Hi guys!
Just wanted to make this post for those not aware, like myself until today, but I recognize it may be obvious to a lot of you with the ORB.
Summary:
Why does an uneven bed happen? It happens when the water flows from the kettle cleanly right through the floor of the water chamber and onto the coffee bed, as if flowing through a sieve. So if you don't see the chamber filling up with water instantly you know you poured it right onto your nicely tamped bed like a meteor strike.
Method of prevention: You can put a top paper filter which mitigates the impact of the water or you can instead do a super light pour at the start from a low height and then gradually increase the flow while gently waving the kettle so the water begins to pile in the chamber nicely and begins flowing onto the bed and dripping from the little holes instead. I had been doing this now like maybe 20 brews in a row without knowing it was why I was getting great beds like the photo even without the top filter.
(no need to read this below it's just story time):
Lately I prepare a 10:160 (with only bottom filter) every day, and I kept getting 1 in 10 brews have a horrendous bed with a sort of crater. I had naively thought it was CO2 releasing, or not tamping hard enough, but it had always stumped me because those wouldn't explain why with the same coffee and prep I was getting occasionally different beds. Until, the one time I got the worst bed I've ever seen and I instantly discovered why.
I brought my gear to my friends' place to share some coffee and borrowed his kettle (which he had fully filled so it was super heavy) and I poured from it and the water came crashing down and directly in the center of the water chamber, when it happened I also noticed oddly enough the water chamber wasn't filling up like it normally does with my kettle; rather the water seemed to be going straight through.
After I finished the brew, I opened up the bottom chamber to discover even though I'd done the exact same normal prep I always do, that water had clearly crashed onto my nicely tamped bed and absolutely destroyed it like a meteor strike in the middle.
I can't believe I just discovered this after brewing over like 80 times on the ORB. I had always thought that bottom of the chamber protected the bed or something.