Vacuum Coffee Maker: Frequently Asked Questions

Simon Calvin
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What is a Vacuum/Siphon Brewer?

Vacuum/Siphon brewing is one of the oldest methods of coffee preparation. The vacuum brewing system requires the user to slowly heat water to a boil, and then virtually "vacuum" the coffee grounds into the bottom chamber where they will steep in the near-boiling water.

This is one of the most labor-intensive ways in which to brew coffee, but unlike the French press or AeroPress, the end result is a full-flavored, less acidic cup of coffee. You'll need to have at least a basic understanding of the process before you sit down to make your first cup.

The vacuum-style coffee maker design consists of two glass chambers, a lower boiling chamber and an upper holding chamber… and a bit of complicated physics. The vacuum brewer’s operation relies on three scientific principles—specifically: 1) converting the water from a liquid to a gas in a vacuum 2) the gas release properties of air and 3) thermodynamics.

The first principle can be understood by examining the operation of a steam engine. Just as the steam engine converts liquid water to a gaseous water vapor, the vacuum-style brewing does the same in reverse. Simple enough.

Why should I use a vacuum brewer?

The vacuum brewer uses vacuum brewing technology to concentrate the coffee flavor, increase the aromatic oils, and create a clean cup. Coffee grounds are placed in a vacuum brewer and injected with hot water. Coffee is then brewed for about six minutes.

This gives the coffee grounds a bit more time to interact in the water, resulting in maximum extraction of flavor during brewing.

How does a vacuum brewer work?

In some ways, this is where the art of making coffee meet the science of coffee. To produce a cup of coffee using vacuum coffee makers, you need whole coffee beans, water and a vacuum.

The vacuum coffee maker does not only those things. It also serves as its own grinder. The coffee is ground at the optimum coarseness before it is brewed. The water and the coffee grounds are put in the top chamber of the vacuum coffee maker. The water, once it is heated, flows into the bottom chamber where it is pushed up a tube into the top chamber, creating atmospheric pressure. Atmospheric pressure then pushes out the vacuum through a hole in the bottom of the lower chamber.

Two brew baskets work in tandem to produce good coffee. The lower basket sits on top of the lower chamber and is filled with coffee grounds. The upper basket is then placed on top of the lower basket and the heated water is poured into the bottom chamber. The coffee is then forced through a filter and then flows into the upper chamber. The coffee is dispensed from the upper basket and then sits in the upper chamber to finish off the brewing process until it is ready to be served.

While waiting, the brewed coffee stays warm in the upper chamber. This means that some of the flavor compounds are preserved in the coffee. Some coffee oil is also locked in the grounds. These are the flavors that gets lost from the coffee if it is brewed in other ways.

What type of heat source should I use?

Heat sources vary, so be mindful of the particular instructions provided with your specific brand.

If you prefer a more simple setup without additional temperature control, the most affordable method is a standard propane burner or an inexpensive charcoal briquette burner. (If you choose to use the propane method, using a valve regulator will save you money in the long run.)

If you prefer to use an electrical appliance, the Waring Pro WMK600 is a popular choice among coffee enthusiasts for home use.

Another simple, affordable option is to choose a stainless steel coffee maker, which will heat water more efficiently.

Should I preheat the water?

Yes! Never scoop some coffee into your vacuum brewer, fill the remainder of the chamber with hot water from the tap and expect it to taste good. The water that your brewer provides should be close to boiling in order to extract the most from your grounds.

How concerned about my water quality should I be?

You can brew delicious coffee with soft water. However, if your water is too soft or too alkaline, you might not be able to get the best taste out of your coffee.

For example, if your water is too hard or too full of minerals, your coffee may taste off. It might be bitter, metallic, or otherwise unappealing. Sometimes it could be difficult to determine what’s causing this off flavor. Keep in mind that the more unsettled or less delicious your coffee tastes, the more you’ll want to run the machine with fresh water before brewing your first cup.

Riverside, California in the United States has hard water and makes the most delicious coffee. The exceptional quality of their water is one of the reasons why coffee drinkers love the San Francisco Bay area.

What type of coffee should I use?

