# Get your thermometers out, we're doing some tests on the Classic



## chimpsinties (Jun 13, 2011)

Today I had a bit of time to experiment with some temp surfing. It's been bugging me for a while, so I thought I'd actually take some measurements to put my mind at ease. Here are the results.










A -86C (187F) 92C Machine had been sat for a while so I just drew some water into the cup

B -76C (170F) 82C I flushed 4 fl/oz through the group head then waited for the light to come back on and drew this water.

C - 75C (169F) 81C Flushed another 4 fl/oz then waited for the light to come on and drew this

D - 85C (185F) 91C Waited for 7 mins then drew this

E - 94 C (201F) 100C As a control I boiled the kettle and the moment it clicked off I poured this.

Of course there are numerous problems with my experiment. First of all I have no idea if the thermometer is accurate. Looking at the control I'd say probably not but saying that I have no idea how many degrees boiling water would lose on the way from the kettle to the cup. This is water in the cup temp, not group head temp so I guess again it's not totally accurate but it gives an idea. I've added the corrected temps if we assume that what came out of the kettle is 100 degrees.

What do you think? Could anyone else reproduce this with their own Classic so we can compare across machines?

Espresso should be made at between 92C-96C and by the looks of it I'm struggling to get in that range even with a long wait. I guess the next thing is to try using the steam switch to raise the temp but that idea doesn't really appeal to me as it's just such guess work.

For ages I was flushing before a shot because that's what most people do on the interwebs. Recently I've been just flushing for a tiny bit basically to release any built up steam then doing the shot straight away (not even waiting for the heat to cycle) which looks from my results like the best way to get near the desired temp. I wouldn't say my shots were by any means bad in fact I'd say they've been pretty consistently great but then again, I'm using a 2nd hand Classic and not some £1000+ machine







(soon Evoluzione you will be mine)


----------



## MikeHag (Mar 13, 2011)

Good effort, and this is something that is hugely worth doing. I blogged about my efforts on this front recently, although this was with a HX machine rather than single boiler http://www.haggieslab.blogspot.co.uk/2012/04/heat-exchanger-temperature-surfing.html

Measuring the water in the cup won't help you though. It will lose quite a lot during the transfer, and won't be anywhere near accurate enough to be meaningful. (see here http://coffeeforums.co.uk/showthread.php?5089-What-Bar-is-best)

But you're almost there, and what some people have done in the past is cut down the polystyrene cup so it fits in the naked portafilter holder, then insert the probe through the side of the cup. Still not great but better.

Hope that's useful.


----------



## forzajuve (Feb 2, 2011)

Have you tried switching the steam switch on for 10 secs, then off and draw water out through the group head? Another method that some use, I think it has definitely helped my shots but never actually checked on temperatures. Very interesting that the most common method yielded the worst results.

Maybe try Mike's suggestion and see if you can increase the accuracy. Relative results, if carried out consistently are very interesting though. Nice work!


----------



## chimpsinties (Jun 13, 2011)

I think the next time I try it will be Saturday now. I'm gonna try and fashion something using my naked PF, some selotape and my thermometer. Sounds like something from BluePeter. Haha! This time I'll try the steam switch thingy too.

Watch this space...


----------



## tribs (Feb 21, 2012)

I've said it before, but I think it is different from machine to machine.

Mine is the latest model and if left to get up to temp the first 2 floz at least are boiling, measured from the portafilter spout. Noticeably there is steam flashing at this point.

This is definitely worth doing and has provided you with some valuable insight into the best temp surfing technique for your machine.

I would do the tests again though. This time I would calibrate the thermometer by placing in the spout of the kettle as it boils so the probe is under the surface of the water. Then I would re run the tests wedging the poly cup against the group and poking the probe through the side at a downward angle as near to the top as possible, thus minimising inevitable temp losses to air.

Having said that, I think your conclusions are on the right lines in that your temp is a little below the ideal and that your current technique (purging the steam and then pull the shot) is best for your machine.

My current method is with portafilter attached purge measuring temp at spout until correct range. Remove portafilter fill with grounds and tamp, then actually follow your current method of purging the steam refit portafilter then pull the shot. I have found the boiler stat light doesn't really help in determining group water temp. This makes me wonder about the usefulness of a PID on this machine.


