Hook up a blow off tube, until it slows down. There are two ways to do this. The first is if you only have small tubing- take apart the airlock (but be careful when you remove it, as liquid will come shooting out the top when you take off the airlock), and stick some tubing for your racking cane over the middle part of the airlock. Stick that back in the bung, and put the other end of the tubing under water in a pitcher. If you have bigger tubing that would fit, it's ideal to santize some tubing and jam one end of it in the carboy, and then stick the other other of the pitcher of water. I think it's 1" tubing that fits perfectly.
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