At the end of a multi-page discussion of which temperature measurement technique was "more accurate," Greg Scace wrote this:

gscace wrote:Time to jump in on this business of which measurement is more accurate or whatever. Let's be clear on what we are measuring when we do the surface thermocouple on top of the cake (ST) or the thermofilter thing (TF).

In ST, you are measuring the temperature of water and coffee on top of the coffee cake. The cake starts cool, and warms up as water percolates through it. The percolation rate is approx 30ml / 25 seconds and the pressure is 9 bars.

With TF you are measuring the water temperature in a warmed, insulated environment as it leaves the dispersion screen. The cake facsimile is preheated. the flow rate in TF is identical to that of ST as is the pressure.


Which is more accurate? The answer is that they are both accurate and if you're using the same measuring equipment, let's say uncalibrated type T wire and the same readout device between the two, then they are equally as accurate, but the measurements are of slightly different things.

And Chris Tacy recently wrote this on his blog:

malachi wrote:For example - using the old school methods (pioneered by Schomer et al) for measuring brew temp I had the idea that the Hairbender was best at around 199 or 200 F. Using the Scace [thermofilter thingie], I've determined that the optimal brew temp is more like 197 or 198 F. This is a big difference.

Chris, given the evidence presented in this thread, I think it would be more accurate to state something like: "On machine 'X,' I get the best results with Hairbender when I set it to brew at 197-198F as measured by the Scace Device."

IOW, I interpret the thread to conclude that it's a matter of interpretation whether the espresso is "actually brewing" at 197-198F or "actually brewing" at 199-200F. But it IS important to state how you arrived at the temp measurement. The point of the Scace Device is that someone across the globe can reliably reproduce your measurement. If you're simply sticking a thermocouple into the basket, reproducibility is much dicier.

Yippie I invited a fellow home roaster and recent Silvia owner who lives nearby over to check out the Silvia gasket mod. (I also had a gasket on hand to do his but he didn't have time today, wife duties to attend to, something about a 2 year late 10th anniversary diamond upgrade, which has become highly necessary now do to his recent various coffee related purchases this year like Z&D roaster, HotTop roaster , RK-Drum roaster, I-RoastII roaster, a SECOND Rocky, Silvia and PID mod...) I ordered a PF gauge and thought about ordering Greg's PF temp device, but opted to pass for now. While playing with my Silvia tweaking the pressure via sanding the gasket Greg tells me he ordered one yesterday after reading about my recent styro cup measurements and obvious limitations! (not Greg Scace, Greg who lives a few blocks away) Cool, will have ready access for real temp measurements. Oh, and it's gonna have to be a big diamond upgrade for Trisha 'cuz he's jazzed about the GS3!

I haven't read the complete thread. I ask this seriously. Are the materials used in this device all food-grade? My thought would be if there were any chance of trace amounts of cyanoacrylate or other toxic chemicals contacting the machine. Don't want to scare but it's a valid question.

Keith

MOSFET wrote:I haven't read the complete thread. I ask this seriously. Are the materials used in this device all food-grade? My thought would be if there were any chance of trace amounts of cyanoacrylate or other toxic chemicals contacting the machine. Don't want to scare but it's a valid question.

Keith

Interesting question. Suppose to be on the safe side wouldn't hurt to do a cleaning backflush after a temp measurement session.

MOSFET wrote:I haven't read the complete thread. I ask this seriously. Are the materials used in this device all food-grade? My thought would be if there were any chance of trace amounts of cyanoacrylate or other toxic chemicals contacting the machine. Don't want to scare but it's a valid question.

Keith

Have you evaluated the water coming through your portafilters for heavy metals?

OK, everyone who's used a Scace Device has been very enthusiastic. It makes temperature measurement so much easier and repeatable.

I recently got one, but I noticed some weird things happening. I think I know what the problem was.



If you look at this image you'll see the tip of the thermocouple sheath in the area of the red arrow. The tip is where the temperature is actually sensed. You'll also notice that the sheath runs parallel to the rim of the basket. That is good.

When I originally received The Device, the sheath was bent down slightly. The sensing tip was about a millimeter or so lower, just about touching the plastic. I believe that silly millimeter made a big difference. It meant that the probe had more of a tendency to report a composite temperature, part hot incoming water and part slightly cooler water that was running along the surface of the plastic. This made the readings artificially low, and it meant the readings were highly sensitive to how warm the plastic was before starting the shot.

I carefully bent the sheath back up so that it was parallel to the basket rim (the photo shows The Device after corrective rebending). My temp readings went up, and they became much less sensitive to the temp of the plastic before commencing the extraction.

I talked about this with Greg on the phone and he agreed that the sheath should be horizontal, not tipped downwards. [EDIT: I don't believe he said it had to be PERFECTLY horizontal, just that it shouldn't obviously tip downwards and shouldn't tip up too much or it might not have sufficient clearance from the shower screen. Hopefully Greg will comment.]

So check your sheaths, everyone.

AndyS wrote:So check your sheaths, everyone.

Thanks for the heads up. The instructions warn about handling:

The Thermofilter is also a precision measuring instrument that is easily damaged by careless handling, and storage. Examples of careless handling and storage include dropping it, bending the thermometer probe, storing an unprotected thermofilter in a toolbox or drawer with a bunch of mean and nasty hammers and wrenches that could hurt it.

Greg may want to add a few words specifically about recognizing the proper position / angle of the sensor. I just looked at mine and it's not easy to judge if the sensor is perfectly parallel because of the viewing angle.

The Thermofilter is also a precision measuring instrument that is easily damaged by careless handling, and storage. Examples of careless handling and storage include dropping it, bending the thermometer probe, storing an unprotected thermofilter in a toolbox or drawer with a bunch of mean and nasty hammers and wrenches that could hurt it.

A tool like this costing as much as it does and requiring another tool costing almost as much to even use it ought to come in a protective case. Being sold bare as it is now is cheap & cheesy IMO.

miKe mcKoffee wrote:A tool like this costing as much as it does and requiring another tool costing almost as much to even use it ought to come in a protective case. Being sold bare as it is now is cheap & cheesy IMO.

first run of a new product. lots to learn. i know greg was trying to keep the price down and yet still make it worth his time and effort. if you want to add $50 for a case, maybe it should be an option.

barry wrote:first run of a new product. lots to learn. i know greg was trying to keep the price down and yet still make it worth his time and effort. if you want to add $50 for a case, maybe it should be an option.

True, and easy enough to -pick up a $15-$20 padded camcorder case that'll work just fine.

BTW, has the correct diameter/gauge wire been determined for cleaning the brass regulator to return it to 2oz flow. I've tried to clean it without poking something true the tiny hole, and still can now only test about ristretto flow volume... Seems a cleaner needs to come with it in the future.