Why Brew Temperature Control Is So Important

Before we start – a bit of a glossary for the uninitiated…

Portafilter – the bit with a basket where you pack you coffee grinds into that has a large handle extending from it.

coffee machine portafilter

Group head – the block of metal where you lock the portafilter into before starting the pump on your coffee machine.

File Name :DSCN1566.JPG File Size :367.9KB (376698 bytes) Date Taken :0000/00/00 00:00:00 Image Size :2048 x 1536 Resolution :300 x 300 dpi Number of Bits :8 bits/channel Protection :Off Camera ID :N/A Camera :E885 Quality Mode :BASIC Metering Mode :Matrix Exposure Mode :Programmed auto Speed Light :Off Focal Length :8.0 mm Shutter Speed :1/11.9 seconds Aperture :F2.8 Exposure Compensation :0.0 EV White Balance :Auto Lens :Built-in Flash Sync Mode :N/A Exposure Difference :N/A Flexible Program :N/A Sensitivity :Auto Sharpening :Auto Image Type :Color Color Mode :N/A Hue Adjustment :N/A Saturation Control :Normal Tone Compensation :Auto Latitude(GPS) :N/A Longitude(GPS) :N/A Altitude(GPS) :N/A

PID – (nerd alert on this one…) usually represented as a digital display (either solely or within a menu) of a number (that represents the output temperature of your machine) – this is a fancy thing that controls the temperature in your brew boiler (usually only found on fancy machines) by monitoring the rate of rise and fall of the temperature and anticipating when to turn the element on and off and for how long to achieve an acceptable (pre-programmed) modulation offset both sides of the target temperature – like I said – ‘fancy’.

coffee machine pid

Shot – a slang term for a coffee extraction.

Mother in law – a painful person.

Who cares you say (re brew temperature)?… Trust me, you do – or at least you should… Some of you will have previously controlled brew temperature, but hopefully all who read this thread are given the opportunity to play with brew temperature on a machine for a session – allowing you to taste the difference when you have enough control to unlock so much more from a bean – getting a significantly better cup of coffee as a result.

This is one of the most important aspects of coffee making that you as the consumer can have great control over with minimal effort – and it’s a technique that will yield a tremendous difference of improvement to what you can taste in the cup. This is something I bang on about nearly more than anything else to my customers to help give them better results. I have even gone to the level of printing instructions on the labelled bags I sell to assist them. After all, ensuring that what my customers taste is amazing is the first priority of my work.

Have you ever made a coffee for yourself and loved it, only to be told by a guest or your partner that they don’t like it at all?… I have (plenty of times). Some years ago, I just figured that they were a coffee luddite and should stick to instant (how naïve was I)…

Brew temperature control is something whereby you can have great effect to remedy any such situation so that you both can get the different flavours you want from the same bean – true story.

It’s actually fairly simple. The first bit of knowledge for you to appreciate and understand is that temperature is just a number – nothing more – people really get hung up on this – going to the extent of using temperature calibration tools (Sace device or similar), etc to monitor the group head output water temperature whilst the user alters temperature offsets so that the brew water coming out of the machine is exactly what the machine is showing on the digital PID display. This is a very expensive process (if you need to buy the calibration tool) and completely unnecessary – as I’ll explain below. They (the fancy shmancy coffee snobs) will then enquire as to the optimum setting (from where they purchased the beans) relative to temperature for that particular bean to make it ‘shine’.

Well, listen up deary, just because your mate or the roaster whom supplied you the beans tells you that 94°C is the perfect temperature for this bean – it does not necessarily mean it’s right for you – or your machine for that matter. Remember, taste is a very personal thing – and yours (as I have also learned) is in no way superior or more correct than the next punter – i’ll give you the big tip….

You’re up against 2 issues relative to brew temperature here which make your result vary greatly from the next chap…

– Firstly, their machine may be different (most likely is) from yours – and even if it is the identical machine, variances still exist in temperature offsets (the temperature inside the brew boiler vs the actual temperature that comes out of your group head), calibration/function of thermostats inside the boiler and was the other person’s machine properly warmed up during testing (possibly too cold resulting in a non-linear temperature profile during the extraction) – or perhaps the machine was on for half the day and suffering slight overheating (if only by a little)…

– The second problem that exists (as I mentioned above) is that everyone’s palate is different – what one person claims is the correct temperature to make a bean taste perfect, may actually taste like toilet to you…

The best advice is to use any such recommendation from your supplier/roaster as a guide or a starting point – I say this because if you haven’t purchased beans from this supplier/roaster, then it will give you a start point – but, if you’re a regular, then you can base your palate offset to their recommendation like you normally would – i.e. a suggestion of 94°C might mean that you program your machine at 95°C to get what you’re after in taste.

