All About Vacuum Brewing And Why It’s Not Siphon Brewing

vacuum brewing coffee thailand

First of all vacuum brewing is probably the coolest way to brew black coffee. The whole setup looks like a science experiment and if done correctly, it is a delicious experiment indeed! Vacuum brewing is actually a slightly older brewing method than espresso (1830s vs 1880s) and just by looking at both methods you can see them as these kind of steampunk-coffee contraptions. But vacuum brewing (sometimes called siphon brewing) is finicky and certainly not an express way of brewing coffee, which is why it is not seen on every coffee shop counter…yet.

Though vac pots (vacuum brewing) were common up until the middle of the 20th century, they are now over shadowed by other speedier coffee brewing methods. However, I think pour over coffee has grabbed hold of counter space, even though it is not as fast as espresso or pre-brewed drip coffee, because it has a show to the brewing process which highlights the coffee, and the careful attention of the barista. Pour over coffee offers time for the barista to engage with the customers and share their love of coffee. Because of this slower approach the vacuum brewing method is perfect for putting on a show and really giving baristas and customers time to anticipate and appreciate their beautifully brewed cup of black coffee.

The Mechanics of Vacuum Brewing Coffee

This method is a vacuum because of physical processes behind the brewing process. This process is often called “siphon brewing” by pros in the industry. So who am I to go against that? However, the brewing process does not use a siphon (noun) nor does it siphon (verb) – it uses vacuum. Let’s look at a step by step of brewing coffee with this wonderful coffee contraption.

Step 1 – Assemble the Glass Hopper

vacuum coffee brewing Thailand

All brewing methods require a filter. The vac pot filter needs to be soaked for about five minutes in warm water. Connect the filter to your hopper and drop it into place so it covers the glass tubing extending down.

Step 2 – Prepare to Lift the Water

Fill the bottom bulb with 300ml of hot water and insert the hopper into the bulb. You do not have to press down, the hopper should fit evenly in place to create the vacuum.

Once the filter is in place, the bottom bulb has hot water in it and both pieces are assembled, position them over your heat source. There are many different heat sources. Such as, flame (as seen in the picture), halogen lamp, or contact with a heat source (like an electric burner). Turn on the heat and while your water is coming to a boil move on to step 3.

Step 3 – The COFFEE!

Of course you need roasted coffee beans, so now is the time to grind it. Set your grinder (if you don’t have one you may want to consider a manual coffee grinder) to just a little finer than you would make for regular drip coffee. Remember grind size will dramatically change the way your final cup will taste, so if your coffee didn’t come out quite right this is one area you should try to adjust. Grind 20-25g and set aside.

Step 4 – The Rising Water and Brew

At this point the hot water from the bottom bulb should have moved up to the top hopper. This happens because the bottom chamber is changing from liquid water to steam, creating pressure that moves the water up through the tube into the upper chamber.

Once the water has moved (there will still be some water remaining in the lower bulb) to the upper hopper lower the heat and use a thermometer to get the water in the hopper to be between 85 and 90 degrees Celsius.

Step 5 – Brewing the Coffee

Finally, it is time to add your freshly ground coffee to the upper hopper that is at the perfect brewing temperature. Use a paddle or butter knife to gently stir the coffee grounds and make sure they are all submerged in the water.

Let the coffee brew (with the heat source still on low) for about one minute and ten seconds (really you just have to experiment for yourself on what brew time will work for the coffee you like).

Step 6 – Getting Closer to a Cup of Coffee

After your coffee has brewed about a minute then remove the heat source and stir once again. Without heat creating steam in the lower chamber the pressure that was holding the water in the upper chamber will drop and begin to allow your brewed coffee to drop through the filter back into the lower bulb. This is the vacuum part of the vacuum pot! The lower chamber is actually sucking (vacuuming) the coffee liquid down through the filter.

It should take about another minute for your coffee to completely descend down into the lower bulb. Once the grounds form a dome over the filter you will know you have all your amazing brew down in the lower chamber. Blue Bottle, a specialty coffee roaster from Oakland California, further suggests you will know your coffee is ready when,

…when the coffee at the bottom has begun to bubble at approximately the pace and strength of a kitten’s heartbeat.

This funny quote is meant to show how difficult and delicate the brewing process can be.

Step 7 – Time to enjoy…

…well in a few more minutes. Didn’t I say this was not a fast way to brew? Remove the top hopper of coffee ground from the bottom chamber and allow to cool for another couple of minutes.

Is It Better Coffee?

Vacuum brewers are just about opposite the French Press in terms of how the coffee will turn out. French press is full bodied where the siphon is more tea-like. Vac pots have three characteristics that should yield a better cup of coffee over typical drip brewing:

  1. water temperature remains consistent throughout the brew
  2. coffee grounds get thoroughly wet
  3. extraction of all that coffee goodness is even 

I look forward to seeing more vacuum brewing her in Bangkok so I can see how it stacks up. Also I would love to see the use of a balance siphon just because it looks even more ridiculous than the vac pots.

Here is a nice video showing how to operate a vacuum pot.

This article was heavily influenced by a couple of articles: