another_jim wrote:But surprisingly, the five scale invariant shots were indistinguishable cold and easily distinguished when hot.

This explains a mystery I've run into this past week. I've not been at this long but over the past few months I've gained consistency, at least somewhat.

I typically make two doubles each morning. After brewing each shot, I had been stirring the shot with a spoon and tasting a spoonful of it. I was doing this within a minute of making each shot. This was a good way to judge the consistency of my shots. I could certainly taste differences but the shot to shot consistency was reasonably high.

Last week, I changed my habit. For some reason, I started tasting both shots after the second one was pulled. Being that I'm still fairly new at this, it might be 3-5 minutes after the first shot was pulled. By then, much of the crema from the first shot had settled. So, I'd be tasting one shot that had much less crema compared to one which was still mostly crema. I have been surprised and dismayed for the last several days why the two shots tasted so different when they had previously been tasting similar. I could not see any substantive difference between my preparation methods of the two shots. I could not figure it out, it was driving me nuts!

Reading this post today brings me a lot of comfort because it explains something that really puzzled me. While that one sentence might have been lost amongst the really good information to others it really popped out to me. Thanks for solving my mystery!

Ian_G wrote:However as James Hoffman pointed out, commercial grinders have not really evolved since the sixties and more importantly a commercial grinder running flat out in a commercial setting overheats and the burrs expand causing inconsistency. Compare that to a domestic machine that runs maybe once an hour, if that, and perhaps the difference in variability is not so much.

You're hitting your head against a wall of misunderstanding so high you're obscuring your actual questions. The behavior of a commercial grinder running flat out in a commercial setting is not at issue here (at least not so far). Comparing a high-quality, commercial type grinder to a domestic grinder in a domestic setting is one issue you're actually pointing towards; another is whether a particular grinder can satisfy the quality requirements of a given basket.

Cutting to the chase: The overriding issue is whether or not your grinder can satisfy your needs, or whether you need a new one.

... consistency within a dose vs consistency dose to dose.

Consistency with a dose: How consistent are the fines in an individual basket? Just by way of example, consider the fines from a double-sized, 17g dose. Are they all the same size? All the same shape? What causes the variation? Is it the beans, the grinder, the environment, some combination? How many samples, under what variety of conditions will we need to get meaningful results? Do we need any sort of "control" for comparison?

Consistency dose to dose: How consistent is the grinder's output from dose to dose (i.e., from one basket to another)? By way of example, consider the fines from six double-sized, 17g doses -- 102g in total. Again, we're looking at the same questions of variation and causation; but we're adding some other variables and questions. For instance what if the basket to basket samples come from different grinds done at different times, or from grinding a large weight at once. What changes -- if any -- will we see from the different grinding methods?

Hope this begins to clarify,
BDL