So, turn on your machine and warm it up for 3 to 4 minutes until the lights come on and get cracking…. kidding… Your machine will take approximately 20 to 30 minutes to warm up properly with several flushes of water run through the group head during the period to keep things nice and wet from the hot water in the boiler (as water is a good heat conductor that will help heat the group head quicker).

If 20 to 30 minutes is too long for you to wait – you basically have 3 choices – toughen up princess and be patient – or – get a plug in electronic timer cut off switch to turn the machine on automatically before you need it – or – put up with average coffee. But, why on earth would you put up with ‘average’? You can drive down the road and get that from your local deli or poorer performing café. Strive for perfection – this way you’ll never overachieve and you’ll always have room for improvement.

Side point – do you find that your first shot/shots taste like a fish’s backside and after the third or fourth shot, life gets back in balance and your coffee taste sublime? A tip to save that first and any subsequent shots of coffee from tasting terrible and get it as close as possible to spot on each time is to set your machine to overheat during warm up – i.e. if you wanted 94, set it for 95 or even 96. To give you some base understanding of why you would do this, you would need to take the outer casing off your machine (please don’t) and looked inside – the pipes that lead from your boiler are ‘so’ long and uninsulated – and all the metal in your group head needs to heat up too – remembering that the thermostat that measures the temperature is inside the boiler with the heating element – not the group head – (and if you have a basic understanding of refrigeration – you’ll appreciate that all the pipes and the outer skin of the boiler are losing heat to the surrounding air all the time (fairly rapidly); thereby fighting to stay warm). Now, imagine how much heat is lost constantly to the surrounding air from the pipes and your group head considering that neither of these has a heating element inside them to help maintain a consistent temperature or even a thermostat to monitor said temperature…. Actually, that’s a point for the ultra fussy aficionados who get the Sace instruments and calibrate their machines – your offset settings for the temperature are worth nothing unless you also warm your machine up in the same way, for the same amount of time and from the same start up ambient temperature and conduct your coffee making process at the same time offset from start up also (as your newly calibrated PID reading is still subject to everything being heated exactly as it was at the time of calibration)…. What I’m trying to say is good luck champions!… – you’ve perhaps focussed too much on an area that didn’t really need any focus – remember, temperature is just a number. Get a good routine that produces coffee that tastes great to you – first extraction out of the group, every time – and stick to it.

Geez Louise, I get side tracked….

So what? I hear you say again (about the loss of temperature stuff – not the aficionados & side tracking) – ‘Temperature is just a number’ I hear you repeating my words back to me… Well, whilst this is true – it is a constant temperature that you are chasing; the flat profile of a graph depicting the output temperature throughout each extraction (as in your target output brew temperature is ‘x’ and as the extraction progresses, the temperature should barely move above or below ‘x’ throughout) – that is the absolute goal. The best way to achieve this quicker is as I suggested earlier – simply overheat your machine before the first shot. This hotter water running through the system will bring everything up to temperature quicker so that when you drop your boiler temperature to your target seconds before your first extraction, the temperature at the group head during your first extraction will better mimic (by no means perfectly) the performance of a machine that had been left on to warm up for a lot longer – saving you time and coffee – because 1 degree really does make a significant difference to taste….

Try it – I’m right.

….Oh, and ensure you get rid of the stale grinds (only a small amount) that usually collect under your grinder’s burrs just prior to coming into the dosing chamber or out of the chute. You can do this by turning your grinder on for 2 or 3 seconds and disposing of the stale grinds that come out – fresh grinds also make a large difference.

