hthec Could use the same idea and target alkalinity instead?
@PartySausage How did you go about controlling this – changing water in the reservoir is one thing but getting it into the boiler is another. Did you perform any control by using water with hardness and no alkalinity and vice versa?
Would think hardness from Magnesium and sulfates are unlikely to have had an effect visually, though alkalinity may have had an impact on the appearance of crema and extraction due to the interaction with acids and CO2, so could see how that would affect the appearance of shots and volume of crema. While things may have looked different it doesn’t make sense that there would be more or less channelling because of the water – an extraction that looks thin and patchy isn’t necessarily a sign of channeling, crema that has more volume/is more foamy and stable will cover the bottom of the basket better than one that isn’t – realistically the water will be going through the puck as consistently as is allowed by your prep.
I’m surprised you couldn’t taste the differences. I’d have expected more acidity to be fairly obvious, maybe the perception of less body is suggestive of a greater perception of acidity?