Coffee Cup
"Espresso! My Espresso!"
An Ongoing Internet Novelette
by Randy Glass - Copyright 2011 - All rights reserved

Coffee Cup
Weighing the Dose

Tuesday, January 18, 2011

      There is a lot of art in espresso, if for no other reason than it is a food product and the quantitative end of it all is subjective- how does it taste to you? Yet, there is still a lot of science that can be applied. The longer you stay at it, the more attention to details you give, the tighter all the variables get. You work on each variable, honing them to the most narrow of parameters possible, and as those become more and more controlled you work to adjusted them into a synergistic unit. Trying to quantify those variables is difficult (if not impossible)- the bean blend, the roast, the age of the beans, the grind, the range of particle sizes produced by your grinder, water quality, water temperature, temperature curves, tamp, pressure profile of the pump, water dispersion and delivery.. just to name a few! So what did that list leave out?
      By accident, about a month ago, I discovered that I had gotten into the habit of dosing too great of a mass of coffee. It happened after I received a Mypressi Twist. I measured my dose of beans and ground them. The Twist's filter basket was not as full as I usually would have made it in other machines, but I went ahead and pulled the shot anyway, and voila! It was an excellent pull... "Hmm....," he said to himself.
      The next day I lowered the dose for an extraction on the Vibiemme and the same result. A definite improvement in the quality of the espresso. So it was off to the "Bay of E" and I picked up an inexpensive gram scale capable of displaying mass to 0.1 gram.
      There are a number of ways to use a scale for dosing. You will have to figure out which works best for you. If you have a grinder that does not retain much coffee in the grinding chamber or in its chute, you can weigh the beans before grinding. If not, then you might want to weigh the coffee after grinding. Best way for that is to place the entire portafilter on the scale and tare it, then grind, dose, and weigh again. For that you may need to make a little holder of some sort to support the portafilter. Another method is to remove the basket retention spring in the portafilter body. Remove the basket, tare the basket on the scale, then dose the grind into the basket. You can now place the basket into the portafilter body without worrying about snapping it into place.
      Small digital scales made for weighing precious metals and gemstones work well. Be sure that the scale you choose shows a resolution of .1 grams or even .05 grams. The reason you need .1 gram resolution is this: I just counted out 100 roasted coffee beans and weight them. I got a mass of 11.2 grams, or an average of one bean weighing about 0.112 grams. This is an average and will vary depending on the coffee you use. But based on that sample, in a 16 gram dose you will find approximately 143 beans. Just five beans, one way or the other, can make a difference of over half of a gram, and that works out to be a 3.5% difference in the mass of the dose.
      Weighing coffee to that precise of a mass might seem a bit, well, anal, but it adds a consistency that can be very important. With a quality espresso machine that allows control of water temperature and have well designed water-pressure delivery and distribution, a precise dose can make an easily-discerned difference on the palate. I have just started weighing my dose over the last three days or so, and so far I have found 15 grams was OK, 15.5 to be a bit too much, and that 15.2 worked very well and produced a superior cup today. That might change, but without a scale achieving the control necessary to find out would be difficult if not impossible.
      What dose will work best for you? There is virtually no way for me to answer that. A lot of it depends on the filter basket you use and the machine into which it will be inserted. Some shallow baskets do better with 15 grams or a little less, and there are some large baskets which use closer to 18 grams. You can try starting with around 15.5 or 16.0 grams and adjust from there. For more information on adjusting dose, read my article: Easy Guide to Espresso at Home.
      So this was a lesson to me. Don't ignore any possibility that has the potential to make your coffee better. Will weighing your dose make a difference in your espresso? You won't know unless you try. It is a very easy to control variable, and if kept consistent it may give you the opportunity to fine tune other variables which could lead to consistency and better espresso. How will you know when you have achieved the best dose? Simple. Taste the espresso.

Coffee Cup
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