Ale yeast stays on top?

[gkeusch]

I brew ales, use a variety of yeasts. Safale-05 is my go-to dry yeast but what I am going to desribe happens with other yeasts too: Sometimes after complete fermentation there is a layer of inactive yeast still on the top in the fermenter, sometimes it all drops to the bottom. I know fermentation is complete by checking gravity. When it stays on top I just skim it off before transfering to bottling bucket. Can't see any difference in the finished beer. My fermenter has a shallow conical bottom and is bigger in diameter than a 6 gallon bucket - can't imagine that matters but? I ferment in a chamber and usually keep it around 65 deg. F, at least for first few days.
So does anyone have any idea why the yeast stays on top? and can I harvest this yeast for re-pitching as I would the stuff that drops out to the bottom?
Thanks for your comments!

 

[Jag75]

How long are leaving it in your FV?
Could what your seeing on top be co2 and yeast raft particles ?

 

[gkeusch]

I leavi it in FV for a full two weeks. I don't know about co2 and raft particles but it is a layer that looks like krausen but not active. There are no rafts, it is completely across the top surface.

 

[Jag75]

I would post a pic . Someone will be able to tell you what it is .

 

[Miraculix]

Sometimes the Kräusen just won't drop, no need to worry, just ignore it!

 

[Vale71]

Highly flocculent ale yeast can trap CO2 and form a floating mat that won't drop even after fermentation is finished. You can harvest this yeast but shouldn't wait too long to do so as it's exposed to air and tends to dry out which will harm the yeast.