I’ve heard people say that they want a stronger cup of coffee, so they grind it as fine as possible. Depending on your brewing method, this could result in inferior tasting coffee. But when it comes to caffeine, is finely ground coffee stronger?

Coffee strength comes from contact time, extraction rate, and flow rate. Fine grinds have a higher extraction rate and contact time, and slow flow rates. The flavor is strong, but caffeine is the same.

By having longer contact time, slower extraction rates, and slower flow rates, you may think “great, strong coffee!” but what is missing from this is that coffee has certain soluble compounds (soluble = able to dissolve) that release much slower. These compounds make the coffee taste bitter, dry, acidic, empty. Altogether not so great – coffee experts would call this “over-extracted”.

What level of grind do is best?

In general, the longer the brew will be steeping, the coarser the grind should be.

• Turkish coffee and Espressos – extra fine grind sizes, similar to that of flour or powdered sugar.
• Aeropress (non-inverted method) – fine-to-medium grind, depending how strong you want your cup.
• Siphon brewers, pour-overs, Moka pots, single-cup coffee makers – Medium grind is what you’re looking for.
• Drip Coffee, such as most homebrewers – medium to medium-course
• French Press and Aeropress (inverted method) – Coarse grinds, as the coffee is usually sitting in the press for a long time. If you want a faster brew, then you could go more fine – but be careful of over-extraction.
• Cold Brew – since this takes 12-72 hours, you can go with more coarse grinds. If you want to speed it up somewhat at the risk of cloudier coffee, then you could experiment with finer grinds.

How do I know what kind of grind I have?

Since it’s relevant to the quality of your coffee, it’s important to be able to tell the difference. Here’s what I found:

• Extra Fine Grind – Harder/Impossible to do without higher-end grinders, it is as fine as powder, similar to flour or powdered sugar. It’s impossible to get this fine from blade grinders.
• Fine Grind – smooth texture, but you can still make out individual grains. Similar to table salt granules.
• Medium Grind – Grittier, similar to coarse sand
• Coarse – Chunky, distinct pieces of coffee beans; similar to Kosher salt

Here’s a few photos I snapped of various grind levels. Note that it is a blade grinder, so it’s inconsistent:

How do I get more control of my grind level?

Well, the main answer would be through using different methods of grinding the coffee. The methods you can use at home are as follows:

• Blade Grinders
  • The cheapest, easiest to find grinders. They grind by spinning a blade around really quickly, brute-force breaking apart the beans.
  • With the price comes less control, as they cannot grind to Extra Fine levels, and will create inconsistent results.
  • Some also believe that because the blades are spinning so fast, the heat can actually burn the coffee. As a result, they say to grind for less than 20 seconds.
  • If grinding a single cup’s worth, you can shake the grinder as you grind for more consistent results.
• Mortar and Pestle
  • If you want to go the extra mile and really want some extra fine grinds, then first use a blade grinder, then use a mortar and pestle, occasionally using a sieve to continually work down the size of grinds.
  • Yes, I have tried this before because I had never had Turkish coffee before.
  • No, I don’t recommend it.
• Burr Grinders
  • These use a specific kind of mill that was designed for “small food items,” tearing them apart between two revolving, abrasive surfaces that are separated by an adjustable distance, which affects how fine the grind is.
  • Probably one of the first grinding methods, they haven’t much changed since they were first invented.
  • Many use manual cranking and are quite slow as a result – roughly 1min per cup if you can keep a consistent rate of turning the crank.
  • Upside: no chance of burning coffee, and the grind can be adjusted between very coarse and extra fine.
  • You can also find electric forms, which will run you a little more… but the convenience is likely worth it.
• Disc and Conical grinders
  • The beans fall in between two disks (or cones), one of which turns while the other stays still. The disks/cones have grooves cut into them to increase friction, and which work to tear apart the beans.
  • Gives the most consistent grind, and are the grinder-style of choice for high-quality coffee
  • Most expensive

A Warning for Grinders

Never, ever grind flavored coffee in burr, disc, or conical grinders if you ever want to use those grinders for normal coffee again. The flavor extracts will coat the grinding mechanisms and it will forever taint the flavor of future grinds.

For those kinds of coffee, we advise using blade grinders only because they are actually possible to clean, though you will find that getting them completely clean is not easy.

Suggestion: if you want flavored beans, have a cheap, dedicated grinder so that you don’t ruin your more expensive ones.

Why all this fuss over grinders?

The simple answer is this: freshly ground coffee is less likely to be stale, as most pre-ground coffees are.

You ever notice that hole in the bag of coffee that allows you to smell the goodness within? I used to think that would make the coffee go stale, as I thought it was a two-way window.

It’s not.

That little pin-hole is a one-way vent that allows the natural gasses released by the beans to be expelled without the bags exploding in transit. Now imagine the coffee aisle without those little holes. Would probably sound like popcorn.

Coffee packagers follow a process called Modified Atmospheric Packaging (MAP), which has the simpler name of Nitrogen Flushing. Simply put, it pushes all the oxygen out of the bags to preserve freshness, as nitrogen will help increase shelf-life and quality.

If it’s pre-ground, however, it’s much more likely to be stale, especially after the can has been popped, due to the increased ratio surface area that’s exposed to air.

All this is a long way of saying that when you buy whole-beans, it’s more likely to be fresh when you first open the bag.

But, of course, you can’t make coffee very well with whole beans, thus the need for grinding and all of the above information.

The best cups of coffee come from freshly ground beans – and that’s what it’s all about.

Summary

Three important factors for how grind level affects coffee brewing:

1. Contact time – time that the water is touching the coffee
   1. Contact time is negatively related to extraction rate – the higher the extraction rate, the less contact time you want.
2. Extraction rate – the speed at which the coffee’s elements dissolve
   1. If you want a higher extraction rate, increase surface area by using finder grinds
3. Flow rate – the speed that the water is able to flow through the grinds
   1. The finer the grind, the slower the flow rate, which increases contact time.