assembled diy espresso machine

Thought we'd mix things up this week with a low tech How-To courtesy of Hack A Day editor Jason Striegel:

I spent the weekend trying to design a small espresso machine that you can make from readily available parts. What has a homemade espresso machine got that an $800 Williams Sonoma special doesn't?  $770 dollars in your bank account, high-design PVC tubing, and a caulk gun.  You probably have a caulk gun anyway, so let's just make that $785 in your pocket and a fine piece of caffeinated gagetry that you can impress your friends with.

A caulk gun?  Hey, if it?s good enough for Taco Bell guacamole and sour cream, it?s good enough for a fine and delicate espresso, right?

If you just want a nice strong cup of coffee, you can use the homemade espresso machine sans caulk gun too.  Just force the plunger manually and don?t tamp the grounds as hard.  It?s perfect for backpacking!  There?s nothing like brewing a shot or two of espresso atop your favorite 14er? so I?m told.

espresso parts
Ingredients

  • Lengths of 1 1/4-inch and 2-inch PVC tubing

  • Various pipe joints shown in the above picture (hereafter reffered to as a, b, and c from left to right).  You?ll need two of the bottom right, and a part that mates two 2 inch pipes together (d, not shown).

  • PVC cement, and teflon tape

  • Some sort of stopper that will make a sealed fit in a 1 1/4-inch tube

  • 2 inch diameter portafilter cup

  • Caulk gun

  • Hot water and finely ground coffee

Construction
caulk gun espresso machine components
Feel free to skip this section if you want to see the device in action and don?t care about the details of its assembly.  The assembled product is shown above and is comprised of three parts: the plunger, the portafilter attachment (where the coffee goes), and the seal/compression chamber.  Joint b on the portafilter attachment and joint a on the compression chamber screw together to form as seal and can be seperated for cleaning.  The portafilter is sandwiched between joints d and b (which are cemented together with a small length of 2-inch pipe.

The seal is provided by two c joints affixed end to end.  Part c has a small ridge inside of it which exactly accommodates the 1 1/4 inch plunger.  I use two of these end to end so that the dead space between them provides a small buffer for any water that slips past the first seal.  We don?t want anyone getting squirted with pressurised hot water.  The very top of the seal unit is removed and affixed to the bottom of the portafilter unit.  This keeps the length down and prevents the filter basket from striking the end of the caulk gun.

Preparing Your First Cup
loading the portafilter
Just like any espresso machine, you?ll want to grind your coffee and place the appropriate amount in the filter basket.

 tamping the coffee
You can then tamp down the grounds with the plunger unit.  The amount of coffee you use and the pressure with which you tamp it down will determine how much pressure is needed to force the water through the grounds and out of the machine.

pulling a shot
To operate, the two halves of the machine are then screwed together and filled with water to just below the bottom seal.  The plunger is inserted and the entire unit is loaded into the caulk gun.

How It Works

A typical espresso machine circulates water past a radiator, heating it to just under boiling temp.   The water is then pumped through the coffee at about 12 atmospheres of pressure.  When the coffee exits the system and depressurizes, small co2 bubbles form and rise to the top, creating a reddish-brown foam.

With this machine, you?ll heat your water seperately and then just pour it in.  I highly suggest you pressure test the unit for leaks with cold water before trying a hot water run.  You are the pump, so you will control the pressure in the system.  It?s all dependent on how hard you tamp the grounds and what rate you force the plunger through.  You probably won?t be producing 12 bar and I double.. no.. triple suggest you pressure test the system if you are even going to attempt that kind of pressure.

It takes about 20 seconds to produce a couple shots of espresso.  It?s black, strong and, surprise, it tastes like an espresso.  You probably wont be winning any taste-test competitions, but the hack value counts for something, doesn?t it?
finished product