----------



## chimpsinties (Jun 13, 2011)

Ok so today I re-did my experiment. I rebuilt the test equipment to more accurately measure the temperature in the PF. I was quite shocked as to the difference it made tbh but overall pleased my machine isn't miles out.










A - New equipment setup. Styrofoam cup cut and inserted into naked PF. Small breather hole at back (for when it's filling with water) and thermometer inserted so probe is at the bottom of the cup.

B - 90C - After sitting for a while I flsuh out 2 small bits of water (to warm both my rattleware and cup) and vent any steam. Pull shot.

C - 84C - Flushing for 5 secs then waiting for light to come on. Pull shot.

D - 81C - Another flush for 5 secs then waiting for light to come back on. Pull shot.

E - 90C - Waiting for 7 mins then doing 2 small bits of water to warm cups and vent any steam. Pull shot.

F - 95C - Steam switch on for 10 secs then small flush to vent steam. Pull shot.

I think this much more accurately models what's going on in the PF as the espresso is being produced. I didn't bother including the corrected temperatures because I felt it wasn't necessary using this technique.

I was happy to see that my recent method of not flushing a lot of water (B & E) seems to yield the best results. I can forgive it a couple of degrees because that's probably being lost to the equipment.

It's quite clear that on my machine at least the ever popular "flush a load of water out and wait for the light to come on" technique drops the temp too much by introducing fresh cold water into the tank. I'm surprised this technique is talked about so often when it's probably always going to be detrimental to the espresso. I guess that's how laws get made on the internet. If enough people repeat it, it becomes true.

Using the steam switch seems risky to me. I don't think it's actually necessary to raise the temp if you're only making one shot and the machine has had time to warm up before hand. However, I can see it might be needed if you want to bang out a few shots and don't have time to wait between. It is easy to over do it though because as you can see even though I only gave it 10 secs it was still well into the mid 90's on my gauge and this means probably actually too hot in reality.

This has been a real eye opener for me. I hope it has for you too. Maybe together we can change the way folks use their Classics and get brewing temperatures back on track.


----------



## Earlepap (Jan 8, 2012)

Interesting stuff chimp. If I can find a cup I'll try the same on my machine today. Recently I've not been bothering with temp surfing too much - having previously been using the purge till light goes off method - and I reckon there has been more consistency in the shots. Perhaps they were often too cold before.


----------



## chimpsinties (Jun 13, 2011)

I got 24 cups from Morrisons for 99p I think


----------



## forzajuve (Feb 2, 2011)

Great stuff. I will have to re-think my steam switch technique. I went to this method as using the common technique I always found my shots sour indicating it was too cold. The steam switch has improved that for sure but maybe it is an unnecessary step as your temps indicate. I will definitely try a simple short flush now instead and see how I get on.

Always great to see some figures to prove or in this case disprove what current best practice is. Time to update the Gaggia Classic sticky?


----------



## Tryfan (Apr 11, 2012)

chimpsinties said:


> It's quite clear that on my machine at least the ever popular "flush a load of water out and wait for the light to come on" technique drops the temp too much by introducing fresh cold water into the tank. I'm surprised this technique is talked about so often when it's probably always going to be detrimental to the espresso. I guess that's how laws get made on the internet. If enough people repeat it, it becomes true.


Did you just wait for the light to turn on, or turn on then off again...? My understanding of this approach was to force the boiler to kick in (by bringing cold water in) and then wait for the upper limit thermostat to turn the heating element off. At this point the water would be at a very similar temperature between each pull, thereby allowing easier judgement of optimal brewing temp afterwards.

I do stress the word 'theory' though as this is how I understood it from the Interwebs, but I've not had the pleasure of trying it out.


----------



## chimpsinties (Jun 13, 2011)

On the Classic, when the light is off, the boiler is on and heating the water. Hence, when you flush a load of water out, new cold water comes into the boiler and the heater turns on (light goes out). You then wait for the light to come on signifying that the boiler is up to temperature (apparently) then you can start your shot. However, I've basically proven that it doesn't get the temp up to the required level. It takes a couple of heat cycles for this temp 92C-96C to be achieved. Hence the 7 min waiting time between shots.

