a beer this dark (~60srm) and with such a high gravity (1.086). It ended up being a 3.7gal batch because I expected a little more boil off (down to 3.2ish gallons). It had around 10% flaked oats and 10% roast malts and around 5% crystal with Maris Otter base and some DME to make gravity. Since its a smaller batch I thought it would be OK to just pitch 1 rehydrated packet of S-04.
So, here is the problem. I shook my fermenter to try to aerate and it didn't form the kind of bubbles and foam I usually find when I aerate my wort. I pitched the yeast at around 64f and its now at around 61 and fermenting well with lots of bubbles quickly coming out the airlock. The thing is there is no Krausen at all. I can see some tiny bubbles in the blackness on the surface but nothing else. There was a thin layer of foam when the yeast were growing and bubbling started (around 15 hours after pitching) but now they are fully fermenting and I expected it to be at high krausen (36 hours later).
Is this something I should be worried about in terms of fermentation, yeast health or infection? I want to bottle prime this beer and store it for years so health and sanitation are very important for me. I think I'm going to try and RDWHAHB but I still would like to know why this has happened etc
Thanks for reading!