Posted Mon Nov 28, 2005, 5:01pm Subject: Newbies: tc probe at shower head FAR more important than any other mod..2..
Note - I keep editing this... sorry! :o)
Is your expresso bitter? ... or sour? ... or not quite right? or not consistant?
Start here!
This does not void your warranty while a PID will.
In any case, it's the best place to start.
Past: I calibrated a PID with boiling water and installed it in place of my 100C thermostat. I generally ran my PID at 230F(110C) (I now run at 215F). I mounted a Taylor digital cooking thermometer point in to the brewhead bolt with arctic silver epoxy. seemed like a good way to monitor the brew temp. I would shoot for 196 (I experimented with this a lot) I had this in for several months.
Because of the variability of the taste, I felt something was wrong.
Tonight, I disconnected the PID from the circuit and reconnected the 100C thermostat. I calibrated and checked 3 thermocouples and chose a fine wire type K (made by burning the insulation and twisting the 2 together) and put it in under the showerhead screen bolt (what I understand from Andy's pictures page is Bart's mod), using a fork lug and insulating the wire with spaghetti. (see the pictures in the following posts - lossa pictures!)
Though the boiler should have been at a lower heat because the thermostat is running it at 212, the temp of the pf shot to 205, when the Taylor was only reading 180. The Taylor is not the prob, but there is apparently quite a lag and gradient between the outside of the bolt, and what actually comes out the brewhead screen. Hugely bigger that I had expected. It also points up to me the importance of actually knowing the temp of the water hitting the coffee.
I have ordered a cheap digital temp readout for my K tc (it's on order), so I can reconnect my PID to the boiler, for now I will be using the PID only as a temp readout for the brewhead shower screen and running with the stock 100C thermostat.
Proof/pudding... This morning I pulled a couple of shots with my "new" contraption. Unit was preheated for 1/2 hour. with pf in place. I upped the grind because of very cloudy weather. Temp at shower during draw was about 196 +_ 3. The resulting ristretto was quite dreamy and easily (and almost was) consumed straight. I ran steam and turned it into a latte - even more dreamy. Forgetting that I had just heated up the boiler I decided to pull another shot. By the time I got there with ground coffee, the showerhead was running up around 208-204. The resultant ristretto was drinkable straight, but had a slight aftertaste that was indicitive of "cook me any hotter and you'll get a burnt taste"! So I latte'ed that one and it, too, was pretty darn good. BUT I KNEW WHY IT TASTED THE WAY IT DID -ONLY- BECAUSE I HAD A TC ON THE shower screen.
This verified that I was on the right track - the showerhead temp is all important!
I notice that when I am getting a burnt taste I am REALLY overheating things at the shower sceen - quessing 215. This also means to me that the Silvia is a LOT more tollerant of temp ranges than I heretofore thought, especially with the "new" 100C thermostat.
If you don't have a tc in the shower area, you're just guessing, no matter how many timers you use and how much electronics you have on your machine.
imo, this is the FIRST mod that folks should work with - to find out what the temp of the water hitting the coffee really IS.
The only thing that really matters is the temp of the water hitting the coffee (measured directly), next is a preheated pf and next is a preheated cup, and next is/are quality beans, and next is the grind.
It seems that folks are being given the advice to change something 4 or 5 components back in this dynamic system, not knowing if the shower temp is right, high, or low. It's so easy! We have the technology. It's cheap. Let's help folks more quickly get to enjoying their brew!!!!!!!!!!!
Yes, it seems like a new way of thinking. Course Schomer and others have known this for years. Many here on cg do it - they just don't talk about it .
I think the thing that needs to be stressed is to tc and meter the showerhead FIRST. Know what you've got, and you'll much better understand what your later mods do for you.
Here are some pictures. I don't have my meter yet but will post that when I get it in a week.
I posted thermocouple wire info/source a bunch of posts down...
Posted Mon Nov 28, 2005, 5:55pm Subject: Re: Newbies: tc probe at shower head FAR more important than any other mod..2..
Probe detached from shower screw, showing tc wire passing through some wire insulation and through the fork lug (any hardware store) , and the fork lug is crimped GENTLY just to hold the probe in place. You can also see where I burned about an inch of insulation off the tc wire, scraped it clean with my fingernail, and tightly twisted the 2 wires together <- this is the "probe", the "thermocouple". The bare wire is bent away from the fork and the screen. I show a standard sewing pin for scale.
