What WAS this?

I should have taken a picture, but I'll do my best to describe it.

2 weeks ago, I started a Munton's Pale Ale extract kit. Everything went perfectly normally, and I put it in my white plastic pail primary fermenter and set the lid on (not sealed) with a phone book on top to hold it down, but allow CO2 to escape.

Yesterday, I transferred it to secondary. The weird thing is, when I took the lid off, expecting to see clear beer with maybe a little krausen remnants around the edge, instead the entire surface of the beer was covered with what looked like yeast! What WAS that?

There was no bubbling, and it's been 2 weeks, so I was fairly certain fermentation was complete. I took an S.G. reading anyway, and it came out at 1.010. It didn't look "scummy," it really just looked like a uniform layer of yeast, about 1/4" thick. Is it possible it was yeast? Would yeast ever just settle on top like that? I used Safale US-05 yeast, and fermentation was at around 70 F.

I tasted the sample I took for S.G. measurement, and it tasted fine - I'm just curious what I was looking at, since I've never seen that happen before.

Any guesses?

It was probably just that, a layer of yeast or krausen that hadn't settled yet. You could always cold crash if you see that again to try to get it to settle, or just rack from below it which I'm assuming you did. I don't think you have anything to worry about though.

Sounds like yeast. I've had yeast floating on top/krausen that seemed to do everything it could to avoid sinking to the bottom. My method of dealing with it is to cold crash until it finally sinks. Adding gelatin (that's been dissolved in a little bit of water) may also help the yeast flocculate (clump up) and then precipitate to the bottom.