Slow-Brew Coffee might be a better name for it! This is certainly not a way to get a quick morning coffee fix. Thank goodness I can function without coffee in the mornings otherwise I may not have had the coordination needed to finish off my cold-brew coffee experiment.

My coffee mixture sat brewing for 13 hours overnight, although I did check on it a couple of times before I went to sleep. I learned a couple of lessons from the preparation and brewing and extraction process however:

• Don’t max-out your brewing container – I made a litre in this case, and the process was a little messy with a full container, next time I’ll try 750mL. The good thing about cold-brew coffee is that it has a shelf life of more than a hour or two, unlike regular coffee which degrades as it cools.
• It may overflow in the fridge – After checking on the brew after 2 hours I found that somehow the coffee was leaking out of the container. I don’t know whether the mixture expanded in the fridge, or the gladwrap I used to cover it set up some sort of suction, but coffee leaked out and pooled under the container. Another reason not to max-out the container.
• Brewing in a coffee plunger was a good idea – Using a plunger as my brewing container meant I could double-filter the brew when I extracted it, once with the plunger, then again through a coffee filter paper and funnel into a bottle.
• Using filter papers was a good idea – The plunger alone definitely wasn’t enough to filter the grounds but the filter did an excellent job (which is kind of its purpose). The resulting coffee had no sediments which I could see.
• Filtering coffee is a slow process – It took a little over an hour to filter the litre of mixture. My funnel and filter set-up worked well, but I can see why some people would use a special apparatus for this. I went through three filters over the course of the hour.

Once all the filtering was done, I had around 800-900mL of coffee in a bottle, and plunger with a cup of wet coffee grounds in it. With the some sort of vacuum or pressurised set-up you could no doubt extract more out of the grounds as there definitely seemed to be more flavour potential locked up in there.

Finally, the all important taste-test. The coffee mixture I ended up with wasn’t overly concentrated, so it was OK to drink undiluted. The result; still a little too bitter for my tastes, however this was fixed by the addition of a little agave sweetener. It seemed much smoother than regular coffee, and was much easier to drink, even without milk which is something I usually cannot manage. The flavours were not as strong as I hoped, so I think my process needs a bit of refining. Next time I will try brewing a smaller batch, but make it more concentrated, and see if that strengthens the flavour. I’ll also need to investigate how variations in brew time and temperature affect the taste.

There’s also the option of making cold-brew coffee using vodka or whisky instead of water for an extra kick. But that might be an experiment for another day.