Tobias Davis

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Coffee Research

This page contains my notes about how I make coffee. In particular, the preparation method I use for coffee is a little different: I prepare it in the cold-brew style at a high concentration, so that I can easily turn it into a perfect hot or cold cup.

Let’s get right to the recipe, but read the research notes afterward if you want to know more or modify the steps.

Recipe #

Yields 18oz of coffee concentrate, which reconstitutes to 72oz of normal-strength coffee.

Ingredients:

Note: it’s okay to use pre-ground coffee meant for traditional countertop drip brewing, if that’s what you have. Making coffee this way will still be a big improvement.

Preparation:

Reconstitution:

Use a ratio of 1oz concentrate to 4oz water

For a hot cup of coffee, if the concentrate has been refrigerated, reconstituting with boiling water from a kettle will yield a cup of amazing coffee at just the perfect temperature. ☕️

Note: if you are aiming for an 8oz cup of coffee, use 1.4oz of concentrate and fill to the 8oz mark with water.

Research #

I had this idea to make coffee using the cold brew prep method, with a high enough concentration that I could reconstitute it from a refrigerated brew by pouring in hot water from the kettle.

After a bit of experimenting with different ratios and different coffee blends, I found the approach described above, which I think yields an absolutely brilliant cup of coffee.

For a normal “Mr Coffee” style countertop drip brewer, the grounds/water ratio is 1:18 for regular, or about 1:15 for stronger coffee. That would mean 1oz (by weight) of coffee grounds per 18oz or 15oz of water, respectively.

Example: if you’re making a 12oz cup of coffee at regular strength, you only need 0.7oz of coffee grounds.

For my experimentation I purchased 8oz of grounds, coarsely ground for cold brew, of Sumatra beans from a local roastery that I love, which made 24oz of beans by volume.

Based on some guesstimation, I settled on two concentration ratios: 1:4 (4oz coffee to 16oz water) and 1:6 (4oz coffee to 10oz water).

The grounds were poured into two large glass mason jars and faucet temperature cold water was added.

The brew started at 10:45pm and was filtered at 11:15am the following day, so a total of 12.5 hours brew time.

Because of how little liquid was extracted by gravity filtration, for both ratios I pressed the beans to extract maximum liquid.

Results:

I wanted the concentrate to reconstitute to a cup of hot coffee, and my plan was to use the boiling water from my electric kettle.

Here are the temperatures of before and after:

Quality and taste:

Notes #

There are a few notes I found, which will impact you if you are thinking about modifying the recipe.

Acidity #

I did not compare to a cup of e.g. aeropress or pourover prepared coffee, so I am unsure on the comparison there. In my memory, the “Sumatra” bean is very pleasant already, but the cold brew preparation was less acidic than I remember.

I have since compared this method to both aeropress and pourover preparation, and am very confident that this cold brew method has significantly less acidity.

Yield and Waste #

The coffee beans will always retain some volume of water, so the stronger the concentrate, the lower your final yield will be.

For example, in my experiment the same volume of coffee beans (aka the same $ cost) yielded either 36oz or 24oz of final coffee drink, whereas the 1:18 normal drip brew could have yielded as much as 160oz, which is a 4x difference! This does start to matter if you drink a lot of coffee, or if you buy the higher quality (aka more expensive) beans!

If you know that you will only ever serve cold coffee, or if you’ll just be heating it in the microwave (aka not trying to heat it by pouring in boiling water), you would be best suited to brew it at the normal 1:18 ratio (or your preference of course) and not adding water later. Your final yield will be much better, per ounce of coffee purchased.

Ratios #

Before you go brewing 2 gallons and using all your coffee grounds, you should try a smaller batch and see what you think about the ratio you’ve picked. The minimum amount of grounds to use, based on different factors I’ve played around with, is 12 ounces of grounds by volume.

If you go much lower, your results won’t be consistent enough to give you confidence, and if you go much higher you might be wasting a lot of coffee.

Grind #

If what you have is pre-ground “Mr Coffee” pot style coffee, that’s probably close enough. You may get a little more sediment in your final coffee, or need to brew closer to 10 hours instead of 12-14 hours.

If you’re going somewhere with good beans, they’ll know what to do if you say “grind it for cold brew”.

Bean Variety #

Since my main purpose is to have concentrate that is suitable for both hot and cold coffee, I picked a milder coffee bean, and didn’t try to find one specifically designed for cold brewing.

I’ve since used a couple other beans, and I believe that a Sumatra variety is most well suited to this approach, but then again I like Sumatra beans the most so that’s probably just personal preference.

Temperature #

Using the 1:4 ratio that I settled on in the recipe, if you refrigerate the concentrate and use a room temperature coffee mug, boiling water in an electric kettle and pouring it into the coffee to the correct reconstituted ratio made a nearly perfect temperature cup of coffee.

If I take the refrigerated concentrate and use faucet temperature water to reconstitute, putting it in my 1100 Watt microwave it takes 2 minutes exactly to be the perfect temperature.

Your setup will likely be different, so experiment with what you can, and take notes. The perfect cup of coffee is within reach!

Want to send me a message about your coffee drinking habits and experience? I’m normally deep into designing software, so talking about coffee would be a welcome change of pace. 😆


Your thoughts and feedback are always welcome! 🙇‍♂️