Now this is my kind of bar! I would literally be in heaven there, surrounded by all that coffee, but it would be so hard to pick one to try so the 'test plank' sounds like a great idea!
I'm going to try and find a similar place here in the UK, if not, I think it would definitely give me a solid reason to visit Rotterdam! I'm enjoying these blogs of yours, the character and writing is great and it feels like I was there reading it, I love the fact that you were able to go behind the scenes and check out all the raw coffee!