Generally speaking, you can use any type of coffee grounds. Moisture content and roast are generally not the deciding factors when using vacuum coffee makers. However, vacuum coffee makers are best for oily brews. You can use traditional-style drip filters with whole coffee beans but you would be better off using another filter method if you prefer finely grounded coffee. There are some who recommend using finely grounded coffee from vacuum coffee makers because it will prevent the buildup of a layer of oils within the brew basket. The oils can slow down the draining speed and this can affect the taste of the final cup. So if you plan to use a coarse ground, always keep in mind that you might have to clean it more often.

How coarse should I grind coffee beans for vacuum brewing?

The coarseness of the coffee grinds makes a noticeable difference in the quality of the brewed cup, so it is important to get it right. Grind size has a direct consequence on extraction, so it puts an emphasis on short brew times and hotter water. As a general rule, grinds should be quite coarse, at least as coarse as used for Turkish coffee. Brewing manuals usually mention this in the instructions.

There are several ways to measure grind coarseness. The easiest one is to weigh a sample of ground coffee. To do that, you will need a kitchen scale capable of measuring in grams. An accuracy of 0.1 grams is good enough. Dump the ground coffee into a large bowl, and wipe the bowl and the weighing scale prior to use. Put the bowl on the scale and get the maximum reading, then dump out the coffee. Grind the coffee in small batches, and repeat the procedure until you get a consistency of about one gram. Use the average weight for that batch. Luckily, if you have an accurate flat-blade kitchen spatula, like a large metal pancake spatula, you can use that instead of the kitchen scale.

After brewing, how do I clean my vacuum brewer?

The easiest way to clean the vacuum brewer is to use a cleaning brush inside the brewer to remove all residual grounds. Some people may choose to clean it right away after brewing. Others may wait until there’s a fair amount of sediment sitting on top of the grounds.

Due to the nature of the ground coffee, it’s best to clean it without water. So, it’s recommended to rinse it with a damp cloth and then wipe it with a soft cloth.

What are different names for vacuum brewers?

Technically speaking, there is one brewer that goes by many names. The vacuum brewer is called pump pot, coffee machine, siphon, syphon, and vac pot among other names. Its original name is “le marmite de vacuum.”

Technically speaking, the vacuum brewer is not a coffee pot, though many websites refer to it as one. An early model was patented in France in 1806 by De Belloy, as a saucepan with a spout. One hundred years later, in the early 1900s, Luigi di Ponti, a coffee roaster in Italy, used it to brew high quality coffee.

To brew coffee using a vacuum brewer, the brewer is first filled with about two liters of water. Coffee’s grind is measured around 15 to 17 grams per liter of water. Next, the coffee is added to the filter and coffee grounds are rinsed three or four times with hot water. The filter is placed in the brewer and the coffee is left to brew. Once the coffee is ready, the coffee maker is transferred to a service table and the pot is filled with water. The dregs of the coffee are passed through the filter again. Coffee is served. The coffee maker can be disassembled and the parts can go in the dishwasher for cleaning.

Do all VacPots work the same?

The short answer is no. To put it in simple terms, when you make a cup of coffee with your brewer, you’re making it with the water from the tank. Imagine if you had a coffee maker with a tank that was always full of coffee … would that coffee pot brew the same way?

One of the main differences between manufacturers is how hot they allow the water to get. This high temperature is necessary for it to extract flavors from the grounds. Just like coffee makers for example, the Keurig allows it to get much hotter than the Chemex.

With different computers and different monitor settings, it can be difficult to figure out what the temperature really is. I personally know Keurig brews that get as hot as 190°. Hot enough to burn my hand for a few seconds. The Keurig is also known for its slight scalding in the bottom of the cup.

VacPot Coffee Brewers are also known for being able to make coffee at 145° and lower. With the simple add on of a brew basket with screens, the brew temperature can be adjusted to make it as hot or as mild as you like.

What are the different sizes of vacuum brewers?

The majority of the vacuum brewers out there are three or four cup-sized pots that are widely used for camping. There are few out there that are a little larger but they’re the exception rather than the rule.

The larger size vacuum brewers are great for use as a coffee maker you bring for a picnic or vacation as well as for taking on camping trips.

