Zen and the Art of the Pour Over

Daily it seems, new coffee gadgets are being introduced that promise, the greatest cup you will ever make.  While some of these gadgets are useful, a very simple method of brewing coffee, the pour over, continues to be a very efficient, economic and simple way to brew our favorite beverage.

     Pour over coffee starts with freshly ground coffee, a filter, and a filter holder, usually called a “pour over dripper”.  At the most basic level, pour over brewing involves pouring water over and through the grounds to extract the coffee flavors into your cup. Sounds simple, but there is more involved.

     All coffee brewing methods involve the same general phases:  wetting, dissolution and diffusion.  Each phase is linked to the others, and they affect what comes next in important ways.

     Pour over coffee continuously replenishes the liquid surrounding the coffee grounds with new, fresher water.  This promotes a faster, more efficient brew.  Though, fresh water also has a tendency to extract more from the surface layers of the grounds.  Pouring one stream of water, rather than a dozen or more little streams from a coffee-makers shower head, results in a brewing environment that’s a few degrees higher, just from reducing the surface temperature loss from those narrow water streams.  Temperature and water quality affect the overall reaction of coffee chemistry.

     Wetting the coffee is exactly that.  Your coffee is dry and you make it wet.  Sounds simple but once again, let’s go a little deeper.  One of the major byproducts of roasting coffee is carbon dioxide gas. For lighter roasted coffees, that carbon dioxide is literally trapped in the cell structure of the coffee bean, and leaches out slowly over weeks.  With dark roasted coffees, the roasting process has physically blown a hole in every cell and most of the CO2 is out within a few days. 

When you hit the coffee ground s with hot water, the CO2 is able to escape and it bubbles out.  The problem is that if carbon dioxide gas is going out, water isn’t able to get in.  So as you start your pour over brew, you’ll want to add just enough brewing water to wet all of the grounds, then stop and let the gas escape for about 30 seconds.  You will see the bed of grounds swell and expand, resulting in what coffee geeks call a “bloom”.

     The word “dissolution” looks similar to dissolve, actually that is what its all about.  Once the coffee grinds are fully wetted, the hot water will dissolve the solubles in the beans’ cells.  Part of what makes great coffee brewing difficult is that the complex cocktail of organic substances in coffee includes both pleasant and unpalatable types.  Lucky for us, it’s one of the convenient facts of coffee chemistry that the desirable and tasty solubles dissolve in water more readily than the unpleasant-tasting substances.  So, brewing a good cup of coffee is all about stopping the brew at the perfect moment. 

     Diffusion is about taking that dissolved stuff and transporting it out of the coffee grounds via osmosis.  The cell wall structures of our coffee grounds are semi-permeable membranes, so the osmosis pressure drives the brew out of the highly concentrated chambers of the coffee grounds out to the more watery surrounding environment.

     Most of the roasted coffee bean, about two thirds of the bean’s mass is insoluble cellulose.  The other third is dissolvable in water. Of that soluble third, most of it is the good stuff, particularly various organic acids and sugars.  The rest are longer chain molecules that we associate with astringent and bitter tastes.  Where we find the happy balance is at the 19-20% point.  If we extract the first 19-20% of the mass of the coffee, we tend to find the best flavor balance.  More than that and you’ll find those astringent and bitter flavors start to dominate.  Less than that and you’ll find the resulting flavors thin and unbalanced, and with lighter roasted coffees, unusually sour.  Timing, then, is what makes or breaks a cup of coffee.

     Tuning your pour over brewing means finding the right combination of grind size (coarser or finer) recipe (ratio of coffee to water) and brew time.  How quickly the water will drip through your coffee depends on how much the coffee bed itself slows down that flow.  More coffee or finer ground coffee will result in a slower flow, and the opposite is true as well. 

     While pour over brewing doesn’t require a special pouring kettle, a narrow spout does make it easier to control what you’re doing.  Having a narrow-spout kettle helps maximize control, and direct water right where you need it to go.  You can eke a few more degrees out of the brews temperature by maintaining a fully wet brew bed.  Letting your coffee bed dry out can drop your effective brew temperature by 5 degrees or more.  A higher temperature keeps the chemical reactions speedy and while it’s technically possible to have your brewing water too hot, you’re going to be fine in most situations.

     Pour Over Technique:  1. Start with a grind size around that of course sugar ( like Sugar in the Raw).  Most pour over drippers work best when they’re between one half to two-thirds full of coffee grounds.  Any less and there won’t be enough coffee to restrict the flow.  Any more and your dripper may overflow.  A good ratio is between 60-70 grams of coffee per liter of water.  2. Get your clean brew water ready.  You’ll be using water that’s about 30 seconds off the boil.  Temperatures should be 205F for medium to light roasts and about 10F lower for darker roasts.  3. Start your clock and add enough water to soak all of the coffee.  Wait for the coffee bed to stop the initial swelling (about 30 seconds) before adding more water. 4.  Continue your brew.  Try to pour quickly, gently and evenly across the surface of the coffee, pausing between pours to pace your brew time to your target.  The distance that your brew water drops can affect brew temperatures, as well as increase or decrease the amount of agitation that the falling water creates.  In general, the lower you pour from, the better, if for no other reason than it’s the easiest to create and maintain consistency. When you stop adding water, your dripper will continue to drip for between 20 and 60 seconds. Your total target brew time is about 2.5 to 3 minutes for dark roasted coffee, and 3 to 4 minutes for medium to light roasted coffees.  This includes the dripping time after you stop adding water.

     Two and half pages to describe how to brew coffee using the pour over method, seems just a bit extreme.  What I quickly found though was that by paying attention to the four fundamentals of coffee brewing, the result is always a very tasty cup of coffee.  One example, while working on this I ground coffee at two settings, paper and a number four. The cup that resulted from the number four grind was far superior. Same beans, same water, same temperature but different grind. I guess that is why this four factors are called fundamental.