OK, I looked it up in On Food and Cooking, acid will stabilize an egg white foam (why you add cream of tartar), BUT here's what I don't get - the fat in the yolks counteract that, and there's no mention of acid + albumen producing gas, so still not sure why the lid just popped right off (explosively). Plus there wasn't a lot of foam (in the container or on the floor). But the last ime I may have also added the oil to the shaker before closing it and shaking, that would have reduced the volume too.

Sounds like we need to do some volcano experiments for Halloween! Using just the whites and lemon juice, see if there's a visible reaction when stirred gently vs shaken or beaten...

You'll have to try it again, see if you can make it repeat :)

I've had the top push off that same T. shaker putting hot broth in with flour and trying to shake, not letting the broth cool before trying to make a thickener for stews etc.

Let my oven cool enough checking on a big roast that baked potatoes exploded in the oven when I closed the door and the element came back on again....

But never eggs and lemon, that was a new one to me.