Fermenting dipa darkening at top

Four days in to my first all grain brew and I am of course watching my fermentation closely with fascination and excitement. Tonight I noticed the top of my fermenting wort is darkening. It is not a shadow.
I cannot find anything online about it. I'm hoping this is normal. Any help is much appreciated. Sorry if this is a very basic thing but you will put my mind at ease by letting me know.

 

Looks completely normal.

I wouldn't give the the light's reactive index from air to glass to krausen to beer to krausen to glass to air another thought.

Welcome to HBT. Congrats on the brew.

 

Thanks for the reassurance!!!

 

It's just the yeast coming off suspension and leaving clear beer on top.

 

Thanks for the help... that being said, is 4-5 days too soon for flocculation to occur? Does flocculation indicate the sugar to alcohol conversion is finishing up? Or could my yeast be dying and falling out of solution from lack of oxygen?

I'm guessing the best way to test would be to test SG but I'd like to keep it sealed if all seems normal and just let nature take its course. My OG was 1.08 and I used two packets of wyeast 1056 at 70 degrees. I've been fermenting around 65 degrees.

 

I'd just leave it. Some yeast start to floc in a few days. I agree that the top of the wort is just clearing a little. Give it a couple weeks before you test anything.

 

Awesome! Thank you very much!

 

Your yeast are not going to die off due to lack of oxygen. There shouldn't be any oxygen in the fermenter after the initial reproduction stage of the yeast. Fermentation is an anaerobic process, so you do not want any oxygen in the fermenter. Oxygen causes off flavors if introduced to the beer after the first day or so after pitching yeast.

You could check gravities, but it is best to just let it to for at least a couple weeks. Even if the FG is reached early, it is often beneficial to allow the yeast to clean up before bottling or kegging.

 

Thanks! I knew oxygen should be avoided after the initial transfer to fermenter. I was thinking of worst case scenarios and thought I might not have oxygenated my wort enough in the beginning.

I feel better and appreciate your input! I'm going to let my primary hang out for another week or two and continue as planned.