With my latest keg of Guinness, I’ve been playing around with shorter settling times. This hasn’t been in the name of science or anything. More often than not it’s because I’m trying to get back to the tv to watch the Yankees disappoint me. I’ve done some testing before and found that I can’t taste the difference between a properly and improperly poured Guinness. But lately, I’m definitely noticing a difference in viscosity.
In my observations, the longer I allow the Guinness to settle before the final top off, the more “well connected” the beer is. What do I mean by well connected? I mean that you can walk the glass from the tap to your seat without it spilling. It’s anecdotal, but I find that the quicker I pour the beer, the more it kind of sloshes around and is likely to spill. And the more time I allow it to settle the more it’s likely to stick to the inside of the glass. Even when the meniscus starts to look impossible.
Ultimately, does this matter? Not really. Unless your destination is far away and you’re looking for a low ΔGuinness/distance. If you order a Guinness at a bar and it’s overflowing then your bartender was trying to give you as much beer as possible and/or they were trying to get you your beer as fast as possible. Tip them well.