Posted Mon Nov 28, 2005, 5:58pm Subject: Re: Newbies: tc probe at shower head FAR more important than any other mod..2..
kristi Said:
The only thing that really matters is the temp of the water hitting the coffee (measured directly), <snip> It seems that folks are being given the advice to change something 4 or 5 components back in this dynamic system, not knowing if the shower temp is right, high, or low.
I think you are looking at the issue in a rather odd way. Of course the water temp on reaching the coffee is the most critical issue (given pressure anywhere near the 9-15 bar area) but this temperature is affected by those components further back in the system so even if the control is back there, if the temperature change from the control point to the showerscreen is consistent, then adjusting the temperature back at the control point will give a consistent change at the showerscreen. Sparkman has shown that this is pretty much the case with the Sylvia but not the Gaggia.
That fact that most people don't measure the showerscreen temp but adjust by taste doesn't invalidate the approach.
Posted Mon Nov 28, 2005, 5:59pm Subject: Re: Newbies: tc probe at shower head FAR more important than any other mod..2..
Closeup of the thermocouple wire ... red is (-)(negative), yellow is (+)(positive) , Typical of K and J-type thermocouple wire. Note this particular wire is very fine so the pf has no prob sealing while in use.
Chocolate_Dog_Kona Senior Member Joined: 21 Jun 2005 Posts: 143 Location: Over a mile high, CO Expertise: I live coffee
Espresso: SD3C PID Rancilio Silvia! Grinder: Solis Maestro Plus Vac Pot: Bodum Press Pot Drip: Mr. Coffee Roaster: Boosted Poppery I
Posted Mon Nov 28, 2005, 6:04pm Subject: Re: Newbies: tc probe at shower head FAR more important than any other mod..2..
Kristi, May I suggest a couple of things really quick? It may work better to run the TC wire behind the PF gasket. That way, you're not stressing the wire each time you lock in the PF, plus it will still seal. That's what I ended up doing awhile back when I was doing just what you are now doing. I used several of my own TC's along with a couple of very small bead TC's to verify everything many times over. After all my experimentation, I found that an even easier method was to just run the TC wire up through the spout of the portafilter and push it up until it hits the screen, then back it off by about 2mm. The temps were almost always 2 degrees lower (plus or minus a few tenths) off of what I measured during actual brewing when putting the TC behind the gasket.
Also, a trick with your twisted TC wire. Once you have twisted the two wires together really well, use a sharp pair of cutters and cut off all but the last 2-3 twists of wire. This make the TC junction much smaller but just as good, yielding a faster responding TC.
Posted Mon Nov 28, 2005, 7:46pm Subject: Re: Newbies: tc probe at shower head FAR more important than any other mod..2..
Chocolate_Dog_Kona Said:
Kristi, May I suggest a couple of things really quick? It may work better to run the TC wire behind the PF gasket. That way, you're not stressing the wire each time you lock in the PF, plus it will still seal. That's what I ended up doing awhile back when I was doing just what you are now doing. I used several of my own TC's along with a couple of very small bead TC's to verify everything many times over. After all my experimentation, I found that an even easier method was to just run the TC wire up through the spout of the portafilter and push it up until it hits the screen, then back it off by about 2mm. The temps were almost always 2 degrees lower (plus or minus a few tenths) off of what I measured during actual brewing when putting the TC behind the gasket.
Also, a trick with your twisted TC wire. Once you have twisted the two wires together really well, use a sharp pair of cutters and cut off all but the last 2-3 twists of wire. This make the TC junction much smaller but just as good, yielding a faster responding TC.
Hell, I was just tickeled pink that that trick worked (picked it up on SQRL's boiler thread)!
Since I choose to remove it each time I clean, which is weekly, Under the gasket would negate that. Yes on cutting the thing much shorter, and also on stuffing it up poor Silvia's nose. But on that second one, I would clearly suggest running it inside the PF for a while until you fully understand what's happening. Cold filter and cold pf could change things. Too many noobs running around here not really knowing what is going on. Me included. I discover, bit by bit, by reading, and thinking. And unabashadly stealing other folks ideas!!! And this approach is soooo easy. ... and so cheap ... Why not do it!
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