When you take into account price, size, and price, most people end up favoring a three cup brewer.

There are four cup brewers that are perfect if you are going to be using your brewer for a place where you are going to be required to pack everything up at the end of the day. Since you are only going use the vacuum coffee brewer at the end of the day, it’s not a bad idea to use something smaller if you are going to be there for only a short period.

What is the history of vacuum brewing?

Vacuum coffee brewing machines have a very long history. The first ever vacuum coffee maker was invented by an engineer named Pascal with funding provided by Maxwell House of Coffee fame.

Pascal’s machine was not the first vacuum brewer by any stretch of the imagination. But Pascal’s machine was a major improvement over previous devices. His machine provided a much better control over water temperature, and it included a self-contained air pump, which made it much easier for everyday home consumers to use.

Maxwell House went on to become the largest coffee company in the world, and Pascal’s invention was widely used for decades – to the point where it was practically the archetype for a vacuum brewer.

Maxwell House also received the next major innovation in vacuum brewing because they were very much involved with the team that created the first automatic vacuum coffee maker. From the 1930 until the 1990s, the French Press was widely popular. The French Press was created by Italian inventor Attilio Calimani. The French press was one of the first major improvements over Pascal’s design. The design was so revolutionary that it has had a dramatic impact on coffee culture.

How has time changed the VacPot?

Today’s VacPot seems to be a specialty coffee brewer for a small niche, but it had its roots in the 1970’s when it was considered a radical development in the automation of espresso machines. The problems with today’s VacPot seem to be more about the execution than the design. The presence of diacetyl, caramelized sugars and incomplete extraction seem to stem from poor machine designs rather than the brewing method. At least, this is the coffee professional’s perception of the system.

The state of the art in the 1970’s and early 1980’s allowed for very little automation of the brewing process. Thus, the custom espresso machine with its operational complexity and maintenance was the manner in which an espresso drink was composed. There was no decent alternative for the individual who wanted to make a cappuccino or latte. The present day “Vacuum Pot” falls short because of its inherent design characteristics and its shortcomings in its operation. While it produces a superior cup of coffee when used properly, the intricacies of that operation are more complicated than we modern consumers can be bothered with.

Why aren’t vacuum brewers everywhere?

Vacuum brewers were making hearty cups of coffee for a long time before all of the coffee crazes. Vacuum brewers are a very old design and are the most historic of all of the brewing methods.

Unfortunately, around the time of the rise of the big commercial coffee roasters the vacuum brewers were suffering from a price point disadvantage. Vacuum coffee makers take longer than automatic coffee makers to make a delicious cup of coffee. They also have less control over temperature control and must be used in lower volume settings.

The big commercial coffee roasters wanted to be able to make larger batches quickly, at a certain temperature, for a certain price. If you are the big coffee roaster you have many customers who want coffee just like they like it every time they order it.

Smaller shops have been able to make great coffee with vacuum coffee makers since they don’t need to make huge volumes. Brew bar owners continue to use vacuum brewers to be able to offer more variety in their coffee menus.

As vacuum coffee makers became less popular in the 70’s and 80’s they became more affordable. When the third wave movement started to take off again, airpots and vacuum brewers were fairly affordable and manageable.

Where can I buy a vacuum brewer?

Check the Vacuum Coffee Makers category on Amazon. You’ll be able to see which products are currently available.

If you’re looking for a specific brand or a specific model of vacuum brewer, just search for that model number on Amazon. You’ll usually find the vacuum brewer you’re looking for, and you can check user reviews to make sure that it’s a reliable model.

What are some of the best VacPot models?

The best VacPots will extract your coffee and brew it in about 5 minutes flat. The Hario V60 is particularly smart because you can pre-soak your grounds to taste and mix in your ingredients before brewing time. You also have more control over how strong your coffee is because you can control the size of your coffee grounds and add more 12 water. If you need an even stronger brew, you can pre-soak a second time and brew your coffee again in the same cup, which is great for adding a fruity aroma.

The Bonavita also does well in terms of temperature control, with the pre-infusion function in particular being of significant benefit. You can simply hit the switch, and it will take you from pale and weak to dark and strong in under 45 seconds.

