I thought I was really into coffee until I met John Edgar Park, host of Make: television, contributing writer to Make: Online, and author of several MAKE magazine articles. John takes his coffee seriously. Seriously. Case in point was when he devised and wrote a how-to for his Florence Siphon Brewing and Extraction Apparatus for MAKE Volume 17, our Lost Knowledge issue. This apparatus is sure to raise eyebrows (and spirits) next time you invite someone to your workshop for a cup of blessed joe. Check out the whole project in this week’s Flashback, and pick up a back issue of MAKE 17 over in the Maker Shed.
Make your own mad-scientist coffee machine.
By J. Edgar Park II
Aboard the dirigible Aeroship Phaedrus, two men are seated at a table in the onboard Laboratory:
“Doctor Liepold, would you kindly prescribe something to lift my depressed spirits?”
“Why of course, Captain Heffernan. What is it that ails you?”
“My mind feels sluggish and there is still much work to be done before daylight. I am drawing up charts for the expedition.”
“Ah, yes, I have just the thing. Sit a moment while I extract the invigorants from these wondrous beans.”
“Very good, thank you. What is that strange device, Herr Doktor?”
“I call it the Florence Siphon. It is an arabica brewing and extraction apparatus. Allow me to demonstrate. First, I fill this boiling flask with a quantity of pure spring water. It is a vessel of my own devising that can withstand great heat and pressure. I heat the flask, which causes the water to vaporize, passing through this tube here, through a filter, and into the beaker to my left. Here, the water commingles with precisely roasted and ground fruit of Coffea arabica. I give the slurry a rapid stirring to fully saturate the grounds, then wait.
“As my boiling flask cools, a vacuum is created, causing the very atmosphere of the Earth to push the liquid through the filter, leaving the grounds and all unsavory particulate matter behind. Thus the liquid, now filled with essences, oils, solubles, flavors, and vital invigorants, is returned to the flask. Allow me to unstopper it and pour you a dose.”
“Doctor! You have outdone yourself! I feel revitalized by this most miraculous potion.”
The vacuum siphon coffee brewing method dates back to the 1840s. It produces some of the cleanest, smoothest-tasting coffee of any method. Commercial vacuum pots are available, but I wanted to heighten the drama of vacuum brewing by taking it into the realm of the mad scientist’s lab. Thus the Florence Siphon was born!
After studying original patent drawings and existing devices, I identified these key features:
• Water is heated in a boiling flask that has a tube leading to a second vessel containing ground coffee.
• The tube must have a filter, to allow the water to flow through but not the grounds.
• The filter must be submerged during brewing, so as to maintain a seal with the boiling flask.
• The second vessel must be accessible for stirring the slurry.
• The boiling flask must be large enough to create a sufficient vacuum as it cools to “pull” the coffee back through.
One drawback to early vacuum brewers was the constant danger of exploding glass. Today, we have plenty of high-quality borosilicate glassware that’s up to the task — it just happens to be found in the lab, not the kitchen.
Filtration was another challenge. I tinkered with a few options (including an unfortunate foray into shower heads) before arriving at an inverted thistle tube. This is a type of bulbed funnel that’s easy to cover with filter cloth. (Thanks to Dr. Jim Callan from Avogadro’s Lab Supply for this suggestion.)
I assembled my funnel, stopper, tubing, filter, and a beaker for the grounds. I filled my flask with preheated water (small burners can take a while to boil 500ml), poured 38g of medium-ground coffee into the beaker, donned my goggles, and lit the burner.
The water began to bubble quickly, and soon went straight up the glass tube and over to the grounds. After about a minute, the flask was nearly empty and I extinguished the flame. At this point, there was an abundance of expanded water vapor (steam) inside the flask, which prevented the water from returning.
I stirred up the slurry with a stick and then waited with great excitement. Would the siphon be able to draw the coffee back up? At just about the 2-minute mark, I saw the gorgeous brown liquid begin its ascent. This is due to the vacuum created by the cooling and contraction of water vapor in the boiling flask. It was tentative at first, but as the boiling flask continued to cool, the coffee started to move quickly up the tube, over and then back down to the flask below. Within another 20 seconds, the journey was complete: 420ml of coffee made it back, leaving 80ml of water behind with the grounds.
I removed the stopper and poured myself a cup. It was perfect! Smooth, bright, clear, and clean. Vacuum coffee is a step above a French press, and leagues above drip. Plus, when you brew with the Florence Siphon you get to don your lab coat and cackle maniacally. What more could you want from a cup of coffee?
Here’s how to build your own Florence Siphon.
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