How to cold brew coffee

So a while back a friend of mine asked me how to cold brew coffee and I told him I ‘d post a how-to guide that very night.  It’s been a month and I haven’t done anything of that sort yet.  Whoops.

Anyways Mitch, here’s the comprehensive introduction to cold brew that I promised you.  I’m not really sure this counts as an introduction or as comprehensive, but y’know what you’ll ask me questions if this doesn’t make complete sense and then I can use those questions to make another blog post.

The Basics:

So as I’ve said before, cold brewing coffee is more or less the only way I see myself drinking coffee.  Hot coffee is alright and if I have to have a hot coffee I make a drip coffee (we can get into why I think drip is the superior way to drink hot coffee in a later post).  Cold brew more or less breaks down into three areas:

Beans

Time

Heat

So let’s start with…

BEANS

You can vary three things with your beans.  The grind size, the beans themselves and the amount of them you use.  We’ve covered the beans and their various roast types here.  So we’re going to cover grind size here.   The smaller the grind you use the more surface area the coffee beans will have with the water which means they’ll impart more flavor and caffeine.  However having too fine a of a grind size can lead to you over-exposing the coffee to the water which in turn leads to certain unpalatable flavors making their way into your coffee.  In short, you need to figure out how finely – or in this case coarsely – your coffee should be ground for cold brewing.  When I first started I used very finely ground coffee beans for my cold brew and while the coffee itself wasn’t disgusting, it was fairly bitter (though strangely smooth).  I’d personally recommend a more coarse grind paired with a longer brew time over a finer ground and a short brew time as the flavors you extract from coarsely ground beans tends to be more palatable than the finer grinds.  You also are able to better control for small coffee particulates getting into your cold brew.

One important thing to do though when cold brewing is to try and insure that your grind size is consistent.  In order to insure this you will need a burr grinder as most places won’t sell coffee beans ground specifically for cold brewing.  I bought mine from Amazon here.  I elected to go with a hand grinder over electric as it was the cheaper option and at the time I didn’t realize I’d develop a strange obsession with cold brewing.  I chose ceramic burrs over steel ones as ceramic ones tend to be hardier/last longer and from my readings don’t leave any residual flavors (some people who use steel grinders complain about metal tastes).

More beans per volume = more caffeine.  This is kind of true.  While you do get more caffeine if you’re able to fit more coffee per volume of water, I’ve found that the optimal ratio of coffee to water is around 14-16 tablespoons (or about up to the white mesh bit of my coffee “sock”) to 32 – 34 oz. of water.  You could theoretically fill it with more coffee but I’ve found that generally leads to over-extraction/diminishing returns and any less just leaves you with something that isn’t terribly strong or flavorful.

TIME

So when it comes to time, it’s pretty simple.  The longer you leave your coffee in the fridge the more time you’re giving it to extract caffeine and other flavors.  The less time you give it the less time it has to do that.  Granted the amount of time you want to extract for is dependent on your coffee to water ratio and your grind size, but generally speaking using the grind size I’ve pictured above along with the aforementioned ratio I generally find that the optimal amount of time is around 24-36 hours.  Not much else to say here really.  Use your best judgement and experiment accordingly.

HEAT

So why would I bother talking about heat in a post about cold brewing coffee?  Well, it’s because you can actually “prime” your cold brew buy exposing the beans to heat and then arresting that extraction process abruptly with ice or cold water.  What this heat extraction process does is that it causes – supposedly, though anecdotally I’d agree – the coffee beans to release their flavorful oils without extracting the more volatile ones that lead to your hot coffee tasting like dirt when it gets cold.  This process however is very much so an art and I’ve yet to master it.  If you want to avoid this altogether you can just dump your grinds into cold water and leave them alone in the fridge and never think of them again and you’re probably going to be just fine.

However if you do pursue an “flash-brewing” method I’d recommend you invest in some sort of cold brew equipment either something like this or a glass pour-over coffee maker.  Either of these will work and I’ve used both to make coffee in the past.  Personally I prefer the Takeya if only because it comes with a sock, if you use a glass pour-over coffee maker you will have to find a way to submerge your grinds in the container when it is in the fridge.

The key to flash-brewing is to control the amount of time the hot water is in contact with the beans.  You will want to boil the water to boiling and then let it back off slightly so that it is just around 200-210 degrees F (or around 93-96 degrees C) and then to pour small amounts of it over the coffee beans and the filter.  You only want the beans to be exposed to the hot water in approximately 15-20 second intervals so you must douse the beans with cold water periodically to prevent over extraction.  After doing this a few times, i.e. once my ice starts to melt, I fill the rest of the container with cold water and throw the coffee in the fridge.