I have something to confess. I do something which most people would never do, or even would consider weird. It's something I never did before I became a homebrewer.
I mop ceilings.
The first time I mopped a ceiling I had brewed an American Hefeweizen and, when the primary ferment was mostly done, one evening I added a bunch of crushed raspberries and went to bed. Around 5 a.m., I heard a pop loud enough to wake me up.
What had happened is the sugars in the raspberries had kicked off fermentation again and the berry pulp had clogged the airlock. Pressure built and released with a spray of beer big enough to splatter the ceiling. The foamy shit also got all over the wall, the door, the carboy, the selves next to the carboy and the floor. The airlock was laying on the ground and the beer was exposed to oxygen.
Apparently, it had never occurred to me raspberries have fermentable sugar also.
I have noticed a direct correlation between how much mess I make while brewing and the level of my wife’s opposition to the hobby. This makes one of my brewing objectives to reduce the mess as much as possible.
Something which has substantially cut down on spraying yeast all over the place is a blow out tube. Basically this is a bored carboy bung with three or four feet of tubing coming out of it. Stick the bung in the carboy and put the tail of the tubing in a jar with a little water or StarSan. The foam from the ferment will go down the tube and collect in the jar, which is a lot easier to pour out.
One word of caution, if the temp of the carboy goes down it will create negative pressure and pull whatever is in the jar back into the carboy, which is why I just use water or StarSan, not something poisonous like bleach or iodine. You probably don’t want this to happen, so if you are crash cooling just change out the airlock.
Before I discovered the blowout tube, I preferred the 3-piece cup style airlocks because they were easier to clean when they filled up with crap. However, now I never get anything in my airlock so I have switched to the S-style. They have the advantage of working both ways, so when I crash cool it pulls the air through the vodka or sanitizer in the airlock and kills the airborne bacteria.