Of course this is just on my machine. Others might well be different. I've put my own mind at ease regarding my personal technique and I strongly advise everyone else to do the same. If for nothing else than to eliminate one more variable from the equation that is making the perfect espresso.


----------



## Tryfan (Apr 11, 2012)

Interesting. So the indicator light is an 'ready' indicator, rather than a 'heating' indicator. Makes sense.

Does seem odd that it needs to cycle a few times before getting up to temperature - sounds like the thermostat which turns the boiler off isn't accurately measuring the water temperature...

Interesting post.


----------



## tribs (Feb 21, 2012)

Tryfan said:


> sounds like the thermostat which turns the boiler off isn't accurately measuring the water temperature...


This is what I alluded to earlier when I mentioned I have doubts about the effectiveness of a PID on the classic. Effectively the PID replaces this thermostat. It is measuring the boiler temp which isn't neccesarily the same as group water temp. Chimps tests (and indeed my own undocumented tests) seem to bear this out.


----------



## jimbow (Oct 13, 2011)

chimpsinties said:


> On the Classic, when the light is off, the boiler is on and heating the water. Hence, when you flush a load of water out, new cold water comes into the boiler and the heater turns on (light goes out). You then wait for the light to come on signifying that the boiler is up to temperature (apparently) then you can start your shot. However, I've basically proven that it doesn't get the temp up to the required level. It takes a couple of heat cycles for this temp 92C-96C to be achieved. Hence the 7 min waiting time between shots.
> 
> Of course this is just on my machine. Others might well be different. I've put my own mind at ease regarding my personal technique and I strongly advise everyone else to do the same. If for nothing else than to eliminate one more variable from the equation that is making the perfect espresso.


This could partly be caused by the external mounting of the thermostat to the boiler and the placement of the heating element. The thermostat measures the temperature of the boiler and not the water within it. It will take a little additional time for the water to reach the temperature of the boiler.

Sent from my HTC One X using Tapatalk 2


----------



## tribs (Feb 21, 2012)

jimbow said:


> This could partly be caused by the external mounting of the thermostat to the boiler and the placement of the heating element. The thermostat measures the temperature of the boiler and not the water within it. It will take a little additional time for the water to reach the temperature of the boiler.


I think you are probably correct.


----------



## carbonkid85 (Jan 19, 2011)

Just to add my own completely unscientific research to this thread, I have a digital thermometer atop my Classic with the thermocouple crudely secured the the top of the boiler with heat conducticting tape. A poor man's PID if you will.

As you correctly observe, the Classic's thermostat kicks in when the temp outside the boiler drops, not when the water inside cools. My thermometer shows that the heat cycle goes from 93.4 to 102.2

So as a guess, assuming a few degrees variance, the bottom of the cycle is going to give you a really sour shot. Perhaps the top of the cycle is a little too much though?


----------



## GS11 (Feb 20, 2013)

I was checking my temps and was a concerned to see only 70 degrees (albeit incorrectly measured at a stainless jug!)

Rigged up the test correctly and confirm classic running within spec.

Great thread....Thanks Op!


----------



## coffeechap (Apr 5, 2012)

Do you know the real shame with the classic, gaggia make the boilers for the kitchen aid artisan and both of the boilers they produce ( albeit separate use) have temp probe chutes on them that the dials on the front of kitchen aid slot into. I am trying to mod one of these boilers and slot it into the classic, to put a guage on the front of my classic, the temp reading at the chute should be much more accurate as it is insulated better from the external elements and takes a reading from the centre of the boiler. Anyway just goes to show that gaggia already make a better boiler, but for another manufacturers machine, guess that is why the gaggia is much cheaper


----------



## RoloD (Oct 13, 2010)

coffeechap said:


> Do you know the real shame with the classic, gaggia make the boilers for the kitchen aid artisan and both of the boilers they produce ( albeit separate use) have temp probe chutes on them that the dials on the front of kitchen aid slot into... Anyway just goes to show that gaggia already make a better boiler, but for another manufacturers machine, guess that is why the gaggia is much cheaper


Not sure about that - if you read the reviews for the Kitchen Aid machine online the machine seems a complete disaster.


----------



## coffeechap (Apr 5, 2012)

RoloD said:


> Not sure about that - if you read the reviews for the Kitchen Aid machine online the machine seems a complete disaster.


