Bottling 1st lager/ foamy head in carboy

cooked up a lager in late Feb, ran thru primary fermentation at about 55F for 8 days, with a 2 day acetyl rest. Then racked to secondary on 3/7, and put in slowly cooled to 33F. Pulled it out of the fridge last night for bottling but, lo and behold, as the carboy sat on my kitchen counter, the airlock started bubbling @ about a bubble every 3-5 sec, and the beer in the carboy developed a lovely 1/2 inch frothy head. Still has a bit of a head on it today, with some airlock activity.

Before racking, there really was no more activity, esp after the diacetyl rest. And the foam i observe today sure looks like a beer head, nor krausen.

Is this something that is expected w/lagers fresh from the fridge? Some kind of de-gassing phenomenon? i aborted my bottling mission for concern about bottle bombs; can't find any reference to this phenomenon in ny suds books.

thanks

Try giving the beer an extended secondary lager conditioning before bottling, at least thirty days at 40 degrees or lower, that should knock out the yeast so no bottle bombs. If you cant use a refridgerator Ive had good luck using a igloo cooler, Let lid lean against airlock and wrap sleeping bag around it for insulation. I put three water filled frozen pop liter bottles every morning with the carboy, then repeat that night, swaping them out with frozen bottles in refridgerator freezer. This keeps temps at 40 degrees and I keep indoor temps at 75 degrees in summer. it is kind of labor intensive though.

What was the og and fg?

I think if your fg tells you that it was done fermenting, which I think you will find. The most likely answer is the CO2 coming out of solution. The warmer the temperature the less soluble the gas is in the liquid. The foam is probably just bubbles as a result if this, kind of like head when you pour. Should not take long for this to clear, once the temperature equilibrates.