The AeroPress Coffee Maker is also impressive, although it's really well-suited for home use, given its price tag and the fact that you need to mix and measure the ingredients. You'll also find that the coffee produced is pretty strong, but not really much fun.

Can I buy my VacPot off Ebay?

Since its inception, there have been a few different manufacturers of the VacPot. The most prominent was Fetco. After they stopped manufacturing them, there was a gap of close to a decade before the next version came out.

So if you searched on Ebay for a VacPot, you would likely have found the Fetco version. However, at this time, the only manufacture still producing this model is Vacu Vin. This is the new and improved VacPot.

Currently, the Fetco still dominates the auction market, but at this point it is becoming increasingly difficult to find one.

There is a small but vocal group of people still advocating and practicing the merits of the Fetco VacPot. If you do a quick search online, you can find forums, articles and other information dedicated to the Fetco VacPot, and still learning how to do the best coffee possible with it.

The biggest advantage of the Fetco design was the ability to adjust the fan speed and temperature. Although the new Ventti will allow you to do this, the Fetco had direct controls on the showerhead. The Ventti allows you to do this through halogen lights, but only one at a time.

A new Fetco is readily available through eBay if you should decide to buy one from this small group of enthusiasts. The Vacu Vin Ventti is readily available, and the user controls are improved from the original model.

What kind of filter should I buy?

In choosing the right filter there are a few things to consider in terms of type, cost, grind consistency, and how quickly you want to consume your filtered coffee.

The most popular and most affordable filter is a thin metal filter. This is used with finely ground coffee and is the type of filter that is commonly used in automatic drip coffee makers. A major benefit to this kind of filter is that the water passes through the coffee as quickly as it is poured, so your coffee is ready very quickly. This type of filter also allows for a lot of crema (the foam on top of your espresso drink that is rich in flavor) to develop, and provides an easy and mess-free way to store your ground coffee after it has been used. One downside to this kind of filter is that it can expose your ground coffee to oxygen, which can cause your coffee to develop a stale taste within a couple of days.

Does my choice of filter effect other coffee making variables?

The filter material does not effect the brewing parameters and the flow rate. However, the filter is material is what effects the resistance to flow for the different coffee makers.

This resistance is the only thing that effects the total brew time (total contact time), and the total brew time is then reflected in the the brew ratio (total water/coffee ratio) of the brew.

As you will see in the end, the brew ratio is the most deciding factor for taste, and therefore, the coffee style that you prefer. In the end it will define how your coffee tastes.

You will also find that all of the filter materials below work excellent for any type of coffee maker.

Is vacuum brewing feasible for everyday coffee drinkers?

Vacuum brewing is a wonderful way to make flavorful coffee without using paper filters or having to buy gourmet coffee beans. With the help of some basic filters you can create an awesome cup of coffee. The whole process takes about 5 minutes and you never have to use filters again. If you are wondering whether vacuum coffee is feasible for you and your budget, we would say it’s a great option.

The reason vacuum coffee is so popular is because one pot of coffee can last you up to 1 week, if brewed correctly. It’s a great alternative to traditional forms of coffee. Also, if you are worried about the coffee being made with paper filters, we have you covered. We have given you the option of either using a paper filter with our device or removing it to enjoy coffee without the filter. If you are looking for an environmentally friendly way to brew your coffee, you can rest easy knowing that you are not using paper filters.

Are VacPots the new trend?

A recent Google search for vacuum coffee maker or Vac Pot turned up about 35,000 results, from coffee connoisseurs and coffee brewers alike. It seems that many people are interested in trying out this brewing method.

Reading over the results, possibly the most central question was: What is the best vacuum coffee maker?

Finding the right vacuum pot is important. You want to ensure that the vacuum coffee maker you buy is capable of producing a coffee that is tasty and satisfying.

The good news is that there a variety of coffee makers on the market and it is possible to find one that is both affordable and capable of producing great coffee. Budget is often a factor for most individuals when making a purchase, so you will want to take a look in several price ranges, while still remaining within a budget. A major consideration is durability and usability, since many of the cheaper models may not be able to stand up to everyday use.

Here, a look is being taken at some of the questions that are frequently asked when it comes to vacuum coffee makers.