The kitchen aid is a disaster at the £600 price point!!


----------



## coffeechap (Apr 5, 2012)

Ps not saying the overall kitchen aid machine is any good, but the boilers are identical apart from what I previously pointed out, read the reviews the concerns are about build quality not shot quality. There is no difference in the quality of the shot compared to the gaggia.


----------



## rodabod (Dec 4, 2011)

chimpsinties said:


> It's quite clear that on my machine at least the ever popular "flush a load of water out and wait for the light to come on" technique drops the temp too much by introducing fresh cold water into the tank. I'm surprised this technique is talked about so often when it's probably always going to be detrimental to the espresso. I guess that's how laws get made on the internet. If enough people repeat it, it becomes true.


I need to try these experiments too. I do purge some water to speed up the heating cycle, but only for about three seconds (heats up shot glass).


----------



## chimpsinties (Jun 13, 2011)

I do A small purge too, to warm my cup. Just don't go crazy and empty the boiler.

Sent from my HTC One X using Tapatalk 2


----------



## Big Tony (Dec 18, 2012)

Hi All,

Reading this thread with interest because I've just bought a second hand Gaggia. I haven't even tried my Gaggia yet! Anyway, I'm trying to learn a technique to get me started and it appears that purging for a few seconds and then pulling the shot is the way forward.

It all sounds very good but I don't really know what you mean... can anyone tell a newbie how to do this?


----------



## coffeechap (Apr 5, 2012)

As the temperature fluctuates on the classic, basically what you do is runs the pumps via the coffee button for three seconds, this allows fresh water into the boiler and brings down the temperature to reactivity the elements, the light on the coffee button will go out and when it comes back on again it is ready to use, some here like to leave it for 30 seconds to allow a slight rise in temperature before pulling the shot. Make sure your portafilter is nice and hot, leaving on the machine while it heats up is sufficient, prepare your portafilter with the ground coffee as discussed in another thread, then do your flush, use the water coming out of the brew head to heat your espresso cups, then attach the portafilter and wait for the light to come on. Simples


----------



## chimpsinties (Jun 13, 2011)

Just run a bit of water through by turning the brew switch on for about 2 sec (usually into the cup you're about to make your drink into to warm it). Then grind your beans. Then make your drink. Easy.

I actually find with my machine that when it's been sat for a while (so well up to temperature) when I purge it, I get water for about 2-3 secs then it stops coming out or a second or two, as soon as it starts to come out again that's when I stop it.


----------



## Big Tony (Dec 18, 2012)

Yep, got it now. The step by step guide here... http://www.coffeecrew.com/learning/255-gaggia-classic-step-by-step is really good but doesn't mention this. Thanks


----------



## talktotheduck (Feb 26, 2013)

I wonder if maybe the boilers suffer slightly from stratification where there's an uneven mix of hot and cooler water within the boiler...where is the element in relation to the boiler ?and where is the thermostat? top of the boiler or low down, I might be tempted to give the machine a small wack or light shake to mix the water in the boiler and see if the thermostat comes on quicker.


----------



## Mazza (Aug 11, 2010)

chimpsinties said:


> On the Classic, when the light is off, the boiler is on and heating the water.


So when I switch the machine on from cold the light comes on straight away, surely the water is then being heated?


----------



## chimpsinties (Jun 13, 2011)

One light is on all the time (the left) This shows the machine is on. The one on the right shows if the boiler is heating or not.

Light on=boiler off

light off=boiler heating.


----------



## Mazza (Aug 11, 2010)

chimpsinties said:


> One light is on all the time (the left) This shows the machine is on. The one on the right shows if the boiler is heating or not.
> 
> Light on=boiler off
> 
> light off=boiler heating.


lol oh yeah, just me being dumb !


----------



## Mazza (Aug 11, 2010)

I was going to check the water temp of my Classic but thought I'd do a control 1st with boiling water, my frothing thermometer didn't show 100 deg c in boiling water so didn't bother as the readings would be out anyway.


----------



## chimpsinties (Jun 13, 2011)

Was it boiling? or boiling poured from the kettle into a cup then measured?

You could calibrate it by boiling some water, sticking it in, noting the temp as 100 then working backwards from there?


----------

