First Coffee Experiments

I've been in the habit of making weekly batches of 24 hour cold brewed coffee. Taking the name literally, this meant tossing one cup of medium grind into my french press, topping it up with water, stirring a bit, and tossing it in the fridge until the next morning. I'd noticed that every time it came time to take the coffee out, a semi-solid puck of coffee ground has floated to the top. An independent island where no extraction could occur. I decided to make an experiment of it, seeing what happens when the grounds are constantly agitated and this agglomeration wasn't allowed to happen.

The first step was figuring out how I would manage to agitate it. Stir plates are relatively expensive, but seemed like the right way to go about it. I found a few tutorials on putting together one for cheap using a computer fan, some super magnets, glue and a power supply. Save for the magnets which I was able to get for about $7 from amazon, and the fan (which was  donated by an awesome friend) I had everything on hand. It came together in just about an hour, and is still without a housing. Still, it does the job.

For the first real experiment I kept constant everything I could (being time, water/coffee ratio), though the temperature was higher than previously as I haven't found a good way to squirrel the whole setup into my fridge. After the full 24 hours of agitation (making plenty of noise) the resultant liquid was what could best be described as "muddy".

After being french-pressed to remove the larger particles, the resulting liquid passed freely through a coffee filter, but rapidly clogged a #1 United standard filter paper (11 micron pore size). The solid left behind had the consistency of clay, indicating that the agitation may well have been crushing the grounds into fine dust. This was further suggested by the fact that even in the flask I was filtering into, a sedimentation became apparent. I decided to allow the liquid to settle (in the fridge) for four hours before carefully removing all but the bottom-most liquid. Eight hours later there was no sediment apparent, so I decided that I'd gotten out what was going to settle out.

Shortly here I should be able to isolate the caffeine from this batch as well as a similar batch prepared under identical conditions excepting agitation, and will toss my results up then.