Batch-Brew Basics by Scott Rao

One of the first posts on this blog was "Batch Brew Basics, Part 1".   I've wanted to write Part 2 for a long time, but have been deterred by what I see in cafes:  almost no one has the basics down.  What's the point of an advanced post if almost no one has mastered the basics?   Am I in the minority in thinking cafes should treat their batch-brew setup with respect?  

I'd like to restate a few things that should be obvious to coffee professionals, but even well-known cafes seem to not get these points.  To the 99.9% of readers who aren't coffee consultants, you'd be shocked at how many excuses cafe owners and baristas give me for why they can't be bothered to implement these simple practices that would greatly improve the quality of their batch brews.   


1. Brew batches no larger than 2 liters.  The only cafe I've been to in the last five years that was too busy to get by on 2-liter batches was in Grand Central Station.  I can't even fathom how many cups of filter coffee they sell per day-- it's well over 1000.  For almost everyone else, if you're serving fewer than 500 cups of filter coffee per day, two liters per batch is sufficient.  If you're really busy, ie you serve more than 50 cups (12oz or 350ml) of batch brew per hour, it may be best to brew into a rotation of three tw0-liter carafes during those busy hours.  That system will keep the coffee fresher and tasting better than will brewing fewer, but larger, batches. 

There is no reasonable excuse for brewing 4-liter batches, or brewing into 4-liter urns, as I see so many cafes do.  If you want your customers to respect batch-brew coffee, it will help to show it more respect from behind the counter first.  Small batches, brewed into full carafes, turned over at least once per half hour is the way to go.  Please. 

2. Your bed depth should be 3cm--5cm... I applaud the many cafes, especially in Australia, trying to promote batch brew to a disinterested population, and brewing tiny batches (often 1--1.5 liters) to limit coffee waste.  But if you want to brew one-liter batches, you either need a wire basket insert to narrow the diameter of your coffee bed (hence increasing its depth) or you need to find a machine designed properly to brew such small batches (and, honestly, the home-version of the Moccamaster is not a cafe-quality  machine.)

3. This will shock many readers:

 If your batch-brew grind setting is not in the 15% coarsest section of your grinder dial, there is a problem somewhere in your system. 

That's not a misprint.  You know that "auto drip" icon in the middle of the spectrum of grind settings on the old Bunn and Grindmaster machines?  It's in the wrong spot*--- those settings were chosen years ago when 99% of those grinders were used in American restaurants where they skimped on grounds.  Back then restauranteurs were using 30-40g/L (seriously-- in the 90s, when I tried to get my restaurant accounts to use 60g/L they thought I was mad) and grinding too fine in order to reach a palatable brew strength.   A professional using a reasonable ratio ( i.e. 16:1--18:1) should grind very coarse.  If you find the coffee is too weak in that coarse range of grind settings, at least one of these things is a problem: 

  • The grinder burrs are too dull.

  • The bed depth is too shallow.

  • The brew time is too short.

  • The sprayhead may not be making use of the whole coffee bed.

  • There is no prewet phase at the beginning of brewing.

There are other potential problems, but these are the most common culprits.

*While we're at it, you may as well swap the "auto drip" and "French press' positions on the grinder.

4. Total Contact Time should be 6:00--6:30

This advice is more flexible than the other recommendations in this post, but 6:00--6:30 seems to be the sweet spot for batch brews.  Try to get there without extending the programmed brew time past 4:30. 

Thanks for reading. 

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