Dear Dr. Brew,Answer
I checked your "coffee brewing control chart" and I have a question about measuring Solubles Concentration - percent (strength of the coffee). What do you use to measure this variable? I am using the recommended amount of coffee for my brewing cycles ( 3.75 oz for 0.5 gal of water, 7.5 oz for 1 gal, etc. ); however, the coffee is way too strong even though I am adjusting the bypass flow for 20%. I am using a blend consisting of 75% Sumatra and 25% Ethiopia and I roast it dark.
I just want to be able to measure the strength of the coffee to get the optimal balance for my blend.
There are several equipment options available. A handheld TDS (Total Dissolved Solids) meter is likely the least costly (approximately $80 to $200) although, you can spend upwards of $700 for TDS meters that have multiple functions. There is also a hand-held refractometer designed for coffee testing. You can get information and instruction for use on both systems from the resource center at SCAA.org.
SCAA Coffee Brewing Control Chart
You know your formula (coffee-to-water ratio) and you have access to a brew chart. After measuring your brew strength (% soluble on the left hand side of the chart), draw a line across the chart to find the intersect point of your formula line, then draw a line down from that point to read the extraction percentage.
Depending on where your coffee falls on the brew chart, you may want to grind slightly coarser to lighten the strength. A great cup is a balance of strength and extraction that pleases your taste.
Charting a brew using bypass requires additional calculations due to the change in coffee to water ratio. As an example with your 128-ounce brew at 20% bypass, you are only running ~104 ounces over the 7.5 ounces of coffee.
A good primer on coffee brewing is BUNN Coffee Basics, which contains an explanation of how to use the Coffee Brewing Control Chart.
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