Alternatively, you could just use those grinds to make a coffee for the mother in law…

So… how does this help you to satisfy more than just your palate?… (not the mother in law stuff – as no one really cares about their mother in law’s palate – be honest). Well, as I mentioned before – I print information on the labels of my bags of beans to help you, the consumer. My labels basically read – Gradual adjustment from a lower temperature to a higher one will affect taste as per the following – Sour, Tangy/Fruity, Sweet, Chocolate, Cocoa, Bitter, Astringent.

Once you’re up and running, you’ll want to start playing with the temperature settings to progressively modify the flavours in each extraction. You should allow your machine a minimum of 5 minutes between each temperature adjustment (after the initial warm up and testing at the initial temperature) with a few flushes of water run through the group head between temperature adjustments to allow everything to stabilise – it’s about eliminating variables (good to be as scientific about this as possible – otherwise your comparisons cup to cup will be flawed and inaccurate).

What might you be aiming for in flavours of your coffee?… This will probably depend on how you like your coffee – perhaps you’re an espresso drinker and like the origins of the cup to shine through – drop the temperature a little to mute some of the chocolates and reveal a greater acidic fruit loading in the cup (highlighting more of the bean’s origin’s offerings – as in – beans from different regions have very different tastes; even if you rate yourself as a very average punter with an unrefined palate, you would still clearly taste the difference in a side by side comparison) – too large a temperature drop though and it will taste sour. Your partner may like a stronger tasting cup to help cut through the milk with smooth, dark chocolates – raise the temperature a little to increase the depth of chocolate flavours – too far though and you’ll turn it bitter… The difference between these 2 results may be as little as 1 degree – and is more than likely exactly just that.

The last thing I mention on my labels is that if your current machine’s brew temperature is not adjustable – then buy a machine with a brew temperature that is. Simple.

I cannot bear to see roasted beans that I have worked for years to perfect be turned to toilet water in a matter of seconds… it’s just criminal.

You’ll be surprised at the flavours you can reveal from a single bean – and (more importantly) your partner will be happy….. perhaps justifying the upgrade if required….. lol.

So, you now know what you should be doing to get a desired result from your new beans. Did you realise that this temperature is by no means a ‘set and forget’ scenario? As the beans age, the more volitile acids within them change in their intensities – thereby allowing the flavours of the coffee to change also.

I get asked regularly about how long before a coffee should be consumed (to which I usually reply “on the day they were roasted” tounge in cheek). This is a very subjective question indeed – as a coffee will change radically initially (with the most volatile acids muting the quickest) – but, at a certain age and brewed at a specific temperature – that coffee will taste perfect to you. This may happen straight out of the roaster at 96°C brewing temp – or it may happen at the 10 day mark with a brewing temp of 94°C. What is certain though is that there is a sweet spot within each roast. The trick though is to extend that sweet spot for as long as possible to give you enough time to consume all the coffee brewed exactly as you like it, each and every cup until the bag is finished. You can achieve this by gradually lowering the brew temperature as the coffee ages.

Please don’t take liberties on this advice. Just because you’ve had the beans for 2 days doesn’t mean you need to drop the brew temp. What it means is that at a certain point from the roast date (perhaps 2 weeks / less / more), the coffee may start to taste a little flat, seemingly losing a good amount of its highlights. At this point, drop your brew temp by between 1°C and 2°C. This will increase the perceptable acidity within the coffee extraction (through changing the acid balance) and really bring it back to life – thereby greatly extending the time frame for you to finish enjoying the entire coffee bag’s contents at the originally intended high standard of flavours you began with. The flavours may have altered slightly from what you started with – but chances are that it has unlocked a new level of flavour – being something to savour and explore.

I hope you got something out of reading this. It is entirely in my interest that you do – as when you can better enjoy the coffees that I put so much care into roasting, you are more likely to become a returning (and very important) customer. Please feel free to debate this article’s contents and correct any inaccuracies by making comments below – Join and carry on the conversation. A topic is only as strong as its contributors…

Cheers and thanks so much for your time,


(Just for info – if you include any sort of link back to your website without seeking approval, your comment will end up in the spam folder. I’m chasing constructive comments please. Cheers).

3 thoughts on “Why Brew Temperature Control Is So Important

  1. Thank you for your excellent technical take on what’s required to produce consistent good Coffee. I am a Industrial Electrician so have a technical understanding on PID control. I to appreciate good coffee and are interested in re building a machine or starting from scratch. Your explanations here are right on the mark.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.