On another message board I belong to, someone asked why some beer manufacturers hand dip the top of the capped bottle in wax. This is part of one reply given by a home brewer:
Can this be correct? Since the pressure inside the bottle is higher than the pressure outside of the bottle, can oxygen from the air actually want to enter the bottle more than other gasses because "oxygen still wants to be in there"? Isn't it possible for a properly sealed capped bottle to never allow gasses to get in or out?A brewer’s perspective:
A crown cap is not an absolute seal. Even though the headspace may be entirely CO2 (it rarely is), Oxygen still wants to be in there. It’s a simple law of partial pressures. With little to no O2 in there, there’s an inbalance, and the O2 will equalize eventually. Even if the brewer uses oxycaps, eventually the O2 absorbing properties will be used up, and you’ll be left with a beer that will oxidize. Besides, a brewer using oxycaps is practically admitting their bottling line is ****, and they need more help to get low airs in the headspace.
Now, putting a wax seal on prevents intake of oxygen, but in the case of beers not made for aging, it’s a pain in the ass. You need to get the beer cold, then trim the wax around the cap with a sharp knife in one smooth motion. I’ve only ever done 2 beers with this type of finish - a russian imperial stout, and a belgian dubbel. The stout is aging nicely, and the Dubbel, which was also bottle conditioned, showed no signs of oxidization(when tasted two years later).