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Thread: Temperature measurements on Silvia

  1. #1
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    Temperature measurements on Silvia

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Some may say that pulling shots on Silvia doesnt require any temperature surfing or more elaborate (read PID) control. However, when I measure the temperature of a Silvia I find it is far from temperature stable.

    Installment one: Heres a measurement of the group temperature (with PF locked in and after more than 24 hours of running). Mid way through the measurement I flushed some water through the group to see what effect that had.

    The thermal cycle is about 15 minutes and the element is on for less than 2 minutes. The temperature in the group will vary far less than that within the boiler. The boiler temperature excursion will be in the range of about 15 C. As the recommended temperature for brewing coffee is about a 6 C range (88-94 C), this 15 C swing will take the brew temperature outside this range for some of the thermal cycle.

    The group cycles by 4-5 C. You can see that after a flush it will remain hotter for some time. So a walk-up shot without flushing will be cooler than one with flushing. I saw this effect pretty clearly when thermologging actual shots. Ill prepare that data and post it a bit later.

    Its all academic as the machine certainly makes great shots, but to state that its a walk-up and brew a shot machine is ignoring its physical behaviour.


  2. #2
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    Re: Temperature measurements on Silvia

    Heres a walk-up shot on a Silvia (not watching the boiler cycle). Temperature is measured with a K-type thermocouple inserted on top of the coffee puck over the lip of the basket. So the water temp between the shower screen and coffee puck is measured. I did a couple of these measurements in succession and they all came out low. Well below the accepted brewing temperature range.

    Subsequent measurements on a different day and different machine and synchronized with the boiler cycle yielded proper brewing temps. My take home message is that you need to temperature surf if you want consistent results with a Silvia.




  3. #3
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    Re: Temperature measurements on Silvia

    Hi Sparky,

    Just to add a few more numbers, I have a small digital thermometer with the probe on the top of my silvias boiler, near the thermostats. Before the thermostat switches the element on, the thermometer reads about 89-90C. After the element switches off, temperature stabilises at 108-110C.

    Cheers,

    Luca

  4. #4
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    Re: Temperature measurements on Silvia

    This is why I love this site!! :D I love that there are people here who want us to have as much information as possible and I love that there are others who are just happy to sit back and enjoy the ride, not really knowing where theyre going but having fun all the same! I think Im one of those latter people! ;)

    Thanks Sparky, I like the graphs, theyre easy to read and understand but you probably wont see me temp surfing my Silvia anytime soon. Im just not that technical. I pull a shot and mostly it goes to a milk based drink for my self or my friends. When I do an espresso or long black, I can generally get a sweet shot with no bitterness, or so the drinkers tell me. I can smell it for myself too.

    My taste buds tell me that the coffee I make is a God Shot every day! :P But of course, if I was to have half of you lot around for coffee, youd probably be offering up different opinions as to what the God Shot should taste like! :D Which is perfectly okay with me cause thats what were here about!

    Ill be looking forward to more graphs, Sparky!

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    Re: Temperature measurements on Silvia

    All I can say is "thanks Sparky". Was beginning to think that I was kidding myself after reading some recent articles.

    Ive been using a thermocouple on the top of the boiler connected to a DMM to monitor boiler temp, and have found that best shots generally seem to be within a certain temp range, on the cool down after a heating cycle.

    The actual range I use is 206-210 Deg C for starting the pour (which might seem a bit high, but some of this is due to actual position of the thermocouple). I did some testing on installation and found this gives brew water temp around the suggested optimum range.

    Not as nice as a PID controller but at around $30 its a bit (lot) cheaper and helps consistency. Still some refining to do but I have some reference point at least to work from.

    Also agree with Scoota gal that visual and aroma of the pour can tell you a lot about how well things are working.

    Regards
    Bullitt


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    Re: Temperature measurements on Silvia

    Hey Scoota,

    At the end of the day, there are no temp surf police - tis all about what tastes good to you. No-one has customers on a silvia ;P

    Hey Bullitt,

    Weve got the same setup! Phenomenal value for $30 ... especially seeing as I doubt that a PID is really going to be able to do much for the intra-shot temperature. twill dispense with all of the surfing nonsense, though, but Id probably still want to flush the group before extracting ... actually ....

