By March 1, 2010 Read Article
Breaking the Crust During Cupping

Coffee Tasting Sheets and the ‘Heisenberg Uncertainty Principle’

Recently I was involved in a couple of tasting programs.  One was a roasters’ competition for espresso and another was research for a rural industries organization evaluating coffee cherry maturity on taste quality.  In both cases it was necessary to use tasting sheets.

For the cherry maturity tasting, we used the Cup of Excellence® Tasting sheets devised by George Howell.  These sheets were a huge leap forward in comparison to the old SCAA cupping sheets which automatically gave the coffees 50% and evaluated only five characteristics.  George based this sheet on wine tasting sheets to try and introduce some more sophistication to coffee tasting.  There is no doubt he succeeded with this as the SCAA proceeded to modify its very basic form to its current form which is largely based on the COE one.

For the World Barista Championships the tasting forms were originally based around the Italian Espresso Tasters wheel, which I had a hand in adapting for the judges of these competitions.

The trouble with tasting sheets is Heisenberg’s Uncertainty Principle (HUP).  It was Tim Castle who pointed out to me in a rather philosophical conversation we were having some years ago about the best coffee tasting sheet being a blank sheet of paper.  Although at first it sounds unrealistic, there is actually a lot of sense in this statement.

The reason for this is that in very laymen’s terms, HUP basically means that the very act of measuring something interferes and alters the very thing you are trying to measure and so it is impossible to be accurate. In other words by having prompts on a tasting sheet this will pre-dispose us to think about a coffee in a certain (biased) way.  If for instance acidity is not mentioned on a sheet then you can’t evaluate it.  The COE tasting sheets introduced sweetness for instance, whereas previously it wasn’t on the SCAA sheet. So suddenly sweetness becomes more important.  It could be body or any other characteristic that is affected in a similar way.

For the research project I was responsible for placing a range of coffees from a particular terroir within an international benchmarking configuration: i.e. exactly how the coffees would fit in internationally in relation to all levels: NY Exchange, >70% Specialty Coffee Association >80% or Cup of Excellence >84% whether for drip, plunger or espresso.

These simple bench-marks make it a bit easier for a context without bending your perception too much and most professional cuppers are somewhat familiar with them.  Keeping in mind that acidity still tends to be the most defining single characteristic for both Specialty and COE coffees.

While tasting the roasters’ competition I came under fire for not filling out all the boxes.  I was aiming to be as consistent as possible but also trying to place the coffees in this international context with more of an emphasis on body rather than acidity. As a result I put a final score of where I believed the coffee sat in an international configuration.

I always insist on no collusion between judges during scoring unlike some barista competitions where there is considerable discussion by judges about their scores behind closed doors. Consequently these barista judges tend to be very uniform and I might add timid, rather than expressive.  In COE competitions, new and inexperienced judges tend to be very conservative as they don’t want to stand out on their own in comparison to everyone else.  Having all the judges within a narrow range is not necessarily good judging.

I would rather a judge is confident and expresses their view of a coffee, honestly openly and without inhibition as long as they are consistent.  If one judge consistently scores low and another consistently scores high it will not make the competition unfair as long as they are consistent.  But in the end I tend to agree with Mr Heisenberg: the less interference in the scoring process the better, so to speak anyway.

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5 Comments on "Coffee Tasting Sheets and the ‘Heisenberg Uncertainty Principle’"

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  1. Lance Leasure says:

    Another advantage to the blank sheet of paper is that those new to tasting and unfamiliar with established norms may inadvertently bring to light new or previously unconsidered perspectives on the subject. Perhaps it’s my own relatively untrained palate, but I often find myself describing a tasting differently that the pros in the room. Great subject. Thanks for the post!

  2. Lance, you are exactly correct. An acquaintance of mine did his PHD thesis on wine tasting where he compared ‘professional’ wine-tasters to uninitiated novices. He found the novices were no less accurate in blind tasting and in fact were better when it came to tasting ‘placebo varietals’. This was because the professionals had a large memory bank of pre-dispositions as to how a particular varietal should or would taste and if they were told a placebo was a particular varietal they believed it had a whole lot of characteristics that simply weren’t present whereas the novices had no idea how it ‘should’ taste and were consequently more accurate!

  3. the Heisenberg uncertainty principle exists in quantum mechanics, not in everyday life. Are you seriously suggesting that measuring a length of string will affect its length?

    Changing a tasting system on a false premise is dangerous for producers, consumers and the industry as a whole.

  4. Stanley says:


    Thank you for the great post. It’s very interesting that you believe the formula should be changed for judging coffee. I think that no matter how its changed, it will undoubtedly remain an arbitrary process. However, less collaboration would certainly help make the process less biased. Would that be counter-productive however, and make the process more based on opinion?

  5. Heisenberg’s uncertainty principle pertains to linked elements, properties that are related and the measuring of one interferes with the other property. For example the speed and location of electrons in orbit in an atom. You cannot measure the speed (momentum) without interfering with the position and vice versa. This is why the location of electrons in orbit, in atomic diagrams is mostly plotted in terms of probability.

    As Jason quite rightly pointed out, it is a specious argument to make.