Sparkman Senior Member Joined: 14 Jun 2005 Posts: 358 Location: Brisbane, Australia Expertise: I love coffee
Espresso: La Pavoni Bar T2/Faema... Grinder: Cimbali Cadet/Gaggia MDF
Posted Sat Jul 9, 2005, 7:40pm Subject: Silvia and Classic temperature profiles
For anyone who may be interested. I have logged temperature during a shot by placing a K-type thermocouple in the filter basket of both a stock standard Rancilio Silvia and a stock standard Gaggia Classic. Both macnines were operating side-by-side and the tests were conducted consecutively, first on the Classic, then on the Silvia. As I was only interested in the temperature stability during the shot, no attempt at temperature surfing was made, so the starting temperatures were random and conducted during the element off period.
Hi Mark, Yes, extremely interesting. It confirms what others have found with these two machines. I am wondering, though, if it might indeed make a difference if you were to start at the top of the cycle for each machine. I would be interested, firstly, to see what temperature range this gave the Silvia, since most info I've seen derives from Nth American models. But it would also be interesting to see if a higher starting temp affects stability and by how much - not that anyone could complain about this for the Silvia. The starting temp for the Classic was obviously higher, though, and it still loses a lot through the shot (compare to the new Sunbeam).
Next, how about doing a pressure test to see where the pump OPV is set on both machines. 8-)
Thanks for doing this, Mark, as hard data is always interesting and useful (and pretty scarce).
Sparkman Senior Member Joined: 14 Jun 2005 Posts: 358 Location: Brisbane, Australia Expertise: I love coffee
Espresso: La Pavoni Bar T2/Faema... Grinder: Cimbali Cadet/Gaggia MDF
Posted Sat Jul 9, 2005, 9:39pm Subject: Re: Silvia and Classic temperature profiles
First of all, it is through the good will of Chris and Jack at Barazi in Brisbane that I was able to do these tests. The machines were floor stock, so both new machines. Unfortunately, I was pressed for time and the Silvia had to be demo'd for a customer during the test period. So I didn't even try to optimise the starting temperatures at all. The Silvia shots were all over the place as they were from different parts of the temperature cycle. Nevertheless, the stability within the shot was always within 2 deg C.
I might get back there and run some more tests when I have more time. Next time I'll look at different temp surfing protocols as well. But in the mean time, these preliminary tests are sufficient to show how different the Silvia and Classic are with respect to temperature stability during a shot.
alanfrew Senior Member Joined: 19 Dec 2001 Posts: 482 Location: Melbourne Expertise: Professional
Posted Sun Jul 10, 2005, 12:01am Subject: Re: Silvia and Classic temperature profiles
I noticed Alan had his TC in a cup from the Silvia at 93C in the comparison with the Sunbeam EM6900 so he obviously got the cycle right there.
Temp surfing? I don' do no steenkin' temp surfing!! <VBG> Just both machines on for 24 hours, it's amazing the temp. stability you get when everything's hot.
Note that the temperature of the water leaving the showerscreen (what I was measuring) is NOT the same as the overall "system" temperature, BUT.... Silvia temp started at 94C as water first hit the probe, dropped to 93C and stayed there as the cup filled up. The whole "system" is remarkably thermally stable over a normal shot time, and doesn't vary much (+/-1C) over subsequent shots, no matter what the heating light, element, thermostats etc. are doing.
The Sunbeam didn't do... as well.. and it shows up in the cup. But it certainly isn't any WORSE than a similarly priced Gaggia Classic, and has a good deal more in the way of features & capability. An interesting month ahead.
Posted Sun Jul 10, 2005, 12:33am Subject: Re: Silvia and Classic temperature profiles
Dear Alan:
Yes, maybe we have to wait jeest a leeetle beet longer for your detailed review.
It is interesting about the surfing bit or lack of it for the Silivia. I do it as it fits in with my routine anyway, ie warming up the cup so it's no hassle.
I am pleased that you think surfing is a waste of time because I have to say I have never noticed any difference doing it.
Yes, really hope you do a temp analysis under real espresso conditions to be fair to the machine. Sparky, says, that he can fit the wire with the TC under the lip of the portafilter and secure it without any leaks so a drill isn't necessary.
As you say, for the price, it has a lot of features. Even if the temp control isn't quite as good as a Silvia, the machine still has a lot going for it.
Mind you the Silvia is built like a tank and you can see the difference between the two machines in the pictures.
Posted Sun Jul 10, 2005, 8:47pm Subject: Re: Silvia and Classic temperature profiles
The "practical" temperature drop during the gaggia pull is less than indicated by Mark's profiles. The last part of the temperature profile is for water that never makes it into the cup. It remains in the filter holder or is vented by the 3-way value at the end of the shot. On could (over) estimate this volume of water by weighing the portafilter before and after a shot using a gaggia that doesn't have a 3-way value. Anyone with a gaggia espresso and a good scale?
The results suggest that the gaggia is more consistent between shots; that is probably why people often consider them to be less finicky. Once you start temperature surfing, silvia becomes more consistent and more temperataure stable.
Maybe one can reduce the gaggia's temperature decline by hitting the steam switch for a few seconds just before pulling the shot. Try to give the boiler a little extra heat without affecting the interior water temperature.
Sparkman Senior Member Joined: 14 Jun 2005 Posts: 358 Location: Brisbane, Australia Expertise: I love coffee
Espresso: La Pavoni Bar T2/Faema... Grinder: Cimbali Cadet/Gaggia MDF
Posted Sun Jul 10, 2005, 10:45pm Subject: Re: Silvia and Classic temperature profiles
Alas, there's no hitting the steam button during a shot with a Classic. Once you hit the steam switch, while the brew switch is on, the 3-way switches as well, as that's the setting that directs hot water out the steam wand.
I've tried brewing with the elements on full tilt on my machine (by using a second very high PID set point) and only got the temperature profile turning near the end of the shot.
That's a good observation about the "practical" temperature drop. Still looks like an inherintly unstable brew temperature to me. Maybe it is stable enough to make decent coffee though.
Posted Mon Jul 11, 2005, 6:12am Subject: Re: Silvia and Classic temperature profiles
Sparkman Said:
Alas, there's no hitting the steam button during a shot with a Classic. Once you hit the steam switch, while the brew switch is on, the 3-way switches as well, as that's the setting that directs hot water out the steam wand.
I've tried brewing with the elements on full tilt on my machine (by using a second very high PID set point) and only got the temperature profile turning near the end of the shot.
Took a close look at your "full tilt" plot on a.c. before writing the previous post. Seems that you have to turn on the steam switch before you pull the shot because the response time is a little too long. Then the steam switch has to be turned off before pulling the shot unless you want to rewire your machine. Given the response time, heating during the pull may only be a small improvement. That gives you two variables to play with, heater-on time, and delay time between heater-off and pump on. One would need a lot of roasted coffee to figure out the best pair of values.
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