    Hey Sparky,

    You dont have a silvia any more, do you? I was wondering if you could do similar measurements to show us how much the head heats up after a series of simulated shots ... I know that when backflushing a bit the water comes out flashed to boiling, even if the element has just turned on. If I do three or four shots in a row, I usually surf the last two a little bit cooler. But remember that thats running anything up to 150mL through the group to start the temp surf ... so thats potentially 700mL or so going through the group!

    Hey Bullitt, again,

    Thought you might be interested in my current surf technique; since Sparky gave a lot of evidence to show that the most temp stable shots will be two minutes or so after the boiler light goes out and all of the currents have ceased, Ive been surfing by waiting till the thermometer reading stops increasing. By taste, this seems to give me relatively cool shots. I can control the heat by flicking the steam switch for a little bit immediately after the element goes out.

    Currently Im drinking some Daterra Sweet Collection that I roasted last week. I thought that I stopped it at the beginning of the second crack, but it wasnt all that impressive at +5 seconds steam temp; lacking in body and sweetness; crema was relatively pale. I added 20 seconds of heat next shot round and it was probably 5 seconds or so too much; massively increased, syrupy body, a bit of the expected sweetness and crema approaching the colour of my NP cups, but a bit of ashiness when I added the milk. +15 seconds or thereabouts will probably be about right. Ill blog about this one next week after it has run out.

    Cheers,

    Luca

  7. #7
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    Re: Temperature measurements on Silvia

    Sorry Luca the Silvia is long gone. It only lasted one weekend before I realised it was not a good or cost effective upgrade. The Bezzera lobbed up a week later.

    I like your surfing method though. The shot I posted above was probably long after the element switched off. Its pretty flat, but too cool to be usable. Usable temperatures were still pretty good though.

    All in all this temperature stuff is mystifying. My best shot ever has come from a some Dominican Republic Soliman (mail ordered from Melbourne) on my PIDed/pressure modded Gaggia Classic. Nothing has come close to its yumminess on any machine since, and that includes commercial machines, even an FB70. The next best shots have been pulled on BZ35s. My mate pulls a pretty mean shot on his and the fist shot of the Veneziano Forza came out brilliant caramel with very nice body (a bit of a harsh after-taste though)

    Bear in mind that the Gaggia Classic is far from temperature stable during the shot (it has a falling profile), hence the confusion.

    The best shot in question flowed out thick like clotted cream (using a ristretto grind). It was hazel brown with rich sweet chocolate flavours. No sourness or bitterness to be seen. It was a shot destined for a cappuccino, but I gave it a taste test and decided it was too good to use in a cappa... It compelled me to drink it.

    This is the shot that keeps me searching for the magic formula of machine/grind/tamp/bean that will let me re-live this experience... Otherwise I might as well give up and drink tea.



    Cheers,

    Mark.

  8. #8
    JR
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    Re: Temperature measurements on Silvia

    This is the shot that keeps me searching for the magic formula of machine/grind/tamp/bean that will let me re-live this experience... Otherwise I might as well give up and drink tea.
    Hear hear!!

    Dan

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    Re: Temperature measurements on Silvia

    Behmor Brazen - $249 - Free Freight
    Hey Luca,

    Thanks for the comments, although I am a bit confused,
    you said you had the DMM/Thermocouple setup same as I use, then later you were explaining a surfing technique with no reference to your temp readings,..

    And yes my testing that I did some time ago also showed best boiler stability somewhere around 2mins + after the heating element went off (as best I can remember).

    Apart from that thanks for the additional info, I also use the steam switch to modify the pour temp.
    I have seen a couple of really nice looking pours that were destined for a Latte, and I wish I had tried them as a straight shot, (although the latte was very nice),....thing is whenever my mate Razurhead comes over and I want to give him a good shot, it doesnt pour like the best ones do...yet.

    Youve given me a few ideas to play with and try.
    Other thing I guess, as you noted is the beans that you have roasted,
    another area where I am refining as I go, and frequently changing blends lately probably doesnt help.

    Regards
    Bullitt



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