WHAT DOES A “HEAT EXCHANGER” IN A COFFEE MACHINE MEAN?
Basically its one boiler, with one element can produce the two different temperatures required for making a coffee. The lower of the temperatures is for the brewing, and the higher is for the steaming and hot water. The element is used to heat water in the boiler and the water in an inner pipe which supplies the water to the group head. It means that you can brew and steam at the same time.
WHAT IS A DUAL BOILER COFFEE MACHINE?
As the name indicates, the machine has two separate boilers, one is for the brew temperature and the other is for the steaming and hot water.
WHAT IS AN E61 GROUP HEAD?
Patented in 1961 which was the year of an eclipse is why this part of a coffee machine is called and E61 and it has nothing to do with its size!!! This group head is the large “nose” which you see on some coffee machines and it’s where you lock your handle in. It’s made of solid brass and contains a “pre-infusion” chamber which reduces the pressure in the group head and gradually increases it. The pre-infusion improves the flavour of coffee because it doesn’t “shock” the first oils which are extracted from the coffee. An E61 group head is a standard industry part made by various manufacturers and takes what is called a porta filter handle which is a standard 58mm size. There are some slight variations but on the whole, they are almost all the same.
WHAT ARE THE GAUGES FOR ON A COFFEE MACHINE?
If there is one gauge on a machine and this display a number up to two or three then this is the “boiler gauge” and it tells you what the pressure is reading in the boiler. If a machine has a second gauge and the number go up to approximately 12, then this is the group head gauge and tells you what pressure you should expect in your group head. It’s important to know that most group head gauges measure the pressure from between the pump and the solenoid so it’s not an accurate reading at the group head, this can only be achieved by using a manometer connected to a blanked off porta filter handle.
WHAT IS A PORTA FILTER HANDLE?
This is the handle you put the ground coffee into, then lock into the coffee machine. There are various parts to the handle, the actual porta filter handle, then there is the porta filter basket and a spout/spouts. As a general rule, there are three types of handles, a single, double and naked.
WHAT DOES A NAKED OR BOTTOMLESS PORTA FILTER HANDLE MEAN?
This means there is no base to the bowl in the handle, a basket (usually a 21g basket) hangs in the handle and the perforated bottom is exposed. It’s used as an aid to make sure the tamp and grind are correct and if this is achieved there you should see no spraying of coffee and the extraction pours to form a central single pour. It is often said that the extraction is smoother than when using a standard porta filter handle.
WHAT DOES TAMPING MEAN?
Once coffee is put into the porta filter handle it require tamping down, this means compacting the coffee evenly. Various different methods are used but all require a tamper which is a handle with a base the size of your porta filter handle.
WHAT DOES “DISTRIBUTION” MEAN?
This is referred to the method of evening out the coffee in a porta filter handle. Think of it this way – if you make a sandcastle and the sand isn’t even in a bucket, the finished sandcastle with have cracks. It’s similar for coffee and if you have “cracks” then water will always find these as it wants to find the easiest route and will effectively miss out the majority of flavour in the ground coffee. Different methods are used but the end result is to create an even texture of coffee before you tamp.
DOES IT MATTER WHAT PRESSURE I TAMP TO?
If you tamp too hard, then you restrict the flow of water through the coffee often resulting in a bitter tasting coffee. If you don’t tamp hard enough then water simply rushes through and doesn’t pick up the flavours on its way through. It is thought that 30lbs of pressure gives the best results however this will depend on personal taste and the grinder used to grind the coffee.
WHAT DOES A PID MEAN?
A PID is the digital control seen on coffee machines which display the temperature. It stands for PROPORTIONAL INTEGRAL DIRIVITIVE and think of it as a memory for the machine to build up to create temperature stability. Different models will have varying amounts of software and parameters and not all PID’s are the same.
WHAT IS A THERMOBLOCK?
A thermoblock is used to heat water and works very much the same as a domestic shower.
WHAT DOES EXTRACTION MEAN?
This is the rate in which the oils from the coffee are extracted. We time these to determine if the grind texture is correct. If an extraction is too short, then the coffee is ground to course, if the extraction is too long, then the coffee has been ground too fine.
HOW LONG SHOULD AN EXTRACTION BE?
It depends on how you like your coffee and what machine you are using. As a general rule it should take between 22 and 32 seconds.
WHAT IS THE DIFFERENCE BETWEEN A VIBRATION AND ROTARY PUMP?
Both do the same job in providing 9 bar of pressure to the group head (which can be adjusted on a Rotary pump). As a general rule, vibration pumps last approximately 2-5 years and a Rotary pump should last between 4-7 years. Vibration pump are usually considerably less expensive to replace and a Rotary pump as two parts – the pump and the motor and are physically bigger. If noise level is important then Rotary pumps are less noisy than a vibration pump.
WHAT IS A PUCK?
A puck is the compacted coffee left in the porta filter handle after you’ve made a coffee.
DO I NEED TO DESCALE A COFFEE MACHINE?
Absolutely yes!! Lime scale is the biggest killer in coffee machines and causes 99% of problems. If you live in a hard water area then you’ll need to descale more frequently than in soft water areas. Thermoblock coffee machines are more difficult to descale and it’s advisable to check manufacturer’s instruction before a procedure however boilers will need regular cleaning. Aluminium boilers will need specialist cleaning products but stainless steel, brass and copper boilers can be descaled using citric acid or other similar products.
HOW IMPORTANT IS A GOOD GRINDER?
Very!!!! A high quality coffee machine will produce great coffee but if the ground coffee has been damaged by an inferior grinder then the quality is decreased. A cheap grinder can burn the oils in coffee before you’ve even brewed it. Blade grinders are an absolute No No!!! These simply destroy any flavour and must be avoided at all cost. Burr grinders are recommended and if possible, flat burrs produce a better flavour than conical burrs (unless it’s a large commercial grinder). The burrs contain a set of a bottom and top plate which have groves. These spin against each other and depending on how far apart they are set will depend on the texture of the grind. The bigger the burrs, the more they disperse the heat created during the spinning so when greater quantities of coffee are required, the bigger the burrs should be. Grinders are also determined by whether they are a “stepped” adjustment for the coarseness or micro adjustment. For high quality machines the latter is required as it gives more control over the timing of the extraction.
HOW LONG DOES IT TAKE FOR A MACHINE TO HEAT UP?
Most machines will take a matter of minutes to heat up but if your machine has an E61 group head, a large boiler or two boilers you need to allow plenty of time for it to fully heat up. It’ll take several minutes for the machine’s boiler to get up to pressure and in theory, you can now make coffee but you’ll improve your coffee enormously if you can allow for the group head and all the metal in your machine to get nice and warm and this can take up to half an hour.