ok, overcarbonated a fresh wort pilsner by at least 2 days by accident recently, with 40psi for 4 days got her pretty frothy to say the least,
but gave the beer a far superior head retention, and finer, smoother bubble/head after treatment
to remove over carbonation I did this:
left in keg at 40 psi for another day but with gas bottle off,
removed from fridge, shoke her about vigourisly, opened pressure halve slightly, let all gas out till beer squirted out then shut valve
did the same about 2 hours later, then placed back in fridge, cooled and did again the next day,
tested to see if the carbonation was correct at say 5 psi, she was, and drank at a party on the weekend
the head held together better than a commercial beer ever has, and the bubbles were fine and smooth
a stuff up with grand results, will do everytime if I screw up again!!!