## Brewing -- the American Standard:

The graph above is what's called a "Brewing Control
Chart", the key to making whatever coffee you're using
taste as good as possible (and not to mention getting all
the flavor you're paying for into the pot). It may
look a little confusing at first, but a little study will
clear that up and there's a worthwhile payoff for your
time spent understanding the brew
process.

On the left is plotted the strength of the brewed
coffee, along the bottom is the extraction, and the diagonal
lines in red indicate the brew ratio, the amounts
of coffee and water you're brewing with. To use the
SCAA brew control chart below, you need those three basic
measurements -- the weight of ground coffee in the brew
basket, the volume of water poured over that ground
coffee, and the strength of the brewed coffee -- and then
you can plot these to determine the extraction.

The objective, of course, is get into the 'Optimum Balance' area. Way back in the 1950's, the Coffee Brewing Institute, under the direction of Prof E. E. Lockhart at MIT, asked a lot of coffee drinkers their preferences and determined that there was indeed an optimum balance of extraction and strength. The SCAA repeated this survey at one of their annual conferences and confirmed the people's preference is still about the same today, at least if you're American and the coffee is roasted medium. There is a difference for dark roasted coffee -- it tastes stronger than medium roast -- and Europeans like stronger coffee (but at the same extraction).

### How the chart works

Here, 'strength' means how much of the coffee beverage is actually coffee, so 1.25 on the scale above indicates that 1.25% of what you're drinking are coffee solids dissolved in the water. 'Extraction' means what fraction of the original dry ground coffee has ended up in your cup. For example, if you start with 5 oz of ground coffee, and 1 oz dissolves during brewing, then the extraction is 1/5 or 20%. The red diagonal lines show how much coffee you started with -- for example, the line labeled 3.75oz (106 grams) means you put that much ground coffee into the brew basket. On this particular chart, the brewing formula always assumes 1/2 gal (1.9 liters) of hot water with each coffee weight.

Remember that the brew chart applies to the actual
amount of water you pour over the coffee grounds. If you
want to end up with 64oz of brewed beverage, you'll need
to start with more water -- about 70 oz in this case. To
maintain the 4oz/half gallon ratio, you would need to
increase the weight of coffee to (70/64) * 4oz = 4.37
oz.

A complete brew analysis looks also at the temperature of the brew water and how long the water is in contact with the coffee, and includes assessments of how fine or coarse the coffee is ground, the bed depth of ground coffee in the brew basket, and how well the spray head is wets the grounds.

For the algebraically inclined, the calculations assume that about 1.5oz of water per oz of ground coffee will remain in the basket after brewing. So if you start with 4oz of ground coffee, pour 1/2 gallon of hot water over it, and measure the strength to be 1300 ppm (1.3% TDS), then the extraction is just

{[64oz water - (4oz coffee x 1.5oz water/oz coffee)] x .013}/4oz coffee ~ 19% extraction